Study On Crosswind Stability Of Coach With Body Attitude Change

Passenger coaches are an indispensable means of public transportation,and the surrounding environment of driving sections is more complicated.Passenger coaches often encounter crosswinds when passing these sections.Different crosswinds(steadystate and transient crosswinds)have different effects on passenger coaches.In particular,natural gusts(bursts and large wind speeds)cause complex transient changes in the flow field around the bus,causing the bus to deviate from the trajectory,which seriously threatens the safety of driving.And because the coaches have a large lateral area and a high center of gravity position,the side wind sensitivity of the coach is large,and the number of passengers is large,so it is necessary to study the stability of the cross wind of the coach.At the same time,during the actual driving process of the bus,the body attitude change and the surrounding flow field are applied in real time.The transient response characteristics seriously affect the driving stability,and the body attitude change is complicated due to uneven road surfaces and driver interference.Previous studies have only dealt with the effects of unilateral attitude changes on the yaw,pitch,or roll on the flow field,and have not considered the feedback effect of the dynamic model,so there is an error in the calculation of the transient response.In addition,in actual driving,the passenger car is not only traveling at a straight line at a constant speed,such as straight acceleration,lane change overtaking,etc.Acceleration and lane change have a certain impact on the body posture,which in turn affects the changes in the surrounding flow field and stabilizes the vehicle.Sexual impact,so the impact of this scenario also needs to be considered.In order to solve the problems above,the main research contents are as follows:1.Reverse engineering technology is used to establish an aerodynamic model,and a 1:7 scale model of the passenger coach is used for steady-state wind tunnel tests.In order to study the accuracy of the turbulence model,a mesh generation size study was conducted to determine the best mesh generation strategy,and then a digital wind tunnel model was established.The wind tunnel test under different yaw angles was compared with the aerodynamic coefficients of the digital wind tunnel to verify the selected turbulence model accuracy.Parameters establish a multi-body dynamics model of the bus,and verify its reliability。2.Investigate the data exchange strategy of ADAMS/CAR and Star ccm+,and study the realization form of passenger coach attitude change;Study different boundary conditions of crosswind under steady-state crosswind,compare the difference between the dynamic boundary method and the fixed boundary method for calculating the transient response of passenger cars under straight driving conditions to determine the form of crosswind loading;and analyzes the impact of different attitudes on the passenger coach under a standard crosswind at a constant speed and straight line condition.3.Determine the natural wind type,and use the AMC two-way coupling method to study the influence of the speed,acceleration,and attitude change cycles on the stability of the crosswind of a passenger coach in straight driving,and compare the one-way coupling method to determine the necessity of two-way coupling;Research the common lane changing driving,establish an analysis model of crosswind encountered by the coach while changing lanes,and determine the necessity of the application of the two-way coupling method by analyzing the differences in the application of one-way and two-way coupling methods to the crosswind stability of the coach during the course of lane changes,compare the stability problems caused by different attitudes under this condition.In summary,this paper studies the influence of commonly used crosswind implementation forms on crosswind stability analysis,establishes a common highspeed driving aerodynamic stability analysis model,and applies the two-way coupled model for the first time to analyze vehicle acceleration,body attitude changes and changing lane in crosswind stability problem.These methods can be used as a tool to establish a high-speed driving stability evaluation system of vehicles under crosswind.