Large eddy simulation of the pulsation characteristics in the cavitating flow around a NACA0015 hydrofoil

Abstract

Cavitation is common phenomenon in hydraulic machine, which is usually accompanied by velocity and vorticity fluctuations. The cavitation flow around a hydrofoil is simulated based on the large eddy simulation (LES) method. The predicted U-type cavity evolution is verified by the Lumley triangle and experimental data. The pulsation characteristics during the cavity evolution are deeply investigated, and the dynamical mechanism and energy loss caused by cavitation are revealed based on entropy production theory and Lamb vector. The results show that the turbulent kinetic energy and pulsating enstrophy have different behaviors during the cavity evolution process. The turbulent kinetic energy is always distributed in the interior of the U-type vortex, while the pulsating enstrophy is distributed around the U-type vortex, almost covering the whole suction surface. During the evolution of the U-type vortex, the straining and bearing of the vortex force are exerted. The energy loss in the process of cavitation is reflected by four terms of the entropy generation, and the entropy production rate by direct dissipation accounts for 87% or more of the total entropy, the energy loss caused by cavitation can often be ignored due to its small proportion, which is only about 0.1%. However, due to the complex interphase mass transfer of cavitation, interface entropy production rate has a large distribution inside the vapor cavity.