Research On Optimization Of Drag Reduction For Car Body Surface Group Based On Hard Point-skeleton Constraint

In recent years,with the further improvement of the national highway network and the rapid development of the automobile industry,the speed of the vehicle is greatly improved.For the high speed driving,the power consumption of the pneumatic resistance is proportional to the cube of the vehicle speed,which increases the energy crisis and the degree of environmental pollution.At present,due to other technical bottlenecks in reducing energy consumption,the aerodynamic drag reduction based on automobile aerodynamics is favored.At present most of the domestic automobile enterprises mainly used car drag reduction method has the following several kinds: the first kind of local drag reduction technology,which is in the car styling is determined,the local drag reduction technology is adopted,the body is not only the local structure parameters caused by the change of aerodynamic resistance change does not have clear,but mostly depend on the engineers the drag reduction repair experience;second overall drag reduction technology,the ideal form is too single,diversity does not conform to the style;third kinds of bionic drag reduction and drag reduction devices,bionic drag reduction design of the car body is lack of practicability,are still in the exploratory stage,while reducing aerodynamic attachment devices drag technology is mainly used to improve the aerodynamic performance of the local body,similar to the local drag.This paper to a benchmark vehicle as the research object,in body styling features based on the proposed hard point-skeleton constraint of the body surface drag reduction optimization method based on,through the construction of the target surface constraints,inheritance body frame of the original style,won the single best aerodynamic modeling using design of experimental technique.Based,integrated a lot of the body surface.At the same time the as gas dynamic drag reduction optimization object,get the best shape of body surface population.The specific research contents are as follows:1.In this paper,the methods of reducing drag at home and abroadare reviewed,the numerical calculation methods and design of experimental techniques are discussed,and the basic theory of the numerical simulation of the vehicle flow field is discussed.On the basis of this,the accuracy and efficiency of the numerical simulation of the flow field of the vehicle body are comprehensively considered,and the numerical simulation of the turbulent model,the meshing strategy and the algorithm are analyzed.Through numerical simulation and wind tunnel test,the reliability of the numerical calculation method of the car flow field is confirmed,which lays a foundation for the drag reduction optimization.At the same time,the bottleneck of detail drag reduction technology is discussed.2.Aiming at the defects in the current benchmark detail optimization method,the body surface hard-skeleton constraint based drag reduction optimization method.The aerodynamic drag effect of three large surface: the hood,front window,roof as drag reduction optimization research object,combined with body surface hard-skeleton Constraint Principle and design of experimental body drag reduction.First using optimal Latin hypercube method was used to extract the surface samples.Then by numerical calculation obtained aerodynamic drag coefficient response value;followed by the second order response surface model(RSM)approximation,establish the target surface with a variable factor and gas dynamic response relationship between drag coefficient;on this basis,with multi Island genetic algorithm(MIGA)on the surface of global optimization,were obtained three target surface of the best aerodynamic resistance modeling.3.In view of the defects of the detail optimization method of the benchmark vehicle,the optimization method of drag reduction of vehicle body surface is presented based on the hard point-skeleton constraint.Three surfaces which are influenced by aerodynamic resistance: the engine hood,front windshield and roof are used as drag reduction optimization research object,combined with the basic principle of hard point of the body surface and the design of experiment.First using optimal Latin hypercube method was used to extract the surface samples.Then by numerical calculation obtained aerodynamic drag coefficientresponse value;followed by the second order response surface model(RSM)approximation,establish the target surface with a variable factor and gas dynamic response relationship between drag coefficient;on this basis,with multi Island genetic algorithm(MIGA)on the surface of global optimization,were obtained three target surface of the best aerodynamic resistance modeling.