An axisymmetric underwater vehicle-free surface interaction: A numerical study

Underwater vehicles (UWVs) have been widely used in oceanographic applications. Investigation of their interaction with free surface when they are moving near the free surface is of great importance. In the present work, the hydrodynamic characteristics of a standard UWV (Afterbody-1) moving in water and its interaction with free surface are studied numerically using CFD software ANSYSTM CFX. The total drag coefficient including the viscous and wave-making resistances acting over the UWV for its operating speeds ranging from 0.4m/s (Re=1.05×105) to 1.4m/s (Re=3.67×105) at different depths of submergence ranging from 0.75 to 4.0, is obtained. Also the wake formed behind the UWV is characterized to better understand the hydrodynamic behavior of the UWV motion in water at different submergence depths and vehicle speeds. The results were compared with available measured data and good agreements were observed. It was found that, for all submergence depths as the Reynolds number was increased the drag coefficient was decreased. Besides, for a fixed Reynolds number as the submergence depth was decreased the drag coefficient was increased. Finally, for small submergence depths the effect of UWV motion on the free surface became more appreciable if the Reynolds number was increased. •The interaction of an axisymmetric UWV with free surface is studied numerically.•The k−ε turbulence modeling and VOF interface capturing method are employed.•Different depths and Re are considered and wake behind the UWV is characterized.•For a fixed Re, the pressure drag, hence the drag coefficient increases with FrH.•For the Re range considered, free surface-UWV interaction is negligible for H≥3.