Numerical and Experimental Investigation on the Free-surface Flow and Total Resistance of the DTMB Surface Combatant

Abstract

Starting with the initial design stage, the ship resistance constitutes one of the most important hydrodynamic aspects. In order to generate and optimize the body lines plan, the ship resistance performance must be considered. In this case, both numerical and experimental methods must be applied to obtain the minimum ship resistance controlled by the speed domain. In the last years, numerical studies based on the Computational Fluid Dynamic (CFD) were implemented in the initial ship design stage in order to analyse the free-surface flow and to predict the ship resistance. The numerical optimization process of the hull forms must be validated by means of the experimental model tests in the specific towing tanks. The constant evolution of the numerical and experimental methodologies can be noted. As a consequence, the accuracy level of the ship resistance prediction is increased; though, difficult numerical problems can occur in case of the unconventional hull forms. Taking into account this aspect, a complex numerical and experimental investigation of the ship resistance problem and free-surface topology was performed in the case of the DTMB surface combatant. A parallel numerical simulation was carried out by using the viscous flow solver ISIS-CFD of the software FINETM/Marine provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier Stokes (RANS) equation. Closure to turbulence is achieved by making use of the k-? SST model, while the free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. For the validation purpose, the tank conditions are reintroduced in the numerical model to account for any banking effect, especially for the high speed cases. Experimental model tests were performed in accordance with the ITTC standard procedures, while the extrapolation process to the full-scale was obtained by using an in-house code, based on the ITTC 57 method. The experimental results are compared through with some internationally recognized towing tank experiments that have been performed for a similar ship model, showing a good agreement. Also, the numerical results are validated against the experimental data and showed to be within a satisfactory congruence.