Journal of Mechanical Science and Technology

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지

The Effect of Serrated Fins on the Flow Around a Circular Cylinder

  • Boo, Jung-Sook (School of Mechanical Engineering, Pusan National University) ;
  • Ryu, Byong-Nam (School of Mechanical Engineering, Pusan National University) ;
  • Kim, Kyung-Chun (School of Mechanical Engineering, Pusan National University)
  • Published : 2003.06.01
Download PDF
⟨ Previous Next ⟩

Abstract

An experimental study is performed to investigate the characteristics of near wake flow behind a circular cylinder with serrated fins using a constant temperature anemometer and flow visualization. Various vortex shedding modes are observed. Fin height and pitch are closely related to the vortex shedding frequency after a certain transient Reynolds number. The through velocity across the fins decreases with increasing fin height and decreasing fin pitch. Vortex shedding is affected strongly by the velocity distribution just on top of the finned tube. The weaker gradient of velocity distribution is shown as increasing the freestream velocity and the fin height, while decreasing the fin pitch. The weaker velocity gradient delays the entrainment flow and weakens its strength. As a result of this phenomenon, vortex shedding is decreased. The effective diameter is defined as a virtual circular cylinder diameter taking into account the volume of fins, while the hydraulic diameter is proposed to cover the effect of friction by the fin surfaces. The Strouhal number based upon the effective diameters seems to correlate well with that of a circular cylinder without fins. After a certain transient Reynolds number, the trend of the Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter. The normalized velocity and turbulent intensity distributions with the hydraulic diameter exhibit the best correlation with the circular cylinder's data.

Keywords

References

  1. Apelt, C. J., West, G. S. and Szewczyk, A. A., 1973, 'The Effects of Wake Splitter Plates on the Flow Past a Circular Cylinder in the Range $10^4,' J. Fluid Mechl., Vol. 61, Part 1, pp. 187-198 https://doi.org/10.1017/S0022112073000649
  2. Chang, Paul K., 1979, Separation of Flow, Pochinchai Printing Co.,Ltd., Korea, pp. 11-18
  3. Gerrard, J. H., 1966, 'The Mechanics of the Formation Region of Vortices behind Bluff Bodies,' J. Fluid Mech. Vol. 25, Part 2, pp. 401-413 https://doi.org/10.1017/S0022112066001721
  4. Green, R. B. and Gerrard, J. H., 1993, 'Vorticity Measurements in the Near Wake of a Circular Cylinder at Low Reynolds Numbers,' J. Fluid Mech. Vol. 246, pp. 675-691 https://doi.org/10.1017/S002211209300031X
  5. Griffin, Owen M., 1995, 'A Note on BluffBody Vortex Formation,' J. Fluid Mech., Vol. 284, pp. 217-224 https://doi.org/10.1017/S0022112095000322
  6. Kim, K. C. and Jung, Y. B., 1991, 'The Effect of Free Stream Tubulence of the Near Wake behind a Circular Cylinder,' Transactions of the KSME, Vol. 15, No. 6, pp. 2062-2072
  7. Kim, S. J. and Lee, C. M., 2002, 'Numerical Investigation of Cross-Flow Around a Circular Cylinder at a Low-Reynolds Number Flow Under an Electromagnetic Force,' KSME International Journal, Vol. 16, No. 3, pp. 363-375
  8. Lee, S. J. and Daichin, 2001, 'Flow Structrure of the Wake behind an Elliptic Cylinder Close to a Free Surface,' KSME International Journal, Vol. 15, No. 12, pp. 1784-1793 https://doi.org/10.1007/BF03185135
  9. Stock, David E. and Jaballa,Tuhami M., 1985, 'Turbulence Measurement Using Split-Film Anemometry,' Proc. Int. Symp. on Refined Flow Modeling and Tubulence Measurement(University of Iowa), H15-1-10
  10. Stock, D. E., Wells, M. R., Barriga, A. and Crowe, C. T., 1977, 'Application of Split-Film Anemometry to Low-Speed with High Turbulence Intensity and Recirculation as Found in Electrostatic Precipitators,' Proc. Fifth Biennial Symp. on Turbulence(University of Missouri), pp. 117-123