TY - CONF TI - Numerical simulation of film cooling on the tip of a gas turbine blade AU - Acharya, S. AU - Yang, H. AU - Ekkad, S.V. AU - Prakash, C. AU - Bunker, R. AB - Numerical simulations of flow and heat transfer are presented for a GE-E3 turbine blade with a film-cooled tip. Results are presented for both a flat tip and a squealer tip. Straight-through coolant holes are considered, and the calculation domain includes the flow development in the coolant delivery tubes. Results are presented with three different tip gaps representing 1%, 1.5% and 2.5% of blade span, a blowing ratio (ratio of coolant-jet-exit velocity to average passage flow velocity) of 1, and an inlet turbulence intensity of 6.1%. On a flat tip, film coolant injection is shown to lower the local pressure ratio and alters the nature of the leakage vortex. High film cooling effectiveness and low heat transfer coefficients are obtained along the coolant trajectory; these values increase slightly with increasing tip clearances. For a squealer tip, the flow inside the squealer cavity exhibits streamwise directed flow, which alters the trajectory of the coolant jets and reduces their effectiveness. C2 - 2002/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2002/// DO - 10.1115/GT2002-30553 VL - 3 B SP - 1051-1062 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036992043&partnerID=MN8TOARS ER - TY - JOUR TI - Jet impingement heat transfer on dimpled target surfaces AU - Ekkad, S.V. AU - Kontrovitz, D. T2 - International Journal of Heat and Fluid Flow AB - Detailed heat transfer distributions are presented over a jet impingement target surface with dimples. Jet impingement by itself is an extremely effective heat transfer enhancement technique. This study investigates the effect of jet impingement on a target surface with a dimple pattern. The effect of dimple location, underneath the jets or between the jets, is investigated. The effect of dimple depth is also investigated. The average jet Reynolds number is varied from 4800 to 14 800. The heat transfer measurements are obtained using the transient liquid crystal technique. Results for dimpled target surfaces are normalized with data for plane target surfaces to determine whether the presence of dimples enhances heat transfer. Results show that the presence of dimples on the target surface, in-line or staggered with respect to jet location, produce lower heat transfer coefficients than the non-dimpled target surface. The bursting phenomena associated with flow over dimples produces disturbances of the impingement jet structures resulting in lower levels of heat transfer coefficients on the target surface. DA - 2002/// PY - 2002/// DO - 10.1016/S0142-727X(01)00139-4 VL - 23 IS - 1 SP - 22-28 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036471417&partnerID=MN8TOARS ER - TY - CONF TI - Numerical simulation of flow and heat transfer past a turbine blade with a squealer-tip AU - Yang, H. AU - Acharya, S. AU - Ekkad, S.V. AU - Prakash, C. AU - Bunker, R. AB - Numerical calculations are performed to simulate the tip leakage flow and heat transfer on the squealer (recessed) tip of GE-E3 turbine rotor blade. A squealer tip with a 3.77% recess of the blade span is considered in this study, and the results are compared with the predictions for a flat-tip blade. The calculations have been performed for an isothermal blade with an overall pressure ratio of 1.32, an inlet turbulence intensity of 6.1%, and for three different tip gap clearances of 1%, 1.5% and 2.5% of the blade span. These conditions correspond to the experiments reported by Azad et al. [1]. The calculations have been performed for three different turbulence models (the standard high Re k-ε model, the RNG k-ε and the Reynolds Stress Model) in order to assess the capability of the models in correctly predicting the blade heat transfer. The predictions show good agreement with the experimental data, with the Reynolds stress model calculations clearly providing the best results. Substantial reductions in the tip heat transfer and leakage flow is obtained with the squealer tip configuration. With the squealer tip, the heat transfer coefficients on the shroud and on the suction surface of the blade are also considerably reduced. C2 - 2002/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2002/// DO - 10.1115/GT2002-30193 VL - 3 A SP - 295-307 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036998289&partnerID=MN8TOARS ER - TY - JOUR TI - Heat transfer in two-pass turbulated channels connected by holes AU - Ekkad, S.V. AU - Kontrovitz, D. AU - Nasir, H. AU - Pamula, G. AU - Acharya, S. T2 - Journal of Thermophysics and Heat Transfer AB - This is part of a continuing study of a new internal channel cooling design for modern gas-turbine blades. In previous studies, the enhanced cooling in thesecond pass of a serpentine channel was achieved by a combination of impingement and crosse ow-induced swirl. A holed or slotted divider wall replaced the 180-deg U turn connecting the two legs of the serpentine channel. Flow from one coolant pass to the adjoining coolant pass was achieved through a series of straight and angled holes and a two-dimensional slot placed along the dividing wall. The focus is to enhance the heat transfer in the e rst pass of the two-pass channel using traditional rib turbulators. The effect of ribs in the e rst pass on the overall second pass heat transfer enhancement is compared to channels with no rib turbulators. Heat transfer distributions are compared for three channel e ow Reynolds numbers ranging between 1:0 £ 10 4 and 5:0 £ 10 4 . Three different rib cone gurations, 90-deg ribs, 60-deg angled forward facing toward the divider wall, and 60-deg angled backward facing away from divider wall, are studied for all Reynolds numbers and dividerwallgeometries. Thepresenceof ribsin thee rst passdoesnot only decreasethe enhanced heattransfer in the second pass, but also provides higher heat transfer enhancement in the e rst pass, resulting in an increase in overall heat transfer enhancement for the entire two-pass channel. DA - 2002/// PY - 2002/// DO - 10.2514/2.6694 VL - 16 IS - 3 SP - 404-414 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036638366&partnerID=MN8TOARS ER - TY - CONF TI - Effect of rotation on flow and temperature distributions in a two-pass channel connected by two rows of holes AU - Pramanick, A. AU - Ekkad, S.V. AB - This paper presents a computational study of the effect of rotation on the velocity and thermal field for a two-pass channel connected by two rows of holes on the divider wall. Detailed velocity and temperature distributions are presented inside a rotating two-pass coolant channel connected by two rows of holes on the divider walls. The enhanced cooling in this passage design is achieved by a combination of impingement and crossflow-induced swirl. The cross flow is generated from one coolant passage to the adjoining coolant passage through a series of straight or angled holes placed along the dividing wall. The holes deliver the flow from one passage to another typically achieved in a conventional design by an 180° U-bend. In this study, the configuration has two rows of 12 straight holes placed axially. The two hole rows are placed at 1.27-cm distance from the sidewalls and are angled orthogonally. There are 12 holes in each rows of 1.27-cm diameter each. The holes direct flow perpendicular to the axial direction. Commercial software, FLUENT, is used for predicting the flow using the standard k-ε turbulence model. The results are presented at a channel flow Reynolds number of 25000. The effect of rotation number from 0, 0.1, and 0.2 is studied along with inlet coolant-to-wall density ratio of 0.05, 0.1, and 0.15. Results show that the impingement and swirl flow are affected by rotation induced Coriolis and centrifugal forces. There appears to be little effect of centrifugal buoyancy for this geometry as velocity profiles are unaffected by the wall temperature changes. C2 - 2002/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2002/// DO - 10.1115/GT2002-30218 VL - 3 A SP - 543-550 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036998264&partnerID=MN8TOARS ER - TY - CONF TI - Effect of jet-to-jet spacing in impingement arrays on heat transfer AU - Ekkad, S.V. AU - Gao, L. AU - Hebert, R.T. AB - Detailed heat transfer measurements are presented for jet impingement through arrays of jet holes. The effect of jet-to-wall spacing, hole-to-hole spacing are studied for inline arrays of holes. The axial and spanwise spacing (S/D) of holes are varied to produce square and rectangular arrays of holes. The results are presented at a jet average Reynolds numbers of 5000, 10000, and 15000. The jet-to-wall spacing is varied from 1 to 5. The arrays of 25 holes are placed to create four different configurations. The first configuration has an axial jet-to-jet spacing (SX/D) of 4 and a jet-to-jet spanwise spacing (SY/D) of 4, the second configuration has a SX/D of 8 and SY/D of 4, and the last configuration has a SX/D and SY/D of 8. Detailed heat transfer measurements are obtained using the transient liquid crystal technique. Results show that increase in jet-to-wall spacing reduces cross-flow effect. Results also show that the increase spacing between jets increases lateral spreading. C2 - 2002/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 2002/// DO - 10.1115/IMECE2002-32108 VL - 372 SP - 237-244 M1 - 4 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0346884482&partnerID=MN8TOARS ER - TY - CONF TI - Flow and heat transfer predictions for a flat-tip turbine blade AU - Yang, H. AU - Acharya, S. AU - Ekkad, S.V. AU - Prakash, C. AU - Bunker, R. AB - Numerical calculations are performed to simulate the tip leakage flow and heat transfer on the GE-E3 High-Pressure-Turbine (HPT) rotor blade. The calculations are performed for a single blade with periodic conditions imposed along the two boundaries in the circumferential-pitch direction. Cases considered are a flat blade tip at three different tip gap clearances of 1%, 1.5% and 2.5% of the blade span. The numerical results are obtained for two different pressure ratios (ratio of inlet total pressure to exit static pressure) of 1.2 and 1.32 and an inlet turbulence level of 6.1%. To explore the effect of turbulence models on the heat transfer results, three different models of increasing complexity and computational effort (standard high Re k-ε model, RNG k-ε and Reynolds Stress Model) are investigated. The predicted tip heat transfer results are compared with the experimental data of Azad [1], and show satisfactory agreement with the data. Hear transfer predictions for all three turbulence models are comparable, and no significant improvements are obtained with the Reynolds-stress model. C2 - 2002/// C3 - American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI DA - 2002/// DO - 10.1115/GT2002-30190 VL - 3 A SP - 271-283 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037003472&partnerID=MN8TOARS ER - TY - JOUR TI - Health monitoring and reliability of adaptive heterogeneous structures AU - Garg, D.P. AU - Zikry, M.A. AU - Anderson, G.L. AU - Stepp, D. T2 - Structural Health Monitoring AB - New adaptive structural systems comprised of optimal material combinations, innovative sensors and actuators, and control subsystems need to be developed and tailored for damage tolerant applications associated with severe loading conditions and harsh environments. In this position paper, fundamental considerations related to the modeling, design, and performance prediction of adaptive heterogeneous structures and benchmark laboratory experiments that would be needed for developing new and reliable sensor-integrated adaptive structures are discussed. Recent progress in these areas is discussed and new research directions that are needed and the barriers to be overcome to fulfill these objectives are proposed. One major challenge is to optimally integrate a variety of sensors and actuators in the context of health monitoring in order to enhance structural performance and reliability. The other major challenge is of scaling material and structural behavior from the micro- and meso-levels to the macro-level for full-scale adaptive structural system performance. DA - 2002/// PY - 2002/// DO - 10.1177/147592170200100103 VL - 1 IS - 1 SP - 23-39 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542359725&partnerID=MN8TOARS ER - TY - CONF TI - Deformation fields in woven composite plates under impact AU - Bahei-El-Din, Y.A. AU - Zikry, M.A. AU - Rajendran, A. AB - The deformation fields and kinematics of woven composite material systems due to impact loads are analyzed and characterized for various structural parameters. Target plates comprised of woven composites with 3D preforms are considered. The analysis examines fully consolidated as well as cellular systems and simulates actual experiments. Solution of the nonlinear dynamic/contact problem was obtained by a meso-mechanics based finite element model. The results quantify experimental observations, which reveal distinct behavior under impact among nonporous and porous systems. It was found that wave propagation effects at incident energies in the order of 500 J are significant and lead to penetration at the impact face. Localized shear damage in the 3D woven system precede penetration in both the nonporous and the porous systems. The porous system is capable of dissipating more energy prior to penetration due to containment of local damage, which emanates from the void boundaries, within subsurface locations. C2 - 2002/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings DA - 2002/// DO - 10.1115/IMECE2002-39482 SP - 41-45 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78249232051&partnerID=MN8TOARS ER - TY - CONF TI - Numerical Investigation on the Waterjets Issued by Hydroentangling Orifice Nozzles AU - Tafreshi, H.V. AU - Pourdeyhimi, B. AU - Holmes, R. AU - Shiffler, D. T2 - International Nonwovens Technical Conference (INTC 2002) C2 - 2002/9/24/ C3 - International Nonwovens Technical Conference (INTC 2002) CY - Atlanta, Georgia DA - 2002/9/24/ PY - 2002/9/24/ ER - TY - CONF TI - Numerical Simulation of Hydroentangling Orifice Flow AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Fiber Society C2 - 2002/10/16/ C3 - The Fiber Society CY - Natick, Massachusetts DA - 2002/10/16/ PY - 2002/10/16/ ER - TY - CONF TI - The Role of Baffles in Fiber Dispersion in Mixing Tanks AU - Tafreshi, H.V. AU - Pourdeyhimi, B. T2 - Fiber Society C2 - 2002/10/16/ C3 - The Fiber Society CY - Natick, Massachusetts DA - 2002/10/16/ PY - 2002/10/16/ ER - TY - CONF TI - A Simulation on the Effect of Brownian Motion on Nanoparticle Transport in a Pulsed Micro-plasma Cluster Source AU - Tafreshi, H.V. AU - Piseri, P. AU - Milani, P. T2 - Annual Conference of the American Association for Aerosol Research (AAAR) C2 - 2002/10/7/ C3 - Annual Conference of the American Association for Aerosol Research (AAAR) CY - Charlotte, North Carolina DA - 2002/10/7/ PY - 2002/10/7/ ER - TY - CONF TI - Nano-cluster Beam Focusing in an Aerodynamic Lens System AU - Di Fonzo, F. AU - Piseri, P. AU - Tafreshi, H.V. AU - Milani, P. T2 - Annual Conference of the American Association for Aerosol Research (AAAR) C2 - 2002/10/7/ C3 - Annual Conference of the American Association for Aerosol Research (AAAR) CY - Charlotte, North Carolina DA - 2002/10/7/ PY - 2002/10/7/ ER - TY - JOUR TI - A Simple Nozzle Configuration for the Production of Low Divergence Supersonic Cluster Beam by Aerodynamic Focusing AU - Tafreshi, H. Vahedi AU - Benedek, G. AU - Piseri, P. AU - Vinati, S. AU - Barborini, E. AU - Milani, P. T2 - Aerosol Science and Technology AB - A nozzle configuration for the production of an intense and collimated supersonic cluster beam is presented and characterized by numerical modeling. A simple lens added to a cylindrical nozzle exploits aerodynamic focusing effects. The effect of the focalizing nozzle is an enrichment of the core of the jet with clusters of an arbitrary size interval depending on carrier gas pressure and temperature. The influence of the source and nozzle geometrical parameters and of the expansion conditions on the cluster focalization is simulated and compared to the experimental results. A collimating effect on particle velocities and the possibility of obtaining a cluster mass selection is also observed. DA - 2002/5// PY - 2002/5// DO - 10.1080/02786820252883838 VL - 36 IS - 5 SP - 593-606 J2 - Aerosol Science and Technology LA - en OP - SN - 0278-6826 1521-7388 UR - http://dx.doi.org/10.1080/02786820252883838 DB - Crossref ER - TY - CONF TI - Laser Scribing for Use as a Precision Shaping Technique AU - Eischen, J.W. AU - Love, B.M. AU - Dow, T.A. AU - Scattergood, R.O. C2 - 2002/1// C3 - Proceedings of the Seventh Pan American Congress of Applied Mechanics DA - 2002/1// ER - TY - JOUR TI - Similarity solution of thermal boundary layers for laminar narrow axisymmetric jets AU - Fang, T. T2 - International Journal of Heat and Fluid Flow AB - In this work, the similarity equation describing the thermal boundary layers of laminar narrow axisymmetric jets is derived based on boundary layer assumptions. The equation is solved exactly. Some properties of the thermal jet are discussed. By introducing new-defined non-dimensional coordinates, the similarity solution results in a “universal” format. The results can also be applied in the boundary layer problem of species diffusion. DA - 2002/// PY - 2002/// DO - 10.1016/S0142-727X(02)00198-4 VL - 23 IS - 6 SP - 840-843 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036924116&partnerID=MN8TOARS KW - similarity solution KW - narrow axisymmetric jet KW - thermal boundary layer ER - TY - JOUR TI - An extension of wien's displacement law for blackbody radiation AU - Fang, T. T2 - International Communications in Heat and Mass Transfer AB - The purpose of this study is to present statistics related to the integration of cloud and rain liquid water and the profiles for different cloud types and regimes. From 2010 to 2012, the CHUVA project collected information regarding cloud and rain characteristics in different precipitation regimes in Brazil. CHUVA had four field campaigns between 2010 and 2011, located in the North, Northeast and Southeast regions of Brazil, covering the semi-arid, Amazon, coastal and mountain regions. The synergy of several instruments allowed us to classify rain events and describe the cloud processes regionally. Microwave radiometers, LiDAR, radar, and disdrometers were employed in this study. The rain type classification was made using vertical profiles of reflectivity (VPR) and polarimetric variables from dual polarization radar (XPOL). The integrated liquid water (ILWC) for non-precipitating clouds was retrieved with a microwave ground-based radiometer using a neural network. For rainy conditions, the profiles from the rain liquid water content (LWCR) and their integrated (ILWR) properties were estimated by Micro Rain Radar (MRR) and XPOL VPRs. For non-precipitating clouds, the ILWC values were larger for the sites in tropical regions, in particular near the coast, than for Southeast Brazil. For rainy cases, distinct LWCR profiles were observed for different rain classifications and regions. The differences are small for low rain rates and a distinction between different rainfall regimes is more evident for high rain rates. Vale and Belém clouds present the deepest layers and largest convective rain rates. The clouds in the Southeast region of Brazil (Vale do Paraíba) and North region (Belém) showed the largest reflectivity in the mixed and glaciated layers, respectively. In contrast, the Northeast coastal site (e.g. Fortaleza) showed larger values in the warm part of the clouds. Several analyses are presented, describing the cloud processes and the differences among the cloud types, rain rates and regions. DA - 2002/// PY - 2002/// DO - 10.1016/S0735-1933(02)00366-4 VL - 29 IS - 6 SP - 757-761 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036698919&partnerID=MN8TOARS ER - TY - CONF TI - The Effects of Wing Aerodynamics on Race Vehicle Performance AU - Mckay, Noah J. AU - Gopalarathnam†, Ashok T2 - Motorsports Engineering Conference & Exhibition C2 - 2002/12/2/ C3 - SAE Technical Paper Series DA - 2002/12/2/ DO - 10.4271/2002-01-3294 PB - SAE International UR - http://dx.doi.org/10.4271/2002-01-3294 DB - Crossref ER - TY - BOOK TI - One-dimensional stochastic simulation of advection-diffusion-reaction couplings in turbulent combustion AU - Hewson, J.C. AU - Kerstein, A.R. AU - Echekki, T. AB - The study of turbulent reacting flows invariably involves simplifying assumptions. Here an alternative modeling strategy is adopted that explicitly represents certain nonlinear couplings among the various subprocesses governing turbulent combustion, including unsteadiness and multi-scale interactions. This strategy involves fully resolved simulation at moderately large Reynolds numbers, which is rendered affordable for fully turbulent regimes by formulating a one-dimensional stochastic representation of turbulent flow evolution. The modeling challenges that arise, and the present approach to addressing these challenges, are illustrated by applying the new methodology, denoted one-dimensional turbulence (ODT), to nonpremixed jet flames that exhibit varying degrees of localized extinction and reignition. The role of unsteady strain and molecular transport in ODT in representing extinction and reignition processes in a turbulent environment is noted. DA - 2002/// PY - 2002/// DO - 10.1007/978-94-017-1998-8_9 VL - 70 SE - 113-124 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84892839667&partnerID=MN8TOARS ER - TY - JOUR TI - High-temperature combustion in autoigniting non-homogeneous hydrogen/air mixtures AU - Echekki, T. AU - Chen, J.H. T2 - Proceedings of the Combustion Institute DA - 2002/// PY - 2002/// VL - 29 IS - 2 SP - 2061-2068 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84915794542&partnerID=MN8TOARS ER - TY - JOUR TI - Hydrogen sulfide filtration combustion: comparison of theory and experiment AU - Bingue, JP AU - Saveliev, AV AU - Fridman, AA AU - Kennedy, LA T2 - EXPERIMENTAL THERMAL AND FLUID SCIENCE AB - Filtration combustion waves in an inert porous media were analyzed comparatively for lean and rich H2S–air mixtures. Temperature, velocity, and chemical products of the combustion wave were studied experimentally in the range of equivalence ratios from 0.1 to 5.5. Downstream (superadiabatic) wave propagation was observed for ultra-lean (ϕ⩽0.45) and ultra-rich (ϕ⩾1.7) mixtures. Upstream (underadiabatic) propagation corresponds to the range of equivalence ratios from 0.45 to 1.7. It was found that, with equal heat content, rich mixtures have higher combustion temperatures than corresponding lean mixtures. The products of partial H2S oxidation, H2, and S2 are dominant for ultra-rich superadiabatic combustion, where up to 60% of H2S was converted to S2 and H2. For lean mixtures, the dominant products were H2O, SO2, and H2SO4. DA - 2002/6// PY - 2002/6// DO - 10.1016/s0894-1777(02)00151-6 VL - 26 IS - 2-4 SP - 409-415 SN - 0894-1777 ER - TY - JOUR TI - Formation of carbon nanotubes in counter-flow, oxy-methane diffusion flames without catalysts AU - Merchan-Merchan, W AU - Saveliev, A AU - Kennedy, LA AU - Fridman, A T2 - CHEMICAL PHYSICS LETTERS AB - In oxygen enriched methane diffusion flames, carbon nanotubes were discovered to be formed in the region on the fuel-rich side of the flame front at an oxygen enrichment of 50%. No catalyst was employed. An opposed flow diffusion flames with varying strain rate and oxygen content in the oxidizer stream was used. Substantial quantities of nanotube material are produced at atmospheric pressure in this continuous (non-batch) process. Thermophoretic sampling of the flame and collecting the carbon material deposited near the exhaust was done. Both confirm the growth of carbon nanotubes and other carbon clusters. DA - 2002/3/5/ PY - 2002/3/5/ DO - 10.1016/s0009-2614(02)00027-1 VL - 354 IS - 1-2 SP - 20-24 SN - 1873-4448 ER - TY - JOUR TI - Filtration combustion of a methane wave in air for oxygen-enriched and oxygen-depleted environments AU - Kennedy, LA AU - Saveliev, AV AU - Bingue, JP AU - Ridman, AA T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - In this work, filtration combustion waves formed in a packed bed of randomly arranged alumina pellets are studied experimentally. Methane is used as a fuel: the oxygen content of the oxidizer is varied from 10% to 30%. Five oxidizer compositions (10, 15, 21, 25, and 30%) are comparatively analyzed focusing on combustion temperatures, combustion wave velocities, and pollutant characteristics. The studied range of equivalence ratios spans from 0.1 to 2 covering the superadiabatic and underadiabatic combustion waves formed in ultralean, lean, rich, and ultrarich regions. It is found that combustion temperature drops with oxygen enrichment while the absolute propagation rate increases. The opposed variation of adiabatic and combustion temperatures strongly affects regimes of superadiabatic (downstream) and underadiabatic (upstream) wave propagation. For certain oxidizer compositions, the combustion tempertures more than twice exceed the adiabatic temperatures of respective homogeneous flames. To help understand the thermal and chemical structure of filtration combustion wave, two important minor products, oxides of nitrogen (NO2) and carbon monoxide (CO) emissions, were sampled from the product stream. The analysis of emission levels suggests strong influence of equivalence ratio and oxygen enrichment on CO emissions due to the variation of the combustion chemistry and contraction/extension of the reaction zone relative to the characteristic pore size. The prompt mechanism is identified as a major pathway of NO2 formation. Variation of NO with equivalence ratio in filtration combustion reproduces a characteristic bell shape pertinent to homogeneous flames, extending it to the ultralean and ultrarich regions. DA - 2002/// PY - 2002/// DO - 10.1016/s1540-7489(02)80107-9 VL - 29 SP - 835-841 SN - 1873-2704 ER - TY - BOOK TI - Thermodynamics: an engineering approach. (4th ed.) AU - Cengel, Y. A. AU - Boles, M. A. CN - TJ265 .C43 2002 DA - 2002/// PY - 2002/// PB - Boston: McGraw-Hill SN - 0072383321 ER - TY - JOUR TI - Automated cruise flap for airfoil drag reduction over a large lift range AU - McAvoy, CW AU - Gopalarathnam, A T2 - JOURNAL OF AIRCRAFT AB - A small trailing-edge e ap, often referred to as a cruise e ap or camber-changing e ap, can be used to extend the low-drag range of a natural-laminar-e ow airfoil. Automation of such a cruise e ap is likely to result in improved aircraft performance over a large speed range without an increase in the pilot work load. An important step in achieving the automation is to arrive at a simple approach for determination of the optimum e ap angle for a given airfoil lift coefe cient. This optimum e ap angle can then be used in a closed-loop control system to set the e ap automatically. Two pressure-based schemes are presented for determining the optimum e ap angle for any given airfoil lift coefe cient. The schemes use the pressure difference between two pressure sensors on the airfoil surface close to the leading edge. In each of the schemes, for a given lift coefe cient, this nondimensionalized pressure difference is brought to a predetermined target value by dee ecting the e ap. It is shown that the drag bucket is then shifted to bracket the given lift coefe cient. This nondimensional pressure difference, therefore, can be used to determine and set the optimum e ap angle for a specie ed lift coefe cient. The two schemes differ in the method used for the nondimensionalization. The effectiveness of the two schemesisverie ed using computational and windtunnel results for two NASA laminar e ow airfoils. Finally, an aircraft performance simulation approach is used to analyze the potential aircraft performance benee ts while addressing trim drag considerations. DA - 2002/// PY - 2002/// DO - 10.2514/2.3051 VL - 39 IS - 6 SP - 981-988 SN - 0021-8669 ER - TY - JOUR TI - Simulation on the effect of Brownian motion on nanoparticle trajectories in a pulsed microplasma cluster source AU - Tafreshi, HV AU - Piseri, P AU - Barborini, E AU - Benedek, G AU - Milani, P T2 - JOURNAL OF NANOPARTICLE RESEARCH DA - 2002/12// PY - 2002/12// DO - 10.1023/A:1022845401781 VL - 4 IS - 6 SP - 511-524 SN - 1572-896X KW - Brownian motion KW - cluster beam KW - aerodynamic focusing KW - supersonic flow KW - nanostructured materials KW - aerosols KW - control volume method KW - particle tracking method ER - TY - CONF TI - Models of mass transport during microgravity crystal growth of alloyed semiconductor crystals in a magnetic field AU - Ma, N. C2 - 2002/// C3 - NASA Microgravity Materials Science Conference proceedings, NASA/CP-2003-212339 CN - NAS 1.55:212339 DA - 2002/// SP - 380-382 PB - Huntsville, Ala.: NASA ER - TY - JOUR TI - Simultaneous two-shot CH planar laser-induced fluorescence and particle image velocimetry measurements in lifted CH4/air diffusion flames AU - Watson, KA AU - Lyons, KM AU - Carter, CD AU - Donbar, JM T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Joint two-shot CH planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements near the stabilization region of lifted methane/air diffusion flames stabilized under different flow conditions are presented. The simultaneous technique allows for a determination of the propagation rate of the CH zone relative to the fuel flow. Simultaneous single-shot CH-PLIF and PIV techniques have been used in the past to examine lifted jet flames: however, the double-shot technique of the current study is desirable because it yields information on flame dynamics—as indicated by sequential CH-PLIF—relative to the unburned mixture. Three flow conditions were examined corresponding to three different liftoff heights. While the average velocity at the stabilization point varies between 0.83 m/s for the lowest flow condition (Red=4800) and 1.28 m/s for the highest (Red=8300), the velocity at the stabilization point during instances of zero CH movement (during the time interval of the CH pulses) is constant for all three flow conditions (1.14±0.4 m/s). Furthermore, the flame is able to stabilize itself against the incoming unburned mixture only when the gas velocity is below a certain limit, above which the flame is convected downstream with the flow. DA - 2002/// PY - 2002/// DO - 10.1016/S1540-7489(02)80231-0 VL - 29 SP - 1905-1912 SN - 1873-2704 ER - TY - JOUR TI - Observations on the interaction between a premixed flame kernel and a vortex of different equivalence ratio AU - Xiong, Y AU - Roberts, WL T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Charge stratification by direct local injection has been actively studied as a technology for spark-ignitedlean-burn engines. Local mixture enrichment by direct injection in the vicinity of the spark plug at the time of ignition can significantly affect flame kernel development and extend the lean flammability limit of a given fuel/air mixture. The interaction between a lean premixed spark-ignited flame kernel and a laminar vortex toroid containing a different fuel/air mixture was experimentally investigated to gain an understanding of the effect of “turbulent” bulk transport of material into the growing flame kernel. In this study, flame kernels were ignited in a lean premixed methane/air mixture with equivalence ratio of 0.6, while the equivalence ratio of the vortex core fluid was varied between zero and infinity. Chemiluminescence images from CH* of the kernel-vortex interaction were captured using either a single-shot ICCD camera or a high-speed intensified camera. Results of the flame kernel-vortex interactions for six test cases are presented and discussed. It was observed that vortices composed of fluid outside the traditional flammability limits were completely consumed inside the growing flame kernel. Due to entrainment of ambient fluid as the vortex propagates toward the kernel, the equivalence ratio of the vortex is not constant. The Lewis number of the vortex mixture determines if the vortex is consumed as a single pocket or breaks up into multiple pockets before being consumed. Pure fuel vortices were observed to have both a very diffuse reaction zone as well as a region at the upper rim of the kernel-vortex interface of intense chemiluminescence. DA - 2002/// PY - 2002/// DO - 10.1016/S1540-7489(02)80207-3 VL - 29 SP - 1687-1693 SN - 1873-2704 ER - TY - JOUR TI - Micro-particle transport and deposition in a human oral airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS T2 - JOURNAL OF AEROSOL SCIENCE AB - Laminar-to-turbulent air flow for typical inhalation modes as well as micro-particle transport and wall deposition in a representative human oral airway model have been simulated using a commercial finite-volume code with user-enhanced programs. The computer model has been validated with experimental airflow and particle deposition data sets. For the first time, accurate local and segmentally averaged particle deposition fractions have been computed under transitional and turbulent flow conditions. Specifically, turbulence that occurs after the constriction in the oral airways for moderate and high-level breathing can enhance particle deposition in the trachea near the larynx, but it is more likely to affect the deposition of smaller particles, say, St<0.05. Particles released around the top/bottom zone of the inlet plane more easily deposit on the curved oral airway surface. Although more complicated geometric features of the oral airway may have a measurable effect on particle deposition, the present simulations with a relatively simple geometry exhibit the main features of laminar-transitional-turbulent particle suspension flows in actual human oral airways. Hence, the present model may serve as the “entryway” for simulating and analyzing airflow and particle deposition in the lung. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0021-8502(02)00122-2 VL - 33 IS - 12 SP - 1635-1652 SN - 0021-8502 KW - human oral airway KW - laminar-to-turbulent airflow KW - particle deposition KW - computational fluid-particle dynamics simulations ER - TY - JOUR TI - Nonlinear parameter estimation in laminar forced convection within a circular sector tube AU - Aparecido, JB AU - Ozisik, MN T2 - INVERSE PROBLEMS IN ENGINEERING AB - In this article we examine an inverse heat convection problem of estimating unknown parameters of a parameterized variable boundary heat flux. The physical problem is a hydrodynamically developed, thermally developing, three-dimensional steady state laminar flow of a Newtonian fluid inside a circular sector duct, insulated in the flat walls and subject to unknown wall heat flux at the curved wall. Results are presented for polynomial and sinusoidal trial functions, and the unknown parameters as well as surface heat fluxes are determined. Depending on the nature of the flow, on the position of experimental points the inverse problem sometimes could not be solved. Therefore, an identification condition is defined to specify a condition under which the inverse problem can be solved. Once the parameters have been computed it is possible to obtain the statistical significance of the inverse problem solution. Therefore, approximate confidence bounds based on standard statistical linear procedure, for the estimated parameters, are analyzed and presented. DA - 2002/12// PY - 2002/12// DO - 10.1080/106827603100015659 VL - 10 IS - 6 SP - 503-522 SN - 1068-2767 KW - boundary heat flux KW - Newtonian fluid KW - nonlinear parameter ER - TY - JOUR TI - Life-cycle-based solid waste management. II: Illustrative applications AU - Solano, E. AU - Dumas, R. D. AU - Harrison, K. W. AU - Ranjithan, S. R. AU - Barlaz, M. A. AU - Brill, E. D. T2 - Journal of Environmental Engineering (New York, N.Y.) AB - A companion paper described the development of the integrated solid waste management (ISWM) model that considers cost, energy, and environmental releases associated with management of municipal solid waste. This paper demonstrates the application of the ISWM model to a hypothetical, but realistic, case study. Several solid waste management (SWM) scenarios are studied, including the variation in energy and environmental emissions among alternate SWM strategies; the effect of mandated waste diversion (through recycling and other beneficial uses of waste such as combustion to recover energy) on environmental releases and cost; the tradeoff between cost and the level of waste diversion; and the tradeoff between cost and greenhouse gas emissions. In addition, the flexibility of the model is illustrated by the identification of alternate SWM strategies that meet approximately the same objectives using distinctly different combinations of unit processes. This flexibility may be of importance to local solid waste management planners who must implement new SWM programs. Use of the model illustrates the potential impact of solid waste management policies and regulations on global environmental emissions. DA - 2002/// PY - 2002/// DO - 10.1061/(asce)0733-9372(2002)128:10(993) VL - 128 IS - 10 SP - 993-1005 ER - TY - JOUR TI - Life-cycle-based solid waste management. I: Model development AU - Solano, E. AU - Ranjithan, S. R. AU - Barlaz, M. A. AU - Brill, E. D. T2 - Journal of Environmental Engineering (New York, N.Y.) AB - This paper describes an integrated solid waste management (ISWM) model to assist in identifying alternative SWM strategies that meet cost, energy, and environmental emissions objectives. An SWM system consisting of over 40 unit processes for collection, transfer, separation, treatment (e.g., combustion, composting), and disposal of waste as well as remanufacturing facilities for processing recycled material is defined. Waste is categorized into 48 items and their generation rates are defined for three types of sectors: single-family dwelling, multifamily dwelling, and commercial. The mass flow of each item through all possible combinations of unit processes is represented in a linear programming model using a unique modeling approach. Cost, energy consumption, and environmental emissions associated with waste processing at each unit process are computed in a set of specially implemented unit process models. A life-cycle approach is used to compute energy consumption and emissions of CO, fossil- and biomass-derived CO2,NOx,SOx, particulate matter, PM10 and greenhouse gases. The model is flexible to allow representation of site-specific issues, including waste diversion targets, mass flow restrictions and requirements, and targets for the values of cost, energy, and each emission. A companion paper describes the application of this model to examine several SWM scenarios for a hypothetical, but realistic, case study. DA - 2002/// PY - 2002/// DO - 10.1061/(asce)0733-9372(2002)128:10(981) VL - 128 IS - 10 SP - 981-992 ER - TY - JOUR TI - Improved CVD diamond coatings on WC-Co tool substrates AU - Raghuveer, MS AU - Yoganand, SN AU - Jagannadham, K AU - Lemaster, RL AU - Bailey, J T2 - WEAR AB - Tungsten carbide tools with different cobalt concentrations (3 and 6%) have been treated with different surface cleaning procedures for deposition of diamond and multilayer diamond composite films. Cleaning with organic solvents, surface etching to remove cobalt from the surface, and hydrogen plasma etching to decarburize WC and etch remove cobalt have been used in combination to improve the adhesion of diamond films deposited on the tool substrates. Diamond layers are deposited by microwave plasma chemical vapor deposition (MPCVD) after introducing surface nucleation by suspension with sub-micron size diamond crystallites. TiN and TiC films are deposited as intermediate layers that prevent diffusion of cobalt or as embedding layers that also anchor diamond crystallites to the tool substrate. A continuous top layer of diamond was deposited for different periods of time (15–36 h) to obtain diamond film thickness ranging from 15 to 36 μm. The performance of diamond-coated tools has been tested by machining particleboard. The tool surfaces were characterized using measurements of wear of the cutting edge. Microstructural characterization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of the composite layers on the tool surfaces is performed. The quantitative evaluation of wear and microstructural characterization were used to determine the mechanisms of wear of the cutting edge. The results are used to conclude the diamond tool coating procedure that provides the best performance in machining particleboard. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0043-1648(02)00244-2 VL - 253 IS - 11-12 SP - 1194-1206 SN - 0043-1648 KW - tungsten carbide KW - CVD KW - diamond KW - TiN KW - TiC ER - TY - JOUR TI - Constant voltage anemometer operated hot wire at subsonic speeds over wide overheats in unsteady flows AU - Truzzi, GE AU - Sarma, GR AU - Chokani, N T2 - REVIEW OF SCIENTIFIC INSTRUMENTS AB - The constant voltage anemometer (CVA) was used to calibrate a hot wire over a wide overheat range. Instead of the output voltage (E) of the anemometer which is normally used, at each test point a quantity represented by “pdr” equal to the ratio of power dissipated in the hot wire (Pw) and the associated difference in the heated resistance of the hot wire (Rw) and its resistance (Ra) at the ambient fluid temperature is calculated. It is shown that the calibration curves so obtained with pdr=Pw/(Rw−Ra) as the output variable instead of E can be represented by a single calibration equation covering the wide overheat range. Overheat variation is equivalent to allowing an ambient temperature change of the fluid at a given setting. It demonstrates that this approach can be used to cover measurements using the hot wire with fluid temperature drifts without using a second hot wire for temperature corrections and without any temperature calibration. The calibration data was then applied to measure the unsteady flow in the near orifice region of synthetic jets with very good results. The measurements confirm the computational predictions that show that although there is flow reversal, over a cycle of oscillation, the synthetic jet actuator spends most of the cycle ejecting rather than ingesting fluid. DA - 2002/12// PY - 2002/12// DO - 10.1063/1.1516850 VL - 73 IS - 12 SP - 4363-4368 SN - 0034-6748 ER - TY - JOUR TI - Intelligent bounds on modeling uncertainty: Applications to sliding mode control AU - Buckner, GD T2 - IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART C-APPLICATIONS AND REVIEWS AB - Robust control techniques such as sliding mode control (SMC) require a dynamic model of the plant and bounds on modeling uncertainty to formulate control laws with guaranteed stability. Although techniques for modeling dynamic systems and estimating model parameters are well established, very few procedures exist for estimating uncertainty bounds. In the case of SMC design, a conservative global bound is usually chosen to ensure closed-loop stability over the entire operating space. The primary drawbacks of this conservative, "hard computing" approach are excessive control activity and reduced performance, particularly in regions of the operating space where the model is accurate. In this paper, a novel approach to estimating uncertainty bounds for dynamic systems is introduced. This "soft computing" approach uses a unique artificial neural network, the 2-Sigma network, to bound modeling uncertainty adaptively. This fusion of intelligent uncertainty bound estimation with traditional SMC results in a control algorithm that is both robust and adaptive. Simulations and experimental demonstrations conducted on a magnetic levitation system confirm these capabilities and reveal excellent tracking performance without excessive control activity. DA - 2002/5// PY - 2002/5// DO - 10.1109/TSMCC.2002.801350 VL - 32 IS - 2 SP - 113-124 SN - 1094-6977 KW - hard computing KW - intelligent control KW - modeling uncertainty KW - sliding mode control KW - soft computing ER - TY - JOUR TI - Effect of local thermal non-equilibrium on thermally developing forced convection in a porous medium AU - Nield, DA AU - Kuznetsov, AV AU - Xiong, M T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - The classical Graetz methodology is applied to investigate the effect of local thermal non-equilibrium on the thermal development of forced convection in a parallel-plate channel filled by a saturated porous medium, with walls held at constant temperature. The Brinkman model is employed. The analysis leads to an expression for the local Nusselt number, as a function of the dimensionless longitudinal coordinate, the Péclet number, the Darcy number, the solid–fluid heat exchange parameter, the solid/fluid thermal conductivity ratio, and the porosity. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0017-9310(02)00203-X VL - 45 IS - 25 SP - 4949-4955 SN - 0017-9310 ER - TY - JOUR TI - Dopant segregation during liquid-encapsulated Czochralski crystal growth in a steady axial magnetic field AU - Morton, JL AU - Ma, N AU - Bliss, DF AU - Bryant, GG T2 - JOURNAL OF CRYSTAL GROWTH AB - During the magnetically stabilized liquid-encapsulated Czochralski (MLEC) process, a single compound semiconductor crystal such as indium-phosphide (InP) or gallium-antimonide (GaSb) is grown by the solidification of an initially molten semiconductor (melt) contained in a crucible. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper presents a model for the unsteady transport of a dopant during the MLEC process with a steady axial magnetic field. The convective species transport during growth is driven by the melt motion, which produces segregation, i.e. non-uniformities in the dopant concentration, in both the melt and the crystal. This convective transport is significant even for a magnetic field strength of 2 T. Except for the last-solidified part of the crystal, the crystal's axial dopant homogeneity, i.e. uniformity in the dopant concentration, improves as the magnetic field strength is decreased. Dopant distributions in the crystal and in the melt at several different stages during growth are presented for several magnetic field strengths. DA - 2002/7// PY - 2002/7// DO - 10.1016/S0022-0248(02)01425-2 VL - 242 IS - 3-4 SP - 471-485 SN - 1873-5002 KW - magnetic fields KW - mass transfer KW - segregation KW - growth from melt KW - liquid-encapsulated Czochralski method KW - magnetic field assisted Czochralski method KW - semiconducting III-V compounds ER - TY - JOUR TI - Development of the cylindrical wire electrical discharge machining process, part 2: Surface integrity and roundness AU - Qu, J AU - Shih, AJ AU - Scattergood, RO T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - This study investigates the surface integrity and roundness of parts created by the cylindrical wire EDM process. A mathematical model for the arithmetic average surface roughness on the ideal surface of a cylindrical wire EDM workpiece is first derived. Effects of wire feed rate and part rotational speed on the surface finish and roundness for brass and carbide work-materials at high material removal rates are investigated. The pulse on-time and wire feed rate are varied to explore the best possible surface finish and roundness achievable by the cylindrical wire EDM process. This study has demonstrated that, for carbide parts, an arithmetic average surface roughness and roundness as low as 0.68 and 1.7 μm, respectively, can be achieved. Surfaces of the cylindrical EDM parts were examined using Scanning Electron Microscopy (SEM) to identify the macro-ridges and craters on the surface. Cross-sections of the EDM parts are examined using the SEM to quantify the sub-surface recast layers and heat-affected zones under various process parameters. This study has demonstrated that the cylindrical wire EDM process parameters can be adjusted to achieve either high material removal rate or good surface integrity and roundness. DA - 2002/8// PY - 2002/8// DO - 10.1115/1.1475989 VL - 124 IS - 3 SP - 708-714 SN - 1087-1357 ER - TY - JOUR TI - Optimization of hysteretic characteristics of damping devices based on pseudoelastic shape memory alloys AU - Masuda, A AU - Noori, M T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - In order to develop a fundamental understanding and the feasibility of SMA devices for passive vibration control, an undamped SDOF system with a pseudoelastic SMA restoring force is investigated to find the basic relationship between the shape of the hysteresis loop of SMA elements and their performance as a damping device. The dynamic characteristics of the device are evaluated by the steady-state response at the resonance point in order to focus on the damping effect. Dynamic analysis utilizing the equivalent linearization approach results in two major findings that, to the best of the authors’ knowledge, have not yet been reported in the literature. These results which characterize the unique behavior of the SMA hysteresis include: (a) for a given excitation amplitude, the “scale” of the hysteresis loop, which is a measure of displacement and restoring force, needs to be adjusted so that the response sweeps the maximum loop but does not exceed it; (b) the ratio of the area confined within the hysteresis loop to the area of a corresponding envelope of triangular shape should be as large as possible. The results of this study would be quite useful not only as a guideline for the design of actual SMA devices, but also as a basis for the development of new autoadaptive materials in future. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0020-7462(02)00024-0 VL - 37 IS - 8 SP - 1375-1386 SN - 0020-7462 KW - shape memory alloys KW - pseudoelasticity KW - damping KW - hysteresis KW - optimization ER - TY - JOUR TI - Hysteresis in mechanical systems - modeling and dynamic response AU - Vestroni, F AU - Noori, M T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - Hysteretic behaviour characterizes elements of a wide class of mechanical systems: the dependence of their restoring force on the deformation history has a great influence on the dynamic response. For this reason, an increasing interest has been registered in the study of typical phenomena of nonlinear dynamics, also because hysteresis belongs to the class of strong nonlinearities. The paper is devoted to the analysis of the modification of the response of two degrees-of-freedom chain systems due to the characteristics of the restoring force of a hysteretic element; attention is given to its dissipation characteristic, comparing the cases of full and reduced hysteresis. With increasing excitation amplitude, the strong hysteretic nonlinearity modifies the nonlinear frequencies and in turn their ratio, easily leading to internal resonance conditions. For a system close to a 3:1 resonance condition, the modification of the frequency response curves (frcs) for increasing excitation intensity is illustrated and compared with the response of similar systems not in internal resonance. The general trend of the phenomena is slightly qualitatively influenced by the dissipation property, whereas the quantitative differences are notable. The only evident difference is the presence of a frequency range of coexisting solutions in the case of reduced hysteresis. In both cases, after a bifurcation a novel mode arises around the first resonance, with similar frequency and different shape. The case of reduced hysteresis makes it possible to better investigate the evolution of nonlinear modes of a system, close to the Hamiltonian system embedded by the actual dissipative one. The occurrence of this novel mode, peculiar of systems with strong nonlinearities, is responsible of a substantial transfer of energy between the two modes in internal resonance conditions. Finally, an example of quasiperiodic oscillations is presented to show one of the other possible scenarios which arise even in the presence of significant dissipation. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0020-7462(02)00059-8 VL - 37 IS - 8 SP - 1261-1262 SN - 0020-7462 ER - TY - JOUR TI - Diffusive behavior and structural characterization of a hard-sphere fluid through a narrow channel with roughened walls AU - Tafreshi, H AU - Benedek, G AU - Zamankhan, P AU - Sarkomaa, P T2 - CANADIAN JOURNAL OF PHYSICS AB - A molecular dynamics technique is devised to simulate the flow of a hard-sphere fluid between two parallel roughened walls separated by a 10 particle diameter distance. The structural state of the system in different solid-volume fractions is characterized by analyzing the static-structure factor contour plot. At solids concentrations below [Formula: see text] [Formula: see text] 0.3, the calculations have shown no remarkable signature of the presence of the roughened confining walls similar to the previous unbounded simulation results (wide channel). At high concentrations, walls manifest their presence by reducing the particle diffusion in the direction of velocity gradient. Due to the metastability of the assembly, further increase in the solid fraction, [Formula: see text] [Formula: see text] 0.6, may yield a crystalline phase wherein diffusion coefficients vanish locally. PACS Nos.: 51.20+d, 61.20-p, 66.10Cb DA - 2002/7// PY - 2002/7// DO - 10.1139/P02-016 VL - 80 IS - 7 SP - 723-731 SN - 1208-6045 ER - TY - JOUR TI - Development of the cylindrical wire electrical discharge machining process, part 1: Concept, design, and material removal rate AU - Qu, J AU - Shih, AJ AU - Scattergood, RO T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. The design of a precise, flexible, and corrosion-resistant underwater rotary spindle is first introduced. A detailed spindle error analysis identifies the major sources of error at different frequency spectrum. The spindle has been added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. The mathematical model for material removal rate of the free-form cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the conventional 2D wire EDM of the same work-material, higher maximum material removal rates may be achieved in the cylindrical wire EDM, possibly due to better debris flushing condition. DA - 2002/8// PY - 2002/8// DO - 10.1115/1.1475321 VL - 124 IS - 3 SP - 702-707 SN - 1528-8935 ER - TY - JOUR TI - Transient airflow structures and particle transport in a sequentially branching lung airway model AU - Zhang, Z. AU - Kleinstreuer, C. T2 - Physics of Fluids (Woodbury, N.Y.) AB - Considering oscillatory laminar incompressible three-dimensional flow in triple planar and nonplanar bifurcations representing generations three to six of the human respiratory system, air flow fields and micron-particle transport have been simulated under normal breathing and high-frequency ventilation (HFV) conditions. A finite-volume code (CFX4.3 from AEA Technology, Pittsburgh, PA) and its user-enhanced FORTRAN programs were validated with experimental velocity data points for a single bifurcation. The airflow structures and micron-particle motion in the triple bifurcations were analyzed for a representative normal breathing cycle as well as HFV condition. While both the peak inspiratory and expiratory velocity profiles for the low Womersley case (α=0.93) agree well with those of instantaneously equivalent steady-state cases, some differences can be observed between flow acceleration and deceleration at off-peak periods or near flow reversal, especially during inspiratory flow. Similarly, the basic features of instantaneous particle motion closely resemble the steady-state case at equivalent inlet Reynolds numbers. The preferential concentration of particles caused by the coherent vortical structures was found in both inhalation and exhalation; however, it is more complicated during expiration. The effects of Womersley number and non-planar geometries as well as the variations in secondary flow intensity plus pressure drops across various bifurcations under normal breathing and HFV conditions were analyzed as well. This work may elucidate basic physical insight of aerosol transport relevant in dosimetry-and-health-effect studies as well as for drug aerosol delivery analyses. DA - 2002/// PY - 2002/// DO - 10.1063/1.1433495 VL - 14 IS - 2 SP - 862-880 ER - TY - JOUR TI - Investigation of gaseous acoustic damping rates by transient grating spectroscopy AU - Li, YY AU - Roberts, WL AU - Brown, MS T2 - AIAA JOURNAL AB - An investigation of acoustic damping ratesin a pressurized gaseous medium by analyzing thetemporal behavior of laser-induced gratings is reported. Experiments were performed in various nonresonant gas samples as a function of pressure and grating spacing. Acoustic damping rates were determined through model e ts to the acquired signals. The results were compared with theoretical calculations using both classical acoustic damping rates and a more comprehensive model that includes rotational and vibrational energy transfer mechanisms. The relationships between the measured acoustic damping rate and molecular structure and pressure and grating spacing are discussed. The utility of exploiting the temporal signature from laser-induced gratings to determine acoustic damping rates in high-pressure gases is identie ed. Nomenclature cp = heat capacity at constant pressure crot = heat capacity of rotational modes cs = local speed of sound cv = heat capacity at constant volume cvib = heat capacity of vibrational modes Dth = thermal diffusivity f = acoustic frequency G = geometric factor I = signal intensity M = molecular weight P = pressure q = grating wave vector, 2 o=3 R = gas constant T = e uid temperature t = time Z = collision number ¯ = damping factor due to energy transfer 0 = acoustic damping coefe cient ° = specie c heat ratio 1n = local modulation in index of refraction ´ = scattering efe ciency of laser-induced grating µ = full angle between beams · = thermal conductivity 3 = grating spacing ¸ = laser wavelength π = dynamic viscosity Ω = e uid density ?rot = rotational relaxation time ?vib = vibrational relaxation time DA - 2002/6// PY - 2002/6// DO - 10.2514/2.1790 VL - 40 IS - 6 SP - 1071-1077 SN - 0001-1452 ER - TY - JOUR TI - Cyclic micron-size particle inhalation and deposition in a triple bifurcation lung airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS T2 - JOURNAL OF AEROSOL SCIENCE AB - Laminar oscillatory inhalation flow as well as micron-particle transport and wall deposition in a representative triple bifurcation airway model have been simulated using a commercial finite-volume code with user-enhanced programs. The computer model has been validated with experimental particle deposition data and deposition patterns for double bifurcations. The transient air flow, particle transport, and wall deposition patterns were analyzed and summarized in terms of particle deposition efficiencies (DEs) and surface density maps. Particle deposition may increase under cyclic flow conditions, i.e., DE-values are typically larger for cyclic flow than for steady flow at the mean flow rate of a given inhalation pulse. The maximal relative difference between these two DE-values may be as high as 50% for 0.02⩽Stmean⩽0.12 during normal inspiration (Qin=30l/min). However, matching inlet Reynolds and Stokes numbers are proposed, which generate under quasi-steady flow conditions very similar DE-values and deposition patterns as in equivalent pulsatile flow. The relative differences between DE-values for cyclic and matching steady cases are less than 5%. The quantitative results of this work are of interest to researchers either conducting health risk assessment studies for inhaled particulate pollutants or analyzing drug aerosol deposition at desired lung target sites. DA - 2002/2// PY - 2002/2// DO - 10.1016/S0021-8502(01)00170-7 VL - 33 IS - 2 SP - 257-281 SN - 1879-1964 KW - cyclic inhalation KW - particle deposition KW - symmetric triple bifurcation KW - computational fluid-particle dynamics KW - simulations ER - TY - JOUR TI - Aerosol deposition efficiencies and upstream release positions for different inhalation modes in an upper bronchial airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - Accurate predictions of micron-particle deposition patterns and surface concentrations in lung airways are most desirable for researchers assessing health effects of toxic particles or those concerned with inhalation delivery of therapeutic aerosols. Focusing on a rigid, symmetric triple bifurcation lung airway model, i.e., Weibel's generations G3-G6, a user-enhanced and experimentally validated finite volume program has been employed to simulate the airflow and particle transport under transient laminar three-dimensional flow conditions. Specifically, the effects of 3 inhalation modes, i.e., resting and light and moderate activities, were analyzed for typical ranges of Stokes numbers (St h 0.2) and Reynolds numbers (0 h Re h 2100). The detailed results show particle deposition patterns and efficiencies in the triple bifurcation under cyclic as well as steady-state inhalation conditions. Cyclic inhalation generates higher local and segmentally-averaged deposition rates when compared to steady mean Reynolds number inhalation; however, matching Stokes and Reynolds numbers, i.e., the average between mean and peak values, were found to provide fully equivalent results for all inhalation modes and bifurcations. In addition, particle maps were developed that show the release positions of deposited aerosols. DA - 2002/7// PY - 2002/7// DO - 10.1080/02786820290092078 VL - 36 IS - 7 SP - 828-844 SN - 1521-7388 ER - TY - JOUR TI - Tool coatings for wood machining: Problems and prospects AU - Sheikh-Ahmad, J. Y. AU - Morita, T. T2 - Forest Products Journal DA - 2002/// PY - 2002/// VL - 52 IS - 10 SP - 43-51 ER - TY - JOUR TI - Synthesis of a single-loop, overconstrained six revolute joint spatial mechanism for two-position cylindrical rigid body guidance AU - Shih, AJ AU - Yan, HS T2 - MECHANISM AND MACHINE THEORY AB - The synthesis and analysis of a single-loop, overconstrained spatial mechanism with six binary links and six revolute joints for the guidance of a cylindrical rigid body between two positions are presented. The geometric constraints that make the spatial 6R mechanism movable are first introduced. Four features of the geometrical constraints of this mechanism are summarized to demonstrate its mobility and used for dimensional synthesis. Steps for mechanism dimensional synthesis are developed based on the descriptive and analytical geometry. The mechanism analysis based on analytical geometry is also presented. One of the advantages of this spatial mechanism is that the toggle position can be integrated into the synthesis. This is especially attractive in the synthesis of the wheel retract and twist mechanism for aircraft landing gears and the automated grinding wheel or tool changer for machine tools. A detailed example is used to illustrate the mathematical models for mechanism synthesis and analysis. DA - 2002/1// PY - 2002/1// DO - 10.1016/S0094-114X(01)00055-6 VL - 37 IS - 1 SP - 61-73 SN - 0094-114X ER - TY - JOUR TI - Particle flow, mixing, and chemical reaction in circulating fluidized bed absorbers AU - Mao, D AU - Edwards, , JR AU - Kuznetsov, AV AU - Srivastava, R T2 - CHEMICAL ENGINEERING SCIENCE AB - Abstract A mixing model has been developed to simulate the particle residence time distribution (RTD) in a circulating fluidized bed absorber (CFBA). Also, a gas/solid reaction model for sulfur dioxide (SO 2 ) removal by lime has been developed. For the reaction model that considers RTD distribution inside the core and annulus regions of a CFBA, a macrochemical reaction can be simulated based on microchemical reaction dynamics. The presented model can predict SO 2 and lime concentration distributions inside the CFBA, and give the amount of lime needed to remove a given percentage of SO 2 . It is found that SO 2 concentration decreases with the increase of CFBA distance from the bottom in the core region. However, lime concentration exhibits a very slight variation in the core region. This means that lime is efficiently utilized to remove SO 2 . The model also predicts that SO 2 partial pressure at the exit of the CFBA decreases with the increase in the percentage of fresh lime injected in the CFBA. DA - 2002/8// PY - 2002/8// DO - 10.1016/S0009-2509(02)00168-9 VL - 57 IS - 15 SP - 3107-3117 SN - 0009-2509 KW - circulating fluidized bed KW - residence time distribution KW - SO2 removal ER - TY - JOUR TI - Hybrid inverse airfoil design method for complex three-dimensional lifting surfaces AU - Gopalarathnam, A AU - Selig, MS T2 - JOURNAL OF AIRCRAFT AB - A method is presented for inverse design of airfoils for complex three-dimensional wings in incompressible e ow. The method allows for prescription of inviscid velocity distributions over different cross sections of the wing in a multipoint fashion. A hybrid approach is used to determine the shapes of the wing cross sections that satisfy the design specie cations. The airfoils forming the cross sections of the wing are generated using an inverse code for isolated airfoil design. A three-dimensional panel method is then used to obtain the velocity distributions over the resulting wing. The isolated airfoil velocity distributions are then used as design variables in a multidimensional Newton iteration method to achieve the design specie cations on the wing. The method is particularly useful for complex geometries such as junctures, where three-dimensional and interference effects have to be accounted for in the design process. Akey feature ofthedesign method is a schemeto avoid using thepanel method for sensitivity computations for the Newton iterations. This scheme not only results in signie cant reductions in computation time but also enables the integration of any readily available three-dimensional analysis code in executable form. Examples are shown to demonstrate the usefulness of the method. Nomenclature Cl = airfoil lift coefe cient, chord D1 c = airfoil/section chord F = vector containing the residuals J = Jacobian matrix n = number of design variables V = airfoil/section velocity nondimensionalized by the freestream velocity v = desired value for the velocity difference over a segment ® = angle of attack, deg 1V = velocity difference over a segment normalized by the freestream velocity ±x = vector containing the corrections to the design variables Subscripts i = index of design variable for the Newton iteration r = property associated with the wing root t = property associated with the wing tip w = property associated with the wing 2D = property associated with an airfoil in isolation 3D = property associated with a cross section of a three-dimensional lifting surface DA - 2002/// PY - 2002/// DO - 10.2514/2.2966 VL - 39 IS - 3 SP - 409-417 SN - 0021-8669 ER - TY - JOUR TI - Coupling of buoyant convections in boron oxide and a molten semiconductor in a vertical magnetic field AU - Farrell, M. V. AU - Ma, N. T2 - Journal of Heat Transfer AB - This paper treats the buoyant convection in a layer of boron oxide, called a liquid encapsulant, which lies above a layer of a molten compound semiconductor (melt) between cold and hot vertical walls in a rectangular container with a steady vertical magnetic field B. The magnetic field provides an electromagnetic (EM) damping of the molten semiconductor which is an excellent electrical conductor but has no direct effect on the motion of the liquid encapsulant. The temperature gradient drives counter clockwise circulations in both the melt and encapsulant. These circulations alone would lead to positive and negative values of the horizontal velocity in the encapsulant and melt, respectively, near the interface. The competition between the two buoyant convections determines the direction of the horizontal velocity of the interface. For B=5 T, there is significant EM damping of the melt motion and the encapsulant drives a positive interfacial velocity and a small clockwise circulation in the melt. For a much weaker field B=0.1 T, the maximum velocity in the melt is hundreds of times larger than that of the encapsulant, thus causing nearly all the encapsulant to circulate in the clockwise direction. DA - 2002/// PY - 2002/// DO - 10.1115/1.1473141 VL - 124 IS - 4 SP - 643-649 ER - TY - JOUR TI - Aerosol transport and deposition in a triple bifurcation bronchial airway model with local tumors AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS AU - Hickey, AJ T2 - INHALATION TOXICOLOGY AB - Airflow characteristics and particle deposition have been numerically simulated in a triple bifurcation lung airway model (from generation 3-6 airways) with local tumors protruded from the sidewalls of generation 5 airways. The effects of tumors in terms of size and location on airflow, particle transport, and deposition patterns were analyzed for constant inspiratory flow rates with inlet Reynolds (Re(match) = 463 and 1882) and Stokes number (St(match) = 0.02-0.12) combinations that match different cyclic inhalation waveforms. The size of tumors was varied to induce an obstruction of airway lumen by 16-74%. Extreme conditions, 2 and 100% obstruction, were also examined. The results show that enhanced deposition occurs in the carina region at each bifurcation, and deposition increases with increasing Stokes and Reynolds number as expected from earlier studies. In addition, deposition increases at the tumor site until the tumor blocks about half of the airway lumen and then decreases with a further obstruction. In other words, there exists a maximum particle deposition fraction (DF) for a protruding tumor that occludes the lumen. The maximum DF at the tumor was 10.2% within the test conditions used. Deposition occurs mainly on the frontal surface of the tumors, but spreads out to the opposite wall, or upstream sections, or sister branches of the tumor at high flow rates and Stokes number. The present results (1) help in the understanding of the complex toxic or therapeutic aerosol dynamics in the lung with local airways obstruction, and (2) provide quantitative information on critical tumor size and particle deposition to health care specialists. DA - 2002/11// PY - 2002/11// DO - 10.1080/08958370290084809 VL - 14 IS - 11 SP - 1111-1133 SN - 1091-7691 ER - TY - JOUR TI - Wire electrical discharge machining of metal bond diamond wheels for ceramic grinding AU - Rhoney, BK AU - Shih, AJ AU - Scattergood, RO AU - Akemon, JL AU - Gust, DJ AU - Grant, MB T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - The application of cylindrical wire Electrical Discharge Machining (EDM) for profile truing of metal bond diamond wheels is presented. Instead of using the mechanical force to break the diamond and matrix in the grinding wheel, the wire EDM process uses the thermal energy or electrical sparks between the wire and rotating grinding wheel to remove the metal bond and form the wheel. The design and manufacture of a corrosion-resistant, precise spindle with the high-electrical current capability for wire EDM truing of grinding wheel is first introduced. Three truing configurations were designed to study effects of wire EDM process parameters and to investigate the level of form accuracy and corner radii achievable by the wire EDM truing of diamond wheels. Results show that the wire EDM process can efficiently generate the μm-scale precision form on the diamond wheels. The wheel, after truing, was used to grind the silicon nitride workpiece. Grinding forces and wheel wear rate were measured. In the beginning of the grinding, high wheel wear rate was identified. The subsequent wheel wear rate was considerably lower and stabilized. DA - 2002/9// PY - 2002/9// DO - 10.1016/S0890-6955(02)00056-1 VL - 42 IS - 12 SP - 1355-1362 SN - 1879-2170 ER - TY - JOUR TI - Wear mechanism of metal bond diamond wheels trued by wire electrical discharge machining AU - Rhoney, BK AU - Shih, AJ AU - Scattergood, RO AU - Ott, R AU - McSpadden, SB T2 - WEAR AB - The stereographic scanning electron microscopy (SEM) imaging was used to investigate the wear mechanism in wire electrical discharge machining (EDM) truing of metal bond diamond wheels for ceramic grinding. A piece of the grinding wheel was removed after truing and grinding to enable the examination of wheel surface and measurement of diamond protrusion heights using a SEM and stereographic imaging software. The stereographic SEM imaging method was calibrated by comparing with the profilometer measurement results. On the wheel surface after wire EDM truing and before grinding, some diamond grain protruding heights were measured in the 32 μm level. Comparing to the 54 μm average size of the diamond grain, this indicated that over half of the diamond was exposed. During the wire EDM process, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruded in the gap between the wire electrode and wheel. These protruding diamond grains with weak bond to the wheel were fractured under a light grinding condition. After heavy grinding, the diamond protrusion heights were estimated in the 5–15 μm range above the wear flat. A cavity created by grinding debris erosion wear of the wheel bond could be identified around the diamond grain. DA - 2002/4// PY - 2002/4// DO - 10.1016/S0043-1648(02)00019-4 VL - 252 IS - 7-8 SP - 644-653 SN - 0043-1648 KW - scanning electron microscopy (SEM) KW - diamond wheels KW - electrical discharge machining (EDM) KW - grinding wheel wear ER - TY - JOUR TI - Effects of thermal dispersion and turbulence in forced convection in a composite parallel-plate channel: Investigation of constant wall heat flux and constant wall temperature cases AU - Kuznetsov, AV AU - Cheng, L AU - Xiong, M T2 - NUMERICAL HEAT TRANSFER PART A-APPLICATIONS AB - Abstract In this article, a composite parallel-plate channel whose central portion is occupied by a clear fluid and whose peripheral portion is occupied by a fluid saturated porous medium, is considered. The flow in the porous region of the channel is assumed to be laminar, governed by the Brinkman-Forchheimer-extended Darcy equation, while the flow in the clear fluid region of the channel is assumed to be turbulent. The validity of this laminar/turbulent assumption is validated by estimating Reynolds numbers in the clear fluid and porous regions of the channel. Although the flow in the porous region remains laminar, it is still fast enough for the quadratic drag (Forchheimer) effects to be important. In this situation, hydrodynamic mixing of the interstitial fluid at the pore scale becomes important and may cause significant thermal dispersion. It is shown that thermal dispersion may result in some counterintuitive effects, such as the increase of the Nusselt number when the width of the clear fluid region in the center of the channel is decreased. DA - 2002/9// PY - 2002/9// DO - 10.1080/10407780290059602 VL - 42 IS - 4 SP - 365-383 SN - 1040-7782 ER - TY - JOUR TI - Simulation of a reacting pollutant puff using an adaptive grid algorithm, by R.K. Srivastava et al. - Reply AU - Odman, M. T. AU - Russell, A. G. AU - Srivastava, R. K. AU - McRae, D. S. T2 - Journal of Geophysical Research. Atmospheres DA - 2002/// PY - 2002/// VL - 107 IS - D22 SP - 4644-1 ER - TY - JOUR TI - A model for fine particle agglomeration in circulating fluidized bed absorbers AU - Mao, D AU - Edwards, , JR AU - Kuznetsov, AV AU - Srivastava, R T2 - HEAT AND MASS TRANSFER DA - 2002/4// PY - 2002/4// DO - 10.1007/S002310100260 VL - 38 IS - 4-5 SP - 379-388 SN - 0947-7411 ER - TY - JOUR TI - A 2D analysis of stability of bioconvection in a fluid saturated porous medium - Estimation of the critical permeability value AU - Kuznetsov, AV AU - Avramenko, AA T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Abstract The main purpose of this paper is to perform a 2D stability analysis of bioconvection in a suspension of motile gyrotactic microorganisms in a fluid saturated porous medium and to obtain an analytical expression for the critical permeability of the porous medium. Recent numerical investigation by Kuznetsov and Jiang [1] suggests that permeability is a very important parameter for bioconvection in porous media. Their numerical results indicate that for small permeability bioconvection is stable (the microorganisms swim in the upward direction), while for large permeability it is unstable (variations of density are enhanced and macroscopic fluid circulation is induced). In the present investigation, a simple but elegant criterion of stability of the bioconvection is obtained. This criterion gives the critical permeability of the porous medium through the cell eccentricity, average swimming velocity, fluid viscosity, and other relevant parameters. DA - 2002/2// PY - 2002/2// DO - 10.1016/S0735-1933(02)00308-1 VL - 29 IS - 2 SP - 175-184 SN - 0735-1933 ER - TY - CONF TI - Solutal convection during melt growth of alloyed semiconductor crystals in a steady magnetic field AU - Ma, N. C2 - 2002/// C3 - AIAA Aerospace Sciences Meeting and Exhibit (40th: Reno, NV, 2002). (AIAA paper; no. 2002-1113) DA - 2002/// ER - TY - JOUR TI - Gas-solid two-phase flow in a triple bifurcation lung airway model AU - Zhang, Z AU - Kleinstreuer, C AU - Kim, CS T2 - INTERNATIONAL JOURNAL OF MULTIPHASE FLOW AB - Laminar oscillatory flow as well as micron-particle transport and wall deposition in a triple bifurcation airway model have been simulated using a validated finite-volume code with user-enhanced programs. Three realistic breathing patterns, i.e., resting, light activity and moderate exercise, were considered. Transient air flow, particle transport, and wall deposition results are shown and summarized in terms of regional particle deposition efficiencies (DEs). The effects of skewed inlet profiles on the flow field and particle deposition were recorded as well. Particle deposition may increase under cyclic flow conditions, i.e., DE-values are typically larger for cyclic flow than for steady flow evaluated at the mean flow rate of a given inhalation or exhalation pulse. While particles deposit mainly around the carinal ridges, i.e., flow dividers, during inspiratory flow due to direct impaction, they deposit on the tubular surfaces during exhalation because of strong secondary flows. Moreover, particle deposition during exhalation is much lower than for inhalation at the same local Stokes number. The comparisons of DEs among different lung generations or bifurcation areas for both cyclic inhalation and exhalation show that DEs in the third bifurcation region may be quite different from those at previous bifurcations due to upstream geometry and flow effects. DA - 2002/6// PY - 2002/6// DO - 10.1016/S0301-9322(02)00011-3 VL - 28 IS - 6 SP - 1021-1046 SN - 1879-3533 KW - large bronchial airways KW - aerosol transport and deposition KW - computational two-phase flow ER - TY - JOUR TI - Convective mass transport during bulk growth of semiconductor crystals with steady magnetic fields AU - Walker, J. S. AU - Ma, N. T2 - Annual Review of Heat Transfer DA - 2002/// PY - 2002/// VL - 12 IS - 2002 SP - 223-263 ER - TY - JOUR TI - Prediction of grain-boundary interfacial mechanisms in polycrystalline materials AU - Ashmawi, WM AU - Zikry, MA T2 - JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME AB - A multiple slip dislocation-density based crystalline formulation has been coupled to a kinematically based scheme that accounts for grain-boundary (GB) interfacial interactions with dislocation densities. Specialized finite-element formulations have been used to gain detailed understanding of the initiation and evolution of large inelastic deformation modes due to mechanisms that can result from dislocation-density pile-ups at GB interfaces, partial and total dislocation-density transmission from one grain to neighboring grains, and dislocation density absorption within GBs. These formulations provide a methodology that can be used to understand how interactions at the GB interface scale affect overall macroscopic behavior at different inelastic stages of deformation for polycrystalline aggregates due to the interrelated effects of GB orientations, the evolution of mobile and immobile dislocation-densities, slip system orientation, strain hardening, geometrical softening, geometric slip compatibility, and localized plastic strains. Criteria have been developed to identify and monitor the initiation and evolution of multiple regions where dislocation pile-ups at GBs, or partial and total dislocation density transmission through the GB, or absorption within the GB can occur. It is shown that the accurate prediction of these mechanisms is essential to understanding how interactions at GB interfaces affect and control overall material behavior. DA - 2002/1// PY - 2002/1// DO - 10.1115/1.1421611 VL - 124 IS - 1 SP - 88-96 SN - 0094-4289 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0012448372&partnerID=MN8TOARS ER - TY - JOUR TI - Novel technique to measure axial strain distribution along fiber during pullout test AU - Peters, K AU - Pattis, P AU - Botsis, J T2 - JOURNAL OF MATERIALS SCIENCE LETTERS DA - 2002/6/1/ PY - 2002/6/1/ DO - 10.1023/A:1015734914877 VL - 21 IS - 11 SP - 887-891 SN - 0261-8028 ER - TY - JOUR TI - Analysis of coupled turbulent flow and solidification in the wedge-shaped pool with different nozzles during twin-roll strip casting AU - Kim, DS AU - Kim, WS AU - Kuznetsov, AV T2 - NUMERICAL HEAT TRANSFER PART A-APPLICATIONS AB - Abstract In the twin-roll continuous casting (CC) process that produces a near-net-shaped strip, the mushy zone solidification phenomena are mainly influenced by various process parameters such as nozzle shape, roll-gap thickness, and superheat of melt. This study numerically examines, in a wedge-shaped pool for the twin-roll CC process, the dependence of the solidification phenomena and melt-flow behavior on those process parameters. The turbulent characteristics of the melt flow are considered using a low-Reynolds-number k- k turbulence model. The results show that there exists the distinct region with a well-mixed melt flow and a wide range of mush in the lower part of the pool. The variation of the melt-flow velocity due to different nozzle types mainly affects the liquidus line and has little effect on the solidus line in the outlet region. In the case of a small roll gap, the liquidus line is shifted upward and the solidified shell thickness increases slightly in the outlet region. The variation of melt superheat mainly affects the position of the liquidus line. The direct melt feed onto the free surface has little effect of the melt superheat on an increase in the temperature in the lower part of the pool, while the overall temperature in the lower part of the pool for the submerged nozzle has a high dependence on the melt superheat. DA - 2002/1// PY - 2002/1// DO - 10.1080/104077802317221410 VL - 41 IS - 1 SP - 1-17 SN - 1040-7782 ER - TY - JOUR TI - An experimental study on the seismic response of base-isolated secondary systems AU - Khechfe, H AU - Noori, M AU - Hou, Z AU - Kelly, JM AU - Ahmadi, G T2 - JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME AB - The paper provides an experimental study on the feasibility of base isolation for seismic protection of nonstructural secondary system such as sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission systems housed in nonisolated primary structures. Damages to these secondary systems may result in significant social chaos and costly economic loss. A one-sixth-scaled three-story building model with a single-degree-of-freedom secondary system placed on its third floor is employed in this study. The secondary system is base-isolated by a laminated rubber bearing (LRB) base isolation system from the supporting floor. The ground motion input is simulated by a shaking table which generates three different types of signal including sweeping harmonic sinusoidal, the S00E component of the 1940 E1 Centro earthquake, and the simulated white noise. The experimental results demonstrate significant reduction in both displacement and acceleration responses of the secondary system by using the base isolation. Effects of parameters of the base isolation such as damping ratio and mass on its performance are also investigated. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Hou et al., 2001). Secondary systems in a structure can be divided into two categories: structural and nonstructural. A thorough review of these types of systems and their response behavior under seismic loading has been presented by (Chen and Soong, 1988). In this paper, only nonstructural secondary systems are the subject of the study. These systems include sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission system that reside within a primary structure system. The huge investment made, the mission, and the critical role played by secondary systems in modern day warrant an effective protection strategy against earthquake-induced vibrations. Studies on employing base isolation techniques to protect primary structures have shown the ability of such techniques to limit dynamic response of structures in seismic disturbance (Kelley, 1986; and Ahmadi, 1988); this paper proposes the adoption of a base isolation mechanism for seismic protection of secondary systems and presents the experimental results achieved with this strategy in a scaled-down system designed without primary structural isolation. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Ghantous, 1991; and Samaha, 1992). DA - 2002/2// PY - 2002/2// DO - 10.1115/1.1445795 VL - 124 IS - 1 SP - 81-88 SN - 0094-9930 ER - TY - JOUR TI - Studies on bridging tractions - simultaneous bridging tractions and COD measurements AU - Studer, M AU - Pietrzyk, J AU - Peters, K AU - Botsis, J AU - Giaccari, P T2 - INTERNATIONAL JOURNAL OF FRACTURE AB - The main objective of this work is to investigate the bridging tractions in a model composite using optical fiber Bragg grating (FBG) sensors written into selected reinforcing fibers. Simultaneously, the crack opening displacement (COD) is measured using a speckle interferometry technique. The measurements are useful in the verification of the relation between the COD and bridging tractions established with the use of the weight function method. Center crack specimens made of epoxy and reinforced with one layer of optical fibers are prepared and tested under remote tension parallel to the fibers. Bragg gratings of 0.17 to 0.38 mm in length are introduced in selected fibers for direct, non invasive, local measurements of axial strains in these fibers. A controlled central crack, bridged by intact fibers, is introduced by a laser technique such that the FBGs are located between the crack faces. The results on the forces obtained from the FBGs and the COD-weight function method show good agreement. The experimental results also compare very well with 3-dimensional numerical simulations of the actual specimen geometry and loading configuration. DA - 2002/4// PY - 2002/4// DO - 10.1023/A:1015798126787 VL - 114 IS - 4 SP - 379-399 SN - 0376-9429 ER - TY - JOUR TI - Effect of evaporation on thin film deposition in dip coating process AU - Kuznetsov, AV AU - Xiong, M T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - Evaporation from the free surface is an important phenomenon that occurs during dip coating process. Accounting for evaporation is crucial for correct prediction of film thickness during this process when evaporation rate is large. This paper suggests a method to extend the classical free meniscus theory to account for evaporation from the free surface in a two-component system. The governing equations are solved utilizing a finite difference method. The effects of evaporation on the free surface profile and solute concentration distribution are investigated. DA - 2002/1// PY - 2002/1// DO - 10.1016/S0735-1933(01)00322-0 VL - 29 IS - 1 SP - 35-44 SN - 0735-1933 ER - TY - JOUR TI - Dependence of microporosity formation on the direction of solidification AU - Kuznetsov, AV AU - Xiong, M T2 - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER AB - The aim of this paper is to suggest a new approach in the investigation of the effect of gravity on microporosity formation in solidification of binary alloys. Instead of traditional unidirectional solidification from the bottom, which involves solidification against the gravity, we suggest to carry out solidification from the top, which involves solidification along the gravity. Numerical modeling performed in this paper suggests an experimental study that compares the results of these two experiments, which potentially reveals some important data concerning the influence of gravity on microporosity formation and also could be used as a tool for validation of microporosity formation models. DA - 2002/1// PY - 2002/1// DO - 10.1016/S0735-1933(01)00321-9 VL - 29 IS - 1 SP - 25-34 SN - 0735-1933 ER - TY - JOUR TI - Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer AU - Loh, BG AU - Hyun, S AU - Ro, PI AU - Kleinstreuer, C T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA AB - Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved. DA - 2002/2// PY - 2002/2// DO - 10.1121/1.1433811 VL - 111 IS - 2 SP - 875-883 SN - 0001-4966 ER - TY - JOUR TI - Output-feedback control of LPV sampled-data systems AU - Tan, K AU - Grigoriadis, KM AU - Wu, F T2 - INTERNATIONAL JOURNAL OF CONTROL AB - In this paper, we address the analysis and the output-feedback synthesis problems for linear parameter-varying (LPV) sampled-data control systems with potentially variable sampling rates. We assume that the state-space matrices of the plant and the sampling interval depend on parameters that are measurable in real-time and vary in a compact set with bounded variation rates. We explore criteria such as the stability, the energy-to-energy gain (induced L 2 norm) and the energy-to-peak gain (induced L 2 -to- L X norm) of such sampled-data LPV systems using parameter-dependent Lyapunov functions. Based on these analysis results, the corresponding sampled-data output-feedback control synthesis problems are examined. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved via efficient interior-point algorithms. DA - 2002/3// PY - 2002/3// DO - 10.1080/00207170110101775 VL - 75 IS - 4 SP - 252-264 SN - 0020-7179 ER - TY - JOUR TI - Crack-tip fields in anisotropic shells AU - Yuan, FG AU - Yang, S T2 - INTERNATIONAL JOURNAL OF FRACTURE DA - 2002/2// PY - 2002/2// DO - 10.1023/A:1014245311814 VL - 113 IS - 4 SP - 309-326 SN - 0376-9429 KW - asymptotic crack-tip fields KW - anisotropic shells KW - energy release rate KW - Reissner shallow shell theory KW - stress intensity factor KW - Stroh formalism KW - T-stress ER - TY - JOUR TI - The foundation of the Sommerfeld transformation AU - Maday, CJ T2 - JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME AB - The analysis of the one-dimensional journal bearing leads to an interesting integral that is continuous but has an analytic singularity involving the inverse tangent at π/2. This difficulty was resolved by a clever and non-intuitive transformation attributed to Sommerfeld. In this technical brief we show that the transformation has its origin in the geometry of the ellipse and Kepler’s equation that is based upon his observations of the planets in the Solar system. The derivation of the transformation is a problem or exercise in Sommerfeld’s monograph, Mechanics. The transformation is the relation between the two angles that characterize the ellipse, the closed orbit of a body in a central inverse square force field. The angle measured about the focus is the true anomaly (angle) and the angle measured about the center is the eccentric anomaly (angle). We establish the analogy between the orbital radius in terms of the eccentric anomaly and the film thickness of the journal bearing in terms of its central angle. DA - 2002/7// PY - 2002/7// DO - 10.1115/1.1467596 VL - 124 IS - 3 SP - 645-646 SN - 0742-4787 ER - TY - JOUR TI - High-temperature combustion in autoigniting non-homogeneous hydrogen/air mixtures AU - Echekki, T AU - Chen, JH T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - The burning modes (premixed vs. diffusion burning) in autoigniting non-homogeneous mixtures of hydrogen in heated air are studied using direct numerical simulations (DNS). The simulations show that high-temperature combustion follows an initial autoignition stage in fuel-lean, low-dissipation kernels. These kernels propagate initially as lean premixed fronts. As they expand into richer mixtures, diffusion flames develop in the wake of rich premixed flames along stoichiometric isocontours. These flames are initially stabilized by diffusion of radicals (H) and excess fuel from the rich premixed flames' side against excess radicals (O and OH) and oxidizer from the earlier passage of lean premixed fronts. In time, diffusion flames detach from the rich premixed flames, and their burning intensity is reduced accordingly. Triple flames also form at the interfaces of the rich and lean premixed flames with the stoichiometric mixture isocontours. However, their contribution to the stabilization and burning intensity of the diffusion branches is insignificant. Analysis of the contribution of lean and rich premixed flames and that of the diffusion flames to the volumetric heat release show that the dominant contribution is attributed mainly to the premixed flames: while the dominant contribution to NO formation is attributed to diffusion flames. The results also show that the relative contribution of the different burning modes is strongly dependent on the mixture distribution and the scalar dissipation rate field. We believe that these parameters affect the diffusion flames' structures and their rates of detachment from the rich premixed flames. DA - 2002/// PY - 2002/// DO - 10.1016/S1540-7489(02)80251-6 VL - 29 SP - 2061-2068 SN - 1873-2704 ER - TY - JOUR TI - Effect of airfoil characteristics on aircraft performance AU - Gopalarathnam, A AU - McAvoy, CW T2 - JOURNAL OF AIRCRAFT AB - Even with all of the advances in airfoil and aircraft design, there remains little guidance on how to tailor an airfoil to suit a particular aircraft. A two-pronged approach is presented to tailor an airfoil for an aircraft: 1) an approach in which aircraft performance simulations are used to study the effects of airfoil changes and to guide the airfoil design and 2) an analytical approach to determine expressions that provide guidance in sizing and locating the airfoil low-drag range. The analytical study shows that there is an ideal value for the lift coefficient for the lower corner of the airfoil low-drag range when the airfoil is tailored for aircraft level-flight maximum speed. Likewise, there is an ideal value for the lift coefficient for the upper corner of the low-drag range when the airfoil is tailored for maximizing the aircraft range. These ideal locations are functions of the amount of laminar flow on the upper and lower surfaces of the airfoil and also depend on the geometry, drag, and power characteristics of the aircraft. Comparison of the results from the two approaches for a hypothetical general aviation aircraft are presented to validate the expressions derived in the analytical approach DA - 2002/// PY - 2002/// DO - 10.2514/2.2968 VL - 39 IS - 3 SP - 427-433 SN - 1533-3868 ER - TY - JOUR TI - An overview of vibration and seismic applications of NiTi shape memory alloy AU - Saadat, S AU - Salichs, J AU - Noori, M AU - Hou, Z AU - Davoodi, H AU - Bar-On, I AU - Suzuki, Y AU - Masuda, A T2 - SMART MATERIALS & STRUCTURES AB - Shape memory alloys (SMAs) exhibit peculiar thermomechanical, thermoelectrical and thermochemical behaviors under mechanical, thermal, electrical and chemical conditions. Examples of these materials are Cu-based SMAs, NiTi SMAs, ferrous SMAs, shape memory ceramics and shape memory polymers. NiTi SMAs in particular, have unique thermomechanical behaviors such as shape memory effect and pseudoelasticity, which have made them attractive candidates for structural vibration control applications. Numerous studies have been conducted in modeling and applications of NiTi SMAs in structural vibration control. Several active, passive and hybrid energy absorption and vibration isolation devices have been developed utilizing NiTi SMAs. In this paper we present an overview of NiTi behaviors, modeling and applications as well as their limitations for structural vibration control and seismic isolation. DA - 2002/4// PY - 2002/4// DO - 10.1088/0964-1726/11/2/305 VL - 11 IS - 2 SP - 218-229 SN - 0964-1726 ER - TY - JOUR TI - An accurate full car ride model using model reducing techniques AU - Kim, C AU - Ro, PI T2 - JOURNAL OF MECHANICAL DESIGN AB - In this study, an approach to obtain an accurate yet simple model for full-vehicle ride analysis is proposed. The approach involves linearization of a full car MBD (multibody dynamics) model to obtain a large-order vehicle model. The states of the model are divided into two groups depending on their effects on the ride quality and handling performance. Singular perturbation method is then applied to reduce the model size. Comparing the responses of the proposed model and the original MBD model shows an accurate matching between the two systems. A set of identified parameters that makes the well-known seven degree-of-freedom model very close to the full car MBD model is obtained. Finally, the benefits of the approach are illustrated through design of an active suspension system. The identified model exhibits improved performance over the nominal models in the sense that the accurate model leads to the appropriate selection of control gains. This study also provides an analytical method to investigate the effects of model complexity on model accuracy for vehicle suspension systems. DA - 2002/12// PY - 2002/12// DO - 10.1115/1.1503065 VL - 124 IS - 4 SP - 697-705 SN - 1528-9001 ER - TY - JOUR TI - Modeling the dynamic behavior of shape memory alloys AU - Seelecke, S T2 - INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS AB - The paper studies the single degree of freedom vibration of a rigid mass suspended by a thin-walled shape memory alloy tube under torsional loading. The behavior is analyzed for the cases of quasiplasticity (low temperatures) and pseudoelasticity (high temperatures) on the basis of an improved version of the Müller–Achenbach model. To illustrate the strong hysteresis-induced damping capacity and the non-linear vibration characteristics, both, free and forced vibrations are considered in the first part of the paper. This is done on the basis of an isothermal version of the model, while the second part of the paper focuses on the effect of non-constant temperature caused by the rate-dependent release and absorption of latent heats. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0020-7462(02)00030-6 VL - 37 IS - 8 SP - 1363-1374 SN - 0020-7462 KW - shape memory alloys KW - modeling KW - damping capacity KW - hysteresis KW - dynamics ER - TY - JOUR TI - An analytical finite element model for predicting three-dimensional tool forces and chip flow AU - Strenkowski, JS AU - Shih, AJ AU - Lin, JC T2 - INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE AB - A model of three-dimensional cutting is developed for predicting tool forces and the chip flow angle. The approach consists of coupling an orthogonal finite element cutting model with an analytical model of three-dimensional cutting. The finite element model is based on an Eulerian approach, which gives excellent agreement with measured tool forces and chip geometries. The analytical model was developed by Usui et al. [ASME J. Engng Indust. 100(1978) 222; 229], in which a minimum energy approach was used to determine the chip flow direction. The model developed by Usui required orthogonal cutting test data to determine the tool forces and chip flow angle. In this paper, a finite element model is used to supply the orthogonal cutting data for Usui's model. With this approach, a predictive model of three-dimensional cutting can be developed that does not require measured data as input. Cutting experiments are described in which good agreement was found between measured and predicted tool forces and chip flow angles for machining of AISI 1020 steel. DA - 2002/5// PY - 2002/5// DO - 10.1016/S0890-6955(01)00162-6 VL - 42 IS - 6 SP - 723-731 SN - 1879-2170 KW - finite element modeling KW - 3D cutting KW - chip flow ER - TY - JOUR TI - A Virtual Sensing method for tonal ANVC systems AU - Tran, CM AU - Southward, SC T2 - JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB - Virtual Sensing (VS) is considered to be an extension for feedforward Active Noise and Vibration Control (ANVC) systems when, for example, it is desired to minimize the response at one or more spatial locations where it is either physically impossible or undesirable to place an actual error sensor. In this context, VS is an estimation technique for predicting the appropriate system response using available measurements and a dynamic system model. A hybrid adaptive feedforward observer is proposed which has the ability to overcome the limitations of conventional dynamic observer designs. The hybrid observer utilizes a conventional dynamic observer augmented with an adaptive feedforward element for estimating the effect of the persistent disturbance. For simplicity, we restrict this development to a single tonal disturbance for which a coherent reference is assumed available. It will be appreciated that this technique may be extended to handle disturbances that contain multiple tones as well as broadband noise, as long as suitable reference signals are available. Numerical simulations and real-time experiments were performed on a one-dimensional acoustic duct. The results demonstrate that the hybrid adaptive feedforward observer is an effective method for predicting the virtual sensor response in an ANVC system. DA - 2002/3// PY - 2002/3// DO - 10.1115/1.1435642 VL - 124 IS - 1 SP - 35-40 SN - 0022-0434 ER - TY - CONF TI - Validation of a three dimensional covered lagoon simulation AU - Fleming, J. G. AU - Johnson, R. R. AU - Cheng, J. C2 - 2002/// C3 - Animal Residuals 2002: Agricultural Animal Manure Management, Policy and Technology (Washington, DC) DA - 2002/// ER -