Abstract
The interaction between the wake of a rotor blade and a downstream cylinder holds the key to the understanding and control of electronic cooling fan noise. In this paper, the aerodynamic characteristics of a circular cylinder are experimentally studied in the presence of an upstream NACA 4412 airfoil for the cylinder-diameter-based Reynolds numbers of Re d =2,100–20,000, and the airfoil chord-length-based Reynolds numbers of Re c =14,700–140,000. Lift and drag fluctuations on the cylinder, and the longitudinal velocity fluctuations of the flow behind the cylinder were measured simultaneously using a load cell and two hot wires, respectively. Data analysis shows that unsteady forces on the cylinder increase significantly in the presence of the airfoil wake. The dependence of the forces on two parameters is investigated, that is, the lateral distance (T) between the airfoil and the cylinder, and the Reynolds number. The forces decline quickly as T increases. For Re c <60,000, the vortices shed from the upstream airfoil make a major contribution to the unsteady forces on the cylinder compared to the vortex shedding from the cylinder itself. For Re c >60,000, no vortices are generated from the airfoil, and the fluctuating forces on the cylinder are caused by its own vortex shedding.
Similar content being viewed by others
References
Arie M, Kiya M, Moriya M, Mori H (1983) Pressure fluctuations on the surface of two circular cylinders in tandem arrangement. ASME J Fluids Eng 105:161–167
Baban F, So RMC, Ötügen MV (1989) Unsteady forces on circular cylinders in a cross-flow. Exp Fluids 7:293–302
Chen SS (1987) Flow-induced vibration of circular cylindrical structures. Hemisphere, Washington, pp 39
Huang L (2003) Characterizing computer cooling fan noise. J Acoust Soc Am 114:3189–3200
Huang RF, Lin CL (1995) Vortex shedding and shear-layer instability of wing at low-Reynolds numbers. AIAA J 33:1398–1403
Kaji S, Okazaki T (1970) Generation of sound by rotor–stator interaction. J Sound Vib 13:281–307
Kemp NH, Sears WR (1955) The unsteady forces due to viscous wakes in turbomachines. J Aeron Sci 22:478–483
Lissaman PBS (1983) Low-Reynolds-number airfoils. Ann Rev Fluid Mech 15:223–239
Sijtsma P, Rademaker ER, Schulten JBHM (1998) Experimental validation of lifting surface theory for rotor–stator interaction noise generation. AIAA J 36:900–906
Tyler JM, Sofrin TG (1962) Axial flow compressor noise studies. Soc Autom Eng Trans 70:309–332
Williamson CHK, Roshko A (1988) Vortex formation in the wake of an oscillating cylinder. J Fluids Struct 2:355–381
Zhou Y, So RMC, Liu MH, Zhang HJ (2000) Complex turbulent wakes generated by two and three side-by-side cylinders. Int J Heat Fluid Flow 12:125–133
Zhou Y, Wang ZJ, So RMC, Xu SJ, Jin W (2001) Free vibrations of two side-by-side cylinders in a cross flow. J Fluid Mech 443:197–229
Acknowledgements
The authors wish to acknowledge the support given to them by the Central Research Grant of The Hong Kong Polytechnic University through grants G-T235 and G-T408. Dr. R.J. Cao’s contribution through valuable suggestions and discussions is also acknowledged.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Zhang, H.J., Huang, L. & Zhou, Y. Aerodynamic loading on a cylinder behind an airfoil. Exp Fluids 38, 588–593 (2005). https://doi.org/10.1007/s00348-004-0915-y
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00348-004-0915-y