Roll Motion Analysis of Deepwater Pipelay Crane Vessel

J. Marine Sci. Appl. (2013) 12: 459-462DOI: 10.1007/s1 1804-013-1217-7Roll Motion Analysis of Deepwater Pipelay Crane VesselDandan You, Liping Sun，Zhiguo Qu and Tao Wang1. College of Shipbuilding Engineering, Harbin Engineering Universiry, 150001, ChinaAbstract: For a large floating vessel in waves, radiation dampingpipelay crane vessel. In this paper, we give special focus onis not an accurate prediction of the degree of roll unlike otherinvestigating the roll motion performance. This idea is thedegrees of freedom motion. Therefore, to get the knowledge of rollresult of two reasons. One reason is that the roll motionmotion performance of deepwater pipelay crane vessels and tomakes a significant contribution to the vessel's workingkeep the vessel working safety, the paper presents the relationshipperformance. The other factor is that the roll potentialbetween a series of dimensionless roll damping coefficients and theroll response amplitude operator (RAO). By using two kinds ofdamping calculated from the potential theory is not enoughempirical data, the roll damping is estimatedin the Calculation flow. to describe the roll damping. The roll damping cofficientAfter getting the roll damping cofficient from the model test, a should be added to the viscid part.prediction of roll motion in regular waves is evaluated. AccordingTherefore, this paper analyzes the relationship between theto the wave condition in the working region, short term statistics ofroll damping cofficient and the roll RAO based on theroll motion are presented under different wave parameters.potential theory and empirical data. Moreover, it is quiteMoreover, the relationship between the maximal roll response levelto peak spectral wave period and the roll damping coefficient isinvestigated. Results may provide some reference to design andstructures with bilge -keels. Until now, some researchers, likeIkeda, Kato and Tanaka, have made large contributions to thisimprove this kind of vessel.Keywords: deepwater pipelay crane vessel; roll damping; RAO;onwatestudy. So we also investigated the roll motion of pipelay craneshort term statistics; roll motion; regular wavesvessels using the empirical expressions of their research.Article ID: 1671-9433(2013)04-0459-042 Methodologies2.1 Linear responses in regular waves1 IntroductionThe linear response in regular waves is a basic problem toThe deepwater pipelay crane vessel is an important vesselsolve for the responses of floating bodies in waves. A briefin the fabrication of marine engineering and laying pipe. It'sdescription is given in this section. The fluid is assumed asa symbol to measure the ability to exploit the marineinviscid and irrotational fluid. Under these assumptions, theresources of a country.“Haiyangshiyou 201" is the firsttotal velocity potential φ(x, y, z, t) can be written:Chinese deepwater pipelay crane vessel. It is designed to中(x, y, t)= Re[p(x, y, z)ei*"]1)accomplish both pipelaying in water as deep as 3000m deepwater and cranes up to 4000t with the dynamic positionThe space potential q(x, y, z) is split into three parts,system. There have been several scholars analyzing theP(x,y,z)=9。+φ, +p,(j=1,2,-,6)2)motion and working performance of this vessel currently (Li,2010). Also, some researchers focus on the refine method ofin which:the roll motion cofficient, like the concept of roll energyg is the incident undisturbed wave potentialdecay function which was put forward based on theφ,(j= 1,2,. ,6) is the radiation potentialsFroude's energy method (Ma, 2013). By use of CFD method,roll and pitch damping derivatives are calculated from an9 is the diffraction potentialunsteady RANS solver (Zhao, 2013). For the motion of shipφ,(j=1,2,7) satisfies the Laplace equation:of conventional shapes like FPSO considering bilge keel inextreme sea state， researchers also show interest(De△φ=03)Oliveira, A.C, 2012). All these works contribute to the studyAlso radiation and diffraction potentials satisfies the freeof the roll motion of the ship. However, few detailed studiessurface condition, body surface condition, sea bed conditionhave been done on the roll damping of the deepwaterr field condition. Taking these into account, theradiation and diffration atantinlo 2 ho o1tlated. Thus,Received date: 2013-07-29the wave forces 8中国煤化工forces andAccepted date: 2013- 10-10Foundation item: Supported by, the Programmeof Introducing Talents ofmoments can beH;CN M H Gring matrixand inertial matrix, the Inearmotion equations in regular*Corresponding author Email: sunliping @ hrbeu .edu.cnwaves can be solved.◎Harbin Engineering University and Springer -Verlag Berlin Heidelberg 201346Dandan You, et al. Roll Motion Analysis of Deepwater Pipelay Crane Vessel2.2 Linear roll equationscomputed according to Kato (1966).When the floating body only rolls in still water with thesmall angle, the damping moment is considered to be3 Numerical Simulationproportional to the angle velocity of the roll with theopposite direction. Thus in the linear damping condition thefree roll motion equation after experiencing the externalthis paper calculates the response amplitude operator offorce is:4000ton pre-crane conditions in regular waves. The(J. +0/、)φ+2N_φ+C_φ=0(4) .principal dimensions and main parameters are shown iTable 1 below.or can be written:+2vo+ngφ=0(5)Table 1 Dimensions and main parameters of deepwaterpipelay crane vessel in 4000t pre-crane conditionin which J and A.J is the moment of inertia and addedJameUnitsValuemoment of inertia, 2v.。 is the roll damping coefficient,m185the other items in (4) and (5) are familiar to us.2vw =-(64J。+N.Tm9.173Dimensionless roll damping coefficient (DRDC as57428.8follows) is defined as equation(7), in which np is theinherent frequency of the roll. DRDC includes the part ofM5.984radiation damping and the damping caused by viscid.The wet surface of this vessel is modeled as seen in Fig.1Radiation damping is related to the incident wave frequency.which has been created into the panel model. The WadamIt can be calculated by the potential theory. The visciddamping part is often evaluated by model tests or empiricalmodule is based on the WAMIT program in Sesam softwareand is used in the hydrodynamic calculation.data.“=vw1n。(73.1 The relationship between DRDC and roll RAO2.3 Constitution of roll dampingAccording to the empirical data of the dimensionless rollWhile using the Sesam software, the Wadam moduledamping cofficient (DRDC)， Firsov advises that thecalculates the roll damping which is made of contributionscofficient of the bilge keel vessel is 2400= 0.11~0.14.from four kinds of hydrodynamic effects, potential damping,Now considering the vessel motion in the beam sea, thisdamping of skin-friction of the hull, damping froncauses the maximal roll response. Based on the principaleddy-making of the bilge-keel and damping from thedimensions and principal parameters in the 4000t pre-cranebilge-keel. All the damping is linearised to solve thcondition, Table.2 shows the peak amplitude of the rollharmonic equations of motion. The roll damping frolRAO in different DRDC. Peak amplitude always happens ineddy-making due to the naked hull is computed based onthe same frequency w = 0.386rad/s because damping torqueempirical data given by Tanaka (1960), while the dampinghas negligible influence on the roll motion frequency.of skin-friction and eddy-making from bilge keels isFig. 1 The panel model of the wet surface of the vesselTable 2 The relationship between dimensionless rollThe roll motion of the vessel in working conditionsdamping cofficient and roll RAO in beam seashould be controlled gently. Full-scale data of DRDC isu0(C)increased because of current speed and appendages such asshaft bossing. Thus it's necessary to calculate the peak0.0554.996amplitude of the rIL RAQin laroer DRDC Fio.2 ilustrates0.060 .4.524the relationship bet中国煤化工he roll RAO0.0654.231and DRDC. The cuMHCNMHGnofsecond0.0703.956order y = 0.03655+ 9.4005. 1 ne horizontalordinate is one hundred times DRDC in Fig.2.Journal of Marine Science and Application (2013) 12: 459-46261Fig.2 shows that the peak amplitude of the roll RAO Moreover, it is of utmost importance that a good estimate ofdecreases as the DRDC increases. Also we can get the trendthe nonlinear components of the roll damping is made forof the two parameters. In the DRDC range of 0.055 ~0.090,such structures. This detailed calculation of roll dampingDRDC has a great influence on the peak amplitude of the will help the designer to refine the motion performance ofroll RAO, roll angle decreases 0.55 as DRDC increases 0.01; such vessels more efcienty. Moreover, it's essential toWhen DRDC is in the range of 0.09 ~0.14, the curve establish the stripp model for the calculation of roll damping,changes gently and the roll angle decreases 0.21°as the rollin which we can get the bilge radius at each strip. The bilgedamping coefficient increases 0.01.radius is used in the expression of the naked hull's frictionThe roll damping model test demonstrates that thedamping and eddy making damping. It should be noticeddimensionless roll damping coefficient uo is 0.065. Thehere that these empirical cofficients of damping arederived from model tests of a limited number ofresults are in the range of Firsov s model test values.ships/barges neglecting the scale effect. For conventionalIn the study above, we computed the roll damping fromvessel shapes, they are considered to be adequate. Fig.3experimental data directly. The idea is to examine theshows the sketch map of the panel model with the bilge-keelrelationship between the roll motion and the roll damping.highlighted in black.The bile keelFig. 3 The panel model of the vessel with the bilge keel十45°十90°士135g3E|7.5 10.012.5T5.020.40.60.8°1.02T4100X dimensionless roll damping coefficientwave frequency/(rad ●s ")Fig. 2 The relationship between the roll dampingFig. 4 RAO of roll motion which is given bycoefficient and the peak amplitude of roll RAOcalculating each component of roll dampingFig.4 ilustrates the RAO of roll motion in the presence ofTable 3 Working condition of deepwater pipelay craneregular waves with different incident angles. It can be foundvesselthat the results of calculating each component of rolldamping are acceptable. The amplitude of roll motion fallsWave condition Wave spectrumHs/mTp/swithin the range gotten above.Wind waves .Jonswap2..-83.2 Short term statistics of roll motionAlthough we can get the dimensionless roll dampingSwell10-12 .cofficient from the model test, it's reasonable to believethat the real DRDC is in the neighborhood of the test value.This is caused by the scale effect, etc. Also we want to getTable 3 shows中国煤化工include thethe relationhip between the DRDC and maximal rollwind waves and.MHCNMHG principalresponse level. Thus it's necessary to discuss the short termdimensions and main parameters 1n tne 4u0)t pre-cranestatitics of the rolling motion in a series of possible DRDC.condition, short term statistics of roll motion in beam sea is46Dandan You, et al. Roll Motion Analysis of Deepwater Pipelay Crane Vesselcalculated. To demonstrate the effects of DRDC, wavedimensionless roll damping coefficient is analysed. Thenheight and peak spectral wave period (T) on maximal rollshort term statistics of rolling motion were calculated by useresponse level, two examples are shown (Fig.5 and Fig.6).of the roll damping coefficient which is gotten from themodel tests under different wave conditions. It finds that themaximal roll response amplitude decreases as the rolldamping coefficient increases, and the maximal rollresponse amplitude varies monotonically from low to highas the increasing of the peak spectral wave period..4-●References).2-。De Oliveira AC, Fernandes AC (2012). An empirical nonlinearmodel to estimate FPSO with extended bilge keel roll linearequivalent damping in extreme seas. Proceedings of the0.05 0.07 0.09 0.11 0.130.15International Conference on Offshore Mechanics and Arcticdimensionless roll damping coefficentEngineering, Rio de Janeiro, Brazil, 413-428.Fig.5 Short term statistics of roll in the wind wavesDet NV(2007). SESAM User Manual Prostresp 86-3315. 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Shanghai(A) In wind waves conditions calculations are done by choosingJiao Tong University, Shanghai, 136- 144peak spectral wave periods 9s, 8s, 7s and 6s;(B) In swell conditions calculations are done by choosing peakMa XM, Pan YT, Chang LZ (2013). Estimated nonlinear dampingcofficients of amphibious vehicle roll motion. Journal of Shipspectral wave periods 12s, 11s and 10s;Mechanics, 17(5), 488-493. (in Chinese)(C) The difference between the two wave conditions is the waveMo RF, Liu YD (2011). The analysis and short- term prediction ofheight in Table 3.seakeeping of a 1500 ton semi-submerged ship. Ship andFig.6 Short term statistis of roll in sell conditionsOcean Engineering, 33(2), 20-24Sheng ZB, Liu YZ (2004). Principle of ship. Shanghai Jiao TongThe two figures show that at constant wave height, theUniversity, Shanghai, 363-364.maximal roll response level decreases rapidly with the TpTanaka N (1960). A study on the bilge keel, Part 4. on theeddy-making resistance to the rolling of a ship hull. Japan Soc.decreasing. Compared with DRDC, the maximal rollof Naval Arch, 109.response level is much more influenced by Tp. Fig.Zhao ZL, Wang HB, Tao Y, Wang YJ (2013). Predictions ofdemonstrates thatmaximal roll response level alsodynamic damping cofficients of basic finner based on CFD.reduces with DRDC increasing and has a large impact whenApplied Mechanics and Materials, 380(3), 215-218.Tp is 12s. At the Tp levels of 12s, 11s and 10s, responselevel decreases by 0.0837*, 0.0421*and 0.0150°when theAuthor biographyDRDC increases by 0.01. Fig.3 shows a specialphenomenon. In the wind waves condition, response levelLiping Sun was born in 1962. She is a professor atHarbin Engineering University, and a member ofdoesn't change much as DRDC increases to the Tp levels ofthe Chinese Society of Ocean Engineering, as well9s, 8s, 7s and 6s.as a member of the Chinese Society of NavalArchitects and Marine Engineers. Her current4 Conclusionresearch interests include floating structureis， and safety中国煤化工“In this paper, the research on the roll motion of the firstChinese pipelay crane vessel is conducted based on the 3DMYHCNM HGpotential theory and empirical expressions. The relationshipbetween the peak amplitude of the roll RAO and the