Browse > Article

CHARACTERISTICS OF UNSTEADY PLANAR-SYMMETRIC AND ASYMMETRIC FLOWS OVER A SPHERE  

Kim, Dong-Joo (금오공과대학교 기계공학부)
Publication Information
Journal of computational fluids engineering / v.13, no.4, 2008 , pp. 39-44 More about this Journal
Abstract
Numerical simulations of laminar flow over a sphere are conducted to investigate the effect of the Reynolds number on the characteristics of vortex shedding. The Reynolds numbers considered are between 300 and 475, covering unsteady planar-symmetric and asymmetric flows. Results show that the unsteady planar-symmetric flow can be categorized into two different regimes: single-frequency regime and multiple-frequency regime. The former has a single frequency component due to periodic shedding of the vortices with the same strength in every shedding cycle, while the latter has multiple frequency components due to cycle-to-cycle variation in the strength of shed vortices with the shedding angle fixed. The multiple-frequency planar-symmetric flow, which is newly found in the present study, occurs at Re=330${\sim}$360 between the single-frequency planar-symmetric flow and the asymmetric flow. On the other hand, the asymmetric flow occurs at Re${\geq}$365, where the vortices shed from the sphere show variation both in strength and shedding angle unlike the planar-symmetric flow. Also, it is shown that the breaking of planar symmetry is closely related to the imbalance of vortical strength between a pair of streamwise vortices.
Keywords
Sphere; Vortex Shedding; Planar-Symmetric flow; Asymmetric Flow;
Citations & Related Records
연도 인용수 순위
  • Reference
1 1990, Sakamoto, H. and Haniu, H., "A study on vortex shedding from spheres in a uniform flow," J. Fluids Eng., Vol.112, pp.386-392   DOI
2 1999, Johnson, T.A. and Patel, V.C., "Flow past a sphere up to a Reynolds number of 300," J. Fluid Mech., Vol.378, pp.19-70   DOI   ScienceOn
3 2002, Kim, D. and Choi, H., "Laminar flow past a sphere rotating in the streamwise direction," J. Fluid Mech., Vol.461, pp.365-386
4 2001, Kim, J., Kim, D. and Choi, H., "An immersed boundary finite-volume method for simulations of flow in complex geometries," J. Comput. Phys., Vol.171, pp.132-150   DOI   ScienceOn
5 1995, Jeong, J. and Hussain, F., "On the identification of a vortex," J. Fluid Mech., Vol.285, pp.69-94   DOI   ScienceOn
6 2003, Yun, G., Kim, D. and Choi, H., "Turbulent flow past a sphere at Re=3700 and $10^{4}$," Phys. Fluids, Vol.15, No.3, S6
7 1999, Mittal, R., "Planar symmetry in the unsteady wake of a sphere," AIAA J., Vol.37, No.3, pp.388-390   DOI   ScienceOn
8 2000, Tomboulides, A.G. and Orszag, S.A., "Numerical investigation of transitional and weak turbulent flow past a sphere," J. Fluid Mech., Vol.416, pp.45-73   DOI   ScienceOn
9 2002, Mittal, R., "Symmetry properties of the transitional sphere wake," AIAA J., Vol.40, No.3, pp.579-581   DOI   ScienceOn
10 2006, Yun, G., Kim, D. and Choi, H., "Vortical structures behind a sphere at subcritical Reynolds numbers," Phys. Fluids, Vol.18, pp.015102-1-14   DOI   ScienceOn