ComparativeAnalysisoftheDynamicAngleofHeelofaShipe 888ProjectTypeDefinedoftheCalculationandModelTests

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1 journal of maritime research Vol. IX. No. 3 (2012), pp ISSN: ComparativeAnalysisoftheDynamicAngleofHeelofaShipe 888ProjectTypeDefinedoftheCalculationandModelTests W.Mironiuk 1 A R T I C L E I N F O Article history: Received06June2012; inrevisedform09june2012; accepted30july2012 Keywords: Stability,Warshipmodel, Laboratory,Dynamicheel SEECMAR /All rights reserved A b S T R A C T Resultsofinitialresearchonairflow sdynamicimpactonashipmodelof888projecttypearepresented intheelaboration.theresearchhasbeenexecutedatateststandlocatedinthepolishnavalacademy. Theshipmodelof888projecttypehasbeenanobjectofthetests.Resultsofexecutedmeasurements havebeencomparedwiththeoreticalcalculationsforanangleofdynamicheel.inputparametersfor thetestsandcalculationshavebeendefinedinaccordancewithrecommendationsofpolishregister ofshipping(prs)andimo(imoinstruments1993,2008,prs2007).determinationofaheelingmomentbywindoperationhasbeenakeyissue.theexecutedresearchhasrevealedthatthewaythecriteriaoftheship sdynamicstabilityaredefinedbyprsandimotakesacertainsafetymargininto account. 1. Introduction Duringoperation,ashipisopentodynamiceffectsresultingfromspecificsofmarineenvironment.Amongthese effects,winddynamicimpacttogetherwithawavymotion isespeciallyhazardousfortheship.therefore,thereare applicable criteria, taking the above said situations into consideration,inclassificationsocieties regulations.away tocalculateaheelingmomentoriginatedbythewindoperation is given in dynamic stability criteria. One may determineanangleofdynamicheelbasedonafunctionof thismomentandrightinglevers curve.but,assumptions andsimplificationsacceptedbytheclassificationsocieties resultinomissionofsomephenomenaandtheangleof dynamic heel, determined based on theoretical calculations,differsfromtherealone(moreno,chaos,aranda, Muñoz, Díaz, Dormido, 2009). Determination of a real valueofthedynamicangleofheelispossiblebyexecuting modeltestsperformedwithgeometricanddynamicsimilarityscaletakenintoconsideration.resultsoftheoretical calculationsandmeasurementsofdynamicangleofheel, executedwithashipmodelof888projecttypeasanexample, are given in this elaboration (Lewandowski, 2010). 1 NavalAcademy,FacultyofNavigationandNavalWeapons;ŚmidowiczaStreet69, Gdynia,Poland;tel , w.mironiuk@amw.gdynia.pl, wmiro@o2.pl. Resultsofthepresentedtestsallowformulatingpractical conclusionsthatmaybeusedbytheclassificationsocieties, amongtheothers. 2. Research facility and object of the test TestsonthewinddynamicimpactonashiphavebeenexecutedatafacilitylocatedinthePolishNavalAcademy (Mironiuk,W.2006).Mainelementsofthestandareasthe following: Modelbasinforsurfaceshipsofinternaldimensionsof LxbxH3x2x0,5m, Shipmodelof888projecttype, Shipmodelof660projecttype, Computerregisteringparametersoftheshipmodel position, Devicegeneratingairflow. Thereisasetoffansfixedinacasingmakingajetofa changeablesectiononthebasin sshorterside.dimensions ofthejet soutletaresufficienttolettheairflowoperateon entireflankofthemodel,withasuitablereserve.thereare 5bigand5smallfansinthejet shousing alltogether,they arecapableofgeneratingairflowfasterthan5m/s. Ashipmodelof888projecttypehasbeentheobjectof thestudy.itwasmadeinascale1:50inrespecttoareal vessel.theschemeofthemodelisshowninthefigure2.

2 34 Journal of Maritime Research, Vol. IX. No. 3 (2012) permanentbecause,itdepends amongtheothers ondynamics ofthewindeffect.locationofthe ship model s axis of rotation is crucialtodeterminetheheeling moment. The IMO s stability code (IMO Instruments, 1993, 2008,)provideswithinstructions thattheheelingmoment slever shouldbecalculatedasadistance fromacentreofthetopsideprojected area to the centre of the underwaterpartofthehull sprojectiononthesymmetryplane,or approximately tothevessel s halfdraughtdepth.inthisconnection,resultsofmeasurements of and calculations for the dynamicanglesofheel,executedin compliancewiththeimo srecommendations,shalldiffer. A sensor of the heeling and trimanglesregisteringtheangles withanaccuracyofupto0,01of degreeisinstalledonthemodel. Signalsfromthesensoraretransmittedbymeansofacabletoa computer.influenceofthecables connectedtothemodelhasbeen omittedbecauseoftheirinsignificantweightandsectionareas. Fig. 1. Facilityfortestsondynamicimpactofwind. Itsbasicdatahavebeenasthefollowing (Mironiuk,W. 2006): Overalllengthofthemodel:Lc=1,444m; Lengthbetweenperpendiculars:Lpp=1,284m; Displacementofthemodel:D=13,15kg; Averagedraughtofthevessel:T=0,078m; Depthofthemodel scentreofgravity:z G =0,096m. 1,2and3-ValvesforapuncturesimulationinthecompartmentsPIII,PVandPVII;4,5,6,7and8-Valvesfor flooding the compartment PVI, PIV, PIII, PII and PI; 9,10,11-WaterlevelindicatorsinthecompartmentPVII, PVandPI;12.Indicatorofshipdraught;13.Listindicator. Attheleveloffloatationline,openings horizontally arranged aremadeinthemodel sstemandsternframe. Rodslimitingtheship sdriftcausedbytheairflowoperationmaybeplacedintheopenings.suchanarrangement resultsindefiningafixedaxisofrotationoftheshipmodel. Infact,positionoftheshipmodel saxisofrotationisnot 3. Problem of geometric and dynamic similarity scale Solving the geometric and dynamic similarity scale problem has consisted in meeting given conditions.theshipmodelwasmadeinthe1:50scalethatiswhyallgeometricquantitiescouldhavebeeneasily calculated.valuesoftherightingleverscurveoftheship modelalsohavebeensubjecttothegeometricsimilarity principle.theheelingmomentshouldeffectinproportion tothevessel srightinglevers,i.e.ratiooftheship srighting leversmaximumvalueandvalueofthewindaffectedheelingmoment slevershouldbethesameforboththemodel andtheship,asbelow: wherethe o subscriptreferstothevessel,whilethe m subscriptreferstothemodel.figure3makesagraphical mappingofthe(1)dependence. Windpressureaffectingthevesseldependsonthewind affectedheelingmoment.therefore,thepressureshould bedefinedincompliancewithasuitabledynamicscalein (1)

3 W. Mironiuk 35 Fig. 2. Dispositionofelementsinthemodel oftheshiptype888. (2) relationtothemodel.valueofthepressurehavingdynamic impactonarealobject,i.e.imoandprsregulations(imo Instruments1993,2008,PRS2007).Itis504Paforshipsof unrestrictedoperationalwaterareasandwindoperating statically.however,avalue1,5timesbigger,i.e.756pais givenfordynamicwind.agivenwindvelocitycorresponds withthispressurevalue,andthevelocitymaybedeterminedwithmanyways.usingdependenceonthedynamic pressureisoneofthem,asthefollowing: Thepressurevalueof756 Pagivestheairspeedof35m/s atthedensityof1,2kg/m 3. Todeterminethewindvelocity inrespecttothepressure,one mayalsousetablevaluesprovidedinpublishedreferences (Dudziak, J. 2006). It follows from them that the velocity should be some 29 m/s for squallof756papressure. Theairspeedobtainedfortheshipshouldberecalculatedforaspeedforthemodel.Suitablerecalculationsmay bedonewithmanyways.usingeulercoordinateisoneof them(grobyś1998),asbelow: Thepressureof756Paandthespeedof32m/sboth definedfortheshipgivesthewindvelocityof4,52m/s,i.e. thevelocitythatshouldhaveimpactonthemodel. Incasethefollowingdependenceonthewindaffected heelingmomentisapplied(prs2008): (3) Where: F w topsideprojectedarea[m 2 ], z w distancefromcentreofwindprojectedareatowaterline positioned at height of T/2 above basic plane,atgivenloadcondition[m], j angleofheel, v w windvelocityatheightofwindprojectedflank s geometriccentre,definedwiththefollowingformula(prs2008), (4) Where: v 10 windvelocityatheightof10metresabovewaterline,v 10 =80knotsisacceptedfortheshipsofunrestricted operationalwaterareas. Thewindvelocityis4,51m/sfortheshipmodel. Thepresentedsolutionsfortheproblemofdynamic similarity scale follow to similar results of the air flow speed.therefore,itisprobablethatthecalculationsforthe windvelocityhavebeendonecorrectly. (5) 4. Execution of the tests Fig. 3. Determinationofwindaffectedheelingmomentlever svalue forshipmodel. The study s programme has been executed in several stages.determinationoftheairflowspeeddistributionhas

4 36 Journal of Maritime Research, Vol. IX. No. 3 (2012) beenoneofthefirstactivitiesattheresearchstand.measurementsoftheairflowspeedhavebeenexecutedin18 points.resultsofthemeasurementsforthespeedofthe airflowgeneratedonlybythebigfansaregivenintable1. Average value of the speed of the airflow affecting the modelhad4,52m/s. Table 1. Resultsofmeasurementsofairflowspeed. Measurement Place of measurement and Average value height value of speed [m/s] [m/s] ,5cm 4,57 4,68 4,69 4,16 4,10 4,53 4,46 18,5cm 4,67 4,86 4,77 4,53 4,16 4,65 4,61 8,5cm 4,33 4,63 4,60 4,65 4,65 4,10 4,49 4,52 a) b) Nextstageoftheresearchhasbeentodeterminethe dynamicangleofheel.testsatthestandhavebeenexecuted,amongtheothers,forthefollowingvaluesoftheanglesofheeltowardsthewindwardshipboard:6,15,18. Valuesoftheseanglesresultfromcalculationsofweather criteriaexecutedfortheshipprojectoftype888inaccordancewiththeregulationsofimoandprs. Thefanshaveworkedwithconstantvelocityduringregisteringtheanglesofheelwhatcorrespondswithconstant characteristicsoftheheelingmoment.resultsofthemeasurementsoftheregisteredanglesofheelsaregiveninfig.4. Table2containsalistingoftheresultsforthemeasurementsexecutedatthestand.Thebiggestvaluesofthedynamicangleofheelhavebeenobtainedwhenthemodel hasbeendeflectedtotheangleof18degreestowardsthe windwardshipboard. Table 2. Valuesofdynamicanglesofheel. No Angleofheeltowardswindwardshipboard[deg] Dynamicangleofheel[deg] Theoretical calculations Calculationsfortheship sdynamicangleofheelhavebeen executedfortheheelingmomentdefinedinaccordancewith theimoandprsrecommendations.basedonthem,lever ofthedynamicallyoperatingheelingmomenthasbeendeterminedassumingthatthedistanceofthetopsideprojected area scentrewasmeasuredfromthehalfdraughtdepth.the prospectedleverhasbeencalculatedwiththefollowingdependence(imoinstruments,1993,2008,prs2007). where:q v =504Pa windpressure; F w topsideprojectedarea[m 2 ]; Z v measuredperpendicularly,distancefromcentreof topsideprojectedareatocentreofunderwaterpart ofhull sprojectiononsymmetryplane,or approximately tovessel shalfdraughtdepth[m]; D ship sdisplacement[t]; g 9,81m/s 2 ; andforthedata: Fw =533m 2 ; Zv =6.46m; D=1643.7t, toresultinobtainingvalueofthewindaffectedheeling leverequal0,162m. Forthisvalue,thedynamicanglesofheelhavebeen readonagraph(fig.5)andplacedinatable 3. (6) Table 3. Valuesofdynamicanglesofheel. c) No Angleofheeltowardswindwardshipboard[deg] Dynamicangleofheel[deg] Fig.4. Measurementsofdynamicangleofheelafterdeflectingmodeltowards windwardshipboardtoangleof:a)6 ;b)15 ;c)18. Theresultsshowthatthevaluesofthedynamicangles ofheelobtainedfromthecalculationsareseriouslybigger thanthevaluesobtainedfromthemeasurements.thefact thatleveronwhichforceofthewindpressureoperateswas definedfromtheship shalfdraughtdepth,insteadoffrom theoperativewaterline,isoneofthereasons.shouldone

5 W. Mironiuk 37 This time, the results of the dynamicangleofheelcalculationsand measurementsareverysimilar.differencesarefrom10to16%.itispossible to obtain more similar results after dampingofmovementandsizeofthe windexposedarea sprojection,which changesduringtheheel,aretakeninto account. 6. Summary Fig.5. Determinationofdynamicanglesofheelforshipof888projecttype forzv=6.46m. Fig.6.Determinationofdynamicanglesofheelforshipof888projecttype forzv=4.49m. Theexecutedinitialresearchonthe dynamic influence of the wind affected heeling moment shows high convergenceofthetheoreticalcalculationswiththemeasuredvalues.the obtained results prove that the way thewindaffectedheelingleverisdeterminedhassignificantimpactonthe valuesofthedynamicanglesofheel. Theshipmodelhashadthefixedaxis ofrotation,positionedinnotwaving waterplane.therefore,ithasnotbeen possible to compare the measurementsresultswiththeresultsofcalculationsforthedynamicangleofheel accurately,ifdeterminedbasedonthe heeling moment imposed by IMO. Further research on the described issueshallallowexecutingmoreaccurateanalysis. take this note into consideration, the wind affected dynamicleverl w shallequal0.111m.anextgraph,givenon Figure6,allowingdefiningthedynamicanglesofheel,has beenexecutedforthiscase.obtainedvaluesoftheangles arepresentedinatable4.moreover,alinewithvaluesof thedynamicstabilityanglesmeasuredatthestandhasbeen added-toenabletocomparetheresults. Table 4. Valuesofdynamicanglesofheel. No Angleofheeltowardswindwardshipboard[deg] Dynamicangleofheeldetermined forzv=4.49m[deg] Dynamicangleofheelmeasuredatstand[deg] References Dudziak,J.(2006)Teoria okrętu.gdańsk:wm. GrybośR.(1998)Podstawy mechaniki płynów część 2.Warszawa:PWN. IMOInstruments(1993).Code on Intact Stability of All Types of Ships.London. IMOInstruments(2008)International Code on Intact Stability.London. Lewandowski,G.(2010)Badania modelowe stateczności dynamicznej okrętu projketu888 poddanego oddziaływaniu wiatru.gdynia:amw. Mironiuk,W.(2006)Preliminaryresearchonstabilityofwarshipmodels.Proceedings of the 9th international conference on stability of ships and ocean vehicles, 23-30September,RiodeJaneiro,brazil,pp Moreno,D.;Chaos,D.;Aranda,J.;Muñoz,R.;Díaz,J.M.;Dormido,S. (2009) Applicationofanaeronauticcontrolforshippathfollowing.Journal of Maritime Research. Volume6,Issue2,August,Pages Pawłowski,M.(2004)Subdivision and damage stability of ships. Gdańsk. PRS(2007)Przepisy klasyfikacji i budowy statków morskich, Część IV.Gdańsk. PRS(2008)Przepisy klasyfikacji i budowy okrętów wojennych, Część IV.Gdańsk.

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