Ventilated cavitation of flow around a sphere at subcritical Reynolds number

Ventilated cavitation over a sphere at Re = 10⁴ is computationally investigated in the presence of surface tension and the absence of gravity using direct numerical simulations. The air is injected from a circular strip on the sphere’s surface into the water domain. The direction of injection is perpendicular to the sphere’s axis, passing through its forward stagnation point and its center. The magnitude of the injection velocity is half of the freestream velocity. We consider the flow to be a homogeneous incompressible mixture of water and air. The air-water interface is tracked using the volume of fluid model. The cavity exhibits re-entrant jet cavity closure. Air injection decelerates the flow upstream of the injection position, causing an adverse pressure gradient. This artificial ventilation alters the pressure and the skin friction distribution over the sphere surface, such that the hydrodynamic drag around the sphere reduces.