Stream vortex in the Peak District National Park —Tamsin Spelman (Sainsbury Laboratory, University of Cambridge)

Generated from a video of a natural vortex taken on Wessenden Head Moor in the Peak District. The video frames were z-projected in Image-J with naturally-occurring foam acting as tracer particles, and then this image was contrasted, cropped to an ellipse, and superimposed on the first video frame.

https://fluids.ac.uk/files/04_SUM_TwoImages.1662534243.jpg