Performance Evaluation of an Optical Flow Technique for Particle Image Velocimetry
by
Georges M. Quenot
LIPS-IMAG, 385, rue de la Bibliotheque, B.P. 53, 38041 Grenoble Cedex 9, France

Summary This paper presents a quantitative performance evaluation of an Optical Flow technique on the test data of the PIV-STD group of the Visualization Society of Japan. Near the optimal conditions for the method, the accuracy (average velocity error divided by the average velocity module) is below 2 % and it is below 4 % in all other cases except for very high and very low in-plane velocities.

INTRODUCTION The experimental fluid mechanics technique of Particle Image Velocimetry (PIV) has proven to be a valuable method for quantitative, two-dimensional flow structure evaluation¹. It enables the measurement of the instantaneous in-plane velocity vector field within a planar section of the flow field. Nowadays, almost all PIV is done by computer image processing on digital images² and most methods are based on image intercorrelation. Optical Flow techniques^3-4, conventionally developed for detecting motion of large objects in a real world scene, were also recently successfully applied to the PIV problem⁵. The objective of the present study is to better characterize the performance of the optical flow technique for PIV and how it is influenced by experimental parameters (particle density and size, in-plane and out-of-plane velocities). For convenience and easy comparison of results, a standard PIV test set was used⁶.

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Date received: January 31, 1999