FfC v5.0 07 Boundary Conditions

8/17/2019 FfC v5.0 07 Boundary Conditions

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ntroduction to FLUENT

for CAT A V5

Boundary and nitial

Conditions


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© 2009 ANSYS, Inc. All rights reserved.e!r"ary 1#, 2009

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Training Manual

FLUENT for CATIA V5 Version 5.0

Introductory Training, Decemer !00"

F#uent for Catia $u%%ort center

&tt%'(())).f#uentusers.com(ffc

Agenda

% Introduction

% Boundary Condition Types: Inlet

% Boundary Condition Types: Outlet% Boundary Condition Types: Wall

% Boundary Condition Types: Periodic

% Defining Species Mass Fractions

% Defining Inputs for Cavitation and OF

% Special Boundary Conditions

% Creating Boundary !roups% Defining and C"anging Boundary Conditions

% Patc" Functionality

% Boundary Profiles #Data Mapping$% %nsteady Boundary Profiles

% Appendi&

& Spatial Data Mapping File For'ats & Ti'e Data Mapping File For'ats


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Introduction• Assign'ent of (oundary conditions #BCs$ is a

crucial part of t"e 'odel setup for anynu'erical si'ulation)

• A nu'(er of (oundary conditions areavaila(le via t"e (oundary condition tool(ar:inlet* outlet* +all and special (oundaryconditions)

• It includes t"e follo+ing steps:

& Define t"e (oundary type for eac" 'es" part#inlet* outlet or +all* etc)$

& For' (oundary groups in +"ic" severalsurfaces s"are t"e sa'e BC in order to 'a,e it'ore easily 'anagea(le

& Specify appropriate (oundary condition valuesfor eac" (oundary type)

•

Faces of t"e geo'etry can (e groupedtoget"er for purposes of specifying (oundaryconditions)

• Boundary conditions can (e 'odified afterdefinition)

BC Tool(ars


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Boundary Condition Types: Inlet• T"e Inlet (oundary condition re-uires t"e user to set

one of t"e follo+ing values: & elocity: inco'pressi(le flo+s only & Mass flo+ rate: all flo+s

& olu'e flo+ rate: inco'pressi(le flo+s only & Pressure #total$: can (e used for all flo+s

• In addition t"e user "as to set t"e InletDirection: nor'al to inlet or (y a specified direction)

• For Tur(ulent Flo+s* t"e source of flo+ is used todeter'ine tur(ulent inlet conditions:

& .ong tu(e* pipe or duct

& Perforated plate: screen/"ole si0e & Fan or (lo+er: inlet flo+ is driven (y fan or (lo+er & 1&ternal environ'ent: a'(ient air or fluid & Ot"er: tur(ulence intensity and tur(ulence lengt" scale

directly specified (y t"e user)

• Te'perature: is set for cases involving te'peratureeffect)

• Species Mass Fractions is set for cases +it"i''isci(le 'i&tures of gases or li-uids)


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Boundary Condition Types: Outlet• T"e Outlet Boundary Condition re-uires

t"e user to set t"e flo+ conditions at t"e

outlet suc" as: & Static pressure #'ost co''only used$

& Alternately* 'ass flo+ rate or olu'etric

flo+ rate or velocity can (e specified)

& Outlet direction #2or'al or given

direction$

& Do+nstrea' conditions for tur(ulent flo+

• .ong tu(e* pipe or duct for internal#pipe$ flo+s)

• 1&ternal 1nviron'ent

& Te'perature and species 'ass fraction

for species calculations* in case of

(ac,flo+ (ac, into t"e do'ain)


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Boundary Condition Types: Wall• Wall (oundary condition:

– 2o3slip (oundary condition for velocity

#i)e)* stationary or 'oving at a ,no+nspeed$)

– For 'oving #translating or rotating$

+alls* ena(le t"e 'oving +all option in

t"e +all BC panel and specify t"e +all

'otion)

– W"en te'perature effects are 'odeled*

t"er'al (oundary conditions 'ust (e

specified at t"e +all:

• Constant te'perature

• Constant "eat flu&

• Te'perature3dependent "eat flu&

#Convection$:

– 4eat transfer coefficient #4TC$ and t"e

a'(ient te'perature are re-uired to

specify t"is BC


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Defining Species Mass Fractions

• Species Mass Fractions "ave to (e

set for inlets and outlets)

• T"e value for eac" species 'ass

fraction s"ould (e (et+een 5 and 6)

• T"e su' of t"e 'ass fractions

s"ould (e e-ual to or less t"an 6)

• T"e Mass fraction of t"e last

species +ill (e deter'ined (ysu(tracting 'ass fraction of all t"e

ot"er species fro' 6)


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Defining Inputs for Cavitation and OF• T"e volu'e fraction of t"e gas

p"ase generated (y cavitation "as

to (e specified for eac" inlet andoutlet)

• Si'ilarly t"e volu'e fraction of

eac" secondary p"ase is to (e

specified +"ile using OF 'odel)

• T"e volu'e or p"ase fraction is a

nu'(er (et+een 5 and 6)

• W"en cavitation/OF is turned on* a

(utton appears on t"e (oundary

condition panel for eac" inlet/outlet)

• Clic, on t"e (utton to get t"e

P"ases Input panel)


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Special Boundary Conditions

• Ot"er inlet (oundary conditions includeinta,e fan* inlet vent and pressure far

field:

& Inta,e Fan: An e&ternal inta,e fan +it"specified pressure 7u'p #fro' a given8fan curve9$* flo+ direction* inta,epressure and te'perature

& Inlet ent: An inlet vent 0one +it"

specified loss coefficient* total pressure#gauge$* flo+ direction and te'perature

& Pressure Far3field: A free strea'(oundary condition at infinity +it" free3strea' Mac" nu'(er)

& 1&"aust Fan and Outlet ent (oundaryconditions can (e created for outlets)

• Interior (oundary condition typesinclude fans* porous 7u'ps and

radiators:

& Fan is used to si'ulate t"e effects of t"efan on t"e flo+ field +it" a 8fan curve9# Flo+ rate vs pressure drop$)

& Porous u'p: si'ulates t"e pressuredrop due to t"e presence of a

8'e'(rane9 +it" ,no+n pressure3dropversus flo+3rate c"aracteristics

& ;adiator: 'odels t"e presence of aradiator or a condenser #i)e) a "eate&c"anger$ using lu'ped para'eters)

• Please see t"e user 'anual for 'oreinfor'ation on t"ese (oundaryconditions)




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Periodic and Sy''etry Boundary Conditions

• T"e sy''etry (oundary conditions

and t"e periodic (oundary

conditions are useful in cuttingdo+n on t"e 'odeling effort:

& Sy''etry is used +"en t"e flo+

and t"e geo'etry "ave natural

planes of sy''etry* +"ic" can (e

e&ploited)

&Periodic (oundary conditions areused +"en t"e flo+ "as repeating

patterns* eit"er along along a

direction #translational periodicity$

or along t"e circu'ference of t"e

do'ain #rotational periodicity$) Periodic planes

;otational Periodic settings Translational Periodic settings




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Creating Boundary !roups

• By default* any e&ternal (oundaries t"atare not specified as inlets or outlets are

grouped into one or 'ore +alls)• To specify (oundary conditions

separately on particular faces* Boundary!roups can (e created using t"e CreateBoundary !roups icon)

& In t"e panel* select faces to (e groupedand t"en set t"e type of (oundarycondition to (e applied)

& A ne+ (oundary group is created onclic,ing O




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Defining and C"anging Boundary Conditions

• To define a (oundary condition

for t"e first ti'e: – Clic, on t"e icon for (oundary

condition type #inlet* outlet or+all ))$ icon

– Select t"e corresponding(oundary group under !roups toopen t"e dialog (o&)

• To c"ange (oundary type for aparticular (oundary group:

– Dou(le clic, on t"e (oundaryentry under !roups)

– C"ange t"e Type in t"e Definitionof Boundaries panel)

• To 'odify or c"ec, any e&isting(oundary conditions* dou(leclic, on t"e (oundary na'e inBoundary Conditions under

Fluent case• Display of (oundary conditions

data in t"e CATIA specificationstree

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Patc" Functionality

• T"e patc" functionality can (e used to set t"evalues of particular varia(les on fluid or solidregions)

• To patc" a varia(le: & Clic, on t"e Patc" (utton) & In t"e Patc" alues panel* select t"e Flo+

Property corresponding to t"e fluid or solidregion)

& Select t"e Pat" =uantity #varia(le$ and set it>svalue)

& A Patc" alue ite' is added to t"e Initiali0ation

tree) & if +e 'ove t"e 'ouse pointer to t"e initiali0ationvalues* t"e patc" -uantity +"ic" is used is"ig"lig"ted)

• Once t"e patc" is used during co'putation* it+ill (e de3activated)

& It can (e reactivated for t"e ne&t run using t"erig"t 'ouse (utton)

• Multiple patc"es can (e used in t"e sa'eco'putation)

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Boundary Profiles #Data Mapping$

• To specify non3unifor' (oundary

profiles* clic, t"e data 'apping for

selected data or data 'apping forte'perature

• 1na(le ariant Data or ariant

Te'perature* t"en select Data Mapping)

• Clic, on t"e (utton to specify t"e

location of t"e data file)

•

T"e data files can (e in spread3s"eet#&ls$ or ASCII #t&t$ for'ats)

• %nits for eac" -uantity "ave to (e

specified in t"e data file)

• 2ote t"at spatial and ti'e data 'apping

cannot (e specified for t"e sa'e

(oundary condition si'ultaneously)

• Please refer to t"e Appendi& for t"e data

for'at for 'apping)

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%nsteady Boundary Profiles

• For unsteady si'ulation* ti'e3dependent(oundary profiles specify t"e variation ofa selected (oundary condition +it"

respect to ti'e)

• To set ti'e dependent (oundary profiles*t"e ti'e 'odulation "as to (e definedfirst:

& Clic, on t"e Ti'e Modulation (utton) & Select a file #eit"er in &ls or t&t for'ats$

and clic, O< & A Ti'e Modulations)2 ite' +ill (e added

in t"e specification tree)

• T"e input can t"en (e specified for t"eti'e3dependent (oundary data (yclic,ing on to pop up t"e ariationDefinition panel)

& 4ig"lig"t t"e Ti'e 'odulation (o&* t"enclic, on Ti'e Modulation)2 of t"especification tree +"en t"e ti'e 'odulation is selected*

t"e icon>s color is c"anged to green


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Spatial Data Mapping File For'ats

• Sa'ple for'ats for te&t and for spread s"eet used in t"e spatial data'apping #(oundary profile$) T"e first ro+ contains t"e "eading* and

eac" colu'n contains respective &* y* 0 and t"e varia(le data

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Ti'e Data Mapping File For'ats

• Sa'ple ti'e data 'apping files in te&t and in spread s"eetfor'ats) T"e first ro+ contains t"e "eading* and eac" of t"e t+o

colu'ns contains respective ti'e and varia(le data)

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FfC v5.0 07 Boundary Conditions

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