The hydraulic jump occurs when a high velocity flow changes from supercritical to subcritical, in this case caused by a vertical flow hitting a horizontal surface. This causes a a flat layer of liquid then a sharp increase in liquid level, seen the in the boundary of this four leaf clover hydraulic jump. This is a common phenomena can be observed in sinks and typically produce circular boundaries. Using a more viscous fluid different boundary geometry is observed.
Original work: Jeff Aristoff, Princeton, John Bush, MIT
https://www.nsf.gov/news/mmg/mmg_disp.jsp?med_id=66050&from=
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I give this my third prize; I think that the phenomenon of this image is incredibly interesting. I have seen this myself in my sink and had originally thought that I would use this phenomenon for the next project. I didn’t know the name of it until reading your post.