SURFACE FLOW VISUALIZATION OF FLAT PLATES BY TUFT METHOD

This paper describes the relationship between the surface flow and sta ll on the flat plates in relation to angle of attack, and discusses th e effect of the bottom on the flow. Two flat plates (aspect ratio lamb da = 0.5 and 1.5) were used for flow visualization by the tuft method in a circulating water tank. Thin nylon twine tufts were attached to t he suction side of the fat plate surface. The results show that as the angle of attack (alpha) increase, the separation from the leading edg e also increased, extending laterally towards the trailing edge of the suction side. When the suction side was completely covered by the sep aration, the flat plate was stalled. In the case of lambda = 0.5, the suction side in free stream did not completely separate until the angl e of attack reached alpha = 40-degrees, however, there was already com plete separation on the bottom even at alpha = 30-degrees. When lambda = 1.5, the rate of separation in free stream was almost the same as t hat on the bottom.