Research On Vehicle Body Surface Contamination Based On Wheel Splash

With the development of society and the change of people's way of travel,the vehicle has surpassed the property of means of transportation.When people are measuring the dynamic performance,fuel economy,and safety of a vehicle,they are also paying more attention to the vehicle's surface cleanliness,hoping that the bodywork is not easy to be contaminated by mud and dust.When the car is running on wet or muddy roads,the wheels spin or other vehicles will splash pollutants.These pollutants attach on the surface of the body not only undermine the overall appearance of the car,but also influence the driving safety and passenger comfort.Mud deposition on lateral rearview mirror or headlights will hinder the driver get good driving vision,attachment to brake light will affect vehicle's recognized identity and attachment to the door handle will make the passengers' hands or clothing easily soiled when they enter the vehicle.With the development of automotive electronic technology,more and more image equipment are installed on the bodywork,it is of vital significance to keep the camera clean for the maintenance of the function of the system as well as to meet the needs of the consumer.In addition,some trucks or vans' body are painted a giant picture for commercial advertising.Dust on the surface of the bodywork is not only unconducive to the image display,but also increase the washing frequency,thus increasing the operation cost of the automobile.Therefore,it is important to explore the mechanism of the formation of surface contamination and the measures to restrain the pollution on the surface of the body.A combination of theoretical analysis and numerical simulation is adopted to solve the two-phase flow field of air and discrete phase particles in the thesis,aiming to predict the process of pollution on the body surface on the basis of the appropriate assumptions of flow field and particles splashed by rotating wheels.The MIRA notchback sedan model is taken as the research object and a combination of an unsteady Realizable k-? turbulence model and discrete phase model(DPM)is utilized to predict the trajectory of particles by integrating over motion equation under Lagrange coordinate system,thus obtaining the concentration of particles on the surface of the body.This thesis explores the way of surface contamination,analyzes ways pollution particles enter the flow field and the splash models of wheels,sets proper injection source in numerical simulation,and investigates the initial conditions and boundary conditions of discrete phase model.According to different surface cleanliness requirements of different regions,side and rear surface are divided into several regions,the formation mechanism of pollution of side and rear-end surface is analyzed,and the dimensionless number Rc is used to evaluate the pollution degree of each region.According to the deposition process of the pollution particles on the surface of the body,countermeasures to control the pollution were put forward.The original model is respectively provided with wind resistance plate,wheel house shield,mudguard,side skirt and a rear spoiler device.The degree of improvement of the five modifications of the body surface pollution is analyzed and the influence of the installation attachment on the aerodynamic drag coefficient of the vehicle is discussed.Vehicle's surface cleanliness directly affects the overall appearance,comfort and driving vision.This thesis reveals the process of vehicle surface pollution and puts forward countermeasures to control the pollution from the aspect of aerodynamics,which provides theoretical guidance for reducing the pollution of the body surface,and has reference value to the development of bodywork pollution reduction accessories as well.