Research And Optimization Of Aerodynamic Drag Reduction Characteristics Of Non-smooth Surfaces On Different Vehicle Models

With the accelerated construction and popularization of the expressway system,the average speed of automobiles is getting higher and higher,which leads to more pronounced effects of aerodynamic drag and the increase of automobile energy consumption is attracting more and more attention.Related research shows that the aerodynamic drag of a vehicle is approximately proportional to the square of its speed,and every 10% reduction in aerodynamic drag can save about 4% of fuel.Thus,it can be seen that reducing aerodynamic drag can significantly save fuel consumption and improve fuel economy,and is an important measure to achieve energy conservation and emission reduction of automobiles.With the continuous deepening of research on automotive aerodynamics,the traditional aerodynamic drag reduction method has developed relatively mature and has encountered technical bottleneck,so it is urgent to find some new methods and ideas of aerodynamic drag reduction.Studies have found that the non-smooth surface structure of many organisms in nature tends to have remarkable drag reduction effect,inspired by this,this paper introduces the bionic non-smooth structure into the vehicle body for research,in order to reduce the aerodynamic drag of the vehicle.In this paper,the CFD numerical simulation method is used and verified by the wind tunnel test.The pit type non-smooth surface is selected as the research object,which is arranged on the top,tail and bottom of different models of Ahmed passenger car model,GTS truck model and stepped back MIRA sedan model respectively,and the influence of the non-smooth surface location on aerodynamic drag reduction effect of different vehicle models is studied by numerical simulation.Then by comparing the key flow field parameters such as wake structure,velocity,wall shear stress,pressure,and turbulent kinetic energy of smooth and tail non-smooth models,the influence of non-smooth surface on the outflow field of different vehicle models is further analyzed,and based on the comparison results of the flow field parameters,the drag reduction mechanism of the tail non-smooth surface is elaborated briefly from the perspective of the drag reduction mechanism of the pressure difference resistance and the friction resistance.After that,the optimization method based on the approximate model is used to optimize the non-smooth surface so that the best combination of parameters can be obtained to make the drag reduction effect optimal.The optimization results show that for the Ahmed model and the GTS model,the maximum drag reduction rate of theoptimized non-smooth surface can reach 4.69% and 5.18% respectively.Finally,the typical external flow field parameters before and after optimization of the two non-smooth models,such as speed,pressure and turbulent kinetic energy are compared and analyzed to further visually demonstrated the feasibility of the optimization method and the reliability of the optimization results.This paper discusses the influence of the pit type non-smooth structure location on aerodynamic drag reduction effect of different vehicle models,and briefly describes the drag reduction mechanism of the non-smooth structure.Then the main geometric dimensions of the non-smooth structure are optimized by the multi-island genetic algorithm,and the more significant optimization results are obtained.It provides method reference and theoretical guidance for the parameter design and engineering application of the non-smooth surfaces.At the same time,it also provides a new idea for the aerodynamic drag reduction research of different models of passenger cars,trucks and sedans.