海岸动力学英文PPT课件CoastalHydrodynam课件

CoastalHydrodynamics海岸动力学,Chapter2WAVETHEORY,Statingdescriptionofwavemotion,Statingbasicequationsofwavemotion,Statingthesmallamplitudewavetheory,Statingthefiniteamplitudewavetheory,Statingwavetheorylimitsofapplicability,1/21,Chapter2,Wateristreatedasauniform,Assumptions,continuityequation,Thefluidviscosityisnormally,velocitypotential,Thesurfacetensionand,gravityonly,Thebottomisimpermeable.,zerovelocity,ignored.,Coriolisforceareignored.,andincompressiblefluid.,Wavestravelinthex-zplane.,2/21,Chapter2,G.D.E.,B.B.C.,onz=-h,L.B.C.,D.F.S.B.C.,K.F.S.B.C.,onz=,onz=,BoundaryValueProblemofWaveMotion,3/21,1.Linearizationofbasicequations,Chapter2,2.3SmallAmplitudeWaveTheory,2.Solutionofthelinearizedequations,3.Dynamicthusanyproductsofthesevariablesaresmallenoughtobeignored.Thisprocessiscalledlinearization.Linearinthesensethatvariablesareonlyraisedtothefirstpower.,7/21,Chapter2,Asmallamplitudewaveisalsocalledalinearwave.Itisawavewhichtravelsveryslowly,thewaveheightisfarsmallerthanthewavelengthandthewaterdepthismuchgreaterthanitswaveheight.,Whatisasmallamplitudewave?,8/21,Chapter2,Supposethatthewaveisasmallamplitudewave,namelyHLorH1),thesolutionofvelocitypotentialis:,Whiletheelevationofthewatersurfaceis,16/21,Chapter2,SubstitutingthevelocitypotentialandthesurfaceelevationintotheK.F.S.B.Cyieldsthedispersionrelationship.,Dispersionrelationship,17/21,Chapter2,Thisrelationshipshowsthatthewavelengthcontinuallydecreaseswithdecreasingdepthforaconstantwaveperiod.Thatistosay,wavesofconstantperiodslowdownastheyentershallowwater.,Dispersionrelationship,Afieldofpropagatingwavesconsistingofmanyfrequencieswouldseparateduetothedifferentceleritiesofthevariousfrequencycomponents.,18/21,Chapter2,Casestudyof“wavedispersion”,19/21,Chapter2,Hadweusedthesurfaceelevationinsteadof,howwouldthevelocitypotentialbechanged?,MINI-EXAMINATION(1),Homework,Chapter2,Awavewiththeperiodof5stravelsinwaterof5m,whatisitscelerityandwhatisitslength?Youareonaship(100minlength)onthedeepoceantravelingnorth.Theregularwavesarepropagatingnorthalsoandyounotetwoitemsofinformation:(1)whentheshipbowispositionedatacrest,thesternisatatrough,and(2)adifferentcrestispositionedatthebowevery20s.Doyouhaveenoughinformationtodeterminetheshi