In this paper, the six degrees of freedom of rigid body motion are integrated into the commercial RANSE CFD-code Comet, giving the possibility to predict the motion of a free floating body in viscous, turbulent, free-surface flow, taking into account surface waves. The interaction of fluid flow and body motion is captured by coupling the equation of the body motion to the fluid flow analysis via the user-coding interfaces, then solving the equation system iteratively. In order to simulate the displacement of the moving body, a part of the grid adjacent to the body is moved with it, keeping the farther grid fixed, and deforming or regenerating the grid between the two regions, while keeping its topology the same. The accuracy of two ways of wave generation is examined in a numerical tank: (i) Imposing the velocities at inlet boundary set according to the Airy wave theory, and (ii) Simulating movements of a wave-maker in a tank by a moving no-slip wall. The second method is more appropriate for the purpose of validation, whereas the first method is easier and more efficient from the numerical point of view, and, moreover, it is straightforward to generate irregular ocean waves. Wave profiles simulated by the first method agree well with their corresponding analytical solutions, i.e. the Airy wave theory for sinusoidal waves and the second-order Stokes wave theory for nonlinear wave profiles. The waves simulated by the second method show satisfactory agreement with experiments. The method is applied to compute the motion of a Wigley ship in head waves and oblique waves, and to simulate the experiments conducted at the Hamburg Ship Model Basin using a RoRo test model. The coupled RANSE code proved to be capable to reproduce the behaviour of a real ship geometry in three-dimensional seakeeping applications, showing good agreement with experiments.
Simulation of flow-induced ship motions in waves using a RANSE method
Simulation strömungsinduzierter Schiffsbewegungen mittels RANSE-Simulation
Ship Technology Research / Schiffstechnik ; 51 , 2 ; 56-68
2004
13 Seiten, 21 Bilder, 20 Quellen
Article (Journal)
English
Bewegungsgleichung , dreidimensionale Strömung , Gitternetz , Navier-Stokes-Gleichung , numerische Strömungssimulation , Randbedingung , Rollen (Schiffsbewegung) , Schiffkörper , Seegang , Simulationsmodell , Stampfen (Schiffsbewegung) , Strömungsgleichung , Theorie-Experiment-Vergleich , Welle (Meer)
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