Computational Fluid Dynamics - BME Áramlástan …benedek/CFD/icem/icem_1st_practice/2dpipe.pdf ·...

Computational Fluid Dynamics

2016 autumn, 1st week

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• Tamás Benedek

• benedek [at] ara.bme.hu

• www.ara.bme.hu/~benedek/CFD/icem

• Working directory: C:\Work create yourown, for example: Work\quentin_tarantino (ifyou are Quentin Tarantino )

The most important rule: Dont use space or specific characters in:File names, path, part names, etc. (nowhere)

Another important rule: Your work will be deleted, if you turn off thecomputer. When you finished, save yourwork on a flash drive or send it to yourselfattached to an e-mail

Instructors of ICEM courses:

• László Nagy (nagy [at] ara.bme.hu)

• Péter Füle (fule [at] ara.bme.hu)

• András Tomor (tomor [at] ara.bme.hu)

• Week1-5: ICEM and FLUENT practice

• Week6-8: Individual project

• Week9-11: Group project

• Week12-13: Tutorials of specific problems

• Week14: Presentation of the group project, OpenFOAM teaser

Agenda

WORKBENCH

Solving a problem with CFD

CAD model(ICEM/Design Modeler/Import)

Mesh generation(ICEM)

Solver(FLUENT)

Postprocessing(FLUENT/CFD post/…)

Goal of the present practice

• Make your first mesh in ICEM through thesample of a 2D pipe

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Start the Ansys Workbench

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Grab and drag the ICEM CFD from the ComponentSystems to the Project Schematic

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Grab and drag the FLUENT from the ComponentSystems to the Project Schematic

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1) Connect them2) Double click on ICEM

CFD/Model

Geometry

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The original geometry (in cm-s)

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• Settings/Selction/Auto pick mode: turn ON

Settings

Point creation

1.) Select: Geometry, Create Point

2.) Select: Explicit Location

3.) Type the coordinates here

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The coordinates of the first point shouldbe: 0,0,0 Apply

You can work in any dimension, becauseyou can scale your mesh in the solver

Point creation

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We have one point! Yeah!

Point creation

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Click on Fit window to seeall of your points

Point creation

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Right click on Geometry/Points in thedisplay tree Show point names

Point creation – the coordinates of thepoints

Nr. Coordinates (x,y,z)

0 0,0,0

1 32,0,0

2 32,16,0

3 48,32,0

4 48,64,0

5 64,32,0

6 64,64,0

7 50,-5,0

8 54,-5,0

9 16,32,0

10 0,32,0

11 50,16,0

12 54,16,0

13 0,16,019

Point creation

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Curve creation (straight line)1.) Select: Geometry, Create/Modify Curve

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Curve creation (straight line)

To select the endpoint of yourline:- click on the „select location(s)”

button the select point00 and point01 with the L(eft) M(ouse) B(utton)

- accept your selction with theMMB

- The wrong selctions can be canceled with the RMB

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Curve creation (straight lines)

Create the other straight lines thesame way!

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Curve creation (Arcs)

1.) Select: Arc

2.)Method: From 3 Points

Arc 1

Arc 2

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Create arcs, which fit on three points

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1

3

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2

Create intersection points

2.) Select: Curveintersections

3.) Select the large arc and thestraight line with the LMB (youcan cancel with the RMB)

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1.) Select: Geometry/Create Point

4.) Repeat it with the arc and the other straight line

Segment curves

2.) Select: Segment curves

Segment your arcs atthe middle points

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1.) Select: Geometry/Create – Modify curves

Segment your large arc at theintersection points which wascreated in the previous step (youcan select the points together)

Segment your straigth lines atthe intersection ponits as well

Select – LMBAccept – MMBCancel – RMB

Delete curves

Select: Delete curves

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- Select the unnecessarycurves with the LMB

- Accept your selectionwith the MMB

Select – LMBAccept – MMBCancel – RMB

Delete curves – The result

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Create Parts

1) Right click on the parts inthe display tree, Create part

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3) The selected entity: thevertical straight line on theleft hand side

Select – LMBAccept – MMBCancel – RMB

2) The part name should be:Velocity_inlet1 (dont use space)

The parts will be your boundaries and fluid zones in the FLUENT (like thenamed selctions in the WB Mesher)

Create Parts

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3) The selected entity: thetiny horizontal straight line on the bottom

Select – LMBAccept – MMBCancel – RMB

Change the name to:Velocity_inlet2

Create Parts

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Create the other parts!

Select – LMBAccept – MMBCancel – RMB

Outflow

Wall1

Wall2

Interior(the tiny curve)

Wall3

When you finishedsave your work!

Blocking, Meshing

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Block structured mesh

• The mesh is build up from rectangular (2D) orcuboid (3D) segments

• The blocks are divided to quad (2D) or hexa(3D) cells

• The vertices, the edges and the faces of theblocks are associated and shaped to thepoints, curves and surface of the geometry

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Definitions in ICEM

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Geometry Blocking

Point Vertex

Curve Edge

Surface Face

Sample (the present problem)

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Geometry Initial blocking

Sample (the present problem)

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The associated blocking

Sample (the present problem)

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The final mesh

Let’s start blocking

• Save your work before start the blocking!

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Initialize Blocking1.) Select: Blocking, Create Block

3.) Selected Part: FLUID (type it)This will be your fluid zone in the FLUENT

2.) Select: Initialize block

4.) Select: 2D planar39

Initialize Blocking

If you get an infinite block in some directionclose the ICEM and the Workbench withoutsaving (if you saved your work before). Thenrestart it, load your project and repeat thewhole blocking procedure

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The Result

Split block1.) Select: Blocking, Split Block

2.) Select: Split block

3.) Method: Screen select

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Split block

Select one of the verticaledges in order to split yourblock in horizontal direction

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Select – LMBAccept – MMBCancel – RMB

Split block

Split your blocks in verticaldirection two times

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Select – LMBAccept – MMBCancel – RMB

Split block

Delete the two bottomblocks on the left and right hand side

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Select – LMBAccept – MMBCancel – RMB

Select: Delete blocks

Split block

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Associate the edges to the curves

Select the Associate edge tocurve than associate themarked edge to the markedcurve

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Select – LMBAccept – MMBCancel – RMB

Select: Associate

Associate the edges to the curves

If the association is succesful , the edge will be green

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Select – LMBAccept – MMBCancel – RMB

Associate the edges to the curves

Right click on Blocking/Edgesin the display tree, and thearrows will show yourassociation (the picture showsthe final state)

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Select – LMBAccept – MMBCancel – RMB

You can select multiple edgesand curves at the same time

Associate the edges to the curves

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Select – LMBAccept – MMBCancel – RMB

Select the two curvestogether

Associate the edges to the curves

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Select – LMBAccept – MMBCancel – RMB

Select the three edgestogether

Associate the vertices to points

1) Select associate vertex

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Select – LMBAccept – MMBCancel – RMB

2) Entity: point

Associate the vertices to points

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Select – LMBCancel – RMB

Associate the vertices to thepoints as the arrows showYou can see the result on the nextslide

Move unassociated vertices

2) Select: Move vertex

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Select – LMBAccept – MMBCancel – RMB

1) Select: Move vertex

3) Grab (hold the LMB) themarked vertex and drag it tothe right position (see it onthe next slide)

Move unassociated vertices

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Move unassociated vertices

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Repeate it with the othervertex

Setting mesh parameters

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Select: Mesh/ Part meshsetup

Setting mesh parameters

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- LMB on the maximum size, set it to 1 (themaximum length of cell edges will be 1)- Accept, Apply

Setting mesh parameters

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Blocking/Premesh params

Recalculate sizes

Update allApply

Yes

The premesh

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Enable premesh in thedisplay tree

Refine the mesh

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Blocking/Premesh params

Edge parameters, Scrolldown

Refine the mesh

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Enable copy parametersTo all parallel edgesRoll up

Refine the mesh

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1) Select one of the markededges

2) Spacing1, Spacing2=0.33) Ratio1, Ratio2=1.54) Apply5) Right click on premesh in the

display tree: recompute

Spacing: the length of the cellfaces at end of the edgesRatio: the groving ratio of the facelength moving away from the end points

Refine the mesh

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1) Select one of the markededges

2) Set the node number to 153) Apply4) Right click on premesh in the

display tree: recompute

Reducing the cell size change

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1) Select match edges2) Reference: 3) Targets:

Select – LMBCancel – RMB

Reducing the cell size change

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1) Select match edges2) Reference: 3) Targets:

Select – LMBCancel – RMB

Reducing the cell size change

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1) Recompute the premesh (RMB)2) Now the cell size is the same at

meeting of the edges

Create FLUENT input file

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1) Right click on the premesh inthe display tree

2) Convert to unstruct mesh3) (Replace the old mesh if the

Icem asks)4) Output mesh to Ansys FLUENT5) Close the ICEM CFD

Physical model, Solution of theproblem

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• For more detailed descriptions of FLUENT settings check (from page 36):

http://www.ara.bme.hu/~benedek/CFD/workbench/workbench_1st_practice/orifice_1415_eng.pdf (orifice.pdf in hungarian)

• Or ask your instructor

• Or ask the lecturer

Starting FLUENT

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1) Double click on Setup

Starting FLUENT

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OK

Scaling the mesh

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1) Mesh/Scale

Scaling the mesh

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1) Mesh was created in: cm2) Scale3) Close

Turbulence Model

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1) Double click onModel/Viscous

Turbulence model

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1) K-epsilon2) standard

Boundary conditions

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1) Boundary condtions2) Select: velocity_inlet13) Type: velocity-inlet4) Edit

Boundary conditions

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1) Set the same2) OK

Boundary conditions

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Velocity_inlet2

Discretization Schemes

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1) Solution methodes2) Coupling: coupled3) Gradient: G-G-Cell-Bsd4) Everything is second

order

Turn off convergence criterion

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1) Monitors2) Double click: Residuals

Turn off convergence criterions

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1) Covergence criterion: none2) OK

Intialization

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1) Solution intialization2) Hybrid3) Intialize

Calculation

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1) Run Calculation2) # of iterations: 2003) Calculate

OK, whenfinished

Drawing pathlines

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1) Graphics and animation2) Pathlines

Drawing pathlines

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1) Color by: velocitymagnitude

2) From: velocity_inlet1,23) Display

Drawing pathlines

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Contour plots: pressure

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1) Graphics and animation2) Contours

Contour plots: k

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1) Graphics and animation2) Contours

Contour plots: velocity

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1) Graphics and animation2) Contours

Velocity vectors

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