Fluent12 Lecture03 Solver Basics

7/25/2019 Fluent12 Lecture03 Solver Basics

1/20

3-1ANSYS, Inc. Proprietary

2009 ANSYS, Inc. All rights reserve.April 2!, 2009

Inventory "002#00

Chapter 3

Solver Basics

Introductory FLUENTTrainingSharif University of Technology

Lecturer: Ehsan Saadati

ehsansaadati!g"ailco"


2/20

Solver Basics



Inventory "002#00

Training ManualFLUENT #$ %UI Navigation

The FLUENT %UI is arranged such that the tas&s are generally

arranged fro" top to 'otto" in the pro(ect setup tree

Selecting an ite" in the tree opens the relevant input ite"s in the

center pane

$ %eneral

$ )odels$ )aterials

$ Boundary

Conditions

$ Solver Settings

$ Initiali*ation and

Calculation

$ +ostprocessing


3/20

Solver Basics



Inventory "002#00

Training ManualScaling the )esh and Selecting Units

,hen FLUENT reads a "eshfile -"sh./ all physical

di"ensions are assu"ed to 'ein units of "eters$ If your "odel 0as not 'uilt in

"eters/ then it "ust 'e scaled$ 1erify that the 2o"ain Etents

are correct after scaling the"esh

,hen i"porting a "esh under,or&'ench/ the "esh does notneed to 'e scaled4 ho0ever/ theunits are set to the default )5Ssyste"

6ny 7"ied8 units syste" can'e used if desired$ By default/ FLUENT uses the SI

syste" of units -specifically/)5S syste".

$ 6ny units can 'e specified inthe Set Units panel/ accessedfro" the top "enu

%e&ine 'nits(


4/20

Solver Basics

3-)ANSYS, Inc. Proprietary


Inventory "002#00

Training ManualTet User Interface

)ost %UI co""andshave a corresponding

TUI co""and$ )any advanced

co""ands are onlyavaila'le throughthe TUI

$ +ress the Enter &eyto display the

co""and set at thecurrent level

$ q"oves up one level

FLUENT can 'e runin 'atch "ode or

scripted using a(ournal file -see6ppendi.

6 TUI user guide is availa'le on the FLUENT User Services Centerwww.fluentusers.com


5/20

Solver Basics

3-*ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual)ouse Functionality

)ouse 'utton functionality depends on the chosen solver -$2 9 32.and can 'e configured in the solver

2efault settings$ $2 Solver

Left 'utton translates9pans -dolly.

)iddle 'utton *oo"s

ight 'utton selects9pro'es

$ 32 Solver Left 'utton rotates a'out $ aes

)iddle 'utton *oo"s$ )iddle clic& on point in screen centers point

in 0indo0

ight 'utton selects9pro'es

etrieve detailed flo0 field infor"ation at point 0ith +ro'e ena'led$ ight;clic& on the graphics display

)ouse controls can 'e set to e"ulate those in ,or&'enchuire "ultiple "aterialsand dictate 0hich "aterialproperties "ust 'e defined

$ )ultiphase -"ultiple "aterials.$ Co"'ustion -"ultiple species.$ ?eat transfer -ther"al

conductivity.$ adiation -e"issivity and

a'sorptivity.

)aterial properties can 'e directly custo"i*ed as function ofte"perature9pressure$ Use of other solution varia'le-s. re>uires U2F


7/20

Solver Basics

3-ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual)aterials 2ata'ases

FLUENT "aterials data'ase

$ +rovides access to a nu"'er

of pre;defined fluid/ solid and

"iture "aterials

$ )aterials can 'e copied to

the case file and edited if

re>uired

Custo" "aterial data'ase:

$ Create a ne0 custo" data'ase

of "aterial properties and

reaction "echanis"s fro"

"aterials in an eisting casefile for reuse in future cases

$ Custo" data'ases can 'e created/

accessed and "odified fro" the

standard "aterials panel in FLUENT


8/20

Solver Basics

3-!ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual@perating Conditions

The @perating +ressure 0ith a eference

+ressure Location sets the reference

value that is used in co"puting gauge

pressures

The @perating Te"perature sets the

reference te"perature

-used 0hen co"puting

'uoyancy forces

Specified @perating

2ensity sets the referencevalue for flo0s 0ith 0idely

varying density


9/20

Solver Basics



Inventory "002#00

Training Manual+arallel +rocessing

+arallel processing can 'e used to runFLUENT on "ultiple processors to

decrease turnaround ti"e and increasesi"ulation efficiency$ Critical for cases involving large "eshes

and9or co"ple physics$ FLUENT is fully paralleli*ed and capa'le of

running across "ost hard0are andsoft0are configurations/ such as co"puteclusters or "ulti;processor "achines

+arallel FLUENT can 'e launched eitherusing the syste" co""and pro"pt orusing the FLUENT Launcher panel$ For ea"ple/ to launch an n;C+U parallel

session/ use the co""andfluent 3d tn

The "esh can 'e partitioned either

"anually or auto"atically using a nu"'erof different "ethods$ Non;confor"al "eshes/ sliding "esh

interfaces and shell conduction *onesre>uire partitioning in serial

6 0e';'ased lecture is availa'le on theFLUENT User Services Center


10/20

Solver Basics



Inventory "002#00

Training ManualSu""ary

This lecture has presented "any 'asic tas&s that are often perfor"ed

during a CF2 si"ulation setup

+arallel processing can 'e used to reduce calculation ti"e This is

advantageous only on large "eshes

6 later lecture contains "aterial related to the setup and solution ofti"e;dependent pro'le"s

@ther topics not discussed -see 6ppendi for infor"ation.

$ )esh heirarchy and relationships

$ eordering and "odifying the "esh in the solver

$ +olyhedral "esh conversion

$ Solution;'ased "esh adaption


11/203-11ANSYS, Inc. Proprietary


Inventory "002#00

6ppendi


12/20

Solver Basics



Inventory "002#00

Training ManualFLUENT Aournals

FLUENT can 'e run in 'atch "ode using(ournal files

6 (ournal file is a tet file 0hich containsTUI co""ands 0hich FLUENT 0ill eecutese>uentially

The FLUENT TUI accepts a''reviations ofthe co""ands4 for ea"ple/$ ls Lists the files in the 0or&ing

folder

$ rcd eads case and data files$wcd ,rites case and data files$ rc/wc eads90rites case file$ rd/wd eads90rites data file$ it Iterate

TUI co""ands in a 'atch file can 'e usedto auto"ate operations in a non;interactive

"ode$ The TUI co""ands file/read-bcand

file/write-bccan 'e used for readingand 0riting the settings for a FLUENTsession to and fro" a file/ respectively

$ 6 0e';'ased training "odule is availa'le0hich eplains this process

; Read case file

rc example.cas.gz

; Initialize the solution

/sole/initialize/initialize-flow

; !alculate "# iterationsit "#

; $rite data file

wd example"#.dat.gz

; !alculate another "# iterations

it "#

; $rite another data file

wd example%##.dat.gz

; &xit '()&*+exit

,es

Sa"ple Aournal File


13/20

Solver Basics



Inventory "002#00

Training Manualeading the )esh ones

In this ea"ple/ there are t0o cell *ones -fluid;upstrea" and fluid;

do0nstrea". Because of this/ FLUENT splits the eterior 0all *one into t0o *ones

-0all and 0all:DD#. This is 'ecause an eternal 'oundary cannotspan "ultiple cell *ones

FLUENT also splits the orifice plate into t0o 0alls also -plate andplate;shado0. since the plate *one is an internal 0all

inlet

otlet

/all

plate

plate-shao/

&li cell one

2efault;interior *one-s.can al0ays 'e ignored


14/20

Solver Basics

3-1)ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual)esh Infor"ation and ?ierarchy

6ll "esh infor"ation is stored in the "esh file$ Node coordinates

$ Connectivity$ one definition

Si"ilar to the 0ay geo"etry is defined/ "eshentities o'ey a hierarchy:

$ Node Edge intersection 9 grid point$ Edge Boundary of a face -defined 'y

t0o nodes$ Face The 'oundaries of cells/ defined 'y

a collection of edges$ Cell The control volu"es into 0hich the

do"ain is discreti*ed$ one 6 collection of nodes/ edges/ faces

or cells

The co"putational do"ain is defined 'y all"e"'ers of the hierarchy

$ For fluid flo0 si"ulation only/ the do"ain consistsonly of the fluid region

$ For con(ugate heat transfer or fluid;structureinteraction pro'le"s/ the do"ain needs to includeany solid parts that are present

Boundary data is assigned to face *ones )aterial data and source ter"s are assigned to

cell *ones

Si"ple 32 "esh

Si"ple $2 )esh

Node

Boundary

Face

Cell

CellCenter

Cell Face

Node

BoundaryFace

Cell

Edge


15/20

Solver Basics

3-1*ANSYS, Inc. Proprietary


Inventory "002#00

Training Manualeordering and )odifying the %rid

The grid can 'e reordered so that neigh'oring cells are near eachother in the *ones and in "e"ory$ I"proves efficiency of "e"ory access and reduces the 'and0idth of the

co"putation

$ eordering can 'e perfor"ed for the entire do"ain or specific cell*ones

$ The 'and0idth of each partition in the grid can 'e printed for reference

The face9cell *ones can also 'e "odified 'y the follo0ing operationsin the %rid "enu:$ Separation and "erge of *ones

$ Fusing of cell *ones 0ith "erge of duplicate faces and nodes

$ Translate/ rotate/ reflect face or cell *ones

$ Etrusion of face *ones to etend the do"ain

$ eplace a cell *one 0ith another or delete it

ri 4eorer 5onesri 4eorer %o6ain

ri 4eorer Print an/ith


16/20

Solver Basics

3-1#ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual+olyhedral )esh Conversion

6 tetrahedral or hy'rid grid can 'econverted to polyhedra in the FLUENT %UI

-not in the preprocessor.$ %enerate a tetrahedral "esh then convertinside FLUENT

$ 6dvantages I"proved "esh >uality Can reduce cell count significantly User has control of the conversion process

$ 2isadvantages: Cannot 'e adapted or converted again Cannot use tools such as s"ooth/ s0ap/ "erge

and etrude to "odify the "esh

T0o conversion options are availa'le in the%rid "enu:

$ Convert all cells in the do"ain -ecept hecells. to polyhedra

Cannot convert "eshes 0ith hanging nodes ?eCore "esh can 'e converted using the tpoly

standalone utility

$ Convert only highly s&e0ed cells to

polyhedra%rid +olyhedra Convert S&e0ed Cells

%rid +olyhedra Convert 2o"ain

Tet9?y'rid )esh

+olyhedral )esh


17/20

Solver Basics



Inventory "002#00

Training Manual+rofile 2ata and Solution 2ata Interpolation

FLUENT allo0s interpolation of selectedvaria'le data on 'oth face *ones and cell

*ones 'y using profile files and datainterpolation files/ respectively$ For ea"ple/ a velocity profile fro"

eperi"ental data or previous FLUENT runat an inlet/ or a solution interpolated fro"a coarse "esh to fine "esh

+rofile files are data files 0hich containpoint data for selected varia'les onparticular face *ones/ and can 'e 'oth

0ritten and read in a FLUENT session

Si"ilarly/ Interpolation data files containdiscrete data for selected field varia'leson particular cell *ones to 'e 0ritten andread into FLUENT

7ile Pro&ile(8rite

7ile Pro&ile(4ea

7ile Interpolate(


18/20

Solver Basics

3-1!ANSYS, Inc. Proprietary


Inventory "002#00

Training Manual)esh 6daption

)esh adaption refers to refine"entand9or coarsening cells 0here neededto resolve the flo0 field 0ithoutreturning to the preprocessor

$ )ar& cells satisfying the adaptioncriteria and store the" in a 7register8

$ 2isplay and "odify the register ifdesired

$ Clic& 6dapt to adapt the cells listed intheregister

egisters can 'e defined 'ased on:$ %radients or isovalues of all varia'les$ 6ll cells on a 'oundary$ 6ll cells in a region 0ith a defined

shape$ Cell volu"es or volu"e changes$ y in cells ad(acent to 0alls

To assist adaption process/ you can:$ Co"'ine adaption registers$ 2ra0 contours of adaption function$ 2isplay cells "ar&ed for adaption$ Li"it adaption 'ased on cell si*e

and nu"'er of cells

efine Threshold should

'e set to #D of the valuereported in the )a field


19/20

Solver Basics



Inventory "002#00

Training Manual6daption Ea"ple Supersonic +ro(ectile

6dapt grid in regions of large pressure gradient to 'etter resolve the

sudden pressure rise across the shoc&

Initial )esh -%enerated 'y +reprocessor. +ressure Contours on Initial )esh

Large pressure gradient

indicating a shoc& -poor

resolution on coarse

"esh.


20/20

Solver Basics

3 20ANSYS, Inc. Proprietary April 2!, 2009

Training Manual6daption Ea"ple Supersonic +ro(ectile

Solution;'ased "esh adaption allo0s 'etter resolution of the 'o0

shoc& and epansion 0ave

)esh adaption yields

"uch 'etter resolution

of the 'o0 shoc&6dapted cells

in locations of

large pressure

gradients

6dapted )esh -)ultiple 6daptions

Based on %radients of +ressure.

+ressure Contours on 6dapted )esh

Documents

Fluent12 Lecture03 Solver Basics