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ABSTRACT A level set approach for the numerical simulation of high Reynolds number turbulent ows with a free surface is presented. The algorithm is based on a general pseudo-compressible Reynolds Averaged Navier{Stokes Equations (RANSE) solver, already used in conjunction with a surface-fitting approach for the numerical simulation of steady ows past ship hulls. The RANSE solver is coupled with a non-standard level set approach, the original algorithm having been modified in order to gain increased resolution in the nearby of the free surface. To this end, only the liquid phase is simulated; the level set function is used only as a tracking device to locate the actual position of the free surface. Moreover, the solution in the air region is extrapolated in a way that ensures second order accuracy also in the free surface region. Some numerical results for the ow around a submerged profile and two ship hulls are shown. INTRODUCTION Numerical simulation of free surface turbulent ows is a goal of paramount importance for the design and optimization of ship hulls. The results of many efforts dedicated to this topic, done in the past years by many research groups around the world, are summarized, for instance, in the proceedings of the workshop held in Gothenburg (Larson et al., 2000). As it can be seen in these proceedings, most of the computations where performed by means of surface fitting approaches, i.e. with algorithms where the grid moves to fit the actual position of the free surface. Moreover, when dealing with unsteady practical problems, like for instance a ship maneuvering in waves, the topology of the multi-block grid can change in time, and it can turn out to be impossible to handle problems with large geometrical changes of the domain occupied by the water.
- North America > United States (0.68)
- Europe > Sweden > Vaestra Goetaland > Gothenburg (0.25)
- Transportation > Marine (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Shipbuilding (0.75)
ABSTRACT A model for the simulation of spilling breaking waves in wave ows around ships is presented. A hydrostatic pressure is used in order to mimic the weight of the breaker on the underlying ow as in Cointe and Tulin''s model, whereas the algorithm for detecting the breaking inception and the definition of its geometry are completely new. The model has been implemented in a finite volume code developed for wave ows around ships and its performances are validated against experimental data for an S60 hull in drift motion. INTRODUCTION The free surface ow past ship hulls moving at usual cruise speeds is often characterized by the breaking of the bow wave, and often of the shoulder wave too. This phenomenon includes a variety of processes that go from vorticity generation near the free surface and rapid transition to turbulence in the initial phases, followed by air entrainment and spray generation when it is completely developed (Banner and Peregrine, 1993; Melville, 1996). Each of these aspects poses a dire difficulty in the numerical simulations and, as a matter of fact, no hydrodynamics code, developed in the framework of naval engineering, takes into account all the facets of the problem. For these cases, a modeling has been proposed by Cointe and Tulin (1994) that is based on the assumption that the breaker behaves like an eddy set on the forward face of the leading wave of a wave train, exerting on the underlying ow a pressure, due to its weight, and a shear, that ultimately generates a turbulent wake. This model has been revisited in (Muscari and Di Mascio, 2002a; Rhee and Stern, 2002) where it has been implemented in finite volume codes developed for simulations of wave ows around ships.