Laser anemometer measurements of trailing vortices in water

A series of measurements of trailing vortices behind lifting hydrofoils is described. These measurements were made in the Caltech Free-Surface Water Tunnel, using a laser-Doppler velocimeter to measure two components of velocity in the vortex wake. Two different model planforms were tested, and measurements were made a t several free-stream velocities and angles of attack for each. Velocity profiles were measured a t distances downstream of the model of from five to sixty chord lengths. These measurements are the first results of a continuing experimental programme. In 3 3 of this paper, the theory of trailing vortices is discussed. The effects of ' vortex wandering ' upon the measurements are computed, and the corrected results are seen to be in reasonable agreement with the theory.