Numerical study on the effects of modulated ventilation on unsteady cavity dynamics and noise patterns
Tiezhi Sun, Yanyi Ding, Huakun Huang, Bohan Xie, Guiyong Zhang
Abstract
Supercavitating flow is accompanied by significant unsteady characteristics, and it is therefore very important to find methods to control this multiphase flow phenomenon. Ventilation is an important method for creating supercavitation and it affects the evolution, load, and noise characteristics. In this paper, cavity flows with and without modulated ventilation (i.e., the imposition of a sinusoidal component on the ventilation rate) are investigated using computational fluid dynamics techniques incorporating large eddy simulation, coupled with the Ffowcs Williams–Hawkings (FW–H) method. The effects of modulated ventilation on cavity shedding, vortex structure, and the noise characteristics of the cavity are compared and analyzed. The results show that modulated ventilation can change the shedding period of the ventilated cavity and can slightly improve its lift and drag performance. It can also promote the formation and growth of hairpin vortices and impose a periodicity on the evolution of the vortex structure. Furthermore, although modulated ventilation cavitation enhances pressure fluctuations near the vent and increases the self-noise of ventilation, it has little impact on far-field noise while reducing the turbulence of the far field, which decreases the total sound pressure level in the wake of the cavitator.