LESによる粗面上の乱流境界層の数値計算

Abstract

The demand of numerical prediction of wind flow over rough surfaces such as urban areas is increasing. Reproduction of the roughness configuration in the mesh discretization is a direct way for numerical calculations. However, the roughnesses near the ground such as buildings or houses are complicated. Therefore the reproduction increases the computational load and can cost a lot of time and money. In order to reduce this, we applied a filtering operation, that is an averaging in a space containing solid obstacles, to the Navier-Stokes equations and derived filtered equations with a subgrid scale turbulent modeling for the Large Eddy Simulation. Consequently, we can take the obstacles to be porous media distributed uniformly in the mesh. The configuration of the obstacles does not need to be reproduced any further. We can calculate the space-averaged property of flows with coarse meshes and a reduced computational load. We present some calculations of turbulent boundary layer over a rough surface. The performance and effectiveness of the calculation method are examined by comparing with the measured data by wind tunnel experiments.