Direct Numerical Simulations Of Homogeneous Turbulence Based On A Semi-Implicit Scheme

Turbulent flow plays an important role in the research about the flow around the wind turbine and wind resources etc. Direct numerical simulation of turbulence is the most accurate method, without any turbulence model assumptions, and get the instantaneous flow field at different scales. Study on direct numerical simulation method for the development of high reliable wind power CFD analysis tools are of great significance.This document redeveloped the code scheme based on the open-source DNS code Incompact3d, using the semi-implicit scheme for solving the viscosity terms. Develop the post-process time and space averaged statistics program about the first-order moment and second-order moment. Take fully developed channel flow for example, with the improved semi-implicit viscous terms to study the homogeneous turbulent flows with a passive scalar. Budgets of Reynolds stress, heat flow and temperature variance statistics are presented, and statistic were computed along the wall normal direction of the grid to study the characteristic of turbulent among in the turbulent production region, at the location of peak turbulence intensity and in the mean flow region etc. Such data about the budgets of Reynolds stress and heat flow is valuable in the scope of assessing accuracy of wall-modelling. For further learning the variety of the homogeneous turbulent flow structure, 3D Taylor green vortex is performed to study the time evolving of the turbulent kinetic energy and dissipation rate, the influence of the turbulent kinetic energy dissipation rate to the flow structure.A simulation about the 3D Taylor Green vortex using direct numerical simulation is performed.Study the variety of turbulent flow structure, evolving process of the turbulent kinetic energy and dissipation rate, and the influence of the turbulent kinetic energy on the flow structure. The simulation results capture the evolving process of the Taylor Green vortex. It shows that the turbulent kinetic energy dissipation rate calculated by the integral of the enstrophy energy is smaller than the one calculated directly.