Advanced Evaluation Algorithms for Standard and Dual Plane Particle Image Velocimetry

Abstract

The widely-used evaluation algorithms for PIV recording have some short comings, in that they introduce superfluous statistical and systematical errors. For example, they introduce the so-called "peak-locking" effect. These errors can be significantly reduced by using better algorithms. The following considerably improved analysis and algorithms will be described and demonstrated on real PIV recordings: - Analysis of errors of CCD's and the electric transmisson of the video signal. - A FFT-based cross correlation algorithm using completely free-shaped and free-sized interrogation windows which exhibits the same accuracy as an optimally programmed direct correlation. - A Gaussian fit algorithm using different weights for the values in the correlation plane due to the error distribution of correlation coefficients.