Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
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Time-Marching CFD Simulation for Moving Boundary Problems
Time-Marching CFD Simulation for Moving Boundary Problems
Pages 291-311
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From page 291... ...
Simulation results are summarized from the research worI;x of the author's laboratory for the problems of free-surface shock wave, wave resistance, ship maneuvering, sailing mechanism, ocean wave and bubble flow. 1 INTRODUCTION say that the most important part of the progress of ship technology in the past half century is made by the development of production technique and analYSiS technique.
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From page 292... ...
The development of CFD code was started at the author's laboratory in 197cJ when the author noticed the existence of the nonlinear ship wave called freesurface shock wave [1~. The typical codes developed in the past 17 years are listed in Table 1.
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From page 293... ...
However the finite-volume method appeared to have sufficient degree of robustness and the ALE method improved to implement the conservation laws in the boundary cells as shown in Fig.8 [123~133. In the case of Fig.6 the grid points on the body surface remains at the fixed position and the surrounding grids are regenerated.
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From page 294... ...
Wehausen and where the workshop on wave resistance computation was organized by Dr.Bai at DTNSRDC. The MAO method developed at Los Alamos scientific laboratory seemed us most suitable to nonlinear ship waves, since it was already demonstrated that this numerical technique can deal with nonlinear waves including breaking wave.
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From page 295... ...
Sailing boat simulation by the combination of the CFD simulation with the solution of the equations of motion seems to be substantially useful for its design when sufficient degree of accuracy is attained. The development of the WISDAM-VII code for sailing boat was started in the middle of 1993 when the author was assigned to be a general coordinator for the technical team supporting the Nippon 295
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From page 296... ...
6 OCEAN WAVE SIMULATION 6.i 2D breaking wave More than 10 years ago 2D breaking simulation was first completed by use of the movement of freesurface segment within the framework of rectangular grid system 716. A typical result of a 2D bow wave in front of an advancing floating body is shown in Fig.31.
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From page 297... ...
~ In F~g.39 Is common to many other vortex snedd~ng though their reality Is not well guaranteed from blunt bodies such as a sphere and an automoThis simulation technique is easily applied to an- bile other two-layer flow,i.e., water flow above liquefied sand layer by simply changing the density value of the fluid. One feature of scoring sand layer by the water flow interaction with the pillar is shown in Fig.37.
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From page 298... ...
and Miyata, H.," Elucidation of the structure of free surface shock waves about a wedge mode! by finite-difference method," Journal of the Society of Naval Architects of Japan, Vol.
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From page 299... ...
and Miyat.a, H.," Numerical simulation of a bubble flow by modified density function method," Journal of the Society of Naval Architects of J apan, (to app ear)
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From page 300... ...
. a: U2 Figure 4: Schematic sketch for the body boundary condition in the rectangular grid system.
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From page 301... ...
_~ z' u s Kiev S (u-vJ.S =u so I_ Uj=2 ~ _~ ~ ~ _ ~body boundary u; O (dummy point) Figure 8: Schematic sketch for the treatment of the moving velocities on the body boundary.
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From page 302... ...
-th time step FREE S URFACE Figure 10: Schematic sketch for the fulfillment of the kinematic and dynamic conditions on the freesurface in the rectangular grid system. Figure 11: Schematic sketch for the det~ermination of the free-surface location by the density-function method used in the body-boundary-fitted grid system.
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From page 303... ...
_~_ ·..~~ M55F1 1 ) X/DRAUGHT Figure 13: Comparison of computed and measured wave contours of two hull-forms of a 26000 DWT bulk carriers NI55 FO and ~I55 F1 at ~Fn=0 18.
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From page 304... ...
~ area. ~ 1 1 l al Figure 15: Time-variation of nonlinear diffraction waves about a wedge model placed in regular incident waves, Fn=0.5,>=2.0m,c~=30 ~
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From page 305... ...
0 2 0.4 -0.4 -0.2 ° x ( ) 0.2 0.4 _0.4 -0.2 0 0.2 0 4 _0.4 -0.2 0 y 'm; 0.2 0.4 -0.4 -0.2 0 x (m} 0.2 o.4 Figure 16: Simulated wave contours at five phases Figure 17: Measured wave contours for the compar of the incident wave on the condition in Fig.15.
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From page 306... ...
. Figure 18: Perspective view of the computed bow waves about a 20 ° wedge model at three Froude numbers, Fd=0.8, 1.1 and 1.4 from above.
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From page 307... ...
Wbull+sail~ hi;> ~ Ihee! angle I Figure 24: Forces exerted on a sailing boat in a upwind course.
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From page 308... ...
Figure 25: Body and free-surface configuration of sailing boats with different framelinea on a upwind Figure 28: Time-sequential variation of the locasailing condition. tion, sheerline configuration and waterline configuration of a sailing boat in course changing maneuver during upwind sailing, case 1 (left)
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From page 310... ...
~ 450 6CX) Figure 34: Evolution of breaking wave about ~ Yertical cylinder.
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From page 311... ...
i, i / ~ \ \ \ ~ \ \\\\ 1 1 ~ . Figure 36: Same as Fig.35, on the vertical plane including the back-surface of a vertical cylinder.
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