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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

DNS OF TURBULENT FLOW OVER AN AXISYMMETRIC HILL

pages 1205-1210
DOI: 10.1615/TSFP6.1920
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ABSTRAKT

Direct numerical simulation (DNS) of a turbulent flow over an axisymmetric hill has been carried out. The aim is to study three-dimensional flow separation and reattachment that occur on the lee-side of a curved geometry such as a hill shape. Simulation considers the flow conditions at Mach number of M = 0.6 and the Reynolds number of Re = 500, based on the free-stream quantities and the incoming boundary layer displacement thickness. The computational domain follows an existing wind tunnel test with the inlet distance adjusted for different inflow condition treatments. A total of three simulations are performed on the coarse and the fine grids, and a synthetic method is used for the generation of the inflow conditions. For coarse grids, simulations are carried out using both the synthetic method for inflow generation and the feed-in inflow data from a precursor computation. The results have shown good agreements between the two treatments, confirming the feasibility of using the feed-in inflow data technique. For fine grids, the resolutions are Δx+ = 12.5, Δz+ = 6.5, and Δy+1 = 1.0 with about 10 points in the viscous sublayer. Not surprisingly, further detailed flow structures and its development around the hill have been captured, which are quite different from those observed in the coarse grid simulations. It is found that a small separation bubble exists at the foot of the wind-side of the hill and the boundary layer flow laminarization occurs around the crest of the hill. These lead to different flow separation topologies in the lee-side of the hill, where a larger primary separation bubble embedded with a smaller secondary separations have been captured. Simulation results at this low Reynolds number could be used for future experimental validation studies.

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