Research On Vans' Aerodynamic Character Based On Special Running Environment

The quantity of automobiles is rising at very fast speed all over the world. The freeways are developing more perfectly, and the technique level of automobiles is advanced continuously, which cause the quantity and speed of kinds of automobiles on the freeways are increasing continuously. The running condition of automobiles on freeways is more complex, which includes influence of road establishments including central reserve and the frequent phenomena of kinds of automobiles in tandem. The influence of flow field between automobiles and the influence of road establishments on external flow field of automobiles can change aerodynamic character and influence control stability and security, even result in traffic accident. Therefore the research on aerodynamic character of automobiles in tandem and the influence of central reserve on aerodynamic character has very important practical significance.The purpose of this paper is studying aerodynamic character of a van and a car in tandem, the influence of styles, lengthways space, and with or without central reserve on external flow field of automobiles in tandem. This paper can provide theory guidance of automobiles' secure running in tandem.Automobile aerodynamic methods mainly include: theory analysis, examinational research and computation of numerical simulation. This paper analyzes the problems deeply using these methods. Also this paper analyzes and derives the relations between flowing phenomena and dynamical and educes the conclusions that can direct the improvement of the design.In order to achieve the aims of the research, this paper studies aerodynamic character of a van and a car in tandem in several ways:Firstly, having a smoke wind tunnel test on a van and a car in tandem, according to the difference between the data of smoke wind tunnel and numerical simulation, this paper validates the consistency of external flow field in tandem of two different methods, which explains the method of numerical simulation is rational and veracious. This paper computes the aerodynamic character of a van and a car in tandem using numerical simulation, with different styles of the lead automobile and the trail automobile, analyses the influence of automobile styles on aerodynamic character in tandem. Then this paper analyses the influence of different space on the same vans in tandem.The running automobile has relative displacement with central reserve on freeway. In order to simulate the situation, a method of calculating unsteady aerodynamic character is presented, which is realized by dynamic mesh technique and the program UDF module developed by authors. The unsteady numerical simulation of a moving van in 40 m/s is successfully carried out, which is contrasted with fathers' experiments and steady numerical simulation results to prove the method is feasible. Using the method, vans' aerodynamic character in single and in tandem with central reserve is carried out, and the influence of central reserve on vans' external flow field in high speed is analyzed, which provides theory guidance to considering central reserve or not in numerical simulation of automobiles running on freeway. Also aerodynamic character of a running van passing another resting van is simulated with the method. The paper analyses the influence of transverse space on external flow field, which provides theory guidance to automobiles' safe running.The results are: styles of automobiles have more influence on trail vehicles; when two vans in tandem, the resistance coefficients of two vans change as lengthways space in the same direction, and lift coefficient of the lead van changes as lengthways space in the opposite direction; the central reserve has more influence on the trail van in tandem; when a running van is passing a resting van, the influence on vans' aerodynamic character and security is more as the transverse space is small, and the change of space has more influence on the resting van.According to the systemic analysis of computational data, the external flow field of vans in tandem is researched, the influence of styles. Lengthways space on aerodynamic character of vans in tandem is analyzed. The influence of central reserve on aerodynamic character of vans in single and in tandem is analyzed. Aerodynamic character of the running van passing the resting vans is researched. This paper can provide theory guidance to safe running of vans in different situations on freeway, and offers methods to the researches on aerodynamic character of automobiles in complex traveling condition.