Research On Aerodynamic Characteristic Of High Speed Bus

Nowadays, as the technologies of bus develop and the level of manufacture improves, the aerodynamic characteristic of buses are drew attention more and more. The forces and moments which bus experiences influence the fuel economy and steer stability. The researches of cutting down the drag are more and more important along with the crisis of energy becoming more severity. Meanwhile, the aerodynamics when the bus runs in some specific circumstances will engender strong influence of the control and stability, even make traffic accident.Methods mainly adopted in this text include:theory analysis, numerical simulation and experiment, among them theory analysis plays a guidance and supplement role for the calculation and experiment. Meanwhile the results of experiment validate correctness of simulation. Based on the former results the effect and mechanism between the local characters of bus and aerodynamic drag is researched. It also quests the infections between the size of these local characters and aerodynamic characteristic around the bus. The results can provide theory basis for reducing drag. From the control and safety point of view, when the single bus travels under the ventilator, the influence of the high speed airflow from the jet-flow ventilator on the traffic safety is studied first. Then, aerodynamic characteristics of two parallel buses travel under the ventilator are also researched.Last, analyzed the flow field of overtaking buses and compared aerodynamic forces in different travel cases, the aerodynamic characteristics of overtaking are supplied.Research shows that the bigger radii of front side pillar and top pillar is, the lower drag performs on the bus. But, the aerodynamic drag changes strong with the radii of back pillar increased. Increased radii of the bottom pillar, slanted windshield and largen cross section curvature could reduce aerodynamic drag. The space between ground and underpan of bus, position of air condition, and tilted tail don't have relationship with drag, but there is a best result for lower aerodynamic lift. Installed the vortex generator could make the vehicle experience negative lift. As the height of vortex generator is increased the drag becomes down. When the shapes of bus change, pressure-difference has a large variety, and shear drag keeps unalterable.When single car travels in windless tunnel, the aerodynamic drag and lift are larger than it runs on windless open road. And side force points to smaller gap between car and tunnel wall. During the bus travels in wind tunnel, the drag is lower than foregoing case when it doesn't interfere by the jet-flow ventilator. The drag changes quickly in front of fun outlet about 3-4 times of vehicle length. In this interzone the drag appears maximum, lift comes forth minimum and the side force surges fleetly. Aerodynamic characteristics of two parallel buses traveling in windy tunnel have the same trend with single bus does. Because of large blockage ratio, the changing scope of the force is drastic. The side force between buses is repulsive. As the left space of tunnel is smaller than the right, the peak value of left bus is higher than that of right bus. The aerodynamic characteristic that the passed bus got changes drastically. The curve of side force is similar with the sinusoid. The side force of passing car has gently ruleless change.