Investigating the limit behavior of cavitation phenomana around circular cylinder with various diameters at high speed cavitation tunnel

To investigate the limit behaviors of cavitation flow around a circular cylinder at a high speed cavitation tunnel, stainless steel models with different diameters, including 10 mm, 15 mm and 20 mm were made and tested in a supercavitation tunnel.Two holes designed in a way that the radial hole is connected to the axial one to measure the back pressure at various cavitation numbers. Before appearing clear silver regime at the model back pressure fluctuating is violent and after becoming visible stable clear silver regime the fluctuating pressure will be reduced and the length of attached bubble will be increased strongly. In this case, the longitudinal oscillation occurs randomly. The minimum back pressure for all models is the same and is equal to 13500 Pa. When the cavitation length is small, shedding vortices occur regularly, based on von-karmen pattern. In supercavitation regime, the collapse noise of bubble for 20 mm model is very stronger than 10 mm model. The ultimate cavitation number (chocking regime), will be reduced by decreasing the model diameter. The minimum cavitation number for 10 and 20 mm models are 0.125 and 0.49 respectively. The results show that the difference in ultimate cavitation number between experimental and theory methods are approximately 14%.