A PROPOSAL OF A VORTICITY ESTIMATION METHOD WITH MLS AND PTV AND ITS APPLIACATION TO FLOWS UNDER WIND WAVES

Abstract

A method to measure two-dimensional vorticity fields was developed by combining MLS, the Moving Least Square method, with PTV. A velocity vector at a grid point is approximated with a pair of quadratic functions fitted to velocity vectors at particle positions estimated by PTV which randomly distributed around the grid point. The vorticity is calculated by differentiating the quadratic functions. A two-dimensional Gaussian weight function is employed for fitting. The size of the interrogation area is represented with the standard deviation of the weight function. The expression