The Proceedings Fifth International Conference on Numerical Ship Hydrodynamics (1990) / Chapter Skim
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Grid Generation and Flow Computation for Practical Ship Hull Forms and Propellers Using the Geometrical Method and the IAF Scheme
Grid Generation and Flow Computation for Practical Ship Hull Forms and Propellers Using the Geometrical Method and the IAF Scheme
Pages 71-86
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From page 71... ...
Kodama Ship Research Institute Tokyo, Japan Abstract Grid generation for ship hulls and a propeller blade was made using the geometrical method, where an initial grid is modified iteratively under several geometrical requirements such as orthogonality, smoothness, and clustering. Using the generated grid, the computation of the incompressible Navier-Stokes equations was made for flows past a flat plate and four different ship hull forms using the IAF scheme and the Baldwin-Lomax zeros equation turbulence model.
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From page 72... ...
In Chapter 2, the NS solver is described, with dis- where cussions on the conservation property, boundary con- ~ F = IF + (YG + (ZH ditions, and the turbulence model. In Chapter 3, the ~ J J J geometrical grid generation method is described, where ~ G = 92 F + ~9 G + my H the use of bi-cubic splines for representing a body sur- ~ J J J face geometry is explained.
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From page 73... ...
2-1, where the area covered by a discretized governing equation at a grid point is shown hatched, all the numerical flux terms are evaluated at halfway between the grid points, and therefore cancel out when they are summed up, thus the global conservation holds. The added numerical dissipation terms, having constant coefficients, cancel out when they are summed up, and therefore do not affect the conservation property.
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From page 74... ...
3.2 Total Grid After the surface grid is generated, intermediate grid points, which are the points between the inner and outer boundaries, are generated, by simply connecting the corresponding points on the inner and outer boundaries with a straight line, and disributing points on it. Then the initial grid is modified iteratively under the same geometrical requirements as those used in the surface grid modification.
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From page 75... ...
Fig. 4-3, ~4, and 4-5 show respectively the wall shear stress law, the displacement thickness be, and the shape factor H
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From page 76... ...
The difference from the ~ = 1.0 result is small, which implies that the value ~ = 1.0 in Case 2 is small enough such that the added numerical dissipation terms do not affect the computed result. The figure (b)
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From page 77... ...
The NS solver used is the IAF scheme, where the pseudo-compressibility is introduced in the continuity equation, in order to make the system of equations hyperbolic. The accuracy and convergence of the computed results were tested by computing flows rising different numl:>er of grid points, or using different amount of the added numerical dissipation terms.
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From page 78... ...
3-3 Surface grid on a propeller blade (a) Perspective view ~/~/~N (b)
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From page 79... ...
4-2 Flat plate grid '1 ' ' ' ' ' ' ' ' ' 1 O Computed Empirical —v v ~ > Fig. 4-3 NVall shea.r stress ~w on a flat plate ~1 o 0 1 30 1 u 0 Computed _ Empirical O ^~V 1,~.
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From page 80... ...
4-10 Ixinematic eddy viscosity ~` of a Wigley hull at i=53 (x~0.95)
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From page 81... ...
4-15 Log plot of velocity on a Wigley hull -1 1 ~ Measured (z/D=0.80)
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From page 82... ...
i = 53 (x~ 0.95) t-16 Kinematic eddy viscosity u~ on a Wigley hull Computed -- -Measured u=1.0,0.9,0.8,...
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From page 83... ...
i = 38 0 z/D=0.2 z/D=0.5 0 z/D=0.8 ~ ^0 /\ O x 1 Fig. 4-21 Displacement thickness 5~ on a Series 60 (Cb=0.6)
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From page 84... ...
A-1 shows reasonable agreement with the Ol;uno's measurement, whereas it shows significant discrepa.ncy from the Fukuda's measurement in Fig.
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From page 85... ...
Fu jii this morning, the CDF people in aeronautics seem to have progressed to the stage that they can compute the f low about a fully appended airplane. Have you tried to include the sail and stern control surfaces in your computations?
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