Numerical research on hydrodynamic characteristics of the disk-shaped autonomous underwater vehicle near free surface

The hydrodynamic characteristics of a disk-shaped Autonomous Underwater Vehicle (AUV) cruising near the free water surface were investigated using the computational fluid dynamics (CFD) approach. Factors such as the cruising velocity, cursing depth, wave height, and wavelength were considered. The free surface changed the hydrodynamic force applied on the disk-shaped AUV mainly by altering the flowing velocity near the hull. A small cruising depth led to the disturbance of the free surface, which in turn generated additional resistance on the AUH hull. Therefore, the mean resistance and its fluctuation increased. Considering waves occurring at the surface, the evolution of the wave could affect the local flowing velocity around the hull, and therefore, alter the hydrodynamic characteristics of the AUV. Both the wave height and wave length affected the fluctuation amplitude of the hydrodynamic properties of the AUV as well as the time-averaged properties.