LES analysis of the turbulent boundary layer flow over 2 dimensional hills

Abstract eng:
This paper presents Large Eddy Simulation (LES) results of the turbulent boundary layer flow over two dimensional hills. Two kinds of hill shapes, a steep one with separation and a low one without stable separation, and two kinds of surface condition, rough and smooth, are considered. The numerical results are validated by comparison with experimental data obtained at the same Reynolds number. Dynamic procedure proposed by Germano et al is applied to determine the eddy viscosity for the subgrid-scale stress model. The rough surface condition is modeled by placing rectangular cylinders on the hill surface, rather than setting the roughness length. Turbulent boundary layers that develop spatially over smooth flat wall and roughness blocks are simulated individually in order to generate the inflow turbulence. General agreements between the calculated and experimental data are obtained, however the deviation at the steep hill case is noticeable. The reason for the deviation is that the simulated inflow turbulence diverges from the experimental data somewhat. Finally, based on the numerical results, the hill shape effect and roughness effect are discussed.

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