Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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Lock-on Characteristics of Wake Behind a Rotationally Oscillating Circular Cylinder

주기적으로 회전진동하는 원주 후류의 공진특성에 관한 연구

  • 이정엽 (포항공과대학교 대학원 기계공학과) ;
  • 이상준 (포항공과대학교 기계공학과)
  • Published : 2005.08.01
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Abstract

Lock-on characteristics of flow around a circular cylinder oscillating rotationally with a relatively high forcing frequency have been investigated experimentally. Dominant governing parameters are Reynolds number (Re), angular amplitude of oscillation (${\theta}_A$), and frequency ratio $F_R=f_f/f_n,\;where\;f_f$ is a forcing frequency and $f_n$ is a natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14{\times}10^3,\;{\pi}/90{\leq}{\theta_A}{\leq}{\pi}/3,\;and\;F_R=1.0$. The effect of this active flow control technique on the lock-on flow characteristics of the cylinder wake was evaluated with wake velocity measurements and spectral analysis of hot-wire signals. The rotational oscillation modifies the flow structure of near wake significantly. The lock-on phenomenon always occurs at $F_R=1.0$, regardless of the angular amplitude ${\theta}_A$. In addition, when the angular amplitude is less than a certain value, the lock-on characteristics appear only at $F_R=1.0$,. The range of lock-on phenomena expands and vortex formation length is decreased, as the angular amplitude increases. The rotational oscillation create a small-scale vortex structure in the region just near the cylinder surface. At ${\theta}_A=60^{\circ}$, the drag coefficient was reduced about $43.7\%$ at maximum.

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References

  1. Williamson, C. H. K., 1996, 'Vortex Dynamics in the Cylinder Wake,' Ann. Rev. Fluid Mech., Vol. 28, pp. 477-539 https://doi.org/10.1146/annurev.fl.28.010196.002401
  2. Roshko, A., 1954, 'On the Development of Turbulent Wakes from Vortex Streets,' NACA Rep. 1191
  3. Bloor, M. S., 1963, 'The Transition to Turbulence in the Wake of a Circular Cylinder,' J. Fluid Mech., Vol. 19, pp. 290-304 https://doi.org/10.1017/S0022112064000726
  4. Gerrard, J. H., 1966, 'The Mechanics of the Formation Region of Vortices Behind Bluff Bodies,' J. Fluid Mech., Vol. 25, pp. 401-413 https://doi.org/10.1017/S0022112066001721
  5. Roshko, A., 1993, 'Perspectives on Bluff Body Aerodynamics,' J. Wind Eng. and Ind. Aerodyn., Vol. 49, pp. 79-100 https://doi.org/10.1016/0167-6105(93)90007-B
  6. Tokumaru, P. T. and Dimotakis, P. E., 1991, 'Rotary Oscillation Control of a Cylinder Wake,' J. Fluid Mech., Vol. 224, pp. 77-90 https://doi.org/10.1017/S0022112091001659
  7. Choi, S. H., Choi, H. C. and Kang, S. M., 2002, 'Characteristics of Flow over a Rotationally Oscillating Cylinder at Low Reynolds Number,' Physics of Fluids, Vol. 14, No. 8, pp. 2767-2777 https://doi.org/10.1063/1.1491251
  8. Baek, S. J. and Sung, H. J., 1998, 'Numerical Simulation of the Flow Behind a Rotary Oscillating Circular Cylinder,' Physics of Fluids, Vol. 10, No. 4, pp. 869-876 https://doi.org/10.1063/1.869610
  9. Mahfouz, F. M. and Badr. H. M., 2000, 'Flow Structure in the Wake of a Rotationally Oscillating Cylinder,' Transactions of the ASME, Vol. 122, pp. 290-301 https://doi.org/10.1115/1.483257
  10. Shiels, D. and Leonard, A., 2001, 'Investigation of a Drag Reduction on a Circular Cylinder in Rotary Oscillation,' J. Fluid Mech., Vol. 431, pp. 297-322 https://doi.org/10.1017/S002211200000313X
  11. Baek, S. J. and Sung, H. J., 1998, 'Numerical Simlation of the Flow Behind a Circular Cylinder with a Rotary Oscillation,' Trans. of the KSME(B), Vol. 22, No. 3, pp. 267-279
  12. Choi, S. H., Choi, H. C. and Kang, S. M., 2002, 'Characteristics of Flow over a Rotationally Oscillating Cylinder,' Trans. of the KSME(B), Vol. 26, No. 4, pp. 515-523
  13. Stansby, P. K., 1974, 'The Effects of End Plates on the Base Pressure Coefficient of a Circular Cylinder,' Aeronautical Journal, Vol. 78, pp. 36-37
  14. Graham, J. M. R., 1969, 'The Effect of End-Plates on the Two-Dimensionality of a Vortex Wake,' Aero. Quart., Vol. 20, August, pp. 237-247 https://doi.org/10.1017/S0001925900005059
  15. Ongoren, A. and Rockwell, D., 1988, 'Flow Structure from an Oscillating Cylinder : Part 1. Mechanisms of Phase Shift and Recovery in the Near Wake,' J. Fluid Mech., Vol. 191, pp. 197-223 https://doi.org/10.1017/S0022112088001569
  16. Koopman, G H., 1967, 'The Vortex Wakes of Vibrating Cylinders at Low Reynolds Numbers,' J. Fluid Mech., Vol. 28, pp. 501-512 https://doi.org/10.1017/S0022112067002253
  17. Stansby, P. K., 1976, 'The Locking-on Vortex Shedding Due to Cross-Stream Vibration of Circular Cylinder in Uniform and Shear Flow,' J. Fluid Mech., Vol. 74, pp. 641-665 https://doi.org/10.1017/S0022112076001985
  18. Meneghini, J. R. and Bearman, P. W., 1995, 'Numerical Simulation of High Amplitude Oscillatory Flow About a Circular Cylinder,' J. Fluids Struct., Vol. 9, pp. 435-455 https://doi.org/10.1006/jfls.1995.1025