Pattern tracking in consecutive 3D LIF images based on least squares matchi
ng (LSM) of grey levels has been developed recently for velocity and veloci
ty gradient measurements. The shortcomings of this method are dearly 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 dir
ect numerical simulation (DNS) and a synthetic image with grey-level patter
ns. The results show that LMP matching allows the determination of the velo
city and the velocity gradient fields with high accuracy including the seco
nd derivatives. Measurements of a round non-buoyant jet are presented which
demonstrate the-good performance of the method when applied under laborato
ry conditions. This method can also be applied on two-dimensional images pr
ovided that the flow is strictly two-dimensional.