How can I "flatten" (transform) a curved surface in an image prior to directional filtering to track motion?

I have a series of images like the one below that show a wave moving over time in the curved structures seen near Y=10. I need to apply a directional filter that isolates L->R and R->L motion. I've done this and it works great in other samples, but the issue is that it doesn't work here because the motion stops being exclusively L->R and R-> L due to the curvature. Is there a way that I can transform the images so that all motion along this curved region ends up being horizontal? Thanks in advance.