Research On Aerodynamic Characteristics Of Heavy Truck Under Cosine Pulsating Crosswind

China's perfect automotive industry system has made heavy trucks play a vital role in the transportation industry and has become an indispensable part.However,the intricate geographical environment and changing climatic conditions make heavy trucks frequently encounter crosswind effects during transportation.The higher shape sensitivity increases the influence of transient crosswinds on the aerodynamic performance of heavy trucks.Therefore,this paper proposes to divide the cosine pulsating crosswind into two components: cosine pulsating component and DC component,quantitatively study the influence of two components on the aerodynamic performance and external flow field structure of heavy trucks,and use block method for heavy trucks to find the component that contributes the most to aerodynamic performance.The research method helps to improve the safety and comfort of heavy trucks at high speeds under crosswind conditions.The research contents of this paper are as follows:Firstly,the transient numerical model of aerodynamic characteristics of heavy trucks is constructed.The reliability of numerical model is verified by wind tunnel test results,which lays a foundation for subsequent research.Secondly,the User-Defined Function is used to analyze the aerodynamic performance of heavy trucks under cosine pulsating side wind conditions.The results show that when the amplitude of the cosine component increases from 0 to 4,the mean value of the aerodynamic coefficient does not change,but the amplitude of the aerodynamic coefficient fluctuates linearly,and the slope of the amplitude of the lateral force coefficient is the largest.By fitting the lateral force coefficient,a higher degree of fit indicates that the lateral force coefficient exhibits a cosine variation.The amplitude of the cosine component increases the static pressure range of the external flow field,the wall surface pressure difference,and increases the Y-direction pressure gradient.Excessive cosine crosswind fluctuations cause the heavy-duty truck to have a windward side pressure less than the leeward side,causing the lateral force coefficient to be less than zero.The heavy truck is divided into three parts: the front part,the container and the chassis.The contribution of the lateral force coefficient of the container in each working condition dominates the variation of the lateral force coefficient of heavy trucks.Thirdly,the influence of DC component of crosswind on aerodynamic performance is also studied in this paper.The results show that the DC component of crosswind increases from 0 to 12,the mean value of the aerodynamic coefficient increases linearly,and the aerodynamic coefficient amplitude changes little;DC component of crosswind does not change the degree of cosine approximation of the lateral force coefficient,but affects the degree of cosine approximation of the drag coefficient and the lift coefficient.The smaller DC component induces the change of the static pressure on the windward side and the leeward side to determine the change of the flow field structure near the heavy truck,it also increases the frequency of the drag coefficient,but it does not affect the frequency of the lateral force coefficient and the lift coefficient.In summary,this paper mainly researches the aerodynamic performance of the cosine component amplitude and DC component of crosswind on the external flow field of heavy trucks,and summarizes the variation law of aerodynamic coefficient.It is concluded that when the DC component is dominant,the amplitude of the larger cosine component increases the degree of cosine variation of the lateral force coefficient;when the cosine component is dominant,the smaller DC component increases the fluctuation frequency of the drag coefficient,which can be increased by up to one times.The contribution of the container component dominates the aerodynamic performance of heavy trucks under all conditions.