LESによる乱流境界層の数値計算のための流入変動気流の生成

Abstract

現在, 建築物周りの非定常乱流場の解析手法としてはラージエディシミュレーション(LES)が有望視されているが, その実用化に際しては流入境界条件の与え方が大きな障害の一つとなっている。本報では条件付確率場の理論を用いた乱流場の生成手法により, 上流側の乱流場を直接計算することなく希望する統計量をもった乱流場を発生させる方法を示す。発生された乱流場は実験結果と比較され, その有効性が確かめられた。

The interpolating method of the flow fluctuation conditioned by the experimental data was introduced. The flow signals at the inlet boundary in the turbulent boundary layer just behind the roughness elements were generated. The flows were interpolated in Fourier space as stochastic processes in a conditional random fields so as to realize the equivalent statistical quantities of experimental results. The digitally generated signals satisfied the statistics up to the second order moments fairly well.The turbulent field just behind the roughness calculated by LES using these inflow conditions was compared with the experimental data and examined.The calculated result shows rather good agreement in mean wind field but the attenuation of wind fluctuation in high frequency caused by the scale of mesh grids was observed.