Twenty-Third Symposium on Naval Hydrodynamics (2001) / Chapter Skim
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Numerical and Experimental Study of the Wave Breaking Generated by a Submerged Hydrofoil
Numerical and Experimental Study of the Wave Breaking Generated by a Submerged Hydrofoil
Pages 746-761
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From page 746... ...
been g Edna lly varied, mtil She condition for incipient heat mg hr. been reach d D pending on She condition of the experiment, the wave breaking c m start from the fo ward face of the second or thi d wave Rests, hence propagating to the -i t wave, leading to the full developed event INTRODUCTION The knowledge of She mechanisms re ponsible of She breckmg waves is of g et impo tance for She comprehension of m my mutual phffmmerur md th development of several engmeermg processes There are so m my probl ms rel.t ed wish breckmg waves Nat c complete ii t is hard to compile To be cord ted to those rented with ships, breaking waves me producedbyckmo t mymarinevehicle, md are relervnr m She deflmition of Heir operative conditions Beside of bemg re portable of She in x ease of the ship's resistmce, b'ecking use s p By c re levmt r o le m a et ive md pass ive ship detection problems The hyd odynamic noise produced by the breakers m I wer to c g eat extent the efflciency the ship's detection equipment, usually located mside She buk Although She problem may be solved by inmecsmg She depth of She sonar dome, this not clways represent c wimmmg hyd odynamic solution On She of her side, breaking waves me responsible of possible detection of She ship fiom synthetic cpertme radar ISAR!
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From page 747... ...
the signed normal distance from the interface, is introduced and the free surface location is identified as the zero level set (LS) of this quantity.
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From page 748... ...
This kind of scenario for breaking waves has been already experimentally observed by Duncan et al.
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From page 749... ...
The quantity Gmrl J-i (3(m (pro < dxj dx is the mesh skewness tensor. The numerical solution of the Navier-Stokes equations is achieved through a finite difference solver on a non staggered grid similar to that suggested by Zang et al.
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From page 750... ...
6 ough m approximate factorization of She operator of She discreti:osdmoment m equation She pressu e field at She new time step is fo Ed by assummg that the velocity field Ub ~ ~ is rented to ilk, by She relation: I (5)
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From page 751... ...
to be studied On She other h ad, when attention is mainly focused on She flee su la flow, m t coo ate description of She flow clout the body is not sh ictly needed With the al i. e issu s in mind, She presence of She solidbodyhcs been modeled th ough cbodyforces cpproah, gnat is by mtrodu ing Citable body forces in g i d ce ll s ms i de the b o dy c ontou The m agnitude of thi s forces is chosen so that She velocity of the g id pouts mside the body contou tend to be equal to She velocity of She body itself At t = 0 the flow is assumed to be umifomm with (it t 1 = (LO)
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From page 752... ...
region, computed via a BEM solver, and an upper (free surface) region, where the Navier-Stokes solver is coupled with a Level Set technique for solving the air-water;J7ow.
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From page 753... ...
Case study: wxry flow ihdueed by a movihg bottom topogTaphy he wz y flow generctedby cbottom bump movmg m c chumel is studied by usmg fl e full Navier-Stokes solver NS) , fl e domain decomposition cpproah DD)
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From page 754... ...
and t = 6.8 (bottom) In order to show the effectiveness of the Level Set approach in the prediction of wave breaking, the flow over an high bump, leading to the breaking of the free surface, has been also carried out.
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From page 755... ...
One over fourth grid point is shown of the coarse grid. The body andfree surface region are clearly recognizable n n >` 1 1 n 1 1 1 1.5 Figure 1 1: Close up view of the grid in the body region, used in the FNS approach: for clarity, one everyfourth grid point is shown for the coarse grid Free surface profiles obtained with the three grids are shown in Fig.
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From page 756... ...
r Figure 14: VorEcih con tourr behind the hydnofoil f om thetopt thebottomt= 13,t= 20,t=22 On fhe basis of fhe ctove considemtion, c fai comparison with experiments performed et high Rey olds n mber carmot be e tablished mless c tmbulence modeling, beside to m improved body fmce formoktion, is mtroduced DD nerult he problems enco mte~ed m the conect p~ediction of phcse md wave cmplit de, lecd to fhe development of fhe domcm decomposition mprocch fnat uses fhe mviscid rotatiorurl fi w model md the bo mdary element techmiqme to describe the fiow ctout fhe lifimg body wheres uses th Navier-Stokes solver coupled wifh fhe Level-Set techmique to descobe the fiow in the fiee surf a ce ~ egion, where c omp lex mte f a ce t op o logie s m cy de velop m breaking condition N mericcl simoktion have ben carried out by ass mingthematchi gsurfacecty= - 0.2 IndheNavierStokes ~egion c 2S6 x 96 g id is employed with g id pomts s itdoly cluste~ed ctout x = I m the horizontal di ection md ctout y = 0 m fhe verticcl di ection in fhis case c mffomm vertical g id spacmg Xy = 0.005 is usedmy ~ ( - 0.2.0.2) ,whe~ecs5=0.03isusedasfhe hcff wid h of fhe j mp ~ Fig 15, the free smface profile obtained by fhe DD mprocch is compared versus fhe fully non Imear BE5d re mlt md wifh the experimental data by D mc m (1983)
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From page 757... ...
For a non - dimensional submergence 0.783, Duncan (1983) observed an intense wave breaking with a high dissipative effect on the following wave.
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From page 758... ...
I en used Ed two different m mericcl codes have been developed, based on She body force Ed on c domain decomposition approach s respectively he bodyfmces approach has been developed in vi w of delmg with She flow cutout mulUbody co flgmations es it is She case of c ship with appendages his approach ht. proved to be useful, although c higher order model for the cssig ement of the body forces, Ed hence of She way in which the shape of the body is represented, is needed in order to gam msight mto the dynamics of She flee surface, She domain decomposition cpproah hits proved to be promising, focusing attention Ed computatiomd efforts in the flee surface region With reference to She quasi - tecdyb~eckingproducedbythehyd of oil, m mericcl re mlts discussed h re suggest Nat, Although She m merical techniques are Cole to detect the inception of the breckmg, the adopted g id w re too coarse to resolve She -I w Possible extension of She work is She inclusion of surface tension effects, allowing c comparison with the set of experimental data he emphasis of She experimental work is on mderst Ming the conditions alder which ccpilk y waves may lorce She breaking on the folowmg wave h cm, subsequently forcing She extension of the t ret mg area to She forward waves Th work is k gerly alder development Ed c new >!
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From page 759... ...
Svendson, I A, Spillmg brekers, bores md hyd mlic j mps, Pnoceed ings of 16th Coost I En gng Conf Hcmburg, Germ my, 1978 Rose feld M, Kwak D md Vmokur M, A fiactiorul step solution method for 6he mstecdy incompressible Navier-Stokes equations in gene~alized coordincte systems, J Comp t Phys,vol 94,102-137,1991 Sus m m M, Smerekc P
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From page 760... ...
In my experiments with surface-tensiondominated unsteady breakers with wavelengths of about 1 meter, a bulge forms at the crest with capillary waves upstream of the leading edge (toe) of the bulge.
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From page 761... ...
DISCUSSION D Dommermuth Science Applications International Corp., USA The authors have developed a unique procedure for modeling breaking waves.
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