Velocity Measurements around a Cavitating Tip Vortex on a 3-D Hydrofoil using Laser Doppler Velocimetry

Abstract

A stationary 3-D free tip hydrofoil was constructed and tested in a water tunnel at the Marine Hydrodynamics Laboratory at the Massachusetts Institute of Technology. The foil had moderate skew and was designed to produce a tip vortex like that typically seen on a modem free tip propeller blade. At the fixed loading condition, studies on the foil and its tip vortex were collected at ca vita ting and non-cavitating conditions. Laser Doppler Velocimetry (LDV) was used to collect the tip vortex velocity profiles at various axial positions at both non-cavitating and cavitating conditions. Also using the LDV system, closed contour velocity profiles were taken at various spanwise positions and used to measure the span loading distribution. Tip vortex circulation growth and core radius growth as a function of streamwise position were extracted from the tip vortex velocity profiles. growth and core radius growth as a function of streamwise position were extracted from the tip vortex velocity profiles. Pictures were taken of the cavitating vortex as well as foil sheet cavities at inception to document cavitation observations.