Numerical predictions of ship-to-ship interaction in shallow water

Using a steady state Reynolds Averaged Navier-Stokes solver, a numerical study of the ship-to-ship interaction during a lightering operation is presented. Since the Froude number is very low, the double model approximation is adopted and sinkage and trim neglected. At the first stage, five different combinations of water depth, speed, and ship-to-ship distance in the transverse and longitudinal directions are used as benchmark test cases. The wave pattern, pressure distribution and forces and moments acting on the two hulls are predicted. A good correspondence between the measured and computed waves is noted, indicating that the pressure on the free surface is well predicted. Assuming that the pressure is accurate also on the hull, the variation in forces and moments between the cases is explained. Comparisons with measured data and with similar computations carried out elsewhere are made. It is seen that the present results correspond better with other computations than with the data. In the second stage, a set of systematic computations is carried out to study the ship-to-ship interaction in shallow water. The forces and moments, as well as the sinkage and trim on the hulls with varying relative longitudinal or transverse position are predicted and explained.