Measurement of Boundary Layer on a Propeller Blade Using LDV Technique

Abstract

The local propeller blade flows are measured by using a new LDV measuring system to obtain boundary layer profile on a propeller blade. Measurements are made on a five bladed propeller whose diameter is 0.4m in the cavitation tunnel of the Ship Research Institute. The newLDV measuring system consists of a one component, dual beam, backscatter LDV, signal processor and a data processing system. The velocity paralell to the geometrical pitch angle is measured by setting the measuring volume of the LDV at the section of the propeller blade. The mechanism for the boundary layer traverse is simply the rotation of the blade, since the LDV measuring volume remained stationary. The results are shown as equi-velocity contour curves and boundary layer profiles on the section of the blade It is found that the boundary layer growth with the increase of the chord of the blade section. The existence of separation bubble at the leading edge of the blade is made clear and verified by the flow visualization.