TY - CHAP TI - Measurements on Augmented Heat Transfer Surfaces Using a Transient Liquid Crystal Technique AU - Han, J.C. AU - Ekkad, S.V. AU - Huang, Y. T2 - Process, Enhanced, and Multiphase Heat Transfer: A Festschrift for A.E. Bergles A2 - Manglik, R.M. A2 - Kraus, A.D. PY - 1996/// SP - 339–349 PB - Begell House, Inc ER - TY - JOUR TI - Surface heat transfer visualization on a model gas turbine blade using a transient liquid crystal image technique AU - Du, H. AU - Ekkad, S. AU - Han, J.-C. T2 - Journal of Flow Visualization and Image Processing AB - A transient liquid crystal technique has been developed to visualize the convective heat transfer coefficient distributions on a model gas turbine blade. A five-blade linear cascade is installed into a low-speed wind tunnel to simulate the gas turbine blade cascade. A color image processing system is used to measure the color change of the liquid crystal layer coated on the middle test blade at the center of the cascade. Detailed heat transfer coefficient distributions on a turbine blade are presented for the different flow Reynolds numbers. The cascade exit flow Reynolds number of the flow passing the cascade based on the blade chord is varied from 7.1 × 105 to 1.02 × 106. Results are compared with those obtained with the thin-foil thermocouple method under the same conditions. It is found that the transient liquid crystal image technique gives more detailed information than the classic thin-foil thermocouple method. Some findings with this technique, such as separation bubble effect on heat transfer coefficient on the pressure surface of the blade, flow transition location, and high heat transfer coefficients near the trailing edges on both the suction and the pressure surfaces of the blade, are an improvement over the classic method. The detailed information obtained using this technique may significantly influence the cooling design of the gas turbine blade. DA - 1996/// PY - 1996/// DO - 10.1615/jflowvisimageproc.v3.i2-3.30 VL - 3 IS - 2-3 SP - 141-152 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27844522045&partnerID=MN8TOARS ER - TY - JOUR TI - Local heat transfer coefficient and film effectiveness distributions on a cylindrical leading edge model using a transient liquid crystal image method AU - Ekkad, S.V. AU - Du, H. AU - Han, J.-C. T2 - Journal of Flow Visualization and Image Processing AB - A transient liquid crystal technique is presented for measuring detailed heat transfer coefficients and film effectiveness on a cylindrical test model with film cooling. The technique uses a thin liquid crystal coating on the test surface and two similar transients tests. The cylinder, coated with a thin layer of liquid crystals, is heated to a uniform surface temperature and suddenly exposed to a cooler mainstream. The time history of color change at each pixel location is analyzed to obtain the local heat transfer coefficient and film effectiveness. Tests were run at a mainstream Reynolds number based on cylinder diameter of 100,900. The effect of blowing ratio on heat transfer coefficient and film effectiveness was studied for five blowing ratios ranging between 0.2 and 1.2. Two roles of holes at ±15° from stagnation and hole spacing of four-hole diameters apart and angled at 30° and 90° to the surface in the spanwise and streamwise directions were used for coolant ejection. Air was used as coolant. Detailed distributions obtained using the present technique provide a better understanding of the film cooling phenomena on the cylinder surface. The technique provides high resolution and more accurate results compared with classic heat transfer measurement techniques. Some of the results from the present study are compared with results obtained using classic heat transfer measurement methods. DA - 1996/// PY - 1996/// DO - 10.1615/JFlowVisImageProc.v3.i2-3.20 VL - 3 IS - 2-3 SP - 129-140 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27844443743&partnerID=MN8TOARS ER - TY - JOUR TI - Heat transfer inside and downstream of cavities using transient liquid crystal method AU - Ekkad, S.V. AU - Han, J.-C. T2 - Journal of Thermophysics and Heat Transfer AB - Local heat transfer coefficient distributions are investigated inside and downstream of various cavities on a flat surface. The effect of cavity size, depth, and shape are studied using a transient liquid crystal image method. Liquid crystals are sprayed on the test surface and a hot mainstream is imposed, suddenly causing a color change. The time of color change is obtained using an image processing system. An increase in cavity size for the same depth increases heat transfer coefficients on the test surface. An increase hi cavity depth increases downstream heat transfer coefficients. Five cavity shapes are studied to compare local heat transfer behavior for the effect of various shapes. Nomenclature cp = specific heat of test surface material D = hydraulic diameter of cavity d = cavity depth h = local convection heat transfer coefficient with cavity h0 = local convection heat transfer coefficient without cavity k = thermal conductivity of test surface material Rex = Reynolds number based on axial distance, Ree = momentum thickness Reynolds number, T = temperature Tu = freestream turbulence intensity t = time of liquid crystal color change U = mainstream velocity x = axial distance along the mainstream z = spanwise distance a = thermal diffusivity of test surface material A = temperature step 8 = boundary-layer thickness 8* = displacement thickness 6 = momentum thickness of the boundary layer IJL = fluid dynamic viscosity p = fluid density r = time step DA - 1996/// PY - 1996/// DO - 10.2514/3.818 VL - 10 IS - 3 SP - 511-516 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030195475&partnerID=MN8TOARS ER - TY - CONF TI - Effect of unsteady wake with trailing edge coolant ejection on detailed heat transfer coefficient distributions for a gas turbine blade AU - Du, H. AU - Ekkad, S. AU - Han, J.-C. C2 - 1996/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 1996/// VL - 327 SP - 81-88 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030413744&partnerID=MN8TOARS ER - TY - CONF TI - Detailed heat transfer distributions in two-pass smooth and turbulated square channels with bleed holes AU - Ekkad, S.V. AU - Huang, Y. AU - Han, J.-C. C2 - 1996/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 1996/// VL - 330 SP - 133-140 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030398909&partnerID=MN8TOARS ER - TY - CONF TI - Detailed heat transfer coefficient distributions under an array of impinging jets with coolant extraction AU - Huang, Y. AU - Ekkad, S.V. AU - Han, J.-C. C2 - 1996/// C3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD DA - 1996/// VL - 333 SP - 143-150 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030386706&partnerID=MN8TOARS ER - TY - JOUR TI - Inelastic microstructural failure mechanisms in crystalline materials with high angle grain boundaries AU - Zikry, M.A. AU - Kao, M. T2 - Journal of the Mechanics and Physics of Solids AB - Microstructurally-induced failure mechanisms in crystalline materials with coincident site-lattice (CSL) high angle grain boundaries (GBs) have been investigated. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation densities and specialized computational schemes have been developed to obtain a detailed understanding of the interrelated physical mechanisms that result in material failure. A transmission scalar has also been introduced to investigate slip-rate transmission, blockage and incompatibility at the GB. The combined effects of high angle GB misorientation, mobile and immobile dislocation densities, strain hardening, geometrical softening, localized plastic strains, and slip-rate transmission and blockage on failure evolution in face centered cubic (f.c.c.) crystalline materials have been studied. Results from the present study are consistent with experimental observations that single dislocation pile-ups result in a transgranular failure mode for the ∑9 CSL GB, and that symmetric double dislocation pile-ups result in an intergranular failure mode for the ∑17b CSL GB. DA - 1996/// PY - 1996/// DO - 10.1016/0022-5096(96)00049-X VL - 44 IS - 11 SP - 1765-1798 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030290888&partnerID=MN8TOARS ER - TY - JOUR TI - Dislocation based multiple-slip crystalline constitutive formulation for finite-strain plasticity AU - Zikry, M.A. AU - Kao, M. T2 - Scripta Materialia AB - Revisiting the classical topic of the strain hardening behaviour from a perspective of the analytical model based on the evolution of dislocation density with strain, we extended the capacity of the single internal variable model towards predicting necking instability and re-examined the grain size dependence of the flow stress. An excellent agreement is observed between the model predictions of the necking strain and stress and the results of tensile testing of nickel polycrystals with grain sizes varied from sub-micrometres to hundred micrometres. The pivotal significance of the dynamic recovery in the occurrence of necking has been analysed and emphasised in the context of the discussion on the effect of grain size on flow stress. The most interesting corollary of the analysis made is that not only the simple modelling of the dislocation density evolution, which can be traced back from the very early stage of plastic flow in materials with different grain sizes, can be used for realistic approximation of the stress-strain behaviour during homogeneous deformation under constant plastic strain rate, but also for predicting the onset of necking instability with high confidence. DA - 1996/// PY - 1996/// DO - 10.1016/1359-6462(95)00629-X VL - 34 IS - 7 SP - 1115-1121 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030129988&partnerID=MN8TOARS ER - TY - CONF TI - Thermal Loading of Bimaterial BeamsElastic Plastic Response AU - Eischen, J.W. AU - Reagan, S. T2 - XVIII Southeastern Conference on Theoretical and Applied Mechanics C2 - 1996/// C3 - Proceedings of the XVIII Southeastern Conference on Theoretical and Applied Mechanics CY - Tuscaloosa, AL DA - 1996/// PY - 1996/// ER - TY - CONF TI - Control of a Super-Articulated Robot Manipulator with Joint Elasticity AU - Reyhanoglu, M. T2 - 4th International Conference on Control, Automation, Robotics and Vision C2 - 1996/// C3 - Proceedings of the 4th International Conference on Control, Automation, Robotics and Vision CY - Singapore DA - 1996/// PY - 1996/12/3/ VL - 1 SP - 172–176 PB - NTU ER - TY - CONF TI - Velocity Stabilization of an Underactuated Rigid Body AU - Reyhanoglu, M. AU - van der Schaft, A.J. T2 - 4th International Conference on Control, Automation, Robotics and Vision C2 - 1996/// C3 - Proceedings of the 4th International Conference on Control, Automation, Robotics and Vision CY - Singapore DA - 1996/// PY - 1996/12/3/ VL - 3 SP - 2065–2069 PB - NTU ER - TY - CONF TI - Nonlinear control of a class of underactuated systems AU - Reyhanoglu, M. AU - van der Schaft, A. AU - McClamroch, N.H. AU - Kolmanovsky, I. T2 - 35th IEEE Conference on Decision and Control AB - A theoretical framework is established for the dynamics and control of underactuated systems, defined as systems which have fewer inputs than degrees of freedom. Control system formulation of underactuated systems is addressed and the class of second-order nonholonomic systems is identified. Controllability and stabilizability results are derived for this class of underactuated systems. Examples are included to illustrate the results. C2 - 1996/12/24/ C3 - Proceedings of 35th IEEE Conference on Decision and Control CY - Kobe, Japan DA - 1996/12/24/ PY - 1996/12/13/ DO - 10.1109/cdc.1996.572793 PB - IEEE SN - 0780335902 UR - http://dx.doi.org/10.1109/cdc.1996.572793 ER - TY - CONF TI - Control and stabilization of an underactuated surface vessel AU - Reyhanoglu, M. T2 - 35th IEEE Conference on Decision and Control AB - This paper studies the problem of controlling the planar position and orientation of an autonomous surface vessel using two independent thrusters. It is first shown that although the system is not asymptotically stabilizable to a given equilibrium configuration using a time-invariant continuous feedback, it is strongly accessible and small-time locally controllable at any equilibrium. Time-invariant discontinuous feedback control laws are then constructed to asymptotically stabilize the system to the desired configuration with exponential convergence rates. A simulation example is included to demonstrate the results. C2 - 1996/12/24/ C3 - Proceedings of 35th IEEE Conference on Decision and Control CY - Kobe, Japan DA - 1996/12/24/ PY - 1996/12/13/ DO - 10.1109/cdc.1996.573439 PB - IEEE SN - 0780335902 UR - http://dx.doi.org/10.1109/cdc.1996.573439 ER - TY - CONF TI - Discontinuous feedback stabilization of the angular velocity of a rigid body with two control torques AU - Reyhanoglu, N. T2 - 35th IEEE Conference on Decision and Control AB - There has been much interest over the past decade in the problem of asymptotic stabilization of the angular velocity of a rigid body with only two torque inputs. The smooth feedback laws proposed in the literature provide asymptotic stability with nonexponential convergence rates. This paper proposes discontinuous feedback laws to achieve asymptotic stability with exponential convergence rates. C2 - 1996/// C3 - Proceedings of 35th IEEE Conference on Decision and Control CY - Kobe, Japan DA - 1996/// PY - 1996/12/13/ DO - 10.1109/cdc.1996.573511 PB - IEEE SN - 0780335902 UR - http://dx.doi.org/10.1109/cdc.1996.573511 ER - TY - JOUR TI - Switched mode feedback control laws for nonholonomic systems in extended power form AU - Kolmanovsky, Ilya AU - Reyhanoglu, Mahmut AU - McClamroch, N.Harris T2 - Systems & Control Letters AB - A class of nonholonomic control systems in extended power form is studied. It is demonstrated that under appropriate assumptions Lagrange's equations, including classical nonholonomic constraints, can be transformed into the extended power form. A switched mode feedback controller is used to obtain global convergence of the states of the extended power form to the origin. This feedback controller can be interpreted as a hybrid system consisting of a high level discrete event supervisor and a family of low level feedback controllers. The closed loop system exhibits finite-time responses. DA - 1996/1// PY - 1996/1// DO - 10.1016/0167-6911(95)00036-4 VL - 27 IS - 1 SP - 29-36 J2 - Systems & Control Letters LA - en OP - SN - 0167-6911 UR - http://dx.doi.org/10.1016/0167-6911(95)00036-4 DB - Crossref KW - control of nonholonomic systems KW - nonsmooth feedback stabilization KW - hybrid systems ER - TY - JOUR TI - Fracture Behavior in 6061 Al Alloy Matrix Composites with Different Reinforcements AU - Rabiei, Afsaneh AU - Kim, Byung-Nam AU - Enoki, Manabu AU - Kishi, Teruo T2 - Materials Transactions, JIM AB - The effect of reinforcement size and volume fraction on fracture toughness in powder metallurgy (P/M)-processed 6061 Al alloy matrix composites with different kinds of reinforcements (Si3N4 whiskers, and SiC particles) are analyzed. The acoustic emission (AE) activities has also been investigated during three point bending fracture toughness test.Comparing the fracture toughness results in MMCs containing different volume fractions (Vf) of whiskers and particles show higher fracture toughness in materials with lower Vf. On the other hand, the fracture behavior in 10 percent reinforced composites regardless of the type of reinforcement, particle or whisker, is ductile fracture, but it is semi-brittle in the case of 30 percent reinforced materials. Regarding the amplitude and the number of AE events during three point bending fracture toughness test, 30 percent reinforced materials with brittle fracture mode show very high amplitude signals with less number of events in the onset of plastic deformation. 10 percent reinforced composites with a ductile mode fracture show lower AE amplitude and higher number of events. Totally, a kind of interaction between the different parameters like volume fraction, reinforcement type and reinforcement size on the fracture behavior of 6061 Al alloy matrix composites are observed and discussed. DA - 1996/// PY - 1996/// DO - 10.2320/matertrans1989.37.1148 VL - 37 IS - 5 SP - 1148-1155 J2 - Mater. Trans., JIM LA - en OP - SN - 0916-1821 2432-471X UR - http://dx.doi.org/10.2320/matertrans1989.37.1148 DB - Crossref ER - TY - JOUR TI - Double averaging approach to the study of spinup dynamics of flexible satellites AU - Mazzoleni, Andre P. AU - Hall, Christopher D. AU - Stabb, Mark C. T2 - Journal of Guidance, Control, and Dynamics AB - We study the dynamics of a class of flexible dual-spin satellites in which the rotor is spun up by a small constant torque T applied by the platform. We use a previously published zero torque solution that was obtained using the Krylov-Bogoliubov-Mitropolski averaging method. A second application of averaging developed herein leads to a reduction of the equations of motion from a sixth-order system to a single first-order equation describing the slow evolution of energy as a function of the axial angular momentum of the rotor. The geometrical interpretation of this reduction involves projecting solutions onto a certain bifurcation diagram. Numerical solutions of the averaged equation agree with numerical solutions to the full sixth-order system and show that the flexible spacecraft behaves essentially the same as its rigid counterpart during the spinup maneuver. DA - 1996/1// PY - 1996/1// DO - 10.2514/3.21579 VL - 19 IS - 1 SP - 54-59 J2 - Journal of Guidance, Control, and Dynamics LA - en OP - SN - 0731-5090 1533-3884 UR - http://dx.doi.org/10.2514/3.21579 DB - Crossref ER - TY - JOUR TI - The mechanism of mutual annihilation of stoichiometric premixed methane-air flames AU - Echekki, T. AU - Chen, J.H. AU - Gran, I. T2 - Symposium (International) on Combustion AB - The mechanism of head-on quenching of two stoichiometric premixed methane-air flames by mutual annihilation is investigated numerically using detailed chemistry. The mutually annihilating flames initially accelerate before quenching as observed by other studies involving reduced chemistry. The mechanism of this acceleration is investigated by comparing the balance between transport and reaction of O2 at different times. The primary contribution to the enhanced flame propagation is attributed to a change in the balance between reaction and diffusion. This effect is further enhanced by a decrease in the concentration gradients of the reactants during diffusional interactions of the mutually annihilating flames. The rates of fuel consumption and oxidation of H2 and CO are significantly enhanced before the merging of the various consumption/oxidation layers. The diffusion of H2 from the reaction zone to the unburned reactants is reversed, resulting in a buildup of H2 concentration in the reaction zone. H2 plays a key role in enhancing the chemistry before the merging of the various consumption layers because of its high mass diffusivity and its importance in the production of radicals. In particular, the accumulation of H2 in the reaction zone results in the enhancement of reactions that produce H from the H2/O2 system and in a buildup of radicals including H, O, and OH. The increased contribution of the H2/O2 system continues until the onset of quenching of the H2 oxidation layer, CO oxidation then becomes the dominant contribution to H-radical production. During the flame deceleration phase, H-radical production is significantly reduced. The key reactions governing the production of radicals shift from the fuel (HCO and CH3) to H2 and CO oxidation. Radical recombination reactions, which play a key role in flame-wall quenching, are insignificant until all fuel and H2/CO oxidation layers are quenched. DA - 1996/// PY - 1996/// DO - 10.1016/S0082-0784(96)80295-5 VL - 26 IS - 1 SP - 855-863 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030350195&partnerID=MN8TOARS ER - TY - JOUR TI - Negative flame speed in an unsteady 2-D premixed flame: A computational study AU - Gran, I.R. AU - Echekki, T. AU - Chen, J.H. T2 - Symposium (International) on Combustion AB - This study analyzes a stoichiometric premixed methane flame perturbed by two-dimensional turbulence using direct numerical simulation. The chemistry is described with a detailed reaction scheme. Differential diffusion is accounted for by prescribing the Lewis number for each species. The turbulent Reynolds number based on the integral scale is 136 and the ratio of rms velocity to laminar flame speed u′/SL=12. When regions of steep scalar gradients are curved, a large second derivative is created in the direction tangential to the isoscalar lines. This opposes the distortion of the isolines by the imposed velocity field. Negative burning arises when the magnitude of the diffusive flux excreeds that of the adverse convective flux. In the present flow, this occurs in regions of high positive curvature. In these regions, both reaction and diffusion in the direction normal to the isolines generally contribute to decrease the negative flame speed. However, the contribution of diffusion in the direction tangential to the flame front by far exceeds the other contributions to the flame speed. The direct effect of chemical reaction on the flame speed is negligible compared to the effect of diffusion in the highly curved regions. The significance of using a detailed description of the chemistry and diffusion in the present context is that it allows the gradients in the flame to be computed with sufficient accuracy. DA - 1996/// PY - 1996/// DO - 10.1016/S0082-0784(96)80232-3 VL - 26 IS - 1 SP - 323-329 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030374038&partnerID=MN8TOARS ER - TY - JOUR TI - Unsteady strain rate and curvature effects in turbulent premixed methane-air flames AU - Echekki, T. AU - Chen, J.H. T2 - Combustion and Flame DA - 1996/// PY - 1996/// VL - 106 IS - 1-2 SP - 184-202 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030005570&partnerID=MN8TOARS ER - TY - JOUR TI - Finite-element modeling and control of flexible fabric parts AU - Eischen, JW AU - Deng, SG AU - Clapp, TG T2 - IEEE COMPUTER GRAPHICS AND APPLICATIONS AB - Software based on nonlinear shell theory can simulate 3D motions related to real fabric-manufacturing processes. This simulation capability advances the technologies necessary for automating the textile and apparel industries. DA - 1996/9// PY - 1996/9// DO - 10.1109/38.536277 VL - 16 IS - 5 SP - 71-80 SN - 0272-1716 ER - TY - JOUR TI - Chlorine dioxide use in pickling cucumber hydrocooler operations AU - Humphries, E. G. AU - Fleming, H. P. T2 - Applied Engineering in Agriculture AB - Typical operating parameters for a chlorine dioxide generator installed on a hydrocooler (7560 L water capacity) for pickling cucumbers were ascertained. The recycled hydrocooler water (2-8C) was maintained at 1.3 ppm chlorine dioxide to effectively control microorganisms. The rates of chlorite, hypochlorite, and hydrochloric acid use to generate chlorine dioxide were linearly related to the quantity of cucumbers hydrocooled for operating runs of 172 and 304 field boxes (705 L each, 20 bushels) intermittently hydrocooled over two 16 h periods. Use rates were 0.056 to 0.082 (chlorite), 0.052 to 0.078 (hypochlorite) and 0.022 to 0.029 (hydrochloric acid) kg/box hydrocooled. Materials cost for chlorine dioxide treatment was $0.24 to $0.29 per box. Optical density increased and total solids accumulated in the hydrocooler water in direct proportion to product throughput for both tests. DA - 1996/// PY - 1996/// DO - 10.13031/2013.25703 VL - 12 IS - 6 SP - 715 ER - TY - JOUR TI - Temperature measurement by degenerate four-wave mixing with strong absorption of the excitation beams AU - Herring, GC AU - Roberts, WL AU - Brown, MS AU - DeBarber, PA T2 - APPLIED OPTICS AB - We have made simultaneous temperature measurements by degenerate four-wave mixing (DFWM) and absorption spectroscopy of OH in a CH(4)-air, lifted-diffusion flame. After we corrected the DFWM data for laser beam absorption of as much as 60%, the DFWM-based temperatures were in good agreement with temperatures derived strictly from the absorption data, as well as a one-dimensional reacting flow simulation. DA - 1996/11/20/ PY - 1996/11/20/ DO - 10.1364/ao.35.006544 VL - 35 IS - 33 SP - 6544-6547 SN - 0003-6935 ER -