Numerical investigation of cavitation-vortex structures around a sphere with boundary data immersion method

Abstract

The boundary data immersion method (BDIM) coupled with the artificial compressibility method is applied to investigate the interaction of the cavitation-vortex dynamics around a sphere. The convolution of governing equation with a nascent delta kernel is employed to smooth the transition region between the solid and the fluid subdomain. Therefore, the BDIM addresses a key problem with smooth immersion boundary method in representing the discontinuity of the velocity gradient ∂u/∂y at the wall when considering flows with intermediate to high Reynolds numbers. In addition, a pseudo-time derivative of the pressure multiplied by an artificial-compressibility factor is added to the continuity equation. The developed coupling algorithm can accurately capture the unsteady cavitation characteristics, which is consistent with the previous experimental data. Subsequently, the typical vortex identification methods and the turbulent kinetic energy (TKE) transport equation are applied to analyze the interaction between the cavitation dynamics and turbulence vortices structures. A series of turbulent vortices are captured with the cloud cavity shedding. Moreover, it is found that the unsteady cavity topology will promote the generation of TKE.