船舶专业英语06

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1、The.externalenv,ronmentWATERANDAIRApartfromsubmergedsubmarines,shipsoperateontheinterfacebetweenairandwater.Thepropertiesofbothfluidsareimportant.Wateriseffectivelyincompressiblesoitsdensitydoesnotvarywithdepthassuch.Densityofwaterdoesvarywithtemperatureandsalinityasdoesitsk

2、inematicviscosity.ThevariationsareshowninTable6.1,basedonsaltwaterofstandardsalinityof3.5percent.Table6.1Waterproperties7~mperatu~(°C)1)ensitvKinematicviscosi~(kg/n(:~)(m2/s×106)FreshwaterSaltwaterFreshwaterSaltwater0999.81028.01.7871.82810999.61026.91.3061.35420998.11024.71

3、.0041.05430995.61021.70.8010.849Thenavalarchitectusesstandardfiguresincalculations,includingamassdensityoffreshwaterof1.000tonne/m3andofsea1.025tonne/m3.Forairatstandardbarometricpressureandtemperature,with70percenthumiditymassof1.28kg/m3isused.AmbienttemperaturesTheambientt

4、emperaturesofseaandairashipislikelytomeetinser-vicedeterminetheamountofairconditioningandinsulationtobeprovidedbesidesaffectingthepowerproducedbymachinery.Extremeairtemperaturesof52°Cinthetropicsinharbourand38°Catsea,havebeenrecorded:also-40°CintheArcticinharbourand-30°Catse

5、a.Lessextremevaluesaretakenfordesignpurposesandtypicaldesignfiguresforwarships,indegreesCelsius,areasinTable6.2.8788THEEXTERNALEN~qRONMENTTable6.2DesigntemperaturesAreaofwarldAveragemax,summerAveragerain.wintertemperaturetemperature,4irSeaAirSeaDBIIBDBI~7~Extremetropic34.530

6、33Tropics312730Temperate302429Temperatewinter-4-2SubArcticwinter-10-1Arctic/Antarcticwinter-29--2Notes1.TemperaturesindegreesCelsius.2.Watertemperaturesmeasuredileal"ttlesurfacemdeepwater.WINDUnfortunatelyfortheshipdesignerandoperatortheairandtheseaareseldomstill.Strongwinds

7、canaddtotheresistanceashipexperi-encesandmakemanoeuvringdifficult.Beamwindswillmakeashipheelandwindscreatewaves.Thewavecharacteristicsdependuponthewind'sstrength,thetimeforwhichitacts,itsdurationandthedistanceoverwhichitacts,itsfetch.Thetermseaisappliedtowavesgeneratedlocall

8、ybyawind.Whenwaveshavetravelledoutofthegenerationareatheyaretermedswell.The