Research On Influence Of Truck Within Different Road Terrains On Aerodynamic Characteristics In Cross-wind

With the fast construction of Chinese highway and continuous development ofautomotive industry, heavy commercial truck is becoming the main force in thetransportation industry in urban and rural highway transportation. However, thedriving environment for heavy commercial truck is special, and it is easily affected bythe environmental crosswind, especially when the vehicle is on the highway, road,bridge, tunnel. And the vehicle handling characteristics are inevitably affected by thecrosswind which badly threats the driving safety. At the same time, it makes theeffects of crosswind more sensitive because of the shape with large length-width ratioand lightweight trend for heavy commercial truck. So the rollover accidents caused bycrosswind lead to wide attentions, and it has a realistic significance to study theinfluences of roads and topography under crosswind on driving stability of truck.People simply evaluate vehicle aerodynamic characteristics before, and seldom studythe effects of crosswind on vehicle stability. In order to more comprehensivelyevaluate the effects of roads and topography on crosswind driving stability for truck,this paper takes the highway embankment and mountain roads as the special drivingconditions for heavy commercial truck. And analyze the influence rules of structuralparameters of roads and topography under crosswind on truck aerodynamiccharacteristics and the detailed effects of aerodynamic forces on driving stability byapplying CFD numerical simulation method combined with the vehicle dynamicsimulation.This paper can be mainly divided into three parts. The first part mainly studiesthe influence rules of different characteristic parameters for highway embankment ontruck aerodynamic characteristics; The second part mainly studies the influence rulesof characteristic parameters for different mountains on truck aerodynamic characteristics; The third part is on the basis of the first part and the second part, andthis part mainly studies the influence rules of aerodynamic characteristics on vehicledriving stability with different roads and topography under crosswind.In the first part, respectively simulate for heavy commercial truck when it is inthe upper side of embankment and in the leeward of embankment, and when underdifferent embankment heights and different side slopes. And the embankment heightsare selected for1m,2m,3m,4m,5m,and the side slopes are selected for1:0.5,1:0.75,1:1,1:1.5,1:2.The simulation results indicated that the positions of truckdidn’t affect the aerodynamic forces much, but affected the flow field structure larger.To sum up, the aerodynamic forces for truck increased with the increase ofembankment heights. In the second part, on the basis of typical three-dimensionalsinusoidal mountain, study the influence rules of three groups of different shapeparameter combinations on truck aerodynamic characteristics when the truck is in theleeward side of the mountain. The H represents the mountain height, the L representsthe mountain section parameter, and the R represents the shape factor. in this study,the L is same but the R and H are different; The results indicated that cd, cl, cs, cymare all decrease rapidly when the truck drives into the mountain leeward flow field,minimum value of them are appeared while the truck at the middle of the mountain,then increase when the drives away. They all changes during the time t=3.5s-5.5s,andthe change rate is very large which makes the truck stability rather worse.