Study On CFD Modeling Of Steady Equilibrium Atmospheric Boundary Layer

The purpose of the research of the steady equilibrium atmospheric boundary layer is to make all the aspects of the fluid, such as velocity, turbulent kinetic energy, turbulence intensity, turbulent kinetic energy dissipation rate, do not change when the fluid flowing through the computational domain. There are three ways commonly been used in this research:The first way is to propose a new inflow conditions; The second way is to modify the the wall parameter (roughness constant, roughness height, wall shear stress, wall boundary conditions set and wall functions, etc.) and the parameters of the first layer near the wall (velocity, turbulent kinetic energy and turbulent kinetic energy dissipation rate, etc); and the third way is to modify the internal parameters of the flow field (turbulence model constants and user-defined source term). When simulating of two-dimensional steady incompressible flow, this dissertation proposed different assumptions from previous studies, it is assumed that the pressure along the horizontal direction changes uniformly while doesn’t change in the height direction. According to the derivation of the momentum equation, this dissertation get a new set of inflow conditions, the turbulent kinetic energy of this inlet boundary conditions changes linearly with height. Taking into account the actual situation, the turbulent kinetic energy near the wall is nearly zero, so a new inlet turbulent kinematic energy with broken line is also proposed. Based on the assumption of this article, the relationship between the wall shear stress and inflow conditions can also be obtained. A variety of inflow conditions are used in calculation. Comparing the methods of modification of wall shear stress, modification of the turbulent viscosity, modification of the turbulent kinetic energy and turbulent kinetic energy dissipation rate of the first layer near the wall and application of source term, it is found the methods of modification of wall shear stress and turbulent kinetic energy dissipation rate near the wall are simple and effective.