CEL教程Word文档下载推荐.docx

CEL教程Word文档下载推荐.docx

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∙CELExamples

∙CELTechnicalDetails

Release13.0-©

2010SASIP,Inc.Allrightsreserved.

13.1. 

CELFundamentals

Thefollowingtopicswillbediscussed:

∙ValuesandExpressions

∙CFXExpressionLanguageStatements

13.1.1. 

ValuesandExpressions

CELcanbeusedtogeneratebothvaluesandexpressions.Valuesaredimensional（thatis,withunits）ordimensionlessconstants.Thesimplesttypeofdefinitionisthedimensionlessvalue,forexample:

b=3.743

Youcanalsospecifyavaluewithunits,forexample:

g=9.81[ms^-2]

ThedimensionsofthequantitiesofinterestforCFDcalculationscanbewrittenintermsofmass,length,time,temperatureandangle.Theconceptofunitsisfundamentaltothebehaviorofvaluesandexpressions.

Valuescanbeuseddirectly,ortheycanbeusedaspartofanexpression.Forexample,youcanuseanexpressiontoaddtwovaluestogether:

<

Expr_1>

= 

Value_1>

+ 

Value_2>

Inthisexample,youmaywanttopredefine<

and<

butthisisnotrequired.However,inordertoaddtwoquantitiestogether,theymusthavethesamedimension;

thatis,itismeaningfultoaddaquantityininchestooneexpressedinmeters,butitisnotmeaningfultoaddoneexpressedinkilogramstooneinsquarefeet.

Expressionscanalsobefunctionsofother（predefined）expressions:

Expr_2>

Value_3>

UnitsfollowtheconventionsintherestofCFX,inthatacalculationhasasetofsolutionunits（bydefault,SIunits）,andthatanyquantitycanbedefinedeitherintermsofthesolutionunits,oranyothersetofunitswiththecorrectform.

Anexpressiondoesnothaveitsownunitsstring,butifitreferencesquantitiesthathavedimensions,thesewilldeterminetheresultingunitsfortheexpression.Forexample,ifanexpressiondependsinverselyonthesquareofthex 

coordinate,thenithasimplieddimensionsoflengthtothepower-2.

13.1.1.1. 

UsingLocatorsinExpressions

ACFXsimulationhasphysicsareasandmeshareas;

physicsareasareboundarieswhilemeshareasareregions.Thesetwotypesofareacanoccupycompletelydifferentspacesinasimulation;

however,thereisnorequirementthatareanamesbeuniquebetweenphysicsandmesh.Thiscanleadtoambiguitieswhenyouusethesenamesinexpressions.

Toavoidtheseambiguities,ANSYSCFXfirstcheckstoseeif"

@<

locator>

"

isaphysicsname;

ifthisisnotfound,thenameischeckedinthelistofmeshnames.Thusif"

in1"

isboththenameofaphysicsareaandthenameofamesharea,"

istakentoindicatethephysicsarea.

ANSYSCFXalsohas@REGIONCELsyntaxsothatyoucanidentifyanamedareaasbeingamesharea.Thustoidentifythemeshareain1,youwouldusethesyntax:

@REGION:

in1

Notethatif<

doesnotappearasaphysicsnameorameshname,theexpressionfails.

13.1.2. 

CFXExpressionLanguageStatements

TheCFXExpressionLanguageisdeclarative.Youdeclarethenameanddefinitionoftheexpressionusingexpressionlanguagestatements.ThestatementsmustconformtoapredefinedsyntaxthatissimilartoFortranmathematicalstatementsandtoCstatementsforlogicalexpressions.

Thestatementmustconsistofthefollowing:

∙anumber,optionallywithassociatedunits.Thisdefinesaconstant.Constantswithoutunitsaretermeddimensionless.

∙formathematicalexpressions,oneormorereferencestomathematicalconstants,systemvariables,orexistinguservariables,separatedby+（addition）,-（subtraction）,* 

（multiplication）,/（division）and^（exponentiation）,withoptionalgroupingofthesebyparentheses.Thesyntaxrulesfortheseexpressionsarethesameasthoseforconventionalarithmetic.

∙forlogicalexpressionsinvolvingrelationaloperators,oneormorereferencestomathematicalconstantsorresultsfrommathematicalexpressions,separatedby<

=（islessthanorequalto）,<

（islessthan）,==（isequalto）,!

=（isnotequalto）,>

（isgreaterthan）and>

=（isgreaterthanorequalto）withoptionalgroupingofthesebyparentheses.

∙forlogicalexpressionsinvolvinglogicaloperators,oneormorereferencestologicalconstantsorresultsfromrelationaloperationsseparatedby!

（negation）,&

&

（logicalAND）and||（logicalOR）,withoptionalgroupingbyparentheses.

13.1.2.1. 

UseofConstants

Constantsdonotneedtobedefinedpriortobeingusedinanexpression.Forexample,youcouldchoosetoevaluatetheexpressionx+5[m].Or,youcoulddefineaconstant,b=5[m]andthencreateanexpressionx+b.

Thelogicalconstantsarefalseandtrue.Resultsoflogicalexpressionsareexpressedas0and1（correspondingtofalseandtrue,respectively）.

Theuseofconstantsmaybeofbenefitingeneratingcomplicatedexpressionsorifyouhaveseveralexpressionsthatusethesameconstants.

13.1.2.2. 

ExpressionSyntax

Allnumbersaretreatedasrealnumbers.

Theprecedenceofmathematicaloperatorsisasfollows（fromhighesttolowest）:

∙Thepoweroperator^asinx^y.

∙Theunaryminusornegationoperator-asin-x.

∙Multiplicationanddivisionasinx*y/z.

∙Additionandsubtractionasinx+y-z.

Pleasenotethat,asofANSYSCFX10.0,theprecedenceofmathematicaloperatorshasbeenmadeconsistentwithstandardprogramminglanguagessuchasFortranandC.Therefore,thepoweroperator,whichpreviouslyhadlowerprecedencethanunaryminus,nowhasthehighestprecedence.

Theprecedenceoflogicalandrelationaloperatorsisasfollows（fromhighesttolowest）:

∙Thenegationoperator!

asin!

x.

∙Therelationaloperatorsinvolvinglessthanorgreaterthan（<

=,<

>

and>

=）asinx>

=y.

∙Therelationaloperatorisequaltoandisnotequalto（==and!

=）asinx!

∙ThelogicalANDoperator（&

）asinx&

y.

∙ThelogicalORoperator（||）asinx||y.

13.1.2.3. 

Multiple-LineExpressions

Itisoftenuseful,particularlywithcomplexexpressions,tousemorethanonelinewhencreatingyourexpression.CFXallowsyoutousemultiplelinestogenerateanexpression,providedeachlineisseparatedbyanappropriateoperator.

Forexample,youmayhaveanequation,A+B/C,thatconsistsofthreecomplexterms,A,B,andC.Inthiscase,youcouldusethreelinestosimplifycreatingtheexpression:

A+

B

/C

Notethattheoperatormaybeusedattheendofaline（A+）oratthebeginningofaline（/C）.Youdonotneedtoentertheoperatortwice.

Oncetheexpressionhasbeencreated,itwillappearintheExistingDefinitionslistboxasifitweregeneratedonasingleline（A+B/C）.

13.2. 

CELOperators,Constants,andExpressions

Thefollowingtopicsarediscussed:

∙CELOperators

∙ConditionalifStatement

∙CELConstants

∙UsingExpressions

13.2.1. 

CELOperators

CFXprovidesarangeofmathematical,logicalandoperationaloperatorsasbuilt-infunctionstohelpyoucreatecomplexexpressionsusingtheExpressiondetailsview.

Table 

13.1 

Operator

FirstOperand’sDimensions[x]

SecondOperand’sDimensions[y]

Operands’Values（Approx）

Result’sDimensions

-x

Any

[x]

x+y

Any

x-y

x*y

[x]*[y]

x/y

[x]/[y]

x^y（ifyisasimple,constant,integerexpression）

Dimensionless

Any[a]

[x]^y

x^y（ifyisanysimple,constant,expression）

x>

0

x^y（ifyisnotsimple&

constant）

!

x

0or1

x<

=y

y

x==y

x!

x&

x||y

[a]Fory<

0,xmustbenon-zero.

13.2.2. 

ConditionalifStatement

CELsupportstheconditionalifstatementusingthefollowingsyntax:

if（cond_expr,true_expr,false_expr）

where:

∙cond_expr:

isthelogicalexpressionusedastheconditionaltest

∙true_expr:

isthemathematicalexpressionusedtodeterminetheresultiftheconditionaltestistrue.

∙false_expr:

isthemathematicalexpressionusedtodeterminetheresultiftheconditionaltestisfalse.

Note:

Theexpressionstrue_exprandfalse_exprarealwaysevaluatedindependentofwhethertheevaluationofcond_expristrueorfalse.Asaconsequence,aconditionalstate