The Proceedings Fifth International Conference on Numerical Ship Hydrodynamics (1990) / Chapter Skim
Currently Skimming:
Wave Resistance and Squat of a Slender Ship Moving near the Critical Speed in Restricted Water
Wave Resistance and Squat of a Slender Ship Moving near the Critical Speed in Restricted Water
Pages 439-454
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 439... ...
C Mel Massachusetts Institute of Technology Cambridge, USA Abstract The wave resistance and implied squat of a slender ship advancing near the critical speed in restricted water are studied.
|
From page 440... ...
(1989) found a broad agreement between the experiment and two theoretical models, the generalized Boussinesq and the forced KdV equations, for a moving two-dimensional bottom topography in a shallow water tank.
|
From page 441... ...
, (13) where RO denotes the characteristic transverse radius of ship and the blockage coefficient is simply the area ratio of the midship section to the channel cross-section.
|
From page 442... ...
- (29) and differentiating with respect to x, we finally get the leading order wave equation Liz= ~ 8~1 - 2~ Ace+ ~1 - 22 + + ~38¢xtx+ (~3/~, (34)
|
From page 443... ...
. Applying the law of mass conservation to the fluid domain surrounded by the ship, the free surface and a control surface located far away from the ship, the source strength is readily 443 2 F2 q = 2 SBSXKX)
|
From page 444... ...
again corresponds to the response to a line source at the ship's centerline, hence takes the following form for small r <,(2)
|
From page 445... ...
For this purpose, let us consider a slender ship whose cross-sectional area varies parabolically 445 In Fig.2, the evolution of the wave field at the critical speed is illustrated with time interval T=0.2 Up to ~=~.o. The parameters are chosen as below: ~=h / L =0.25, W / L= 1.0 (~o=4~0~, SB=0.105 (~=25.6)
|
From page 446... ...
At transcritical speeds, the wave resistance indeed oscillates. The amplitude of oscillation reaches its maximum not at the critical but at a slightly faster speed, and the period becomes longer as speed increases, which supports the experimental findings.
|
From page 447... ...
They found that the maximum channel width is about 20 h for an elongated pressure distribution. Since we are dealing with a slender ship, it may be possible that the downstream waves remain practically two dimensional upto a certain range of channel width.
|
From page 448... ...
& Choi,H.S. 1987 Forces on a slender ship advancing near the critical speed in a canal.
|
From page 449... ...
(a) T = 0' Fig.2 Evolution of wave field generated by a slender ship 449 (b)
|
From page 450... ...
40 0.60 0.80 1 .00 1 .20 1 . 40 Fig.4 Evolution of wave resistance, sinkage and trim for a slender shin ~ a = 0.0, ~ = 1!
|
From page 451... ...
8 ~ 1 o of Rw (U] o: _ /< ~ ~ ~o,o 8- ~ g: /, , 1 , o `,.00 0.40 0.60 1.20 Fig.S Evolution of wave resistance on a slender ship for five different speeds (,s = 5.0, ~0 = 3.t)
|
From page 452... ...
it, it' 'by\ (C) W/L = 3.0 -I ,~ —o ,— ,~ Fig.S Wave pattern generated by a slender ship for three different channel widths at ~ = 1.0 ( ~ = 0.0, ,u = 0.333)
|
From page 453... ...
For all subcritical speeds it is not clear that steady state cannot be reached, since soliton amplitudes (if 2nd, 3rd, etc. solitons)
|
From page 454... ...
In our slender-body approximation, it can be done only indirectly, if we include the temporal variation of the longitudinal distribution of ship's cross section in terms of source strength .
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.