Stacked cross-correlation analysis of simulated images of a spine-sheath (“two-fluid”) jet with two constant velocity components (left) and a jet with random velocity field (right). For each test, a total of ten epochs are simulated. The resulting cross-correlation map is shown in greyscale in the respective top panel. The bottom panels shows the derived significance of the velocity components obtained. The significance is measured along the slice corresponding to the zero transverse speed. For the stratified spine-sheath flow on the left, the SCC successfully identifies the velocities of the two layers with a significance of ≥5σ. For the jet on the right with the random velocity field, no peak with a significance greater than 2 σ is found.