Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Validation and Application of Chimera RANS Method for Ship-Ship Interactions in Shallow Water and Restricted Waterway
Validation and Application of Chimera RANS Method for Ship-Ship Interactions in Shallow Water and Restricted Waterway
Pages 458-474
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From page 458... ...
More than 40 time-domain simulations were carried out parametrically for different ship types, wharf line distances, ship speeds, and wind directions that are manifested in ship crabbing angles. The results of these computations were systematically organized and compared to investigate the ship speed effect, wind direction effect, wharf line distance effect, ship type effect, ship sheltering effect, and bottom clearance effect.
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From page 459... ...
A total of 44 runs were carried out parametrically for various combinations of ship speeds, wind directions, ship types and wharf line distances. The results of these computations were systematically analyzed to determine the ship speed effect, wind direction effect, wharf line distance effect, ship type effect, ship sheltering effect, and bottom clearance effect.
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From page 460... ...
In addition, the model test data underwent a screening process to reject 'wild' data values and also a curve-fitting procedure to fit the data into a modified sine function format. The curve fitting strategy was probably influenced by the observations of typical calculations of interactions based on potential flow and rigid free surface flow assumptions.
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From page 461... ...
clearly showed that the two pressure wave fronts met near the center of the towing tank even though the passing ship travels at a significantly higher speed than the own ship. This indicates that the propagation speed of the pressure waves is nearly independent of the actual ship speed.
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From page 462... ...
Longitudinal velocity (left) and pressure (right)
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From page 463... ...
and pressure (right) contours for overtaking encounter case (case 2)
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From page 464... ...
A total of 44 simulations were performed to examine the effects of passing ship speed, wharf line distance from the channel boundary (i.e., lateral separation distance) , crabbing angle of the passing ship (a manifestation of the wind effects)
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From page 465... ...
In addition, there is no 2:1 slope at the wharf line and the vertical quay wall is located at a distance of 2h away from the moored ship-C (to the starboard side)
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From page 466... ...
Bird-eye view of blanking between grid blocks Detailed Flow Field Time-domain simulations were performed for each case listed in Table 1 with various combinations of ship speed, wind direction, and wharf line distance. A total of 2000 time steps were used for each simulation with a constant non-dimensional time increment of 0.0025.
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From page 467... ...
It is believed that these high frequency oscillations were caused by the small underkeel clearance of the moored vessel and will be discussed in more details later when the effects of bottom clearance is considered. In the mooring line analysis, the sway forces and yaw moments are of particular concern because they produce lateral displacements and rotations perpendicular to the wharf line.
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From page 468... ...
.0.4 0.2 0.0 0.2 0.6 0.8 Figure 14. Longitudinal velocity (left)
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From page 469... ...
It is seen that both the phase and magnitude of the peak sway force and yaw moment change with the ship -0.1 0.2 speed. The phase lag for higher speed cases is to be expected since the faster ship will be closer to the moored ship when the pressure waves generated by initial ship acceleration reach the moored vessel.
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From page 470... ...
In addition, the yaw moments and sway forces induced by the larger ship-B are also considerably higher than those observed in Figure 18 for ships A-A configuration. In general, it was observed that crabbing angle introduced additional interaction forces and moments depending on the passing ship speed and crabbing direction.
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From page 471... ...
Yaw Moment -2 -1 0 X/L 1 2 3 Figure 20. Wharf line distance effects: (a)
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From page 472... ...
The free surface pressure contours shown in Figure 22 clearly illustrates the complexity of the nonlinear interactions between the (a) Case 7, Ship A-A, t/T = 2.0 inbound ship, outbound ship, moored ship, and the bank.
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From page 473... ...
In the navigation channel design study, the numerical results were systematically organized and compared to investigate the ship speed effect, wind direction effect, wharf line distance effect, bottom clearance effect, and ship sheltering effect while there are more than two ships in the channel. For safe operation of a ship while operating in the proximity of other ships and near obstacles with variable-depth bottom topography, accurate interaction forces and moments acting on the ships are required.
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From page 474... ...
Depending on the test condition, it is actually quite common to observe solitary waves running in front of the ship in shallow water ship model tests. In the current study, the ship speed was ramp up from zero to a constant value in a fairly short distance.
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