Research On Global Optimization Design Of Aerodynamic Drag Reduction For SUV

With the rapid development of the automobile industry,the number of motor vehicles in the country is increasing,and the consequent energy shortage and environmental protection problems have become increasingly serious.The vehicle will experience a lot of aerodynamic resistance when driving at high speed,and a large part of the fuel is used to overcome aerodynamic resistance.Therefore,the ideal aerodynamic shape of the car will help the car have a lower aerodynamic drag coefficient,thereby improving its fuel economy and utilization.The traditional aerodynamic optimization of car shape is a partial iterative and cumulative process,which relies on the experience of engineers,consumes a lot of manpower and material resources and is full of blindness,resulting in the optimization result falling into the local optimal solution.In order to make the aerodynamic resistance of the whole vehicle reach a lower level in the automobile modeling stage,this paper adopts the research ideas of global deformation and global optimization to carry out global optimization design.This paper takes a domestic SUV as the research object.Through the wind tunnel test of the SUV 1:3 model,the results are compared with the numerical simulation results.The error between the simulation and the test results is minimum 1.49%,which meets the requirements,thereby verifying the accuracy of the simulation.Then determine the simulation settings such as the simulation strategy,and lay the foundation of numerical simulation for the subsequent optimization of the aerodynamic drag reduction of the whole vehicle.The aerodynamic analysis of the external flow field of the SUV is carried out on the basic model of the SUV.The aerodynamic characteristics of the key parts of the car body are studied in combination with the pressure cloud diagram and the turbulent flow energy diagram.The deformation of the modeling surface is parameterized.A total of 12 modeling parameters are set and the deformation range is set.To reduce the aerodynamic drag coefficient Cd as the research goal,the STAR-CCM+ simulation software and the Isight optimization software are combined to establish a complete global optimization process.The Latin Hypercube Design of Experiments(DOE)is used to generate 100 sets of samples.STAR-CCM+ is based on the recorded data.The macro file realizes automatic mesh deformation and performs simulation calculation.The Kriging model is selected through Isight software to establish an approximate model to fit the data of known sample points,and the global optimization algorithm is combined to perform global optimization.According to DOE,the influence degree of each design variable on the aerodynamic drag coefficient is analyzed,and the fitting function relationship between each parameter and the aerodynamic drag coefficient is analyzed.The global optimal solution scheme is simulated and analyzed,and the aerodynamic characteristics of the optimized external flow field are compared and analyzed through the pressure cloud graph and the turbulent energy cloud graph,and the drag reduction mechanism is studied.According to the research idea of global optimization and local analysis,the rear parameters of the car body and the parameters of the front car body are respectively analyzed.Through the correlation between the two variables and the three-dimensional fitting surface with the aerodynamic drag coefficient,the interaction effect between the parameters is studied.A comparative study of the local flow field was carried out.During this process,it was found that there are obvious interaction effects between the design parameters and have a greater impact on the aerodynamic drag coefficient.In the end,the global optimal solution reduced the aerodynamic drag coefficient by 31 counts,and the drag reduction effect reached 8.05%,which achieved a significant optimization effect.The global optimization research not only saves a lot of time,but also has done sufficient research on the interaction effects between parameters,and made more useful explorations for the research of SUV aerodynamic modeling optimization design.