Numerical Simulation Of Viscous Flow Field Around The Similar Vehicle With Moving Boundary

With the rapid development of economy and industry of our country, undoubtedly more and more people would like to buy cars, which leads to the development the auto industry and freeway. Therefore, it is very important to study the flow field around vehicles.A user-defined function, or UDF, is dynamically loaded with the FLUENT solver to fit particular modeling needs. Numerical calculations are performed by the standard K-εmodel and dynamic mesh capability on vehicles being in crosswinds, running in tunnel, passing by and overtaking each other. Their aerodynamic characteristics are analyzed and some different turbulence properties are obtained.For vehicles in crosswinds, with the increase of crosswind angle, static pressure and side force of the vehicle windward increase and reach maximums at crosswind of 90 degree, and then decrease when the angle of crosswind continues increasing. For vehicle passing through tunnels with single and double driveway, the wind flowfield and pressure on the vehicle are analyzed. The change becomes large when the vehicle entering into tunnel and is steady during its moving in tunnel, but the change becomes small when the vehicle going out. But flowfield distribution is symmetrical when the vehicle running on the single driveway. For vehicles passing by and overtaking each other, the influence of the vehicles velocity and the distance between vehicles on flowfield is studied. For vehicles overtaking, with the increase of the other vehicle speed, pressure and side force of the overtaken vehicle also increase, especially for side force, its change is obvious, but with the increase of distance, the result is contrary. When the overtaken vehicle lies in front of the other, the yawing tendency is strengthened. And when vehicles stand at parity, the roll tendency is also strengthened. For vehicles passing by each other, with the increase of the vehicle velocity and decrease of the distance, vehicle interaction increases. But the interaction on each other is the same if they have the same velocity. Pressure has no distinct changes, but the change of side force is obvious. With the increase of vehicle velocity, the yawing tendency is intensified, and the roll tendency is also intensified during vehicles standing at parity.