Research On Characteristics Of Aerodynamics For A Window-opening Truck

With the rapid development of economy in China,people's life and material need is increasingly.Which shows in the expansion of cities and the connection between urban and rural,and also the development of logistics industry.And along with the constantly build and use of highway in our country,the total mileage increasing year by year,there comes to an unprecedented opportunity and great prospects for development to the truck transportation.The truck transportation promoted our economic development,meanwhile it also brought us energy issues which makes people take more attention on the theme of energy saving and emission reduction.So it is particularly an important thing to reduce the aerodynamic drag coefficient of truck with heavy weight,large frontal area and need to long-distance transport.While driving a truck with lower speed in a long distance and time,many drivers are more likely to open the window.One of the reasons is to let the fresh air into the cockpit to have a good driving condition.The other reason is to turn down the air condition to reduce the load on the engine,keep motivation performance of vehicle.Some scholars have researched that there would be a high drag coefficient on sedan when keep the window open under no yaw angle condition,one of the reasons is a sedan have more window-opening plan than truck.Therefore the aerodynamic characteristics of driving truck with opening windows was studied in this paper.In study of the thesis about drag reduction,research on aerodynamic characteristics of the trucks under the cross wind and the results of the flow field under the opening-window situation,there comes to the basic ideas of this study.The study is mainly divided into four parts.The contents are as follows:The first part is mainly the mechanism study of cockpit of cab over truck,analyze the changes in the flow field under the opening-window and cross wind in able to explore the reasons of the changes of aerodynamic characteristics.According to the analysis can be seen that when the yaw Angle increases from 0° to 15° the aerodynamic drag under opening-window driving is less than the closing-window driving,it is because when the window is opening,a part of the separated flow in the windward side keep moving,the other part flow through the cockpit and converge into the leeward side flow,and this have a great influence on the original flow,reduced the wake region and the pressure drag,then we can find a smaller aerodynamic drag coefficient.Based on the study of the simplified model,the second part of this paper will have a study on numerical simulation of complex model of the truck.The second part in this paper is to make further analysis of the flow field by using numerical simulation method.Comparing with the pressure distribution,velocity vector changes and total pressure can be seen when the truck under 15° yaw angle and opening-window driving,the rear inside of the cockpit appears a negative pressure zone,and the flow from the windward side into the cockpit and converge into the leeward side flow have moderated the separate of the flow on the leeward side and let the truck have a smaller aerodynamic drag coefficient.The third part is the wind tunnel test to verify the simulation.Using six component balance testing the aerodynamic drag coefficient of the truck with 0° and 15° yaw angle and different opening of the window to find the variations of aerodynamic characteristics.From the analysis can be seen,when the yaw angle reached 15°,the aerodynamic drag under opening-window driving is less than the closing-window driving,which is agree with the mechanism study and the study of complex model in the second part.Above all,the aerodynamic characteristics of driving truck with opening-window and the influence of the flow field and aerodynamic drag coefficient was studied in this paper,and reach a conclusion.When the yaw angle is 0°,the aerodynamic drag under opening-window driving is larger than the closing-window driving,when the yaw angle reach 15°,the aerodynamic drag under opening-window driving is less than the closing-window driving.