Twenty-Third Symposium on Naval Hydrodynamics (2001) / Chapter Skim
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A Design Tool for High Speed Ferries Washes
A Design Tool for High Speed Ferries Washes
Pages 957-967
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From page 957... ...
ABSTRACT The high waves generated by fast ferries may have den imentcl effects v ham cpproahing She co t The aim of this st dy is to detemmme She characteristics of ship wash or g oups of high- peed ship waves m coastal Ed shallow water regions The pmpose of She medhod developed herem is to provide c tool for authorities as regards speed limits Ed routes for fast ferries cpprocchmg the coasts The waves generated by high-sped ships are represented by th ir free wave spectrum This sp ctrum is determined digitally using c wave resi tance prod cm POTFLO) based on the Ne marm Kelvin model It is ass med that She he waves propagate m She same maimer es c short Rested see, defmed by c di ecticrurl energy spectrum This energy pectrum is expressed explicitly in terms of She he wave sp ctrum Spatial wave propagation is then modeled over time using c thi d-generation spechal wave model named TOMAWAC, based on c Quite element tech iq~x Evolution over time is depicted et certain critical positions along the shore Results me given in terms of sig fficmt wave heights Ed me m wave periods for deferent ship ro tes Ed peeds INTRODUCTION In recent years, m merous papers have been published on fat ship wash finish MA 1997, Hem k Kofoed et al 1996, Kirkegsard et al 1998, St mbo et al 1999)
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From page 958... ...
(6) Free wave amplitude spectrum 7he ship wave field usmg c point ~ehted to 6he ship is determined by formok (7)
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From page 959... ...
- formoh (13) is rektive to m O y point ~ehted to the ship; O bemg the bow, O bei g m 6he mmetrical plane md di~ected to the fme md Oy being in the t ms xse phne di ected to po tside - 6he scope of 6he wave field is x = 0 to x = -oo Par'de~dar ease of ~dtra tdgh-speed s tdp s Ult~a high-speed ships sail zt higher speeds 6 m 6he st mdard high-speed ships xrently in service Ult~a high- peed ships c m briefly be descobed zs ships havellmg zt z higher speed 6 m thA cone ponding to the kst b mp on the wave ~esistmce curve Associated wi6h these high speds, the ship wave far-field is composed mainly of diverge t waves, pro idmg 6he hull is st~eamlmed (Ogilvie 1 977)
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From page 960... ...
=cos 3A(3) Fig 3 shows reel part f Ed im33~3ry pan g at 35 k ots COASTAL WAVE PROPAGATION 310DELLING O ce She ship wave field has been computed, one has to detemmme the wave characteristics m She nearshme zone It is Hen necessary to describe the wave field in c fixed geog 3phi 31 f 3me h fi is fixed f 3me Q'X'Y' Z', the Z' axis is di ected ve ticclly upward, X'Y' defining the hori motel pi m coincident with the still water level The ship route is oriented with m male d mch that it is possible to express quantities fiom She fi 3me O ye to the f 3me Q'X'Y'Z' f ou h following formula: a= X'cos,d+Y'sin,d up t)
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From page 961... ...
15 l~ot on B Horbour The computaticrud domcm is illushated on Figme 5 Point B is located I mmtic mile soubhward fiom the East hfht of the Nice harbou Pomt A is roughly located I mmtic mile clong the di~ection 313°N from B md conesponds to the miticl position of the ship in ou simulations We cssume fnat fhe ship wave feld that h~s been genemted before its position in A hcs no influ nce on the cocsbl mec of mte~est Si~lohon 4: Rout A'B' Horboux Speed of 35 Imot on A'B' 15 Imot on B' Horbour In addition to simulation 4 ctove, it hcs been decided to look at fhe case of c ship cpproahing very near the coc tline md keepmg its cruise speed of 35 k ots on fhis A'-B'-Harbou route This lecd to: Si~lohon 4bu: RouteA'B'Horbour Speed of 35 Imot on A' B' 35 Imot on B' Horbour The c mpubtiorud domain for these two simohtions is given on Figme 6 Point B'is located I mtic mile m 6he 159°N cape fiom 6he east iight of 6he Nice harbou Point A' is roughly located et 0 6 m~u ic mile (1000 m)
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From page 962... ...
no influence on She coastal area of interest Simohtions are performed in c m teddy mode, in order to reproduce She time-varymg development of She wave field generated by the high-speed ferry At each time tep, one determines the ship position md assigns the wave vari mce spectrum deduced from She ship speed et each node along the bo mdary of She domain, that coincides wish the ship position This is c realistic procedure which enables to reproduce She wave energy q mtity that is h m fenedbythefer y to She cc mic domain With She help of fmite element tech iq~x, mesh size for all simulations varies fiom 80 m offshore to less thm 15 m near She shore Time step is fixed et I s in addition to the usual processes that effect She wave propagation geomehic refiation md shoaling m~mh 1, the model also taco mts for She dissipative process th o gh depth-induced wave breaking The wave variance sp ctrum is discretied using 25 he.p~ e. fj dime ted wish re pect to c ge met i serie if = lo 05 (I I'd ~ I, ad 'J dmYnons leg larly pa d with AO = 15 For i formation, one simulation, which roughly cone ponds to 6 minutes duration in reel time (time necessary for She ship to reach She harbour from She Initial positi m A or A' or A')
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From page 963... ...
1998 Prediction of 11 bore Ed Nearshore Stomm Waves Using c Third Generation Specnal Wave Model Proc of ISOPE .98 conference, Vol. 111, 71 76, MontreaL Conodo, M y 1998 Benmt M 1995 Log~ciei Tomawa de fneoriqu de h ersion 1 0 R ppo t EDF-DER tnntt~r is /0 cm on avenge with c maxmm m BE-42/95/047/A 6beorencal valet of 90 m The shipping authorities Ed shipyards now base a ess to c rage of calcoktion codes emiblmg She prior q mtitative evalusti m of high-speed ship wash, using con till zone relief Ed badhymet y maps for She are Is crossed by the ship Operators will ah ~ elk e, in She futme, be Cole to eq ip themselves with new highsp cd car ferries satisfying the safety standards laid doss by shipping authorities The aim of cunent research is to optimize calcoktion ules, in parncular es regards hull discretication (m mber of son es)
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From page 964... ...
Elliot, L The Prediction Measurement and Analysis of Wake Figure3: Wave amplitude spectrum at35 knots Wash from Marine Vessels - Marine Technology, vol 36, no 4, Winter 1999, pp 248-260.
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From page 965... ...
| SIMI] LATIONI: 25 knots onA-B; 15 knots on B-Harh~our | N~cel~rhour \ late Mann SIMULATION 2: 35 knots on A- B; 15 knots on B- Harh~our | SIMULATION ~ his: Simulation ~ in steady state B== Nice C - e Cape 00 | anon ~nnn SIMULATION 5: 25 knots on All- B; 15 knots on B1l- Harh~our C TACT IT .
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From page 966... ...
4500 4400 4300 4 2 0 0 4100 4000 3900 SSOO S700 3600 025 r 02-~ 015 -~ 01 0.0s O -, 02s~ 0 015 0.1 0.05 o o 4sOO 4400 4300 4200 4100 4000 3900 SSOO 3700 ~nn 0.70 0.60 0 50 0 40 0.30 0 20 0 1 0 0.00 r~n Pll ~ ~ 1 - \ Pt ~ C~ Niee ~ \~ Pl3 ~ ~ Pl4 _ ~\\ (fer7y Fo~e) 800 900 1000 1100 1200 1300 1400 F~ure ~ SIMULATION 4 4sOO 4400 4300 4200 4100 Time evoIution 4000 of the significant w~e haght Hs 39°° ~ 4 coastal locations ssoo ~oo acoo Pll ~ ~ 1 Pt ~ ~ Niee ~ ~ Cape ~.
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From page 967... ...
of Ship Res 16,1972) For She general case of c ship, to our knowledge, there is no validated prog cmme computing the wa ve resist mce m accelerated moti m Our application to high speed ferries washes cone ponds to She decelerated motion for which no validated solution seems to exist L t us add Nat She as mmption of deep water for the calcu he on of the ship wave spectrum is correct for the case of the approach of the harbour of Nice Indeed, She water depth is very large along She con t except very near the harbour ent mce We co firm also that our calculation is tmly unsteady in the see ond part when the wa ve s pr opagate mto shallow water DISCUSSION D Hend ix Naval Surface W art ne C nter, Carderock Division, USA This pap r presents c very mtere ting application of potential flow to c current design problem Since, es She hors observe, "Solving the Neumarm-Kelvin system of equations is c rather difficult task " I would I ke to suggest Nat the mthors consider using the slender ship theory to detemmme She wave amplitude function As we repo ted earlier this week, (in Practical CFD application to design of Wave Cancellation Multihull Ship)
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