ラフネス上に空間発達する乱流境界層のLESと変動風の評価

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This paper discusses the potential of Large-eddy simulation for predicting the turbulent characteristics in a spatially developed turbulent boundary layer over a rough ground surface. Lund et al. proposed the method using quasi periodic boundary condition for smooth-wall turbulent boundary layer. Here we modify this method so that it could be applied to the flow over a rough ground surface. Roughness elements are arrayed on the ground to match the mean velocity profile with power law with exponent a = 0.25. The roughness length, the roughness displacement and the turbulence intensities are in good agreement with experimental data. The ratios of integral scales of turbulence almost conform to previous investigations. However, we necessarily can not simulate all the turbulent quantities, so the complete periodic boundary condition is required for elimination of unfavorable peak in the spectra of a velocity fluctuation.
2001-03-30