Research On Turbulent Model Of Numerical Simulation About Flow Field Around Vehicles

In fact, the most of flow in nature is the three-dimension turbulence. Turbulence is the most complicated form of viscous fluid movement. Its core features is an almost infinite number of scales in physics and strong nonlinear in mathematics. The automobile external flow field belongs to the typical example of the three-dimensional turbulence. It appears the separated flow in its tail, and the flow is more complicated. The typical characteristics of the flow field are three-dimension, turbulence, viscosity, separation. Separated flow around the vehicle is the typical and inevitable flow phenomenon. And the study about the turbulence and the separated flow is always hot and difficult. The automobile external flow field directly affects the design of car shell, the automobile dynamic performances, the fuel consumption, power, handling, stability , safety and noise level of the vehicles, and so on. For this reason the numerical simulation of flow field around the automobile not only has the principle value but also has the application of the practical Engineering.This article has mainly studied how to simulate the flow field around vehicles and how to choose the model of its numerical simulation. In this article it had started with the three dimensional Navier-Stokes equation of the incompressible flow and establish the mathematical model to describe the flow field around vehicles. The mathematical model is the average Reynolds equation of incompressible flow (RANS). The vehicle model of numerical simulation and the area of the simulation have been chosen. The non-structural and irregular grid method has been selected to generate grid. And the finite element method has been chosen to discrete the RANS equation. According to the turbulent theory, three turbulent models have been selected to simulate the flow field around vehicles. Their names are standard k-e model, Baldwin-Lomax model and low Reynolds k-e model. Using these three kinds of turbulent models to simulate the flow field around vehicles, some information about separated flows behind the automobile has been obtained. By means of analysisng the result of the numerical simulation from the vortex, the velocity field, the pressure field and the pressure coefficient and check them against the experimental result. We obtained that standard k-εmodel is the most suitable turbulent model for the full flow field around vehicles.