Behaviors of Free Bubble Nuclei in Inception of Sheet Cavitation

Inception of sheet cavitation is known to be a complex phenomenon depending upon the working flow conditions, especially on the boundary layer flow and the water quality. Because of this, it seems very difficult to simulate the sheet cavity inception by CFD using homogeneous cavitation model. In the present study, experimental observation of inception of sheet cavitation from a single free nucleus in a two-dimensional convergent-divergent nozzle is conducted under well degassed condition with few free nuclei. Then numerical simulation solving the equation of motion of bubble nuclei with Rayleigh-Plesset equation is conducted to see the effect of slippage of bubble nuclei from liquid flow on their trajectories. The flow field obtained by the single phase CFD is used as a background liquid flow. Finally, using the obtained bubble slip velocity, the spatial distribution of bubble nuclei density is estimated.