Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Computation of Viscous Flow Around Fast Ship Superstructures
Computation of Viscous Flow Around Fast Ship Superstructures
Pages 940-949
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From page 940... ...
Potential applications include: Smoke and exhaust tracing Operational conditions for take-off and landing of helicopters Wind resistance and drift forces Ventilation of rooms The traditional approach to study aerodynamic flows around ships employs model tests in wind tunnels, Fig.1. These tests are a proven tool supporting design and relatively fast and cheap.
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Therefore, it is concluded that determination of wind loads on ships and offshore structures by CFD is a realistic computational alternative to the experimental methods. However, due to the time involved in generating the computational mesh and in computing the solution, the CFD method is not at the moment economically competitive to routine wind-tunnel model testing." SIREHNA in France has simulated aerodynamic flow for smoke tracing at a combatant (www.ec-nantes.fr/sirehna)
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We solve corresponding transport equations for the turbulent kinetic energy k=0.5 v' v' and its dissipation rate £ = (pit) (grad v': (grad V')
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avoiding geometrical modelling with excessive cell counts. The basic transport equations retain their form then, with ds in the surface integral being replaced by P dS, and if the source terms are updated to account for interaction between fluid and solid parts of the porous medium.
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_ it_ Ad. Fig.2: Grid detail for SES with inner cylindrical domain foredeck, there are corresponding low pressure zones.
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Fig.6: Streamlines starting in foreship, upper layer Fig.7: Pressure distribution for '170°
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: : : Fig.10: Streamlines starting in foreship, ~150° Fig.9: Pressure distribution for p=150° Fig. 11: Streamlines further away in foreship, ,u=150° On the downwind side, the flow is sucked partially along the ship sides before it detaches approaching its original flow direction again, as becomes apparent when zooming out to a larger perspective, Fig.
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Ongoing research focuses on determining proper grid resolution, and we expect that 1-2 million cells may suffice for most applications in practice. The aerodynamic CFD analysis showed extensive recirculation regions at the upper deck of the cruise vessel.
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"A CFD-based parametric study on the smoke behaviour of a typical merchant ship," PRADS'01, Shanghai, 2001, pp.459465 Kohsla, P.K.; Rubin, S.G., "A diagonally dominant second-order accurate implicit scheme," Computers & Fluids Vol.2, 1974 Launder, B.E.; Spalding, D.B., "The numerical computation of turbulent flows," Computer Methods in Applied Mechanics and Eng. Vol.3, 1974 Leer-Andersen, M.; Hughes, P.H., "Computations of wind loads on ships and offshore structures," Dept.
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15, 1972 Schmode, D.; Bertram, V.; E1 Moctar, O.M. "Aerodynamic flow computations for a Superfast ferry", 3r~ High-Performance Marine Vehicles Conf.
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