船舶管理Shipmanagement17課件

Teacher：HUHUIHUI(Lisa)船舶管理Shipmanagement江蘇高校省級留學生英文授課精品課程Task5SeakeepingPerformances

目錄/Contents01FloatabilityStabilityRollandPitch

020403FastSpeed

0506Floodability

ManeuverabilityTask5 SeakeepingPerformancesOneoftheimportantseakeepingperformancesisfloatabilitythatindicatestheabilityofvesselfloatingpositivelyonwaterundertheconditionofacertainamountofdeadweight.

Whenwedealwithfloatability,wemustfirstbeclearaboutthefollowingtwotechnicalterms,i.e.reservebuoyancyandload-linemark.

FloatabilityTask5 SeakeepingPerformancesThen,whatisthereservebuoyancy?Asitisknowntoall,ashiphastoobtainacertainamountoffreeboardwhenshe’ssailingatsea.FloatabilityTask5 SeakeepingPerformancesThatistosay,togiveyouaconcreteidea,anyvesselistoretainsomevolumeabovewaterforthesakeofextrabuoyancysothatitsdraftallowedtoincreasewithoutasinkingtragedyunderparticularbutrareconditions,suchasroughseaorseriousfloodingduetohulldamage.FloatabilityTask5 SeakeepingPerformancesFloatabilityTITANICTask5 SeakeepingPerformancesForinstance,thefilm,TITANIC,popularineverycorneroftheworldandpresentingamovinglovestorytothesentimentalaudience,describesthefatalhulldamageowingtoahugeicebergFloatabilityTask5 SeakeepingPerformancesThisextrabuoyancyiscalledreservebuoyancy;or,tobeexact,thereservebuoyancywhichismeasuredbyfreeboardreferstothewatertightvolumeofhullaboveloadline.

FloatabilityTask5 SeakeepingPerformancesOnemoreseakeepingperformanceisthestabilitywhichistheabilitythatvesselswillinclinewhenaffectedbyanexteriorforce,suchaswind,wave,etc.,andwillrestoreitsoriginalpositionontheforceremoval.StabilityTask5 SeakeepingPerformancesStabilityis,ofcourse,ofgreatimportancetoshipbuildingsinceitsfailurewillalwaysleadtoheavylossoflife.Historyhassadlywitnessedtragicsinkingofvesselssomanyatimebyreasonofpoorstability.

StabilityTask5 SeakeepingPerformancesInordertoobtainfinestability,precautionswillnormallybetakenintwodifferentways.Ononehand,gravitycenteristobelowered;ontheotherhand,metacentertoberaised.StabilityTask5 SeakeepingPerformancesThegravitycenterofashiptobecalculatedbymeansofaninclinationtest.Thetestisgenerallytobeperformedincalmwaterandwithlovelyweather.Ifyouhavegotadrydockforthetest,somuchthebetter.

StabilityTask5 SeakeepingPerformancesAnotherseakeepingperformancethefastorrapiditywhichdescribestheabilityforashiptogainfasterspeedatlowerconsumptionofpower.

Vesselswillbeaffectedmainlybywaterresistanceduringvoyage.FastSpeed

Task5 SeakeepingPerformancesWedonotbotherourbrainaboutairresistancebecauseitisfarsmallerthanwaterresistance.Perhapstheonlyexceptionishigh-speedboats.

FastSpeed

Task5 SeakeepingPerformancesWaterresistancetobeencounteredbyashipconsistsoffrictionresistance,swirlresistanceandwave-forming(wave-making)resistance.

FastSpeed

Task5 SeakeepingPerformancesTherearetwowaystoraiseshipspeed,namely,tominimizewaterresistanceandtoincreasemainenginepower.Toachievethis,abulbousbowiswidelyusedinmanytypesofshipsandtheratedhorsepowerofmainenginesisgenerallytobeovertwotimesasbigastheeffectivehorsepowerofships.

FastSpeed

Task5 SeakeepingPerformancesWhenfloatingonwaterorsailingatsea,vesselswillrollorpitchowingtowavemotionsaswellastheinfluenceofwind,currentandpropeller.

Asyouknow,therollperiodisgreatlyconcernedwiththeinitialmetacentricheightand,insomedegree,stabilityiscontrarytoroll.RollandPitch

Task5 SeakeepingPerformancesItseemstobestrangethatviolentroll,asmanypeoplemightthink,isnotderivedfrompoorstability.

RollandPitch

Task5 SeakeepingPerformancesFloodabilitystatestheabilityforavesseltokeepafloatwithsufficientfloatability,stabilityandotherseakeepingperformancesincaseoneorseveralcompartmentsareflooded.Shouldseadamagetakeplace,reservebuoyancewouldbetheprincipalconditiontokeepavesselafloat.FloodabilityTask5 SeakeepingPerformancesWiththehelpofthewatertightbulkheadsanddeckswhichseparatetheinsideofhullintoanumberofcompartmentsandspaces,reservebuoyanceenoughistoberetainedsothattheintakeofseawatermaybeconfinedtothedamagedcompartmentwithoutwaterpouringintotheadjacentcompartments.

FloodabilityTask5 SeakeepingPerformancesThelastseakeepingperformancethatwearecomingtoismaneuverability.Shipmanoeuvrabilityistheabilityofashiptokeeporchangeitsstateofmotionunderthecontrolactions,i.e.tokeepthestraightaheadcoursewithconstantspeed,ortochangethespeed,thecourseand/orthepositionoftheship,accordingtotheintentionofthehelmsman.ManeuverabilityTask5 SeakeepingPerformancesShipmanoeuvrabilityincludesthefollowingcontents:

(1)Inherentdynamicstability,alsocalledstraightlinestability:Ashipisdynamicallystableonastraightcourseifitcan,afterasmalldisturbance,soonsettleonanewstraightcoursewithoutanycontrolactions.ManeuverabilityTask5 SeakeepingPerformancesManeuverabilityDynamicstabilityTask5 SeakeepingPerformancesTheresultantdeviationfromtheoriginalcoursewilldependonthedegreeofinherentstabilityoftheshipandonthemagnitudeanddurationofthedisturbance.ManeuverabilityTask5 SeakeepingPerformancesManeuverabilityDynamicstabilityTask5 SeakeepingPerformances(2)Coursekeepingability,alsocalleddirectionalstability:Thecoursekeepingabilityistheabilityofthesteeredshiptomaintainitsoriginalcoursedirection.Ashipwhichhasinherentdynamicstabilitycanonlymaintainitsoriginalcoursedirectionunderthecontrolaction.ManeuverabilityTask5 SeakeepingPerformancesManeuverabilityDirectionalstabilityTask5 SeakeepingPerformancesAlsoashipwhichisdynamicallyunstableonstraightcoursecanmaintainitsoriginalcoursedirectionbyfrequentlyapplyingthecontrolaction.ManeuverabilityTask5 SeakeepingPerformances(3)Initialturning/coursechangingability:Theseabilitiesaretheabilityofashiptochangeitsheadingasresponsetoacontrolaction.Ashipwithgoodinitialturningabilityand/orcoursechangingabilitywillquicklygetintoturningorchangeitsoriginalcourseafterthecontrolaction.

ManeuverabilityTask5 SeakeepingPerformances(4)Yawcheckingability:Theyawcheckingabilityistheabilityofthesteeredshiptorespondtothecounterrudderactionappliedinacertainstateofturning.ManeuverabilityTask5 SeakeepingPerformances(5)Turningability:Theturningabilityistheabilityofship