Computational Simulation Of External Flow Field Of Truck In Tandem And Research On Its Fuel Economy

With growth of our country economy, truck, especially van body truck, plays a more and more important role in the economy day by day. Therefore, people have begun to attach more and more importance to the external flow field of truck in order to save fuel and reduce aerodynamic drag.Computational fluid dynamic (CFD) is widely used in vehicle development courses. The basic theory of vehicle CFD is studied. Two-equation turbulence model which is widely used, such ask k-εmodel, RNGk k-εmodel, SST model, are introduced and applied respectively to simulate external flow field of Ahmed body. Comparison between simulation results and wind tunnel is given to discuss the advantage of each turbulence model. The result is that SST turbulence model are more accurate than the other two models. Therefore, SST turbulence model is selected in order to get more accurate result.CAD model and CFD simulation grid model based on the CAD model of van body truck are built. The external flow field of one truck and two or three trucks in tandem are simulated using CFD software. The air flow stream and trail vortex of one truck external flow field are deeply researched, mechanism of external flow and the relationship between flow characteristic and aerodynamic drag are analyzed, and the main reasons caused aerodynamic drag are clarified. These researches provide referential basis for reducing aerodynamic drag of van body truck.The external flow field of two trucks and three trucks in tandem between 13 spaces from 5 to 0.2 vehicle lengths are simulated and then the change of the external flow field is deeply researched. The aerodynamic drag force coefficient and fuel economy with space changes are got and studied. It can be concluded that the aerodynamic drag coefficient of each truck in tandem are less than that of one truck; The aerodynamic drag coefficient of lead truck, A truck, B truck reduce with spacing reduction, however, the trail truck and C truck first reduce and then rise; Three trucks in tandem are better than two trucks in tandem in reducing aerodynamic drag force and saving fuel; The average fuel saving of three trucks in tandem is 6.75%~31.2%, two trucks in tandem is 5.53%~24.1%.