Computational Modeling of Air Cavities under Solid Bodies in Water Flow

Significant drag decrease of marine vessels can be achieved by forming thin air cavities on underwater hull surfaces. Modeling of air-ventilated cavities in water flows under solid bodies is rather complex, since a variety of factors are important, including viscosity, turbulence, surface tension, gravity, and periodic air shedding. A finite-volume solver, employing the volume-of-fluid method for the air-water interface and RANS turbulence models, has been applied to model air-ventilated water flows in experimental setups previously tested at moderate and large Reynolds numbers. During computational studies it was found that sufficient refinement of the numerical mesh near the cavity re-attachment to the solid body and sharpening treatment in the interface-capturing method must be incorporated into modeling to achieve reasonable agreement with test data. The solution verification on numerical grids of different mesh density has been carried out. In addition, it is demonstrated how cavity shapes can be changed by modifying body geometry.