Intelligent Aerodynamic Research On Drag Reduction Of A Certain SUV

The purposes of this research are to break through the challenges of the vehicle OEMs to reduce the wind resistance on the vehicle;to quickly find the vehicle body sensitive area that causes high wind resistance;to perform body surface modeling more efficiently and intelligently through optimization;and eventually,systematically and comprehensively to analyze the key factors affecting the drag coefficient,to achieve the aerodynamic performance targets by researching the certain SUV.The main contents of this study are as follows:First of all,based on the characteristics of the car model,the vehicle body is to be divided into several local regions.After that the contribution theory is applied to evaluate the wind drag contribution separately in these local regions and the total vehicle wind drag is obtained from the summation of drag from all local regions.The drag sensitivity analysis theory is applied,and the percentage of contributing factors of all input variables to the drag coefficient index are obtained.Through the body surface sensitivity analysis,the main areas affecting the vehicle’s wind resistance are identified such that the specific local areas or components that have a greater impact on the vehicle’s wind resistance can be accurately located.From the shape characteristics of the critical area or component,the influence factors of wind resistance are analyzed by using grid morphing technology to realize the change of the sensitivity of the grid and to provide an optimization direction for future improvements.The construction of the rapid modeling for calculating drag coefficient is carried out from both results of influence factor and sensitivity analyses.The rapid modeling is using a mathematical model to solve drag coefficient from a single component multivariate problem to a multi-interval multivariable problem,that is,using a mathematical formula to quickly calculate and complete the rapid optimization of drag coefficient.The method provides a theoretical basis for the later use of big data and cloud computing to intelligently compare and calculate the drag coefficient.It is suitable for fast optimizing the wind resistance for the same vehicle model,and at the same time,it verifies the feasibility of analyzing the whole vehicle from the contribution rate of the sub-component or sub-region levels,thus provides a solid foundation for the intelligent realization of the wind resistance reduction.The intelligent aerodynamic optimization uses sensitivity as a feedback mechanism to obtain the adaptability to the drag coefficient target,realize the automatic grid generation to judge the size and moving direction of the grid and find the target adaptively.Re-program the total group sequence formed by sensitive factors,and using the optimal design to improve the judgment of the corresponding output results.Thus,the simulation accuracy is improved,and the misjudgment of the whole solution process by the local interval maximum value can be avoided.The fuzzy control of the optimized variable interval is realized by controlling the specific interval of the vehicle styling,and the entire calculation process is realized by combing the experimental design method with the sensitivity analysis method and the mesh morphing software.The sensitivity of the drag coefficient influencing factors is analyzed in detail,the optimization direction and mesh morphing amount are confirmed,and the final optimized vehicle body shape is perfectly presented.The continuity of the calculation process is ensured.From beginning to end,it is fully automatic in the whole calculation process,the whole process of the high-speed calculation platform is realized,the simulation calculation time is greatly improved,and the intelligent development of the vehicle aerodynamics is finally realized.It can improve the calculation speed by up to 100 times,and at the same time,since the sensitivity is used as a feedback mechanism,the integration of various algorithms has greatly improved the calculation accuracy and optimization effect.A theoretical road model is constructed to generates a typical sinusoidal road spectrum for simulating the real road conditions.The accuracy of vehicle drag coefficient obtained on the sinusoidal bumpy road can be compared with those of virtual and real wind tunnel test on flat road,this paved the way for the aerodynamic testing and validation of the SUV in the BMW wind tunnel.Finally,through the wind tunnel test,the mechanism of the vehicle aerodynamics and the flow characteristics of the air flow on the body surface are realized.The wind tunnel test method verifies the feasibility of using the intelligent optimization method for drag reduction.This drag reduction research subject involves many technique fields such as fluid dynamics,optimization algorithm and computer programming,which proves the importance of Multi-Discipline Optimization(MDO).The processes and methods developed from of this work can be applied to other vehicle development areas for the OEMs to reduce the development cost and shorten the development cycles.