Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Toward Virtual Reality by Computational Physics
Toward Virtual Reality by Computational Physics
Pages 80-97
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From page 80... ...
In the field of naval hydrodynamics we had two major physical phenomena to which elucidation of the structure and mechanism was of substantial importance. They are nonlinear waves including wave breaking and turbulent flow including large-scale separated flow.
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From page 81... ...
The nonlinearity of the bow wave phenomenon was exaggerated by a model ship with an extreme bow shape as shown in Fig.1 t13~23~3~. Fig.1 Free-surface shock wave about a wallsided model with a blunt bow, at En = 0.12, 0.16, 0.24, 0.26.
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From page 82... ...
designed in 1983, Fig.4, which was equipped with two sails for the fuel saving purpose. Fig.3 Results of detailed wave profile measurement, wedge model of halfentrance angle 20° , Fd~draftbased)
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From page 83... ...
The computed wave pattern agreed very well with the measured result, especially when wave breaking is scarcely observed. The comparison of wave pattern is made of a tanker hull on ballast condition in Fig.7, which indicates that some discrepancy is present and it is mostly attributable to the fact that the TUMMAC-tW method cannot cope with the breaking wave.
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From page 84... ...
The wave resistance value obtained by integrating the surface pressure distribution dose not qualitatively coincide with the experimental value. But, hullform designers soon noted that the accuracy was good in the relative relation of wave resistance value due to the modification of hullform.
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From page 85... ...
When constant values of physical parameter such as density, Reynolds number and so on are varied, a variety of two-phase flow can be treated, such as an oil flow on water layer, a water flow on a liquefied sand bed, that is scoring problem, and so forth. Fig.12 Contours of wave height about a vertical cylinder (0.lm long set in a uniform stream 0.9 second after start of acceleration.
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From page 86... ...
Bernoulli constant value across the bow wave crest on the lines parallel to the centerline and the disturbed free-surface. Fig.17 Simulation of continuous casting of iron plate production process.
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From page 87... ...
108 micro bubbles are placed in the turbulent boundary layer and the mechanism to reduce frictional resistance was investigated by numerical simulation as show in Fig.19. This application indicates that such CFD technique with density function method in the framework of rectangular grid system has broad possibility of application to various environmental problems.
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From page 88... ...
Because they are 3D and unsteady phenomena, experimental approach found substantial difficulties. From rather scientific viewpoint the separated flows about a sphere and a body of revolution with conical after body are studied by use of TUMMAC method and a finite-volume method, respectively.
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From page 89... ...
The time-marching technique of the MAC-type algorithm provides good resolution of the periodically- repeated viscous phenomenon of vortex shedding. It may be said that the accordance with physics is, in a sense, better for the separated flow of thick boundary layer and it is a little more difficult and sensitive to have good agreement in the case of thinner boundary layer accompanied with relatively gentle separation as the case of ship flow.
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From page 90... ...
The sailing boat is set in an O-O type boundary-fitted coordinate system with six-degrees of freedom. The motion of the boat is treated by the grid deformation except that the steady advance motion is treated at the outer boundary and the hull surface is allowed to slip for the rolling motion as seen in Fig.29.
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From page 91... ...
The difference of 0.1°trim angle due to the difference of hull form was rigorously estimated which is very important information because such small difference of attitude influences on the balance and maneuverability of the yacht. Since the equation of motion and the Nervier-Stokes equation are simultaneously solved in the time-marching procedure, not only the performance in a steady motion but also that of unsteady motion can be simulated by this PPS technique.
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From page 92... ...
Considering that the motion experiment of sailing boat with sails is very difficult, such a "virtual" sailing simulation seems to be very useful. Nonlinear motion often occurs in the following wave conditions the extreme case is broaching, which may be caused by nonlinear (often sudden)
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From page 93... ...
Fig.35 PITCHING,HEAVING and ROLLING motion of AC boat in oblique incident wave.
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From page 94... ...
With the virtual reality technique by the computational physics this will be done in the future. The extreme sea condition can be realized in the computer and the designed ship is set on this sea surface and all characteristics are derived from the simulation.
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From page 95... ...
Tsuchiya: Experimental investigation on the resistance component due to Wee surface shock waves on series ship models, J Kansai Soc.
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From page 96... ...
Miyata,Direct numerical simulation of wall turbulent flows with microbubbles International Journal for Numerical Methods in Fluids Int.
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From page 97... ...
Reed Naval Surface Warfare Center, Carderock Division, USA Prof Miyata used the term "stability" several times. However, it is not what is meant by stability.
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