| Summary: | 碩士 === 國立屏東科技大學 === 車輛工程系所 === 99 === This study uses the moving grids technique of computational fluid dynamics methods to simulate the variations of fluid field and aerodynamics analysis for a passenger car driving on the road under different crosswind conditions. At the same time, the aerodynamics character will be also investigated when a passenger car with the installation of aerodynamic accessories.
Simulation results show that the drag coefficient (Cd), lift coefficient (Cl), yawing moment coefficient (Cym) and rolling moment coefficient (Crm) could be decreased for the passenger cars with/without aerodynamic accessories when the passenger car speed increases. Meanwhile, the abovementioned coefficients could increase with the increasing crosswind velocity. Moreover, the aerodynamic accessories with different length installed under the car could influence the aerodaynamice chatacter. When the aerodynamic accessories length is very close to the ground, the rolling moment coefficient (Crm) tends to decrease, but the drag coefficient (Cd), lift coefficient (Cl), yawing moment coefficient (Cym) increas at lower crosswind angle. However, the lift coefficient (Cl) will also tend to decrease at higher crosswind angle. Besides, a passenger car installed the front spoiler with holes could effectively decrease the aerodynamics coefficients. Furthermore, a car installed rear spoiler could sensibly drop the lift coefficient that is helpful to give the down force for the car to promote the driving stability, even though the other aerodynamics coefficients could still increase. Finally, the vortex flow field around the car body can be clearly seen with the flow visualization analysis that will contribute to aerodynamic analysis.
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