Measurement of velocity and on pattern tracking in 3D LIF images

• Published in: Experiments in fluids Vol. 29; no. 4; pp. 388 - 401
• Main Authors: Deusch, S, Merava, H, Dracos, T, Rys, P
• Format: Journal Article
• Language: English
• Published: 01.10.2000
• ISSN: 0723-4864

Pattern tracking in consecutive 3D LIF images based on least squares matching (LSM) of gray levels has been developed recently for velocity and velocity gradient measurements. The shortcomings of this method are clearly shown. The present article presents an improvement on this method by introducing a local multi-patch (LMP) technique through the LSM approach. The method is validated using the flow field of a turbulent channel flow obtained by direct numerical simulation (DNS) and a synthetic image with gray-level patterns. The results show that LMP matching allows the determination of the velocity and the velocity gradient fields with high accuracy, including the second derivatives. Measurements of a round nonbuoyant jet are presented which demonstrate the good performance of the method when applied under laboratory conditions. This method can also be applied on two-dimensional images, provided that the flow is strictly two-dimensional. (Author)