Aerodynamic Characteristics Research On Heavy Commercial Vehicles In Several Typical Unsteady Crosswind Situations

Since the establishment of the nation，China road motor transportation has occupied aspecial position in transportation. With the rapid development of China’s national economy,the road infrastructure construction in our country had got a historic breakthrough afterhaving carried out reform and opening-up policy, rising along with which the heavycommercial vehicles transportation was causing concern from all walks of life was catchingthe attention of all walks of life. In order to maximize the economic benefit oftransportation and to improve the transport efficiency, heavy commercial vehicles increasedthe load and speed at the same time. Taking the work nature of heavy commercial vehiclesinto consideration, heavy commercial vehicles will experience a wide variety of complexenvironments, in which the impact of crosswind cannot be ignored. Due to the largelength-width ratio of heavy commercial vehicle body, the higher vehicle height andcentre-of-gravity position will increase the sensitivity of the crosswind, and in turn theeffects brought by different forms of crosswind on heavy commercial vehicles will beobvious. Therefore, the theoretical guiding significance and engineering application value toresearch the aerodynamic characteristics of heavy commercial vehicles in differentcrosswind environment and to improve the operation stability and driving safety areextremely important.According to the change scope of its intensity and direction，the crosswind is dividedinto steady and unsteady crosswind, but the steady one is almost non-existent in the naturalenvironment. There are varieties of unsteady crosswind which has an obvious impact ondriving vehicles. Crosswinds are more likely to appear in the open spaces and the exit orentrance of a mountain tunnel. Basing on the vehicle aerodynamic characteristics research intransient crosswind of predecessors, we selected several typical unsteady crosswinds in the natural environment as the research conditions, to do some researches and analysis onaerodynamic characteristics of heavy commercial vehicles, which can be provided as areliable theoretical basis for improving vehicle stability and security under crosswind effects.The accuracy and reliability of numerical simulation had been verified in numerousstudies about aerodynamics. In this paper, we used the overset mesh technique in thesoftware of STAR-CCM+, combining with a type of heavy commercial vehicle model inChina，to simulate the vehicle going across different intervals of buildings in the road of thecity, increasing the width of the buildings and the working conditions in tunnels. Wecomparatively analyzed the different effects of different building intervals and buildingwidth on aerodynamic characteristics of heavy commercial vehicles. Meanwhile, weanalyzed the aerodynamic changes separately in the exit and entrance of the tunnel.