Numerical investigation of pulsating energy evolution in ventilated cavitation around the NACA0015 hydrofoil

Abstract

The pulsation characteristics of the ventilated cavitation are investigated in this paper with the Large Eddy Simulation method. As the ventilation rate increases, the air entrainment effect aggravates the instability of vapor cavity, and the re-entrant jet further accelerates the separation of attached vapor cavity from the suction surface. The suppression of cloud vapor cavity and the formation of stable ventilated supercavity can significantly reduce the time-averaged pulsation level of pressure and velocity. The pulsating energy of cavitating flows essentially comes from the time-averaged flow in natural cavitation and ventilated cavitation. The gradient diffusion effect tends to transfer the turbulent kinetic energy carried by cavities to the mainstream region, while the redistribution of pulsating enstrophy through the gas-liquid interface can be significantly suppressed by the injected air. The viscous dissipation term cannot be ignored because it does perform some fluctuating strip-like structures near the interface of large-scale vortex in ventilated cavitation. Two fluctuation stages and mechanisms of the ventilated cavity interface on a hydrofoil are revealed, moreover, the transportation of pulsating enstrophy on the surface of ventilated cavity located above the suction surface is clarified as an important mechanism to maintain the interface fluctuating state.