FLAC generate grid.docx
- 文档编号:27509635
- 上传时间:2023-07-02
- 格式:DOCX
- 页数:18
- 大小:1.03MB
FLAC generate grid.docx
《FLAC generate grid.docx》由会员分享,可在线阅读,更多相关《FLAC generate grid.docx(18页珍藏版)》请在冰豆网上搜索。
FLACgenerategrid
3GridGeneration
Atfirst,itmayseemthatthegridgenerationschemeinFLAC3Dislimitedtorathersimple,regularshapedregions;theexamplesgiveninSection2.7arealluniform,polyhedralgrids.TheFLAC3Dgrid,however,canbedistortedtofitarbitraryandcomplicatedvolumetricregions.ApowerfulgridgeneratorisbuiltintoFLAC3Dtomanipulatethegridtofitvariousshapesofthree-dimensionalproblemdomains.
Oneimportantaspectingridgenerationisthatallphysicalboundariestoberepresentedinthemodelsimulation(includingregionsthatwillbeadded,orexcavationscreatedatalaterstageinthesimulation)mustbedefinedbeforethesolutionsteppingbegins.Shapesofstructuresthatwillbeaddedlaterinasequentialanalysismustbedefinedandthenremoved(viaMODELmechanicalnull)untiltheyaretobeactivated.Thepurposeofthegridgeneratoristofacilitatethecreationofallrequiredphysicalshapesinthemodel.
3.2OverviewoftheGridGenerator
GridgenerationinFLAC3Dinvolvespatchingtogethergridshapesofspecificconnectivity(referredtoasprimitives)toformacompletemodelwiththedesiredgeometry.Severaltypesofprimitivesareavailable,andthesecanbeconnectedandconformedtocreatecomplexthree-dimensionalgeometries.
GENERATEkeywordvalue...
TheGENERATEcommandcreatesaFLAC3Dgrid.Gridgenerationisdefinedbythefollowingkeywords:
zonecreateszoneswithinthe3Dvolume.
mergeensuresthatseparategridscreatedwithGENERATEzoneareconnectedifgridpointsoradjacentfacesarewithinaprescribedtolerance.
GridgenerationisinvokedwiththeGENERATEcommand.ThegenerationofzonesforeachprimitivetypeisperformedwiththeGENERATEzonecommand.Referencepointscanbedefinedbycreatinggridpoints(usingtheGPcommand)atspecificlocationsandreferringtothemintheGENERATEzonecommand.TheGENERATEmergecommandcanbeusedtoensurethatseparateprimitivesareconnectedproperly.Allgridpointsalongmatchingfacesofzoneprimitivesmustfallwithinaspecifiedtolerance,fortwoprimitivestobemerged.Alternatively,theATTACHcommandisavailabletoconnectprimitivemeshesofdifferentzonesizes.FISHcanbeusedtoadjustthefinalmesh,ifnecessary,toconformtothesurfacesofthemodelregion.
3.2.1ZoneGeneration
SeveralGENERATEzonecommandscanbegiventoconnecttwoormoreprimitiveshapestogethertobuildaFLAC3Dgrid.ThecommandsGENERATEzonecopyandGENERATEzonereflectareavailabletoassistwithcreatingamodelcomposedofmultipleshapes.
ThecommandGENERATEzonedensifycanbeusedtosubdividezonesintotwoormoresmallerzonesinthesamespace.
keyword
Thecharacteristicsoftheshape(e.g.,globalcoordinatepositions,numberofzones)aredefinedbyspecifyingthekeywordsgivenbelow,aftertheshapekeyword.Notallkeywordsapplytoeveryshape.
dimensiond1
specifiesthedimensionsofinteriorregionsfortheshapes:
radialtunnel,radialcylinder,radialbrick,cylindershell,cylinderintersectionandtunnelintersection.Ifdimensionisnotgiven,defaultvaluesfortheentriesarecalculatedas20%ofthelengthsbetweenreferencepoints.
edgevalue
specifiesanedgelengthforthesidesofthemesh.Ifp1,p2andp3arenotspecified,thenthemagnitudeofthedistancefromp0willbedefinedbyedge.
fill
Iffillisspecified,theinteriorregionfortheshape’sradialtunnel,radialcylinder,radialbrick,cylinderintersectionandtunnelintersectionwillbefilledwithzones.Ifnotspecified,theinteriorregionwillnotcontainzones.Iftheoptionalgroupkeywordisgivenwithavalidname,thennameisassignedtothefilledzones.
groupname
assignsagroupnametothisprimitiveatcreation.
nomerge
DuringexecutionofaGENERATEzonecommand,acheckismadeforeachboundarygridpointagainsttheboundarygridpointsofzonesthatalreadyexist.Iftwoboundarygridpointsfallwithinatoleranceof1×10−7(relativetothemagnitudeofthegridpoints’positionvector)ofeachother,theyareassumedtobethesamepoint,andthefirstgridpointisusedinsteadofcreatingnewonesforallsubsequentcalculations.Ifnomergeisspecified,twogridpointsarenotmergedintoone.
p0
p1
p2
p3
Thekeywordsp0,p1,...p16specifythereference(corner)pointsoftheshapes.Iftheaddkeywordisused,thecurrentpositionforp0isaddedtothelocationspecified.Bydefault,p0islocatedat(x=0,y=0,z=0).Bydefault,p1,p2andp3aresettotheorthogonaldistancesinthex-,y-andz-directions,withamagnitudeequaltothenumberofzonesinthatdirection.Alternatively,pointnmaybespecified,aspreviouslydefinedbytheGENERATEpointcommand.
sizen1
Thisspecifiesthenumberofzonesforeachshape.(默认长度1.0m)
FourGENERATEzonekeywordsareavailabletoassistthezonegenerationphase:
copy,densify,extrudeandreflect.Arangecanbespecifiedtolimittherangeofthesekeywords.
copyxyz
Withthecopykeyword,allzoneswithinthegivenrangearecopiedtoanewpositionbyaddingtheoffsetx,y,z.Ifnomergeisspecified,gridpointsontheouterboundariesofthenewlycreatedzonesarenotmergedwithpreexistinggridpoints.
reflectkeyword...
Withthereflectkeyword,allzoneswithinthegivenrangearereflectedacrosstheplanespecifiedbythefollowingkeywords.Ifnomergeisspecified,gridpointsontheouterboundariesofthenewlycreatedzonesarenotmergedwithpreexistinggridpoints.
ddvalue
Thisspecifiesthedipdirectionvalue[degrees]oftheplanemeasuredintheglobalxy-planeclockwisefromthepositivey-axis.(Thedefaultisvalue=0.)
dipvalue
Thisspecifiesthedipanglevalue[degrees]oftheplane,measuredinthenegativez-directionfromtheglobalxy-plane.(Thedefaultisvalue=0.)
normalxvyvzv
Thisspecifiesanormalvectortotheplane,withthecomponentsxv,yvandzv.Ifnormalisspecified,dipandddarenotrequired.
originxvyvzv
Thisspecifiesthelocationofonepointthroughwhichtheplanecrosses.Thecoordinatesofthepointarexv,yvandzv.
densify
Thiscommandfindsallzonesintherangeandsubdividesthemintosmallerzonesfillingthesamevolume.Notethatthiscancreate“hanging”gridpointsthatarenotperfectlyconnectedtothesurroundinggrid.TheATTACHfacecommandshouldbeusedbeforecycling,toensurecontinuousmodelbehavior.
global
Thisspecifiesthatthezoneedgestowhichnsegmentn1,n2,n3isappliedaretheonesthatmostcloselycorrespondtotheglobalx,yandzaxes.
gradlimit
zoneschosenfordensificationwillbecheckedtoattempttoensurethatadjacentzonesdifferby,atmost,onelevelofdensification.Thismaymeanmorezoneswillbedensifiedthanactuallyfallintotherange.
local
Thisistosetthezonestobedensifiedinalocalsegmentorder.Thelocalsegmentorderisalongtheedgesofe1,e2ande3,wheree1,e2ande3aretheedgesofthefirstandsecond,firstandthird,andfirstandfourthgridpointsofthiszone.
maxlength11<1213>
Thisspecifiesthemaximumedgelengthstobedensified,inorder.Ifl2andl3arenotspecified,theywillbesettothesamenumberasl1.
nsegmentn1
Thisspecifiesthesubdivisionnumberofzonestobedensified,inorder.Ifn2andn3arenotspecified,theywillbesettothesamenumberasn1.
repeat
repeatsthedensificationntimes,causingarecursiveapplicationoftherangeanddensificationsettings.Thiscan,forexample,beusedtocreateanoctreegrid.Notethatifnonumberisgiven,thenFLAC3Dwillrepeatuntilthemaxedgelengthisreached,applyingthedivisionspecifiedinnsegmenteachtime.
Theattachkeywordshouldbeusedafterthisone,toattachfacesofsub-gridstogetherrigidlytoformasinglegrid.
merge
mergessurfacegridpointsthatcoincideinspaceintoasinglegridpoint.Surfacefacesaremergedintointeriorfacesifallgridpointsoneachfacehavebeenmerged.
Theratiokeywordisofparticularsignificancewhendesigningagridtoprovideanaccuratesolutionwithoutrequiringanexcessivenumberofzones.Forexample,iffinezoningisrequiredimmediatelyaroundtheperipheryofthecylindricaltunnelinordertoprovideamoreaccuraterepresentationofhigh-stressgradients,ratiocanbeusedtoadjustthezonesizetobesmallclosetothetunnel,andgraduallyincreaseinsizeawayfromthetunnel.
Toseetheeffectsofusingtheratiokeyword,typethecommand
genzoneradcylsize510612ratio1111.2
Eachsizeentryiscontrolledbyaratio.Inthisexample,thefourthsizeentryhasageometricratioof1.2(i.e.,eachsuccessivezoneis1.2timeslargerthantheprecedingzone,movingfromthetunnelperipherytotheouterboundary–seeFigure3.3).
Sizingthegridforaccurateresults,butwithareasonablenumberofzones,canbecomplicated.Threefactorsshouldberemembered:
1)Finermeshesleadtomoreaccurateresultsinthattheyprovideabetterrepresentationofhigh-stressgradients.
2)Accuracyincreasesaszoneaspectratiostendtounity.
3)Ifdifferentzonesizesareneeded,thenthemoregradualthechangefromthesmallesttothelargest,thebettertheresults.
Theexamplesinthefollowingsectionsillustratesomeapplicationsofthesefactors.
SeveralGENERATEzonecommandscanbegiventoconnecttwoormoreprimitiveshapestogethertobuildagrid.Forexample,tobuildahorseshoe-shapedtunnel,theradcylindera
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- FLAC generate grid