CFD-based numerical simulation of pure sway tests in shallow water towing tank

Abstract

The pure sway tests in shallow water towing tank are numerically simulated for the DTC container ship model by using an unsteady RANS solver. The verification study in terms of mesh and time-step convergence for the assessment of numerical error and uncertainty is conducted. The hydrodynamic forces, the hydrodynamic derivatives and the reconstructed hydrodynamic forces from the resultant hydrodynamic derivatives are validated against experimental data in very shallow water, and a satisfactory agreement is obtained. Using the validated numerical method, systematic simulations are carried out considering the influences of water depth, ship speed and dynamic sinkage and trim on the hydrodynamic quantities during the pure sway tests. The effects of depth restrictions on the hydrodynamic forces are expressed by polynomial regression equations with the corresponding ratios of hydrodynamic derivatives in shallow water to those in deep water. Besides, the side wall effects of tank in very shallow water that affect significantly the results of model tests for ship speed close to the Schijf's limiting speed are analyzed. From the present study, the ability of CFD method in evaluating the shallow water effect and side wall effect on the pure sway test results in shallow water towing tank is demonstrated.