Vortex Shedding at the End of Parallel-plate Thermoacoustic Stack in the Oscillatory Flow Conditions

Authors: Lei Shi, Zhibin Yu, Artur J. Jaworski, Abdulrahman S. Abduljalil

Abstract:

This paper investigates vortex shedding processes occurring at the end of a stack of parallel plates, due to an oscillating flow induced by an acoustic standing wave within an acoustic resonator. Here, Particle Image Velocimetry (PIV) is used to quantify the vortex shedding processes within an acoustic cycle phase-by-phase, in particular during the “ejection" of the fluid out of the stack. Standard hot-wire anemometry measurement is also applied to detect the velocity fluctuations near the end of the stack. Combination of these two measurement techniques allowed a detailed analysis of the vortex shedding phenomena. The results obtained show that, as the Reynolds number varies (by varying the plate thickness and drive ratio), different flow patterns of vortex shedding are observed by the PIV measurement. On the other hand, the time-dependent hot-wire measurements allow obtaining detailed frequency spectra of the velocity signal, used for calculating characteristic Strouhal numbers. The impact of the plate thickness and the Reynolds number on the vortex shedding pattern has been discussed. Furthermore, a detailed map of the relationship between the Strouhal number and Reynolds number has been obtained and discussed.

Keywords: Oscillatory flow, Parallel-plate thermoacoustic stack, Strouhal numbers, Vortex shedding.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1075587

References:

[1] Y. J. Chung and S. H, Kang, "A study on the vortex shedding and lock-on behind a square cylinder in an oscillatory incoming flow," JSME International Journal, Series B, vol. 46, no 2, pp. 250-261, 2003.
[2] C. Barbi, D. P. Favier, C. A. Maresca, and D. P. Telionis, "Vortex shedding and lock-on of a circular cylinder in oscillatory flow," Journal of Fluid Mechanics, vol. 170, pp. 527-544, 1986.
[3] M. Tatsuno and P. W. Bearman, "A visual study of the flow around an oscillating circular cylinder at low Keulegan-Carpenter numbers and low Stokes numbers," Journal of Fluid Mechanics, vol. 211, pp. 157-182, 1990.
[4] A. Okajima, T. Matsumoto, and S. Kimura, "Force measurements and flow visualization of bluff bodies in oscillatory flow," Journal of Wind Engineering and Industrial Aerodynamics, vol. 69-71, pp. 213-228, 1997.
[5] G.W. Swift, "Thermoacoustic engines," The Journal of the Acoustical Society of America, vol. 84, no. 4: pp.1145-1180, Oct. 1988.
[6] G.W. Swift, Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators. New York: Acoustical Society of America, 2002, ch. 4.
[7] P. Blanc-Benon, E. Besnoin, and O. Knio "Experimental and computational visualization of the flow field in a thermoacoustic stack," C.R. Mecanique, vol. 331, pp. 17 - 24, 2003.
[8] X. Mao, Z. Yu, and A. J. Jaworski, "PIV studies of coherent structures generated at the end of a stack of parallel plates in a standing wave acoustic field," Experiments in Fluid, vol. 45, no. 5, pp. 833-846, Nov. 2008.
[9] A. Berson, M. Michard, and P. Blanc-Benon, "Measurement of acoustic velocity in the stack of a thermoacoustic refrigerator using particle image velocimetry," Heat and Mass Transfer, vol. 44, no. 8, pp. 1015-1023, 2007.
[10] M. Hino, M. Sawamoto, and S Takasu, "Experiments on transition to turbulence in an oscillatory pipe flow," Journal of Fluid Mechanics, vol. 75, part 2, pp. 193-207, 1975.