| Dispersion of vehicle exhaust gas is a main source of air pollution in urban areas. It has become an important subject of vehicle field currently. The study on dispersion laws of vehicle exhaust gas is valuable to improve citizen living quality and inhabitation environment and realize the persistence development. In this thesis, numerical simulation and theoretical method were combined to analyze vehicle exhaust gas diffuse laws. Some conclusions will provide a formal theoretical reference for controlling vehicle exhaust gas pollution.Firstly, in this thesis, on the base of analysis of vehicle exhaust gas diffusion, physical and numerical model was established. At the same time, two-dimensional or three-dimensional incompressible turbulent N-S equations with multi-component, which described exhaust diffusion flow, were set up. The discrete process of control equations was performed by finite volume method.Secondly, dynamic mesh generation technique were studied. And in view of dynamic vehicle , dynamic mesh worked technique was discussed. It is major characteristic: building updating grid by interpolation based on the original grid in the computational zones, and the moving state of vehicle was described by UDF procedure with C Programming Language.Thirdly, for example as CO, in idling and normal moving situation, the numerical study of open space vehicle exhaust flow dispersion laws was carried out by the effect of two-dimensional exhaust flow numerical simulation. Taking into account the three-dimensional effect, the dispersion of exhaust diffusion numerical simulation in a high idling state were processed , and the corresponding analysis and discussion were done.Finally, numerical simulation on the effect of vehicle exhaust flow in the limited space were performed. For the section of city streets , the effects on wind speed and building height to CO diffusion flow were numerically studied by using N-S equation. Also, three-dimensional model of CO diffusion flow was set up and numerical computation and analysis were carefully carried out. The research results have important theoretical and practical value for predicting the spread of urban motor vehicle exhaust flow pattern. |
