Research On Aerodynamic Characteristics Analysis And Styling Optimization Of Light Bus

With the development of expressway and the increasing of the road vehicle speed, customers require more stable, safer and more comfortable products than ever. Undoubtedly, automobile aerodynamic characteristics have important effects on the stability, safety and even comfortable cabin environment. Most research on automobile aerodynamics focuse on saloon car and truck, and the aerodynamic characteristics research on light bus is limited. Due to fair price, spacious interspace and better adaptability, light bus has prodigious appropriation ratio in vehicle market, especially, huge potential demand in town and country. So the research on aerodynamic characteristics analysis and styling optimization about light bus is very important and meaningful.Firstly, the method of numerical simulation adopted is validated through wind tunnel experiment. Numerical simulation on ahmed model is carried out with the application of RNG k ?εturbulence model and mix grid of tetrahedron, three-prism and hexahedral. The reason for selecting Ahmed model is that the ahmed shape resembles the shape of light bus. The results of experiments and numerical simulation including aerodynamic drag and the features of external flow field are contrasted, which verify the validity of simulation scheme and correctness of results. Then the analysis of grid no-relation is made about light bus with the validated method. Through calculation, the best number applied to numerical simulation of light bus is confirmed. It ensures the precision and saves the time. On the base of this, the numerical simulation of light bus is carried out. The different distribution of speed and pressure on symmetry plane and car body are exported and the aerodynamic characteristic of external flow field is particularly analyzed. At the same time, wind tunnel experiment is made on simplified model of light bus, which include the experiments of flow display, the results of experiments are studied. The results of experiments and numerical simulation are contrasted and the characteristics of external flow field around light bus are studied, which verify the validity of simulation scheme and correctness of results.The research on remodelling and styling optimization is carried out after characteristic of external flow field is analyzed on the base of the results of wind tunnel experiment and numerical simulation. The variety rules of aerodynamic characteristic on five cases are studied(1) The angle of rear wind window: the numerical simulation is carried out on the case of different angle of 0, 2, 4, 6, 8 and 10 degree, and the aerodynamic drag, lift and the variety rules of aerodynamic characteristics are achieved. The reason of variety of aerodynamics characteristic is studied according to the drawings of pressure external flow field around light bus. The change of rear wind window angle causes the change of trail flow field structure. When the angle is small, the aerodynamic drag decreases with the increasing of angle. When the angle is six degree, the aerodynamic drag is the least. Then the drag increases with the increasing of angle. The aerodynamic lift is the least when the angle is eight degree. When the angle is less than eight degree, lift decreases with the increasing of angle. When the angle is more than eight degree, lift increases with the increasing of angle.(2) The front transition radius: the numerical simulation is made on the case of different radius of 0, 10, 15, 20, 25 and 30mm, and the aerodynamics drag, lift and the variety rules of aerodynamics characteristic are achieved. The aerodynamic drag and lift will decrease much even if the radius is very small. Then with the increasing of transition radius, drag and lift decrease continuously. When the radius is twenty millimeters, the drag and lift are the least. The drag and lift will not change much when the radius is more than twenty millimeters. There is an optimal radius for light bus. The drawings of pressure on the body and energy of turbulence on the section of z are studied; the reason of aerodynamic characteristic variety is analyzed. When the radius is twenty millimeters, the airflow can flow smoothly through the head of light bus, and the energy of turbulence is the least, so the aerodynamic drag is the least. Then the energy of turbulence will not change even if the radius increases.(3) The angle of underbody diffuser: the numerical simulation is carried out on the case of different angle of 0, 2, 4, 6, 8 and 10 degree, and the aerodynamics drag, lift and the variety rules of aerodynamics characteristic are achieved. When the angle is four degree, the aerodynamic drag is the least. The drag decreases with the increasing of angle when the angle is less than four degree, and the drag increases with the increasing of angle when the angle is more than four degree. The aerodynamic lift decreases with the increasing of angle. According to the feature of flow field underbody and trail, the reason of aerodynamic characteristic variety is analyzed. With the increasing of angle, the flow speed underbody increases, and the static pressure decreases, the difference of pressure becomes smaller than before, so the aerodynamic lift decreases. Then the induce drag aroused by lift decreases. But if the angle of underbody diffuser is too big, it makes the pollution of tail worse, and aerodynamic drag increases because of the worsening of trail flow field.(4) The angle of back: the numerical simulation is made on the case of different angle of 0, 2, 4, 6 and 8 degree, and the aerodynamic drag, lift and the variety rules of aerodynamics characteristic are achieved. The aerodynamic drag and lift decrease with the increasing of angle. According to the theory of longitudinal obliquity, the analysis is made. The negative longitudinal obliquity of light bus increases with the increasing of rear angle, then the aerodynamic drag and lift decrease.(5) On the base of part remodel, different combinations including underbody diffuser angle and the angle of rear wind window and back are studied. On the case of underbody diffuser angle and rear wind window angle, when the underbody diffuser angle is four degree and the angle of rear wind window is six degree, the aerodynamic drag is the least, and when the underbody diffuser angle is four degree and the angle of rear wind window is two degree, the aerodynamic lift is the least. On the case of underbody diffuser angle and the angle of back, when the underbody diffuser angle is six degree and the angle of back is eight degree, the aerodynamic drag is the least, and when the underbody diffuser angle is four degree and the angle of back is two degree, the aerodynamic lift is the least. For two instances, the drag is the least and the lift is less when the underbody diffuser angle is six degree and the angle of back is eight degree. According to the results of different combinations, the aerodynamic drag and lift increase possibly. So the angle combination of tail should be validated through calculation and experiment.Then the variety rules obtained through simulation are contrasted with former results from the experiments, which verify the correctness of results through numerical simulation.Finally, on the base of the research of the part remodel and styling optimization, the aerodynamic characteristics of light bus are studied. For new styling, the external flow field is simulated. The aerodynamic resistance coefficient is calculated and compared with primary styling, validate the correctness of the project of styling optimization. The aerodynamic characteristic is analyzed particulary. That provides the theoretical foundation for the aerodynamic optimization.After the research on aerodynamics characteristic of light bus, the part remodel and styling optimization were studied. The rules of aerodynamics coefficient variety are obtained. On the base of this, the different angle combination is adopted and the automobile body styling of lower aerodynamics drag is found out. The styling optimization of light bus is studied systematically and scientifically. The research results offer the theoretical foundation for styling optimization of light bus, which are very helpful to decrease aerodynamics drag,optimize styling and empolder new vehicle styling.