Abstract: Some improvements based on volume of fluid (VOF) method were done to exactly track the free surface with air pocket during the water entry. A continuum surface force (CSF) model was introduced to serialize the pressure on the interface of air and water. A convective term was added to minimize the numerical dissipation of volume fraction, and the level-set function was coupled to keep the sharpness of free surface. Oblique water entry problems of wedge with various inclination angles were simulated numerically based on the improved VOF method, and the characteristics of pressure and free surface were analyzed. The research shows that the free surface can be exactly reconstructed, and the same resolution can be realized in the improved VOF method through reducing 1/3 total number of mesh. The cavitation during oblique water entry is better reflected by the numerical simulation, and the slamming pressure peak agrees well with the published experimental data. When the deadrise angle is below 10°, an obvious air effect will appear. The error between numerical and experimental results is 10%, while it reaches up to 40% in the analytical solution. The results suggest that the air greatly influences the slamming pressure and the numerical high-precision results can be obtained through the improved VOF method.

Key words: volume of fluid (VOF) method; oblique water entry; computational fluid dynamics; gas-liquid two-phase flow; slamming loads