Hydrodynamic Modeling of Fast Semi-Submersible Vehicle in Deep and Shallow Water

Semi-submersible vehicles have several advantages for special operations, such as low-profile above-water structure, better seaworthiness, and potentially lower wave drag in some speed regimes. To achieve higher speeds, semi-submersible hulls can benefit from using finer boat-type bows instead of more common submarine-type elliptic noses. In this study, computational fluid dynamics simulations have been conducted to determine drag and attitude in a broad speed range of one such configuration. The drag curve of the studied hull showed gradual growth with increasing speed in the entire range, while trim demonstrated more abrupt change when a significant bow wave was formed. Finite-depth operations were simulated at one speed, corresponding to the length Froude number of 0.4. Drastic increase of drag and trim were observed when depth Froude number exceeded 0.7 and the vehicle approached the critical shallow-water regime. The presented results can benefit developers of semi-submersible craft which operational conditions include high speeds.