CFDNotes Introducion Course CFX Bueno

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    Computational Fluid Dynamics

    Computational Fluid

    Dynamics

    Course Notes

    Dr PK DysonSep 2004

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    Computational Fluid Dynamics

    CFD Overviewand

    Introduction to CFX

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    Computational Fluid Dynamics

    Introduction

    What do you want to know?

    What do you need to define?

    Whats the physics?

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    Computational Fluid Dynamics

    Solution of the Equations

    Equations are so!ed nu"ericay# at a series ofdiscrete points in the fow do"ain$

    % !aria&es at '00#000 points i"pies what ($?

    )esuts can &e !iewed *raphicay and processedto pro!ide nu"erica outputs$

    +or "ost packa*es# the data strea" is,

    -eo"etry

    .. /esh creation

    .. +uid definition

    .. Pro&e" definition

    .. Soution

    .. iewin* of )esuts

    1D 3usuay

    Pre5processor

    So!er

    Post5processor

    /esh -enerator

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    Computational Fluid Dynamics

    ANSS ! CFX Overview "#$

    Start . 6ni!ersity Software . 7S8S .7S8S '0

    -eo"etry

    Desi*n/odeer39$a*d& fie

    1+:5/esh39$c"d& fie

    -eo"etry fie39$*t"

    /esh 1ontroPara"eters

    ;his starts the 7S8S Work&enchen!iron"ent fro" which the !arious

    indi!idua co"ponents are aunched$

    1D

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    Computational Fluid Dynamics

    ANSS ! CFX Overview "%$

    =oundary

    conditions

    +uidproperties

    Pro&e"type

    Soutioncontro

    Definitionfie 39$def

    Session fie39$ses hods

    record ofco""ands

    entered durin*

    session

    >ourna fie 39$ouhods record ofco""ands for

    particuardata&ase

    1ase fie 39$cf@ 1+:5Pre

    -eo"etry fie39$*t"

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    Computational Fluid Dynamics

    1+:5Post

    So!er

    ANSS ! CFX Overview "&$

    Definition

    fie 39$def

    )esutsfie 39$res

    Autputfie 39$out

    eocities

    Strea"ines

    Pressures;ur&uence

    +orces

    3nu"erica datain te@t fie

    See Bep,5 fro" d!anced 1+: Pane,

    Bep . /aster 1ontents

    7S8S 1+:# )eease '0$0,

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    Computational Fluid Dynamics

    File 'ana(ement

    1reate a C/y1+: foder on the oca hard dri!eand put each o& in a different su&5foder$

    Do not leave spacesin foder or fie na"esanywhere in the path to your workin* foder$

    Work fro" the oca hard dri!e or pen dri!e 3notacross the 7etwork fro" your 6, dri!e

    t the end of the session# dra* and drop yourentire workin* foder to your pen dri!e$

    W)7

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    Computational Fluid Dynamics

    Contact with ANSS)CFX Staff

    I'*O+,AN, NO,E

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    Computational Fluid Dynamics

    ,heory Overview

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    Computational Fluid Dynamics

    /eneral *rinciples ) +evision

    'omentum

    'ass Continuity

    u2u'

    net force actin* on fuid

    F rate of chan*e of "o"entu"F chan*e of rate of "o"" fowF

    222''' !! =

    how?

    +or steady fow

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    Computational Fluid Dynamics

    'ass Continuity Equation "#$

    @

    y

    @#u

    y#!

    "ass5!eocityF u

    !G#w

    7et rate of outfow of "ass Frate of depetion of "ass in contro !ou"e

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    Computational Fluid Dynamics

    'ass Continuity Equation "%$

    ( ) ( ) ( )

    0

    G

    w

    y

    !

    @

    u

    Dt

    D

    0G

    w

    y

    !

    @

    u

    Gw

    y!

    @u

    t

    0Gw

    y!

    @u

    t

    =

    +

    +

    +

    =

    +

    +

    +

    +

    +

    +

    =+

    +

    +

    Su&stantiaderi!ati!e

    +or inco"pressi&e fow# this &eco"es,

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    Computational Fluid Dynamics

    'omentum Equation "#$

    @

    yu

    !

    +orce on 1ontro ou"e

    F )ate of 1han*e of /o"entu"

    +orce on 1ontro ou"e

    F )ate of 1han*e of /o"entu"

    0elocity Chan(es across Control 0olume

    yu

    ,"o"@2

    ( )@

    @

    yuyu

    ,"o"@2

    2

    +

    @

    @

    uu

    +

    yy!!

    + ( ) yy @u!@u!

    ,"o"@

    +

    @u!

    ,"o"@

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    Computational Fluid Dynamics

    'omentum Equation "%$

    Forces Actin( in 1)Direction

    on Control 0olume

    @y

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    Computational Fluid Dynamics

    'omentum Equation "&$

    +ate of Chan(e of 'omentum in 1)direction

    ( ) ( )

    ( ) ( )

    ( ) ( )

    y@y

    u!

    @

    uu

    y

    !

    @

    uu

    y@y

    !u

    y

    u!

    @

    uu

    @

    uu

    y@!uy

    @yu@

    2

    +

    =

    +

    +

    +

    +

    =

    +

    =

    F 0 for steady fow

    3fro" continuity

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    Computational Fluid Dynamics

    'omentum Equation "2$

    Net force in 1)direction

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    Computational Fluid Dynamics

    ,he Navier)Sto3es Equations

    steady state 25di"ensiona inco"pressi&e

    ++= +

    +

    +

    =

    +

    2

    2

    2

    2

    2

    2

    2

    2

    y

    !

    @

    !

    y

    P8y

    !!@

    !u

    y

    u

    @

    u

    @

    P:

    y

    u!

    @

    uu

    +or,

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    Computational Fluid Dynamics

    Navier)Sto3es ) 0ector Notation

    ( )!P+Dt

    !D 2+=

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    Computational Fluid Dynamics

    Navier)Sto3es ) Summation Convention

    ##ii#i#iuPfuu +=

    ;akin* u F u' ! F u2 w F uH

    3separate equation for each of i F ' to H

    where '# 2# H represent @# y# G directions a su&cripted co""a and inde@ represents a

    deri!iti!e

    repeated su&script "eans set it to '# 2# H inturn and su" resutin* !aria&es

    ( ) 22

    H#H#22#' w!uIyuu$e$i ==

    G

    uw

    y

    u!

    @

    uu

    uuuuuuuu$e$i H#'H2#'2'#''#'

    +

    +

    =

    ++=

    3so what does u#F 0 "ean?

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    Computational Fluid Dynamics

    ,he Ener(y Equation

    @

    yu

    !1on!ection

    with "ass transfer 1onduction&y te"perature *radient

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    Computational Fluid Dynamics

    Analytical E1ample ) Couette Flow

    Stationary pate

    /o!in* Pate 5 !e F us

    s

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    Computational Fluid Dynamics

    Solutions to the Equations

    ;he set of equations for inco"pressi&e#

    !iscous# 2D steady fow is,

    0y

    !

    @

    u=

    +

    +

    +

    =

    +

    +

    +

    =

    +

    2

    2

    2

    2

    2

    2

    2

    2

    y

    !

    @

    !

    y

    P8

    y

    !!

    @

    !u

    y

    u

    @

    u

    @

    P

    :y

    u

    !@

    u

    u

    6nknowns are u# !# P which are to &e so!edin ter"s of @ and y 5 i$e$ across fow do"ain$

    Soutions are typicay pots of !eocity!ectors# strea"ines# pressure contours 3andte"perature contours if ener*y equation isadded$

    ;hese "ay &e processed to produce suchdata as forces 3e* ift and dra* on a foi orpressure oss in pipes and fittin*s$

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    Computational Fluid Dynamics

    Computational /rid

    Since anaytica soution is a!aia&e ony in

    si"pest of cases# nu"erica techniques arerequiredI thus a *rid across fow do"ainneeds to &e defined

    6nknowns are deter"ined at each *rid point

    1oncept "ay &e e@tended into ti"e do"ain,

    @ y

    t

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    Computational Fluid Dynamics

    ,ypical /rid Notation

    i#

    i# J'

    i# 5'

    i5'# J'

    i5'#

    i5'# 5'

    iJ'# J'

    iJ'#

    iJ'# 5'

    @

    y

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    Computational Fluid Dynamics

    Solution ,echniques

    =roady speakin*# one of three techniques is

    adopted for the soution of the *o!ernin*equations,

    finite difference# in which the differentiater"s are discretised for each ee"ent

    finite volume# in which the *o!ernin*equations are inte*rated around the "eshee"ents

    finite element# in which !ariation of!aria&es within ee"ents is appro@i"ated&y a function# and a residua 3or error ter"is "ini"ised$

    ;he first of these is perhaps the easiestconceptuay# and thus we wi use this tooutine a typica soution procedure$

    1+: uses the finite !ou"e "ethod$

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    Computational Fluid Dynamics

    Differencin( Formulae "#$

    u

    @

    uiJ'

    ui

    i iJ',aylor E1pansion

    ( ) ( )

    ( )

    ( )2'i'i

    i

    H

    iH

    H

    i'i'i

    H

    i

    H

    H

    2

    i

    2

    2

    i

    i'i

    H

    i

    H

    H2

    i

    2

    2

    i

    i'i

    @A@2

    uu

    @

    u

    $$$$

    @

    @

    u

    2@@

    u

    2uu

    ,*Su&tractin

    $$$$@

    @u

    2

    @

    @

    u@

    @

    uuu

    so

    $$$$

    @

    @

    u

    2

    @

    @

    u@

    @

    uuu

    +

    =

    +

    +

    =

    +

    +

    +

    +=

    +

    +

    +

    +=

    +

    +

    +

    3second ordercentra difference

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    Computational Fluid Dynamics

    Differencin( Formulae "%$

    ddin* the ;ayor Series equations,

    ( )22

    'ii'i

    i

    2

    2

    4

    i

    4

    42

    i

    2

    2

    i'i'i

    @A@

    uu2u

    @

    u

    $$$$'2

    @

    @

    u@

    @

    uu2uu

    +

    +=

    +

    +

    +=+

    +

    +

    ;hus# if we take# say# the @ direction75S equation 3steady for si"picity,

    + +

    +

    =

    +

    +

    +

    =

    +

    ++

    +++

    2 '#i#i'#i2 #'i#i#'i

    #'i#'i'#i'#i

    #i

    #'i#'i

    #i

    2

    2

    2

    2

    y

    uu2u

    @

    uu2u

    @2

    PP

    y2

    uu!

    @2

    uuu

    &eco"es

    yu

    @u

    @P

    yu!

    @uu

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    Computational Fluid Dynamics

    ,he Equation Set

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    Computational Fluid Dynamics

    ,he *ressure Correction Approach

    Se"i5

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    Computational Fluid Dynamics

    4oundary Conditions "#$

    =oundaries "ust &e defined# &ut care "ust &e

    taken not to, under5define &oundaries 3insufficient data

    for soution o!er5define &oundaries 3creatin* a

    physicay i"possi&e situation

    e*$ With para"eters defined on &oundaries asfoows ($$

    uF!aue!F0PF!aue

    uF0#!F0

    uF0#!F0

    wa

    wa

    ((( "ode is over)definedsince!eocity and pressure are stipuated

    at inet and outet$ aues "ay thusnot satisfy the continuity and"o"entu" equations$

    uF!aue!F0PF!aue

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    Computational Fluid Dynamics

    4oundary Conditions "%$

    +or e@a"pe# for steady# inco"pressi&e#!iscous fow# so!ed &y pressure correction"ethod# &oundaries conditions "ay &e,

    ! F 0

    PF !aue PF !aue

    0!#0u ==

    0!#0u ==

    =oundaries defined wi depend on natureof equations to &e so!ed 3steady Nunsteady# inco"pressi&e N co"pressi&e#in!iscid N !iscous

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    Computational Fluid Dynamics

    /rids "#$

    Computational

    Space

    Structured 'esh

    usuay co"prisin* quadriatera ee"ents

    *hysical Space

    e*$ circuar duct

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    Computational Fluid Dynamics

    /rids "%$

    erofoi Section 3E@a"pe of structured"esh# refined in critica re*ions

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    Computational Fluid Dynamics

    /rids "&$

    .nstructured 'esh

    usuay &ased on trian*uar pyra"ids3e* 1+: %

    Important 'odellin( Considerations -rid refine"ent in critica areas -rid independent soution 5 checks required 1o"putationay econo"ic "ode

    coarse *rid in non5critica areas

    "ake use of sy""etry and periodic&oundary conditionsuse 25D and a@i5sy""etric "odeswhere possi&e

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    Computational Fluid Dynamics

    ,ur-ulence

    u

    6

    !e ata point

    ti"e

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    Computational Fluid Dynamics

    Introduction to ,ur-ulence 'odellin(

    La"inar +ow /o"entu"

    diffusion&y !iscosity

    ;ur&uent +owdditiona "o"entu"

    diffusion due to tur&uence

    1oncept oftur&uent 3or eddy!iscosity#

    tt is not a fuid property# &ut dependson e!e of tur&uence in fow

    concept eads to "athe"atica "odesto dea with tur&uenceI each "ode isan appro@i"ation to what is reayhappenin*

    one popuar "ode 3k5epsion "odeintroduces two further unknowns,

    KEtur&uentofndissipatioratethe

    2

    w!uene*ykinetictur&uentthek

    222

    ++=

    KEtur&uentofndissipatioratethe

    2

    w!uene*ykinetictur&uentthek

    222

    ++=

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    Computational Fluid Dynamics

    ,ur-ulence 'odellin( ! the 'aths

    ;hink of u#!#w and p as co"prisin* of two parts,ense"&e a!era*e !aues and tur&uent fuctuations$

    Superscript&ar denotes the ensem-le avera(eor

    the "ean !aue$Dashdenotes the fluctuatin( part$

    ;ur&uence fuctuations usuay ha!e s"a en*th andti"e scaes co"pared to the "ean fow$

    Su&stitutin* this deco"position to the 7a!ier5Stokesequations and takin* the ense"&e a!era*e# we now*et

    pppwwwvvvuuu +=+=+=+= ,,,

    +

    =

    +

    =

    i

    i

    i

    i

    i

    uu@

    u

    @@

    p'

    @

    uu

    t

    u,"o"entu"

    0@

    u,continuity

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    Computational Fluid Dynamics

    Equations 3aso caed )eynods equations forense"&e a!era*e !aues are identica to the 7a!ier5Stokes equation e1cept for the cross)productsofthe fuctuation ter"s$

    Since these ter"s ha!e si"iar functions as !iscousstresses# they are caed Otur&uent stresses or)eynods stresses$

    ;o propery cose the syste"# we ha!e to define the&eha!iour for tur&uence cross5product ter"s$

    ,ur-ulence Closure

    ( ) ( ) ( ) ( ) ( ) ( )w!#wu#!u#w#!#u 222

    ;his is where "any different types and e!es oftur&uence "odein* co"e in$

    t the hi*hest e!e# transport equations can &e

    set up for each of these ter"s$ ;his wi increasethe nu"&er of equations to so!e &y si@$;ur&uence "odes &ased on this approach arecaed )eynods stress equation "ode 3)S/ orthe second5order cosure "ode$

    co""ony used tur&uence "ode inen*ineerin* differs fro" this approach &yreducin* the nu"&er of e@tra equations to onytwo and is known &y the na"e k- "ode$

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    Computational Fluid Dynamics

    3)5 'odel ) ,heory

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    Computational Fluid Dynamics

    ;he 3e"pirica constants in the k5Q "odeare usuay,

    R2$'c#44$'cH0$'I0$'#0R$0c

    2'

    k

    =====

    Where

    ( )

    ( ) ( )k$$H

    2P

    kc

    @

    u

    @

    ueIee2

    w!u2

    'k

    ;tk

    2

    t

    i

    iiii

    222

    ++=

    =

    +

    ==

    ++=

    UUUUU.t

    3

    3)5 'odel ! ,heory "continued$

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    Computational Fluid Dynamics

    3) ,ur-ulence 'odel ) Summary

    requires two further equations# si"iar to

    7a!ier5Stokes equations for k and thus requires

    inet !aues for k and initia *uesses for k and

    esti"ates for these "ay &e o&tained fro"equations such as the foowin*# a!aia&e inthe iterature

    ( )26%$'k =

    sensiti!ity to inet tur&uence quantities

    shoud &e checked# and "ay point tothe need for e@peri"entay deri!ed!aues for use in the 1+D "ode$

    ( )

    = 6

    uensityinttur&uencetheiswhere

    2'

    2

    fowshearfreefor3k

    L

    2H

    =

    widthayershearsticcharacteritheisand

    '$0en*theddysticcharacteriiswhere L

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    Computational Fluid Dynamics

    CFD 6ealth 7arnin( 8

    We ha!e &arey scratched the surface of the

    theory of 1+D$ few of the possi&e areasfor further fruitfu readin* are,

    nature of the equations under different

    conditions 5 hyper&oic# para&oic# eiptic$ transient pro&e"s choice of &oundary and initia conditions coupin* &etween "o"entu" and ener*y

    equations 3especiay in &uoyancy dri!en

    fows supersonic fows and shock capture tur&uence "odein* 5 what aternati!e

    "odes are a!aia&e? wa &oundary conditions 3o* aw of the

    wa

    ;reat 1+D with respect 5 a itte knowed*e isa dan*erous thin* M

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    Computational Fluid Dynamics

    E1ercises

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    Computational Fluid Dynamics

    E1ercise #

    1reate foder 'yCFXand a su&5foder ;utoria'

    Start 7S8S 1+: '0$0$

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    Computational Fluid Dynamics

    E1ercise # "continued$

    1ontinue with this tutoria# &ut note the instructions inpara 4 at the end of the Desi*n/odeer ;utoria,5

    C( "issin* out the instructions in the section C1reatin* a7ew Si"uation$ 7ote that you do not need to copy thesa"pe fie Static/i@er/esh$*t" to your workin*

    directory if you ha!e ust created the "esh in 1+:5/esh#since you wi want to use your new "esh and not theone suppied with 7S8S 1+:$ +or the C

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    Computational Fluid Dynamics

    Now ma3e sure you understand :;;

    Whats the difference &etween

    Sketchin* "ode and "odein* "ode

    Desi*n/odeer and 1+:5/esh

    Surface /esh and ou"e /esh

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    Computational Fluid Dynamics

    Work throu*h ,utorial %? Static 'i1er"+efined

    'esh$which wi show you,

    "ore a&out the "esh *eneration process

    "odifyin* *eo"etry

    use of 1+: 1o""and Lan*ua*e 311L to a!oid

    too "any repetiti!e keystrokes$

    s &efore you wi need to start in theDesi*n/odeerN1+:5/esh 3Soid /odein*;utoria and switch to the 1+: 3+uid /odein*;utoria$

    E1ercise %

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    Computational Fluid Dynamics

    )efine the "esh e!en further in the outet re*ion ofthe "i@er &y insertin* a "esh contro as foows$

    )e5open Static/i@er in 1+:5/esh )i*ht cick Control. Insert*oint Spacin( 1ick *oint Spacin( #in Detai iew and chan*e

    the settin*s to, Len*th scae 0$' "# )adius of

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    Computational Fluid Dynamics

    Findin( Out 'ore ! ,he 6elp *a(es

    6elpon 1+: *re? Solver and*ostis accessed fro"the d!anced 1+D panes 35Pre# 5So!er# 5Post &ycickin*,

    6elp

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    Computational Fluid Dynamics

    Findin( Out 'ore

    ANSS 7or3-ench 6elp < CFX)'esh 6elp

    What is the principe type of "esh utiised &y 1+:?What is its ad!anta*e o!er a quasi5rectan*uar"esh?What is "esh contro? Why use it?What is infation? Why use it?What is a "esh independent soution? 31arry out a

    search usin* mesh NEA+ independentaskeywords$ /ake sure that pa*es referred to are for1+:5/esh or Desi*n/odeerI pa*es referrin* to# fore@a"pe# Desi*n:porer or Si"uation 3top eft ofpa*e are not ree!ant to you

    CFX 6elp < CFX)*re < Fluid DomainsWhat options are a!aia&e for the fuid do"ain"odes?What standard fuids are a!aia&e?

    CFX 6elp < CFX)*re < 4oundary ConditionsWhat &oundary conditions are a!aia&e?

    CFX 6elp < CFX)*re < Initial ConditionsWhy are initia !aues set?

    CFX 6elp < CFX)*re < Solver ControlWhat are con!er*ence criteria?

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    Computational Fluid Dynamics

    ,reatment of 7alls and Flow

    4oundaries

    Near 7all 'odellin(

    37S8S 1+:5So!er '0$0 /odein* . ;ur&uenceT 7ear Wa /odein* 5 /odein* +ow 7ear the

    Wa

    4oundary Condition 'odellin(

    37S8S 1+:5So!er '0$0 /odein* 5 =oundary1ondition /odein*

    +urther readin* fro" 1+: Bep pa*es,

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    Computational Fluid Dynamics

    E1ercise 2

    thou*h this is an e@terna fow# 3as opposed tothe pre!ious pipe e@a"pe which was interna#we sti need to define a i"it to the do"ain$ ;hiswi effecti!ey &e a Cwind tunne in which thecyinder wi &e paced$

    We wi treat this as a 25D e@a"pe &y "akin*the fuid do"ain thin in the @ direction andattachin* the cyinder to the wa at each side$

    8ou shoud create a new foder for this pro&e"$

    y

    zx

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    Computational Fluid Dynamics

    '$ Sketch surface 3the ow5@ surface as arectan*e$

    2$ Sketch the circe 3rectan*e and circe wi &oth&e part of sketch '

    H$ E@trude in the @ direction$

    0$H

    2

    '0

    @ G

    y

    point 0 0 0

    surface

    .sin( Ansys Desi(n'odeller

    '2 dia"eter 0$H

    ;he HD &ody for"ed &y the &o@ with the cyinder cutout# so"eti"es confusin*y referred to as the Csoid# iswhere the fuid wi fow$

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    Computational Fluid Dynamics

    .sin( Ansys CFX)'esh

    4$ Apen 1+:5/esh and create a 25D re*ion for eachof the surfaces 3eft# ri*ht# inet# outet# cyinder ea!e top T &otto" undefined they wi for" theCdefaut 2D re*ion# *i!in* each a suita&e na"e3you wi use these ater to define &oundary

    conditions$%$ Set "esh defaut &ody spacin* to a "a@i"u" of

    0$H "$$ Set up

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    Computational Fluid Dynamics

    U$ Pace "esh contros to refine the "esh in there*ion of the cyinder and its wake$

    V$ 1reate surface "esh# and check it to ensure it isrefined in the appropriate paces$

    R$ 1reate the !ou"e "esh 3thus writin* the $*t" fieand start CFX)*re$

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    Computational Fluid Dynamics

    '0$ 1reate a fuid do"ain 5 use standard air or water#seect steady state# k5tur&uence "ode# scaa&ewa function# isother"a# non5&uoyant$ Setreference pressure at 0 Pa$

    ''$

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    Computational Fluid Dynamics

    'H$ 8ou can check and edit =oundary 1onditions &ydou&e cickin* on the ree!ant condition in CA&ectSeector$ 7ote that the CDefaut &oundarycondition 3a no5sip wa appies to any &oundarywhich is undefined$

    '4$ ppy defauts for initia !aues$

    '%$ ppy defauts for the so!er para"eters# e@ceptnu"&er of iterations which you shoud chan*e to

    %0$

    '$ Write definition fie and *o to So!er$

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    Computational Fluid Dynamics

    'U$ )un the so!er$ Does it con!er*e within the %0iterations which ha!e &een set?

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    Computational Fluid Dynamics

    2'$ Draw !ectors and a pressure profie &ased on one ofthe side was$ E@peri"ent with differentarran*e"ents of strea"ines# different en*ths of!ector arrow# and with a shaded pressure pot 3&ycheckin* the CDraw +aces &o@ on the C)enderpane$

    22$ Print one of the pots to a >PE- fie usin* +ie 5 Print#

    and check the CWhite &ack*round &o@$ ;his coudater &e incuded in a report$

    2H$ 6se the ine which you created earier to produce achart 3ie a *raph showin* how the G5direction!eocity !aries across the wake at a position ust

    downstrea" of the cyinder$

    24$ 6se the cacuator to find the tota force on thecyinder in the G5direction$ 1o"pare this with thedra* shown in the $out fie 3you wi need to add 2!aues fro" $out to*ether to *et the dra* 5 why?$1acuate the dra* coefficient 5 is it anywhere nearcorrect?

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    Computational Fluid Dynamics

    With a &it of cunnin*# and udicious use "esh contros

    and 1+:5Post# this is possi&e ($$

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    Computational Fluid Dynamics

    'odifyin( the 'odel

    ;ry pacin* an e@tra cyinder in cose to the first$What is the effect on the fow and the dra* on thecyinders?

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    Computational Fluid Dynamics

    uestions

    What is the effect of ha!in* a !ery narrow 3say0$0' or a !ery wide 3say H$0 &o@?

    Bow does the pro@i"ity of the top and &otto"was affect the soution?

    Bow does the position of the upstrea" anddownstrea" &oundary affect the soution?

    1oud a pane of sy""etry ha!e &een used toreduce the co"putationa ti"e?

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    Computational Fluid Dynamics

    E1tractin( Numerical Data

    ;he "ost usefu ways of e@tractin* nu"erica data are,

    Output File;9$out fie contains te@t &ased data on &othsoution and resuts$

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    Computational Fluid Dynamics

    Definin( *olylines

    Intersection @ine ine of intersection &etween a &oundary 3defined in1+:5Pre and a pane 3defined in 1+:5Post "ay &eused$

    File Input

    te@t fie is written 3outside 1+: containin* co5ordinates of the points required# in a for"at shown &ythe foowin* e@a"pe$

    1oordinates "ay define a strai*ht or cur!ed ine$ Data

    3e* pressures wi ony &e potted at the points youdefine# so if you want *ood resoution# you need pentyof points# e!en if its a strai*ht ine$

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    Computational Fluid Dynamics

    *olyline Data File

    0 0 0

    0$00% 0$0''RH 0

    0$00U% 0$0'4H 0

    0$0'2% 0$0'V'% 00$02% 0$02%0V 0

    0$0% 0$0H4UU 0

    0$0U% 0$04202 0

    0$' 0$04URR 00$'% 0$0%UH2 0

    0$2 0$042H 0

    etc

    @ y Gcoodinates#dei"ited &yta&s or

    spaces$

    ;he Poyine is oadedusin* the CPoyineicon

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    Computational Fluid Dynamics

    E1portin( Data from CFX)*ost

    Ance a poyine has &een defined a chart"ay &e

    produced$

    so the !aria&es "ay &e e1portedfor points defined&y the poyine usin* +ie E@port$

    Seect the !aria&es required 3e* @# y# G# pressure3hod down Ccontro to "ake "utipe seections andocator 3e* poyine' and *i!e an appropriate fiena"e$

    ;he data is for"atted as a series of @5y5G co5

    ordinates# and !aues for the para"eters potted$

    ;he e@a"pe o!ereaf shows @# y# G co5ordinatesto*ether with !aues for P# u# !# w$ ;his has &eentidied up &y oadin* the fie into E@ce# usin* Cspaceand C3C characters to dei"it data# and then carryin*

    out a search and repace to *et rid of C characters$

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    Computational Fluid Dynamics

    E1portin( Data ) E1ample File

    X@ 5 1oordinates "

    Xy 5 1oordinates " XG 5 1oordinates " X' 5 Pressure k*"Y5'sY52 X2 5 eocity "sY5'5$'2E5' 0$00EJ00 2$00EJ0' 5H$2RE50%'$VRE50U U$22E50U '$VVE505%$4VE5' 0$00EJ00 '$VREJ0' U$VE50UU$R2E50V %$0%E50U '$VUE50H54$VHE5' 0$00EJ00 '$UREJ0' $24E50%2$4VE50 $U0E50U '$R4E50H

    X@ 5 1oordinates "

    Xy 5 1oordinates " XG 5 1oordinates " X' 5 Pressure k*"Y5'sY52 X2 5 eocity "sY5'5$'2E5' 0$00EJ00 2$00EJ0' 5H$2RE50%

    '$VRE50U U$22E50U '$VVE505%$4VE5' 0$00EJ00 '$VREJ0' U$VE50UU$R2E50V %$0%E50U '$VUE50H54$VHE5' 0$00EJ00 '$UREJ0' $24E50%2$4VE50 $U0E50U '$R4E50H

    7ote, data here for each point stretches across 2 ines as!eocity has H co"ponents$

    *ressure around a Cylinder

    0 00EJ00

    %$00EJ0'

    An(le "de($

    fter "anipuation in E@ce# a chart can &e potted,