自動車模型の形状とディフューザー角の変化に対する空力的効果

抄録

Aerodynamic characteristics have great influences on fuel economy and environmental problems nowadays. The aim of this research is to analyze the influence of configurations and diffusers of road vehicles on aerodynamic characteristics. As configuration parameters, the rear window angle and the side window angle are adopted, and together with the diffuser angle, totally 126 patterns of configurations changing from box type through fastback to notchback types are investigated by wind-tunnel experiments using the moving belt. As results, by the rear diffuser, the lift is decreased with the minimum at diffuser angle 15°, but overall the drag is increased except for diffuser angle 5°~10° with the minimum at diffuser angle 5°. The drag is greatly reduced when combined with side angles 30° and diffuser angle 5°. The well-known tendency that the drag increases steeply at rear angle from 20° to 35° appears with side angles 0° and 15° for most diffusers, while this tendency does not with side angle 30°. Visualization by the five-hole Pitot tube suggests that the drag reduction can be obtained by restraining longitudinal vortices.