| Summary: | 碩士 === 國立屏東科技大學 === 車輛工程系所 === 96 === This study constructed the structures of the tunnel and vehicles using a commercial software, Gambit version 2.2.30. Then, the numerical analysis was performed on the flow field around traveling vehicles using Fluent version 6.2.16. In this case, the moving grid (dynamic mesh) available in Fluent was activated through C programming. In the beginning, the situations of a vehicle traveling in an open space and a tunnel were compared. After that, the flow fields corresponding to vehicle meeting and passing were investigated. The goal of analysis was focused the aerodynamics characteristics when two vehicles of different speeds were meeting or overtaking. The current results show: (1) Unlike traveling in the open space, the vehicle traveling in a tunnel experiences a non-symmetric pressure distribution on its surface. As a result, the vehicle is pushed to the tunnel wall. (2) While driving at a high speed in the tunnel, the vehicle is affected by the additional side force and yaw moment the tunnel wall produces making it more difficult to maneuver. (3) When two vehicles meet in a tunnel, the instantaneous change in pressure ratio increases with the difference in the vehicle speeds. (4) When a fast vehicle is passing a slow vehicle in a tunnel, the instantaneous change in maximum pressure acting on the slow vehicle increases with the difference in the vehicle speeds. In contrast, the instantaneous change in maximum pressure acting on the fast vehicle increases when the difference in the vehicle speeds reduces. (5) For vehicles meeting or passing inside the tunnel, aerodynamic forces on the vehicles will produce yaw moment, which jeopardizes the vehicle safety, as well as pitch and roll moments, which influence the vehicle comfortness.
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