The Proceedings Fifth International Conference on Numerical Ship Hydrodynamics (1990) / Chapter Skim
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Time-Domain Calculation of the Nonlinear Hydrodynamics of Wave-Body Interaction
Time-Domain Calculation of the Nonlinear Hydrodynamics of Wave-Body Interaction
Pages 341-350
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From page 341... ...
Takagi Nihon University Chiba, Japan Abstract S source point The boundary element method coupled with time-marchthg finite difference is adopted and improved to calculate the nonlinear hydrodynamics of wave-body interaction. The radiation condition and initial condition have been studied through specially chosen examples such as the cylinder undergoing forced heave motion or forced sway motion and the body floating or standing in periodic waves with wave front, and steady solution of practical interest has been obtaind in a definite calculation domain by less computer time.
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From page 342... ...
The numerical results show good agreement with the tested ones done in Nihon University, Japan. For the diffraction of a solitary wave upon a fixed vertical circular cylinder, the Sommer-feld condition is further extended as a radiation condition by assuming that the scattering of the outergoing wave is small at the outer open boundary.
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From page 343... ...
Assuming that ~ cylinder starts to move in still water, initial condition could be~atisfied easily, so we specially choose the e~amples of forced heave motion and forced sway motion as the calculation models to find out the propriate radiation condition. In numerical calculations we use a cylindrical coordinate system (ores)
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From page 344... ...
3.2 Wave Diffraction Problem For the diffraction of a solitary wave or periodic wave upon a fixed or floating vertical cylinder, the Sommer-feld condition is further extended as a radiation condition by assuming that the scattering of the outergoing wave is mall on the outer open boundary. Replacing O in Eq.(22)
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From page 345... ...
Fig.10 gives the free surface profiles at some fixed time. 6.3 Diffraction Problem The diffraction problems of a vertical circular cylinder standing on the seabed and piercing the free surface by a solitary wave has been calculated.
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From page 346... ...
9. Yang, C., "Time domain calculation of three dimensional nonlinear wave forces", Doctoral thesis, Shanghai Jiao Tong University, China (1987~.
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From page 347... ...
250 347 | ~k~ 4;, ~ ~ t/T ' i/ho ( ~-" ' 00 ) t/T Fig.9 Free surface elevations the fixed point — model test results -- - num e ri cal resul ts t= 1.
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From page 348... ...
18 Incoming wave elevation at ~0 and horizontal wave-force for AD fixed circular cylinder rx/~~ \~//\ /, 2.0 x 10 Fig. 14 Horizontal wave-force variation for 3-D fixed circular cylinder 0.6 !
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From page 349... ...
This is because the nonlinear threedimensional wave will be linear as it spreads out. Recently we have made some numerical tests on the matching of the Kelvin source distribution and the local nonlinear numerical scheme along the numerical radiation boundary, which replaces the radiation condition in Eq.(15)
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From page 350... ...
If the radiation condition and the determination of intersection point are not appropriate, the calculation will diverge after a few time steps. If the free surface has very serious nonlinear, for examples, the body enter into the water suddenly the usual method to deal with the free surface elevation could not be very efficient.
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