Fig. 3: Plot showing cavitation onset when a flat-bottom cylinder impacts a pool of water.

Symbol explanations are shown in the legend and symbol size is proportional to the cylinder diameter, which ranges from 10 to 40 mm. The dashed line plots (5) with k₁ = 3, the solid line plots (7) with k₂ = 0.003 (for P_amb = 1 atm), and the dotted line plots (7) with k₂ = 0.0022 (for P_amb ≤ 1/2 atm). The green and gray arrows indicate the cases shown in Fig. 2b and c respectively and the blue arrow indicates the case shown in Supplemental Movie 4, in which the pressure waves are so weak the schlieren imaging cannot detect them. Each marker represents one impact event. The number of cavitation bubbles varied greatly with 779 bubbles counted for the case indicated by the green arrow and only 6 counted for the case indicated by the purple arrow. The bubble quantity is roughly indicated by the symbol color; see legend. Typical 95%-confidence-uncertainty bands are shown on the left and right of the plot for a 20-mm-diameter cylinder with the uncertainty on α increasing linearly with U_o between them.