@article{loh_hyun_ro_kleinstreuer_2002, title={Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer}, volume={111}, ISSN={["0001-4966"]}, DOI={10.1121/1.1433811}, abstractNote={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 °C with a vibration amplitude of 25 μm at 28.4 kHz is experimentally achieved.}, number={2}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Loh, BG and Hyun, S and Ro, PI and Kleinstreuer, C}, year={2002}, month={Feb}, pages={875–883} }
 @article{ro_loh_2001, title={Feasibility of using ultrasonic flexural waves as a cooling mechanism}, volume={48}, ISSN={["1557-9948"]}, DOI={10.1109/41.904574}, abstractNote={The potential convective heat transfer capability of an ultrasonic flexural wave (UFW) is experimentally investigated. The UFW includes an ultrasonic flexural standing wave (USW) and an ultrasonic flexural traveling wave (UTW). The factors that might affect the cooling performance of the UFW are investigated. Those include the vibration amplitude of the UFW, the gap between the cooling source and the object above it, and the temperature of the object being cooled. It was observed that the temperature drop increased with the vibration amplitude. At gaps below 100 /spl mu/m, a temperature drop was not observed. As the gap was increased to more than 100 /spl mu/m, the temperature drop increased until it reached an optimum gap producing maximum temperature drop. Beyond the optimum gap, the temperature drop began to decrease. Also, it was observed that the temperature drop increased as the temperature difference between the object and ambient air increased. The cooling performance of the USW and UTW was investigated and compared. The differences in cooling performance were found to be insignificant. This indicates that acoustic streaming is the dominant factor in the convective heat transfer using the UFW. However, using resonance, the UTW creates a temperature drop six times greater than the UTW for a given power supply. With the USW having a vibration amplitude of 25 /spl mu/m, an object at 98/spl deg/C was cooled down to 58/spl deg/C in 5 min. The temperature drop obtained by using the USW was approximately 80% of a conventional fan oriented with respect to the heated object such that the maximum heat transfer occurs. The UFW-based fan offers advantages over the conventional fan, such as silent operation, minimal heat dissipation, lack of wearing parts, and slim profile. These benefits make the fan an ideal candidate for cooling miniature parts in an enclosed workspace. Finally, a possible design option for minimizing the fan using thin-film PZT is presented.}, number={1}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Ro, PI and Loh, BG}, year={2001}, month={Feb}, pages={143–150} }
 @misc{loh_ro_2000, title={Changing the propagation direction of flexural ultrasonic progressive waves by modulating excitation frequency}, volume={238}, ISSN={["0022-460X"]}, DOI={10.1006/jsvi.2000.3013}, number={1}, journal={JOURNAL OF SOUND AND VIBRATION}, author={Loh, BG and Ro, PI}, year={2000}, month={Nov}, pages={171–178} }
 @article{ro_loh_2000, title={Feasibility of contact and non-contact approaches to material handling using traveling waves and transition characteristics}, volume={47}, number={6}, journal={IEEE Transactions on Industrial Electronics}, author={Ro, P. I. and Loh, B.G.}, year={2000}, pages={1134–1135} }