Subgrid scale formulation of optical flow for the study of turbulent flow

We propose a new formulation of optical flow in the case of passive scalar or solid particles spreading in turbulent flows. The flow equation is defined from the scalar transport equation and a decomposition of our physical quantities (velocity and concentration fields) into two contributions, large and small scales, to account for the lack of spatial resolution in processed images. A subgrid scale model is introduced to model the small scale contribution. Comparisons are made with existing optical flow methods and Particle Image Velocimetry on synthetic and real sequences. The improvement of the estimation of velocity field by the proposed formulation is discussed in the case of a scalar turbulent propagation.