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

The Korean Society of Mechanical Engineers (대한기계학회)
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Numerical Study on the Vortex Evolution from a Sharp-Edged, Wall-Mounted Obstacle

장애물 주위의 와구조 형성과정에 관한 수치적 연구

  • 황종연 (인하대학교 대학원 기계공학부) ;
  • 양경수 (인하대학교 기계공학부)
  • Published : 2004.06.01
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Abstract

Direct numerical simulation was carried out to study the vortical structures of the flow around a wall-mounted cube in a channel at Re=1,000 and Re=3,500 based on cubic height and bulk mean velocity. The cubic obstacle is situated in the entrance region of the channel flow where the boundary layers are developing. Upstream of the obstacle, steady and unsteady laminar horseshoe vortex systems are observed at Re=1,000 and Re=3,500, respectively; the near-wake flow is turbulent in both cases. The flow separates at each leading sharp edge of the cube, and subsequent vortex roll-up is noticed in the corresponding free-shear layer. The vortex shedding from the upper leading edge (upper vortices) and that from the two lateral leading edges (lateral vortices) are both quasi-periodic and their frequencies are computed. The upper and lateral vortices further develop into hairpin and Λ vortices, respectively. A series of instantaneous contours of the second invariant of velocity gradient tensor helps us identify spatial and temporal behaviors of the vortices in detail. The results indicate that the length and time scales of the vortical structures at Re=3,500 are much shorter than those at Re:1,000. Correlations between the upper and lateral vortices are also reported.

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References

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