Aerodynamic Drag Reduction Of MIRA Model Based On Bionic Characteristics

Environmental pollution is becoming more and more serious,frequent extreme weather has seriously affected people’s life.In order to improve environmental quality and avoid the recurrence of extreme weather,China has made carbon neutral targets.Reducing vehicle fuel consumption is one of the effective ways to reduce carbon emissions,and driving resistance is an important factor affecting fuel consumption,so reducing vehicle driving resistance has become an effective way to protect the environment,which will also become the main direction of future automotive industry research and development.Bionic non-smooth drag reduction technology stands out from many drag reduction technologies by virtue of its advantages of low cost,small implementation difficulty and remarkable drag reduction effect,and is widely used in aerospace,Marine transportation,medical equipment,sports competitions and other fields.Therefore,the application of bionic non-smooth surface in automobiles can not only reduce energy consumption,effectively protect the environment,but also provide effective technical guidance for overcoming the bottleneck of current drag reduction technology.This paper aims to explore the application prospect of biomimetic non-smooth surface.Based on drag reduction theory,combined with practical application,five different forms of biomimetic non-smooth surface are determined,and the MIRA model simulation research is carried out on the non-smooth state,in order to determine the best drag reduction arrangement position and shape of the non-smooth element,and finally obtain good drag reduction effect.Then,according to the analysis of the height,width and layout spacing of the non-smooth surface,the optimization algorithm is used to optimize the drag reduction scheme.In the first part,the paper introduces the method of CFD numerical simulation(Computational Fluid Dynamics),and put forward a kind of high quality of the grid simulation program,after setting the corresponding boundary conditions.The error between the simulation value obtained by simulation experiment and the experimental value of wind tunnel experiment is within 5%,which meets the error requirement of engineering application,verifies the correctness of this grid scheme,and ensures the consistency and accuracy of subsequent experiments.In the second part,25 groups of sample points are selected by orthogonal experiment method and simulated.Through analyzing the data obtained by simulation,the foundation is laid for the subsequent optimization work.Orthogonal test sampling is mainly carried out on five factors of bionic non-smooth surface layout position,shape,height,width and distance,25 sample points are selected,and simulation is carried out.In the data analysis after simulation,within the selected range,the layout position,shape and value range of three structural parameters of the non-smooth element with the best drag reduction effect are obtained,which lays a foundation for the subsequent optimization.In the third part,the influence degree of the bionic non-smooth element on the automobile external field is discussed,including how the bionic non-smooth element affects the differential pressure resistance and friction resistance of the automobile.In addition,the non-smooth surface model of each shape is analyzed in detail and the reason for the reduction of resistance is explained.The influence of different types of non-smooth elements on turbulence state,vorticity,vortex structure and flow field around non-smooth elements is emphatically discussed,including the drag reduction principle of each type of non-smooth elements.In the fourth part,the data obtained from the data analysis in the second part is optimized,and the drag reduction performance of the optimization model is analyzed.It mainly analyzes the simulation results of sample points selected by orthogonal experiment,and determines the layout position,shape and value range of the structural parameters of the non-smooth element with the best drag reduction rate within the selected range.Then,it samples again within the value range of the three structural parameters for simulation.The Pointer optimization algorithm was used in Isight optimization software for global optimization of the simulation results,and the parameter combination of the optimal solution was found,the drag reduction rate was increased to 4.82%,and the drag reduction performance of the optimization model was analyzed.In this paper,the layout position and shape of the non-smooth surface with the best drag reduction effect were obtained by orthogonal test method,and the principle of the resistance change caused by it was deeply analyzed.Finally,a more effective drag reduction scheme was proposed by optimizing Latin Hypercube sampling and optimization algorithm in a small range,and the drag reduction rate was increased to4.82%.It provides a reliable theoretical basis for the engineering application of bionic non-smooth element in automobile.