High Precision Calculation And Optimization Of Aotomobile Aerodynamic Forces Baesd On CFD Method

Calculation of automobile aerodynamic forces is one of the important applicationsof computational fluid dynamics on automobile aerodynamics, and there is certainerror between the calculation results and wind tunnel experiment, thus improvingaerodynamic calculation precision has great significance. Optimization of automobileaerodynamic drag and lift is the key to achieve excellent aerodynamics design.Butthere are conflict issues between programs in the commonly used local optimal dragreduction method, while research on aerodynamic lift optimization is limited. Inaddition, aerodynamic optimization of automobile forces rely greatly on experience,resulting in certain blindness. Based on the CFD numerical simulation method, thispaper elaborated high precision calculation method of car aerodynamic forces,discussed the application of local iterative optimization method in automobileaerodynamic drag reduction, studied the aerodynamic lift of a sports car, and combinedthe approximate model and numerical simulation with CFD simulation to discuss itsapplication on the optimization of automobile aerodynamic attachments.The research background and significance of the paper and automobileaerodynamics research methods are introduced, and domestic and foreign automobileaerodynamics research history and current situation are summed up, focusing onapplication development of the CFD numerical simulation method in automobileaerodynamic calculation.The contents of automobile aerodynamics characteristics are introduced, and thestructure of aerodynamic drag and the mechanism of aerodynamic lift are analyzed indetail. Actual automobiles are taken as examples to discuss optimization methods ofaerodynamic drag and aerodynamic lift respectively.For the aim of aerodynamic force error reduction between car CFD numericalsimulation and wind tunnel test results and improvement of the simulation precision,automobile aerodynamic force high precision calculation method are discussed andstudied from CAD model modification, grid mapping and evaluation, turbulencemodel selection, boundary conditions and parameter setting angles. Simulation resultsof Zhongqi car,MIRA standard model and sports cao model show that calculation results obtained by high precision aerodynamic method has smaller error with windtunnel test results compared to former calculation method.In order to solve the problem of program contradiction in vehicle aerodynamicdrag optimization, a SUV is taken as an example and the thought of iteration isintroduced into local optimization method to discuss the application of local iterationoptimization method in aerodynamic drag CFD optimization. The optimization resultshows that the aerodynamic drag reduces by9.24%after four times of local iterationaloptimization.According to the handling stability and security problems due to car floatingcaused by aerodynamic lift when travelling at high speed, a sports car model is takenas an example to study the aerodynamic lift attachments’ effects on the aerodynamiclift using CFD simulation method.The influence of shape variation of negative liftwing on aerodynamic lift is researched and a new kind of wing type aerodynamicattachment “negative lift fin” is introduced and used to apply for invention patent.Finally, to solve the problem of dependence on experience and certain blindnessin aerodynamic drag optimization, mathematical method is introduced into theoptimization of aerodynamic drag.Based on the Kriging agent model, Zhongqiautomobile is taken as an example, and CFD simulation method and approximatesurrogate model are combined to optimize the height, angle and position parameters ofthe front tyres’ air dam skitrs applying the multi-island genetic algorithm.