Fig. 4: The impacting body must have an edge for cavitation to occur.

a The impact of a 20-mm-diameter sphere at 9.89 m/s forming a weak compression wave (red arrows) that emanates into the pool without causing cavitation. b and c Show two views of a 50-mm-diameter cylinder with a convex curvature of radius 0.60 m on the bottom surface impacting at 7.75 m/s. The tension wave that reflects when the edge submerges ((c) t = 32−42 μs) causes cavitation where the waves overlap. d and e Show two views of the same curved cylinder impacting at 3.47 m/s. By the time the edges submerge the pressure amplitude near the contact line has decreased sufficient such that a reflected tension wave (thick, dark region) is not visible and no cavitation occurs. The gold shapes at the top of each frame indicate the approximate position, shape, and size of the lower portion of the impacting body. a, c and e are schlieren images with light regions indicating increasing pressure in the upward direction and dark regions indicating decreasing pressure. The ambient pressure in all cases is 1 atm. Supplemental movies 7–11 show a–e, respectively.