Numerically determining flow around the ship hull - DTMB 5415

The free surface flow around a model surface ship (DTMB 5415) advancing in calm water under steady conditions is numerically simulated. The geometry of the DTMB 5415 ship hull was provided in igs file format. The combatant has been recommended by the 1996 International Towing Tank Conference as a benchmark case for CFD computations of ship resistance and propulsion.

The SHIPFLOW code was employed to evaluate the flow field structure around the ship hull, the forces acting on bare hull and appendages. The solver computed the incompressible RANS equations on structured overlapping grids by using a finite volume technique. Turbulence modelling was achieved through the k-ε and k-ω SST or EASM models.

The propeller was approximated as an active disk for which the solution has been given by a simplified hydrodynamic model. For practical reasons, XCHAP module has coupled a body forces method and a RANS-based finite volume solver to take into account the interactions between the hull and the appendages mounted on it: propellers, rudders, shaft lines, bossings, and brackets.

Various configurations are investigated to establish the influence induced by the appendages on the flow filed. The numerical solutions obtained are compared with available experimental and other numerical data.

Expected results:

First step towards getting good experimental results is the potential flow calculation using mesh convergence study. After choosing good mesh, a preliminary potential flow resistance computation for five different speeds is being made. Then using the free surface results gained from the potential flow computation, new viscous flow resistance computations of bare hull DTMB 5415 are being made. The latter are compared with specific speeds for which experimental data already exists.

Final viscous flow calculations are done for the same hull but with different appendages using experimental speeds. Results show time averaged velocity, pressure, and turbulent quantities. They together will reveal not only the influences exerted by different configurations of the appendages on the wake structure in the propeller disk but also the forces acting on appendages.

Keywords: Free surface Flow, Overlapping Grids, Finite Volume Technique, Active Disk, Body Force Method

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