Abstract: The unsteady behavior of a two-dimensional cavitating flow around a NACA4412 foil is investigated in a cavitation tunnel by using the high-speed photography. The high speed photographic records show that there is a low frequency pulsating phenomenon caused by the abrupt breakup of cavity. This pulsation of cavitating flow appears significantly in case of the trans-cavitating flow and results in the pseudo-periodic evolution of cavity length and cavity thickness. The frequency characteristics of the low-freq...