Study On The Relationship Between The Front And Side Panels And The Resistance Of A Commercial Vehicle

Affected by the economic crisis, the world's energy problem has been highlighted. It is important to reduce the fuel consumption of high speed vehicles by reducing aerodynamic drag. Heavy commercial vehicles play an important role in today's logistics. With the development of highway, the speed of heavy commercial vehicle is getting higher and higher, and the aerodynamic drag and the vehicle speed is proportional to the square, so the aerodynamic drag of heavy commercial vehicle is also increased. Therefore, it can save a lot of energy by reducing the aerodynamic resistance of heavy commercial vehicles. Because of the functional requirements of goods transportation, the shape of heavy commercial vehicles can not be changed freely as that of passenger cars, but the aerodynamic drag can be reduced with the aerodynamic accessories and the local changes of shape. At present, the heavy commercial vehicles with the aerodynamic accessories to reduce the aerodynamic drag have been investigated more and more in China. However, most of the researches don't refer to the optimization of local shape to reduce aerodynamic drag.Early heavy commercial vehicle is only a tool for the transportation of goods. The styling of heavy commercial vehicle doesn't play an important role in design. However, with the development of commercial vehicles, the styling becomes a key stage in the whole design processes. In the design of heavy commercial vehicles as a result of the specificity of the functional requirements, it focuses on the laws of not only the aesthetics but also the aerodynamics. In recent years, a new design trend emerges in the front and side panels of heavy commercial vehicles. This is different from the original straight shape of the same part. The curved front and side panels are found in the new generation of domestic and foreign brands of heavy commercial vehicles. The curved front and side panels have also been adopted in this paper for the purpose of distinguishing the function relationship between the aesthetics and the aerodynamic drag.This paper has investigated the relationship between the styling of the front and side panels of a heavy commercial vehicle and its aerodynamic drag with the numerical simulation. The six 3D models with the different front and side panels have been created based on the original vehicle by using Alias AutoStudio. Through the simulations of the six models, the shapes of the front and side panels and their aerodynamic drags have been studied.In this paper, the original model has been simplified such as the surfaces of windows, rearview mirrors, handles, the transit surface between carriage and cab, the linking accessories and wheels, suspension. In the six models, one is the original model, and five are models with the changed front and side panels.Because of the styling variety of front panels, which represent the brands of manufacturers, three kinds of changes for the front panels have been used for the numerical simulations: the straight front panel without dent, the curved front panel with small dent, and the curved front panel with big dent. Limited by the width of heavy commercial vehicle cab and its inside space, big dented side panel is not highly recommended. Therefore, two kinds of changes have been used in the side panel design: straight side panel without dent and curved side panel with small dent. Because heavy commercial vehicle is symmetric in shape, and the uniform flow comes from the entrance, a half model is used in order to reduce the number of meshes and save the time. The calculating ranges are set up as follows: nine times of vehicle length, five times of vehicle width, five times of vehicle height, respectively. In this paper, the tetrahedral meshes are used. The precision of meshes can improve the convergence of CFD software and precision of calculation. Therefore, the quality of meshes is crucial to the final simulation result. Finally, FLUENT software is applied to do the numerical simulation with the k ?εhigh Reynolds turbulence model.After the calculation, the aerodynamic drag coefficient, pressure distribution chart and velocity flow field chart of the six different front and side panel models are shown in the paper. The aerodynamic features depend on the velocity and pressure of airflow passing by the vehicles. Aerodynamic drag is related to the pressure distribution and velocity flow field. The conclusions are: Heavy commercial vehicles with curved front panels have smaller aerodynamic drag coefficients than those with straight front panels. Heavy commercial vehicles with curved side panels have smaller aerodynamic drag coefficients than those with straight side panels. Both curved front panel and curved side panel can lower the aerodynamic drag coefficients.According to the above analysis result of relationship between front and side panel models and aerodynamic drags, the original model has been improved in both of aesthetics and aerodynamics, a modified prototype is given. The total size of the vehicle is kept, the front and side panel are changed. Based on the research, the curved front and side panels are adopted to lower the aerodynamic drag. Because heavy truck is used for goods transportation, it should bring people the feeling of might and strength. In the large curved surface, some ridge lines are added to make the whole vehicle muscular and flexible, rounded but powerful, which also represent the moderation in Chinese culture. The design of grille and light is also important, the novel styling of them has also presented.