Twenty-Third Symposium on Naval Hydrodynamics (2001) / Chapter Skim
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Anti-Roll Tank Simulations With A Volume of Fluid (VOF) Based Navier-Stokes Solver
Anti-Roll Tank Simulations With A Volume of Fluid (VOF) Based Navier-Stokes Solver
Pages 457-473
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From page 457... ...
based NavierStokes solver Both fiee-surface mti-roll tmks md U-tube mti-roll tarns me considered Calculated md measured results for She local wave heights, th sway force md roll moment are presented for bodh leg lar md i regular tank motions A simple but effective simulation model for She active co trol of U-tube me roll talk is i nod i ed Finally, She f 11y nonlinear time-domcin coupling of the ship motion md the t mk water motion is estate lished INTRODUCTION A ship subjected to wind md wave forces will perfomm motions m six deg es of freedom, i e surge, sway, he, roll, pitch md yaw The roll motion is the most critical one bec mse it is lightly damped md therefore prone to dynamic mcgmfication, in particohr m th resonance fiequency 9 ge Ship-roll stabilization hr3 Therefore Deceived considerable attention; it till is c major subject of mterest to ship designers md naval architects Among c wide variety of roll-damping devices Vastc et al 1961) , mti-roll tmks me appreciated for their simplicity, low cost md action et low or even zero speed The concept of using fluid tmks for ship-roll reduction was fi st conceived by Froude (1861)
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From page 458... ...
In this way, the fluid flow is blocked and the tank's roll peak period can be matched with the ship's natural period of roll. Finally, the nonlinear coupling of the ship motion and the tank fluid motion is solved with a time domain method adopted from a numerical technique developed for nonlinear fluid sloshing in spinning containers (Gerrits & Veldman 20004.
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From page 459... ...
to collect i formation Croat the performance of fiee-surfae mti-roll ticks A rect mg lar tarn, partially filled with water, was forced to execute sinusoidal oscillations Croat c fixed axis while the moment due to the water motion was amplitude AM cod phase male CM with re pect to the forced rank rolling motion Aft) w re determined Sy tematic measurements w re done for c wide r mge of rank parameters (tick widthB, mean water depth h)
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From page 460... ...
Figme 2 (lef col mn) : Fre-surface tmk in ~eg lar roll motion Sm~pshots tak n from computer simulstions wifh ComFlo 111u tmtion of ws types for dffferent f~equency regimes: (c)
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From page 461... ...
Figme 5: Fn4e-Yurf6 o tamk in n4g 16 roll motioa Moment 6mplitude 6t 6heoretical resonance fiequency 6s function of roll 6mplit de P6 6meters: sB=00; h B=0 06 Lme: 6heory; solid squares: experime ts; Opff~ squares: ComFlo The meam w4ter dep6h h is 6 p6 ticul6 impo tamt p6 6meter. becamM4 it is cie6 th~t for 6 cc tam tamk width B the only possibility to chmge 6he m~tm61 period of 6he water t msfer, 6heoretically gi on by To=2B/ h)
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From page 462... ...
~ htB[ ] Figme 7: Fn4e-surfs s tarDc in n4g lar roll motioa Roll moment rmplitude et theon4ticcl resonance freq~rsucy es function of me m water depth Ps rmeters: s R=0 0; Ao=5 7deg Lme: theory; Solid squares: experiments; Open squares: ComFlo oo~o 0015 \' ~=ooio ~ ~ ~=~ ~ ]
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From page 463... ...
[ ] Figme 10: F'ee-surface rank in red let roll motion Moment amplitude (top)
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From page 464... ...
. Moment amplitude (top)
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From page 465... ...
The water heights in both wing tanks and the sway force and roll moment exerted by the tank on the ship were measured during calm water roll decay tests and in irregular wave conditions. In the computer simulations, the measured sway, heave and roll motions were imposed on the tank (Kleefsman 20004.
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From page 466... ...
m portside wing tarDc es function of time Solid line: experiments; Dcshed line: ComFlo The computer simulation of th ineg lar wave te t is done with 100 cells in horim hl di ection md 44 cells m verticcl di~ection Th te t parameters which have ch mged with ~espect to th values m Tctle 2 are given in Tctle 3: Tctle 3: U-tarDc i regmlar wave test p~meters parameter value V~,d ISlm h~ 2 652 m h~s(t=Os)
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From page 467... ...
Solid line: experiments; Dashed line: ComFlo. U-TANKS WITH ACTIVE CONTROL A major disadvantage of anti-roll tanks is that the free surface always reduces the metacentric height so that roll stability will be reduced.
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From page 468... ...
md phase m ale (bottom) es f motion of roll period Parameters: Ao=4 9deg Squares: AT=0 Os; Rhombs: AT=0 Ss; Trimgles: ~T=I Os; Crosses: AT=1 Ss; I: nclev AT=2 Os; Plusses: AT=2 5s Figme 20 shows the cclcokted moment amplitude es function of roll frequency for various values of the delay time AT The mNturcl flequency of the t mk is ~h=0 56rad/s, which corresponds to c m~tmcl period To=11 2s A smusoidal rolling motion is imposed on the U-tmk When the water reaches it maxim m height in eifner one of the wing t mks, it was block d by me ms of the clove procedure The delay time AT was varied (marmclly)
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From page 469... ...
, M is the (6x6) -mass matrix, A, B Ed C me 6x6-mat ices with the fiequency-dependent add d mass, damping Ed spring coefhcients, Tic is c Component vector vifh the forces Ed moments due to the mcommg Ed dfffi acted waves Ed Fad is the co tobution fiom the radiated waves Th incoming Ed dfffi acted wave conh~butions are calculated with MARIN's ship th ory prod cm SH PMO (1998)
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From page 470... ...
Figme 24 Co pied ship U-tmk slmniatimm Roil oment conh~bution: so id hn = wave itstmn, ds shed line = U-tarDc COUPLED SHIP AND TANK FLUID MOTION \VITH ACTIVE CONTROL Fim~lly, w present the results from s computer simulstion where 6he coupling model smd the conhol model s e combined Figure 25 shows the re mlts fi om s simulstion for ~045rsds, ie off tmk reson~nce Three co flgurstions w ~e sim 5sted: (1) ship with empty tsmk; (2)
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From page 471... ...
G m md Pckzzi, L, "3D fluid sloshing m rect mg lar contamers Vclidation of c Vol me Of Fluid based Ncvier-Stokes solv r", Maritime R search ~stitute Nedherkmds, Rpot No 16131-2-RD, Mcy 2000 Daalen, EFG van md Westhnis, J-H, 'Non-linear oscillations of fluid in c rect mg lar container Vcli dati on of c flr t or der pertmbati on crurlys is base d on 6he non-linear shallow water th ory", Maritime R search Instit te Nedherkmds, R port No 16131-1RD, March2000 Fekkff~, G Veldm m, A E P
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From page 472... ...
43,No 433,1996,pp 70-88 Loots, GE, 'Free smface flow in thee-dimensiopal complex g omehies", Mcster's Th sis, Univ rsity of G onmgen, D partment of Mc6hematics, Apg st 1997 Loots, GE, 'Free smface flow in thee-dimensiopal complex geomehies psmg erJkmced bopmdary hectment", Mcster's Thesis, Univ rsity of G oningen, D partment of Mcthematics, Jpp 1998 Lp6h, HR, 'Desig verifcation st dy for D tch gov rmme t patrol v ssel", MARN R port No 67, 1999,p 11 Scbep, Z Cohen, JE, Steph ps, JR md Veldmcn, AEP, '7p stigation on fiee sp face flow oscillatory impact p~esspres wi6h 6he Volume Of Flpid medhod", ~: Npmericcl Methods m Flpid Dvpcmics Vl C¢lJ Bcip s cd )
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From page 473... ...
our cttff~tion We have not accounted for the effects of inegular waves (L d motions) m our conhol algorithm Undoubtedly, we will be traced to include c prediction algorithm once we start testing our method m Regular wave conditions DISCUSSION M Hir mo Mitsui Akishimc Laboratory, Up m A trolling tactics me usually installed on c ship as c part of ship structure he this sense, such small structure members as stiffeners may be fitted inside the tardy wall Question is whether the effects of stiffeners on both roll moment amplitude Ed phase Ogle c m be computed or not in the computation?
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