Investigation of Boundary Layers and Tip Flows of Helicopter Rotor Blades

摘要

An experimental and analytical study was conducted on the nature of rotor blade boundary layers and flow over rotor blade tips. The experimental study of boundary layers was conducted using a model rotor and included both hovering and forward flight conditions. Flow visualization using an ammonia trace technique and not-wire anemometry were used to determine the boundary layer flow. Both chordwise and spanwise velocity distributions were obtained through the boundary layer. Velocity profile data were obtained at selected chordwise and spanwise locations. The profiles obtained appeared to be consistent with boundary layer behavior. In hovering, the boundary layer flow in the vicinity of a separation bubble was mapped out. The analytical phase of the study was based upon a three-dimensional application of the momentum-integral techniques of handling boundary layer analysis. (Author)