A Photographic Study of Cavitation in Jet Flow

The effect of polymer additives on underwater jet cavitation has been studied using a special camera. Solutions of the drag-reducing additives, polyacrylamide and poly(ethylene oxide), at concentrations of 25 ppm, decreased the cavitation inception index and greatly changed the appearance of the cavitation bubbles. Solutions of the non drag-reducing polymer, Carbopol, produced cavitation bubbles having the same appearance on pure water and did not change the inception index. In pure water, the cavitation appearance resembles ragged groups of small bubbles with the overall impression of sharpness and roughness, but in drag-reducing polymer solutions the bubbles are larger, rounded, and of completely different appearance.