Flow Research, under contract (NAS2-6927) with the NASA Ames Research Center has constructed a water tunnel and investigated the flow field adjacent to an oscillating airfoil. The design and operational procedures of the tunnel are described in detail. Hydrogen bubble and thymol blue techniques are used to visualize the flow field.nResults of the flow visualizations are presented in a series of still pictures and a high speed movie. These results show that the stall is more complicated than simple shedding from the leading edge or the trailing edge, particularly at relatively low frequency oscillations comparable to those of a helicopter blade. Therefore, any successful theory for predicting the stall loads on the helicopter blades must treat an irregular separated region rather than a discrete vortex passing over each blade surface.
展开▼
