flow around a cylinder - hs-augsburg.dethalhof/downloads/tmgfflow.pdf3 setup what: open the tutorial...

$: Flow Around a Cylinder - hs-augsburg.dethalhof/downloads/tmgfflow.pdf3 Setup What: Open the tutorial model file. How:Start FEMAP and load the model:...\tmg\doc\femap\tutorials\cylinder_meshed.MOD$
1TMGFtut93a

Flow Around a CylinderFEMAP TMG Flow Tutorials

Learn how to:

• mesh for the fluid analysis• define fans and vents• solve the fluid analysis• post process the results

An optional part at the end shows how to:• model a heat load and convection.

2

Before you begin...

Software requirements:

1. Demo License or TMG Flow*

2. Your FEMAP installation must includeParasolid capabilities

*The optional section requires a Demo License, orTMG Flow and TMG Thermal Licenses.

Prerequisite tutorials:

1. Getting Started (FEMAP Training Examples)

Note: If these tutorials are not available at yourinstallation, you can still complete this tutorial if youhave someone show you how to start the software anduse the menus and mouse.

Recommended tutorials:

1. Groups, Layers, Viewing and Post Processing

2. Simple Solid

Completed sample modelAfter you finish the tutorial, you can compare yourmodel with a sample model. This sample was createdusing the techniques described in this workshop andshould match your model perfectly.The sample is stored as:.../tmg/doc/femap/tutorials/cylinde_solved.MOD (thefirst part of the path may vary slightly depending onyour FEMAP installation).

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Setup

What: Open the tutorial model file.How:Start FEMAP and load the model:...\tmg\doc\femap\tutorials\cylinder_meshed.MOD(the first part of the path may vary slightly dependingon your FEMAP installation).What: Save a copy of the model.Recovery Point

File > Save As [save the file to a localdirectory]

Open

By default, there are no units in FEMAP. You mustmake sure that the geometry dimensions areconsistent with the unit system of the materialproperties and boundary conditions that will apply tothe model. All dimensions specified in this tutorialare in meters.

Things to notice With TMG, you can specify whetheryour model is unitless (default), in Standard units, or inUser Defined units. For this first tutorial, we will leavethe default option on.

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Modeling Overview 1 of 4

Modeling OverviewThe model consists of a rectangular air duct with acylinder cutting across it.

FRONT VIEW

Air enters from one end of the tunnel and exits at theother end, flowing around the cylinder.The inlet and outlet are modeled by defining boundaryconditions on both surfaces at the ends of the tunnel.

ISOMETRIC VIEW

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The model has already been air meshed in order tohave less than 300 nodes for FEMAP Demo Licensecompatibility.If you have the TMG Flow License and want greateraccuracy, you can delete the existing mesh and createa much finer one.The 3D fluid elements within the geometry define thevolume of air.The cylinder is not meshed. To model the effect of anobstruction, simply leave the volume of the obstructionunmeshed.

Unmeshed volume

Unmeshed Volume Deflects the Flow

Schematic3D air mesh

Unmeshed surfaces are automatically defined asdefault smooth walls by TMG Flow.

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Openings such as fans and vents are typically definedon a surface that forms part of a solid meshed with3–D fluid elements. The 3–D fluid elements (solidelements with fluid properties) represent the fluidvolume. One or more of the surfaces defining the fluidvolume can define the extent of the boundarycondition.During the solve, the boundary condition informationon the surface is transferred to the 3–D element faces.

Free faces of 3–D fluid elements (schematic)

surface

Things to notice The surface must be coplanar with the 3D elementfaces underneath it.

7


Check the material properties for the air elements.

Entity Selection – Select Material(s) to Edit form

Select All

OK

Define Fluid Material formThings to notice

• Air is the only material defined in the model.• Material properties are defined using SI units.• You must use a fluid material to be able to solve

with TMG Flow.

Cancel

Save your model.Recovery Point

File > Save

8

Part 2: Defining and Solving the TMG Model

In this part of the tutorial, you will:• create the fan and vent boundary conditions• specify the Run Directory, Ambient Conditions

and Solver Control• solve• check the solution

9

Define and solve the TMG model 1 of 9

What: Open the TMG panel.

TMG Panel

Things to notice The TMG panel is used for both TMGand TMG Flow. Your license controls the access tosome icons.What: Activate the Flow Panel View option .TMG Panel > Options > Icon Panel Views

Flow (toggle on)

Create an Inlet Fan with a velocity of 0.1 m/s.

Fan

Create Fan form

Name: Inlet

Element Selection: Faces of volumeelem. on surface

Pick...

Entity Selection formSelect the left end surface of the volume.

OK

Fan Type: Inlet

Flow Parameter: Velocity

Velocity: 0.1

OK

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What: Create a Vent.

Vent

Create Vent form

Name: Vent

Element Selection: Faces of volumeelem. on surface

Pick...

Entity Selection formSelect the right end of the volume.

OK

Create Vent formThings to notice For this model, we will accept the

default Vent to ambient option. The TMG Vent entitymodels an opening that allows fluid to enter or leavethe fluid domain. You do not specify a vent as being aninlet or an outlet. It is the flow distribution that willdetermine whether fluid is exiting or entering the modelthrough the vent.

OK

11


It’s good practice to check the boundary conditionsin the model before solving. The TMG ModelManager gives a clear overview of all the boundaryconditions, and provides easy access if you need tochange any values or selections.

What: Start the TMG Model Manager.How:Click on any icon. At the very bottom of the listthat appears, you have two special buttons: Manager...and Dismiss. Pick the Manager... button.

TMG Model Manager formThings to notice

The main panel of the form displays a list of all theentity types in the model.

Fans (double click)

Inlet (click)

Sketch geomThings to notice

The graphics window displays the surface you selectedwhen you defined the thermal coupling.

Redisplay

Inlet (double click)

Fan – Modify formCheck the values in the fields, and make anymodifcations required.

OK

Check the Vent in this way as well.

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Specify a Run DirectoryWhy:Many files are created during the solve. Thesefiles always use the same name. Specifying a RunDirectory facilitates file management and prevents thefiles from being overwritten.

FE Study

FE Study form

Run Directory

Run Directory: cylinder\

The backslash ( “\” ) is required. TMG will create therun directory (if it does not already exist) in thedirectory from which FEMAP was launched.

Things to notice Review the form. The two boundary conditions youcreated are Active in the default FE study.

Do not close the form! In the coming pages you willuse the icons on this form to specify the AmbientConditions and the Solver Controls.

Why:The icons on the FE Study form are also on theTMG panel, but sometimes it is easier to use themfrom the form.

13


Define the Ambient Conditions.Why:These conditions apply to the air outside of thefan and vent. In particular this defines the pressure justoutside of the vent.

Ambient Conditions (icon on form)

Ambients Conditions formThings to notice

In the unitless mode, some values are negative bydefault. This ensures that these required fields arefilled in.

Static Pressure: 101351 (Pa)

Gravitational Acceleration: 9.81 (m2/s)

OK

Things to notice Gravitational acceleration is not used in this model butit must be specified.

14


What: Set the Solver Controls.

Solver Control (icon on form)

Solver Control form

Execute Thermal Solver (toggle off)Why:We are only interested in executing the flowsolver.

OK

Close the Study Setup form.

OK

Boundary conditions and Solver Control are defined.You are ready to solve. Save your model beforecontinuing.Recovery Point

File > Save

15


Solve the model.

Solve

If your Run Directory does not exist, a warningmessage appears asking your permission to create it.Pick Yes.

Things to notice When you launch a solve, FEMAP is frozen and theSolver Monitor appears a few seconds later.

Errors, warnings, and information are displayed in themessage window. Use the scroll bar to scan thesemessages. (All data in this window can be reviewedlater by selecting the View All Messages icon on theTMG panel.)

The Stop button will terminate processing and deleteall intermediate results. Pause suspends the thermal orflow solution and recovers results for post-processing.Even if the solution has not converged, this featurepermits you to inspect the results after a few iterations.

Examine the progress of the solution on the followingpages.

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Examine the solution in progress.

Flow

Things to notice You may examine the Flow Solution monitor at anytime during the solve. This display is updatedautomatically and will graphically show how close youare to the convergence criterion (horizontal line at1E-03).Residuals for the X,Y, and Z velocity (U,V, and Wmomentum), and mass are plotted. Turbulent kineticenergy and dissipation rate are only displayed if the KETurbulence Model is active.

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Once the solve is done, review the solver messages ineither the Solution Monitor window or with View AllMessages icon.

Things to notice • Scroll to the bottom of the window and check the

Solver Convergence Summary. Imbalances formass and momentum are provided. Normally,these imbalances should be smaller than 1% forthe solution to be considered converged.

• A detailed summary for mass and momentum isgiven just after the last solver iteration.

• At the end of the file, just before the SolverConvergence summary, you will find the SolutionSummary. Check this summary to see maximumand minimum fluid velocities and otherinformation about the results.

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Part 3: Post Process the Results

In this part of the tutorial, you will:• post process velocities and pressure• use dynamic cutting plane

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Post proces the results 1 of 5

What: Import the results.

Get Results

What: Close the TMG Panel:

File > Exit

Why:All post processing functionality is availablewithin FEMAP, not TMG.

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Post process the results 2 of 5

Display the air velocities.View Select

View Select form

Vector

Deformed and Contour Data...

Select PostProcessing Data form

Contour: VELOCITY AT ELEMS TWhy:The Output Set contains the magnitude of thevelocity vector at each node. You will use a postprocessing option to color the vectors with the contourselection later.

Contour Vectors...

Contour Vector Options form

3D Components

Vector 1: VELOCITY AT ELEMS X

Vector 1: VELOCITY AT ELEMS Y

Vector 1: VELOCITY AT ELEMS ZThings to notice The velocities must be specified in the

same column. The other columns are ignored.

OK (all forms)

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Color the velocities with the contour selection.View > Options...

View Options form

Category: PostProcessing

Options: Contour Vector Style

Color Mode: Contour Colors

Options: Contour/Criteria Levels

Level Mode: Auto – Group

OK

Things to notice Colors now refer to the color bar.

Zoom in to better see the flow around the cylinder. Youcan also rotate the model.

Use Ctrl–A to resize the graphic.

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Display an isometric view of the model.View > Rotate > Model...

View Rotate form

Isometric

OK

Display the total pressure.View Select

View Select form

Contour



Contour: TOTAL PRESS AT NODES

OK (all forms)

Things to notice Pressure is displayed on the outersurfaces of the volume.

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Display the pressure on a cutting plane.View > Advanced Post > Dynamic Cutting Plane...

Dynamic Section Cut Control form

Plane...

Plane Locate - Define Primary Cutting Plane form

Methods: Global Plane

Base X: 0

Base Y: 0

Base Z: 0

XY Plane

OK

Dynamic Section Cut Control form

Move the cutting plane with the scrollbar on the form.

Close the form.

Cancel

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Wrap up

If you have a TMG Thermal License, you can continueto the next optional section. Otherwise, this is the endof this tutorial.Be sure to save your work before exiting FEMAP.Recovery Point

File > Save

25

Optional: Adding a Thermal BoundaryCondition

In this part of the tutorial, you will:• create the required material and property• mesh the cylinder surface• define a heat load and flow surface for the

cylinder• solve and post process the results

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Add a Thermal Boundary Condition 1 of 12

Display the model as a wireframe.

Wireframe

Turn off the display of nodes and elements

Quick Options

View Quick Options form

All Entities Off

Geometry On

Done

Display the entire model.

Model Data...

Select Model Data for View form

Group: None

OK

27


What: Create a material to be used on the cylinder.

Model Info

Model

Materials (Right–click, select New)

Define Isotropic Material form

Type...

Material Type form

Isometric

OK

Define Isotropic Material form

Title: Cylinder Material

Conductivity, k: 45

OK

Cancel

What: Create a plate property for the cylinder thermalboundary condition elements.

Model Info

Model

Properties (Right–click, select New)

Define Property –* Element Type form

Element / Property Type...

Element Property Type form

Plate

OK

Define Property – PLATE Element Type form

Title: Cylinder Prop

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Thickness, Tavg or T1: 0.001

Material: Cylinder Material

OK

Cancel

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Mesh the cylinder surface.

Surface

Entity Selection – Select Surfaces to Mesh formPick the 2 surfaces as shown in red:

OK

Automesh Surfaces form

Property: Cylinder Prop

OK

Save your model.Recovery Point

File > Save

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Check the mesh for coincident nodes and coincidentelements.

Coincedent Nodes

Entity Selection - Select Node(s) to Check form

Select All

OK

Check/Merge Coincident form

Merge Coincident Entities

OK

Check for coincident elements.

Coincedent Elements

Entity Selection - Select Element(s) to Check form

Select All

OK

Check Coincident Elements form

(Toggle OFF all Check Options.)

OK

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What: Open the TMG panel.

TMG Panel

What: Define a heat load of 100W on the cylinder.

Thermal B.C.

Create Thermal BC form

Name: Cylinder 100 W

Element Selection: Plane elements onsurface

Pick...Pick the 2 surfaces as shown in red:

OK

Type: Total Heat Load

Constant: 100

OK

1

2

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Define a Surface Property characterizing the cylinderroughness. Use a roughness value of 0.0 in. to modelsmooth surfaces.

Surface Property

Create Surface Properties form

Name: Smooth

Use surface roughness of

Use surface roughness of: 0.0

OK

Define a Flow Surface for the cylinder.

Why:Flow Surfaces (and Blockages) are the entitiesthat can convect to the fluid.

Flow Surface

Create Flow Surface form

Name: Cylinder Surface

Element Selection: Plane elements onsurface

1 2 (pick two cylindrical surfaces)

Pick...

OK

Recovery PointFile > Save

33


Specify a new Run Directory

FE Study

FE Study form

Run Directory: thermal\

Activate the Thermal Solver.

Solver Control

Solver Control form

Execute Thermal Solver

OK

Close the FE Study form.

OK

Boundary conditions and solver controls are nowdefined. You are ready to solve. Save your modelbefore continuing.Recovery Point

File > Save

1

2

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What: Create groups for the cylinder elements and thefluid volume.Group > Set...

Create or Activate Group form

Title: Cylinder

OK

Group > Element > on Surface

1 2 (pick two cylindrical surfaces)

OK

Group > Set...

Create or Activate Group form

ID: 2

Title: Air

OK

Group > Element > in Solid / Volume

Enter Curve To Select Elements for Group form

Select All

OK

35


What: Solve the model.

Solve

What: Import the results.

Get Results

What: Close the TMG Panel

File > Exit

36


Display the temperatures on the cylinder.View Select

View Select form

Contour



Output Set: Thermal Steady StateWhy:The Thermal Steady State output set containsthe solid (non–fluid) element results.

Contour: Plate Top ELEM TEMP

Contour Options...

Select Contour Options form

Elemental

No AveragingWhy:For a coarse mesh, averaged results can bemisleading.

OK (all forms)

Continued on next page..

37


Display the cylinder.

Model Data...

Select Model Data for View form

Group: Select

Group: Cylinder

OK

Things to notice The cylinder is colder in the regionswhere the flow is faster.

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Display the temperature of the fluid.View Select

View Select form



Output Set: 2..Flow Steady StateWhy:The second Flow Steady State output set wascreated during the second solve and contains the fluidtemperature.

Contour: FLUID TEMP AT NODES

OK (all forms)

Things to notice The hotter regions correspond to theareas where the flow is the slowest.

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Wrap up

This is the end of this tutorial.Be sure to save your work before exiting FEMAP.Recovery Point

File > Save

flow around a cylinder - hs-augsburg.dethalhof/downloads/tmgfflow.pdf3 setup what: open the tutorial...

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