HEC-RAS实例example

HEC-RASATutorial(ModelDevelopmentofaSmallFlume)HEC-RAS•HydraulicEngineeringCenter:RiverAnalysisSystem•1-Dstepbackwatermodel•Utilizesenergyequationtocomputewatersurfaceelevationforagivendischarge,geometry,andresistanceOrganizationalStructure•Openproject–creates(.prjfile)•Includes:1.Unitsystem(SI/UScustomary)2.Geometry(XS,bridges,weirs,etc.)(.gfile)3.FlowData(steady,unsteady)(.ffile)4.Plandata(whatcombinationofflow/geometrytousefortheanalysis)(.pfile)OpenanewprojectNametheproject(.prjfile)Afteryouhaveenteredtheabove,clickO.K.andO.K.againSelectSIunitsGeometryFiles(.g)•Createareach-singleordendriticClickhereCreateanewriverreachDrawthereachupstreamtodownstreamDoubleclicktoendNametheriverandreachGeometry•Crosssectionsdefinethechannel/flumegeometry•CrosssectionsaredefinedbyStation(x)andelevation(y)intheplaneofthecrosssectionperpendiculartotheflow•Riverstation,downstreamreachlengthandcrosssectionthalwegelevationdefinethechannelslope•Overbankstationsdifferentiatechannelandfloodplaincharacteristics•ResistancetoflowisdefinedbyManningncoefficientsforboththechannelandfloodplain•Expansionandcontractioncoefficientsdefineenergylossesassociatedwithvelocityheadchangesbetweencrosssections•Ineffectiveflowareasarecanstorebutnotconveywaterdownstream•Obstructionareasblockflowcompletely•LeveeelevationsconfineflowtochanneluntiltheleveesareovertoppedMoregeometry•Junctionsdefinewheretworeachesareconnected•Bridgesandculverts•Inlineweirs/gates•Offchannelstorage•Pumpingstations•Allcanbemodeledwithareasonableamountofdetail(canbecoveredatalaterdate)Flumeexample•Width-7.57cm(0.0757m)•Wallheight-12cm(0.12m)•FlumeLength-182cm(1.82m)•Slope-none,horizontal•Roughness-Plexiglass(n~0.0085)•Discharge-1.5l/s(0.0015m3/s)•Crosssectionspacing–10cm(0.1m)•Downstreamboundarycondition(criticaldepthatoutlet,freeoverfall)EntercrosssectiondataClickAddanewcrosssectionStartatdownstreamriverstation0.00m(HECRASESTABLISHESTHEDOWNSTREAMENDASZEROFORASTARTINGDISTANCEANPROGRESSIVELYWORKSUPSTREAMINCHAINAGE)Enterandapplydataassuminganarbitrarydatumof100.00m,noticethedownstreamreachlengthiszerosinceweareatthefurthestdownstreamextentofthemodelCross-sectionaldata-EnteredfromlefttorightlookingdownstreamManningsnvaluesLOB&ROBwouldbetheleftandrightfloodplainsrespectivelyIftherewerefloodplains,thisboxdefinesthehorizontalrightandleftlimitsofthechainagesofthemainchannel(seepageafternextforexample)EnterdesireddescriptionofthecrosssectionYoualsohavetoenterthelocationswhereafloodplainwouldstartiftherewasone,forthismodelwewillassumethetopoftheflumeiswherethefloodplainwouldstart(henceatLOB=0m,ROB=0.0757m).Clickon“ApplyData”toaddthecross-sectiontothemodelandtoviewthesectionMainChannelChainageDefinitionFlumeExampleNotethedifferentManning’snvaluesinthechannelandontherightandleftfloodplainsforariver.AdobeCreekExampleSincethegeometryisuniformfromtheupstreamtodownstreamextent,wecanmakeuseofthecrosssectioninterpolationtooltocomputethegeometrywiththespecifiedcrosssectionspacingThiswilltakeafewsteps….Addanewcrosssectionattheupstreamendriverstation1.82m(Sincewehavethesamegeometrywearegoingtomakeuseofthecopysectionfunction)Enterthestationchainageattheupstreamendoftheflume(fortheflumetheupstreamendwillbelocatedat1.82m)Otherwise,ifthegeometrywasdifferent,youwouldClick–options/addanewcrosssectionThestationidentifieryoujustenteredTheLOB,Channel&ROBdistancesbetweensectionsneedtobeansweredsincethesectionsareparallel,thenallthreedistancearethesame(1.82m)Remembertoclick“applydata”afteryouhaveenteredthegeometryRemembertochangethedescriptiontoreflecttheupstreamcross-sectionLOBROBCHANNELParallelSectionsSectionsOnSkews1.82m1.91m1.82m1.73m1.82m1.82mLOBROBCHANNELNowit’stimetointerpolatecrosssections…Inthemaingeometrymenuclickontools/XSinterpolationandselectbetweentwocross-sectionsEnter0.1masthemaxdistancebetweenXS’s,thenhittheinterpolatebuttonandyourgeometryiscompleteIfyoucontinuedtohavedifferentcrosssectionalgeometryateachcross-section,youwouldcontinuetoaddnewcross-sectionsandenterthedistancesbetweeneachsection.YourmaingeometrymenushouldnowlooklikethisThecrosssectioninterpolationtoolhasplacedthecrosssectionsatintervalsof0.096m(evenlyspaced),noticethereisnoslopeontheprofileNowisagoodtimetosaveyourgeometrydata,rememberthe.gfile?NameandsaveitintheRasprojectdirectoryyouareusing.Let’slookattheprofileforourmodel,clickonthecrosssectiondatamenutab,thenplot/profileNowlet’sputsomewaterinthisflume…Ifyourplotdoesnotlooklikethis:-goto“options”ontheCrosssectiondatawindow-goto“scaling”-changeyaxisminto100.0-changeyaxismaxto100.14-changeyaxisincrementto0.02-clickO.K.-goto“options/variables”-clickonthefirsttwothatareunchecked(leftmainchannelbankelevation&rightmainchannelbankelevation),clickO.K.-click“options/grid”andmakesurethat“thickborder,majorandminortickgrids”areallon.Flowdata(.ffiles)•Steady(constantwithtime)•Unsteady(varieswithtime)•Regimes(supercritical,subcritical,mixed)•Boundaryconditions:1.Supercritical-upstream2.Subcritical-downstream3.Mixed-bothFlowdatacontinued•Boundaryconditiontypes:1.Knownwatersurfaceelevati