Calculations of nonlinear free surface flows around submerged and floating sea caches

摘要

A Reynolds-Averaged Navier-Stokes (RANS) method and a potential-flow method were employed in conjunction with a chimera domain decomposition technique for the prediction of hydrodynamic drag forces of submerged and floating sea caches in shallow water. The finite-analytic numerical method was used to solve unsteady RANS equations for turbulent free surface flows and Laplace equation for inviscid wave field. In order to capture the fully nonlinear free surface waves, the numerical grids were updated during the calculations to conform with the exact free surface elevations. Time-domain simulations were performed for three different sea cache configurations of rectangular, sharp-edged, and round-edged shapes under strong ocean currents. Detailed velocity and pressure fields were obtained for all three sea caches which may be anchored on the sea floor, moored on the free surface, or tethered at mid-height. The drag forces were also computed to determine the optimal sea cache shape in terms of maximizing payload and minimizing drag.