Large eddy simulation of turbulent atmospheric boundary layer flow based on a synthetic volume forcing method

Abstract

A popular inflow turbulence generation (ITG) method is the synthetic random Fourier method because of its concise principle and high computational efficiency. However, the turbulent velocity in this method can hardly satisfy the Navier-Stokes (NS) equation, which usually leads to the re-development of the inflow turbulence field and attenuation of the turbulent energy in the downstream region. To overcome these problems, a synthetic volume forcing (SVF) method that constructs volume forces based on synthetic random Fourier method is proposed in this study. The volume forces can directly import turbulent energy into the mean flow to generate specified turbulent atmospheric boundary layer (ABL) flows by acting as the source terms of the NS equation. Turbulent ABL flows over rural, suburban, and urban terrains are simulated by ITG and SVF methods in the LES model. The results indicate that in SVF cases, the turbulent ABL flows meet the predefined mean velocity, turbulence intensity, and spectrum. The validations in ITG and SVF cases show that the turbulent flows in later cases are compatible with the divergence-free condition and flow dynamics described by the momentum equations, indicating that they have good self-sustainability along the flow direction and do not lead to abnormal pressure fluctuations.