Flow Visualization around Cambered Plates Using Hydrogen Bubbles

Abstract

This paper describes the flow around a cambered otterboard model by the method of flow visualiza-tion using hydrogen bubbles, and discusses the relationship between the characteristics of flow and the stall of the otterboard. Two cambered plates (camber ratio, 10 and 15%; aspect ratio, λ=1.5) were used for the otterboard model. The flow around plates was visualized at the central section and the down tip by generating hydrogen bubbles in a circulating water tank. With increasing angle of attack, the separation point moved from the trailing edge to the leading edge at the central section on the suction side of the plates. Although the separation point reached the leading edge, the stall did not always occur. A spiral wing-tip vortex with an axis caused by the centripetal force was formed at the lower tip of the plates, and disappeared at an angle larger than the stall. This suggests that the stall on the cambered plates with low aspect ratio depends not only on ordinary lift due to circulation but also on vortex lift due to the wing-tip vortex.