Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Application of a 3-D Time Domain Panel Method to Ship Seakeeping Problems
Application of a 3-D Time Domain Panel Method to Ship Seakeeping Problems
Pages 376-392
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From page 376... ...
Hydrodynamic forces, ship motions in waves and wave pressure on the hull surface are computed for several ships. The results are compared with experiments and the calculated results bar strip method.
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From page 377... ...
Euler angles with respect to roll, pitch and yaw are represented as A, §, ~ respectively, and the vector Q Incident waves are generated by movement of flap angle /9 of wave maker attached to tank wall.
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From page 378... ...
3. Numerical Procedure 3.1 Flow of numerical computation Numerical flow for calculating ship motions and hydrodynamic forces is as follows.
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From page 379... ...
/~t (29) Obtaining the hydrodynamic forces, v and ~ are calculated from eqs.~15)
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From page 380... ...
As to, we employ value of to~/377=15.7 to avoid the long period oscillation of hydrodynamic forces appears in case of rapid accelerationt214. In acceleration period until reaching to the steady ship speed, large damping is artificially added to the force term of the motion equation.
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From page 381... ...
This figure includes hull panels above the still water surface. Fig.4 shows time histories of hydrodynamic forces excluding restoring force component for forced heave with w~/~75=3.86.
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From page 382... ...
To obtain the hydrodynamic force coefficients on the lateral motions, 3 forced oscillation tests such as pure swaying, pure rolling and pure yawing tests were conducted at towing tank, Nagasaki R & D center, MHIt234. The size of the towing tank is 120m in length, 6.1m in width and 3.65m in water depth.
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From page 383... ...
5. Ship Motions in Heacl Waves for S175 Container Ship Next, the present method is validated for ship motions in regular head waves.
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From page 384... ...
O —u.u~ O.O , j . i 0 0.2 0.4 0.6 0.8 `,' 1 0 0.2 0.4 0.6 0.8 `o 1 U.U~ 0.0d o.or ~.o, Fig.9: Added mass and damping coefficients in pure swaying mode (Fn=0.2' 62a/B=0.0448)
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From page 385... ...
Flap angle of the wave maker was selected as OO=l.Odeg so as to coincide with the amplitude of incident waves in the tank test. The calculated amplitude was about 2-3m in fullscale.
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From page 386... ...
The ship motions gradually grow and at around T = 50 reach to steady state. We see 2 components of oscillation in (~/L: one is long period oscillation due to artificial restoring force term and the other the surge motion oscillating with encounter frequency.
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From page 387... ...
. a' m18C t n~ ;~ e-~ -- ~ -- -~ -- -- -- -- -- -- -1 1 1.5 A/L 2 Fig.17: Comparison of amplitudes and phases of surge, heave and pitch in regular head waves for S-175 container ship (Fn = 0.25)
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From page 388... ...
The detailed test procedure and the ship model used in the test were described in Ref.~274. Table 4: Principal dimensions of a 4,900TEU large container ship Ship length Lpp Breadth B Depth D draft d ship speed U Model 4.200m 0.652m 0.396m 0.204m 1.38m/s .
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From page 389... ...
All the results except the wave patterns were compared with experiments and the calculated results by strip method. As a result, we found that hydrodynamic forces, ship motions and wave pressures are much better predicted than by strip method.
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From page 390... ...
and Ando, J., "Rankine Source Method using Rectangular Panels on Water Surface", 11th International Workshop on Water Waves and Floating Bodies, 1996, Hamburg. t214 Yasukawa, H., "Time Domain Analysis of Ship Motions in Waves using BEM (1st Report: Computation of Hydrodynamic Forces)
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From page 391... ...
. t26: Yasukawa, H., "Time Domain Analysis of Ship Motions in Waves using BEM (2nd Report: Motions in regular head waves)
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From page 392... ...
Now we are planning another tank test to capture nonlinear behavior of wave loads and wave pressures for other modern container ship. This test includes the cases of oblique waves and irregular waves.
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