am 12 appendix a

Appendix A

Mesh QualityMesh Quality

ANSYS MeshingApplication Introduction

A-1ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

April 28, 2009Inventory #002645

Appendix A: Mesh Quality

Training ManualOverview• Mesh Quality Metrics in ANSYS Meshing

– Skewness– Aspect Ratio– Worst Element

M h Q lit C id ti f th FLUENT S l• Mesh Quality Considerations for the FLUENT Solver– General Considerations– Impact of Mesh Quality on the Solution

• Mesh Quality Considerations for the CFX Solver• Factors Affecting Mesh Quality

– CAD Issues– Mesh Resolution and Distribution– Meshing Method

I fl ti– Inflation• Strategies to Improve Mesh Quality

– CAD Cleanup– Virtual Topology

Pi h C t l– Pinch Controls– Sensible Mesh Sizings and Inflation Settings– General Recommendations

• Workshop A.1 Virtual Topology for an Auto ManifoldWorkshop A 2 FLUENT and CFX Mesh Q alit Metrics



• Workshop A.2 FLUENT and CFX Mesh Quality Metrics


Training ManualMesh Quality Metrics in ANSYS Meshing

• Mesh Metrics are available under Mesh Options to set and review mesh metric information and tomesh metric information and to evaluate mesh quality

• Different physics and different solvers have different requirements for mesh quality

• Mesh metrics available in ANSYS Meshing include:– Element Quality– Aspect Ratio

Jacobian Ration– Jacobian Ration– Warping Factor– Parallel Deviation– Maximum Corner Angle



g– Skewness


Training ManualMesh Quality Metrics

Skewness

Two methods for determining skewness:

optimal (equilateral) cell

1. Based on the Equilateral Volume deviation:

• Skewness = optimal cell size cell sizeoptimal cell size

−

• Applies only to triangles and tetrahedra• Default method for tris and tets

2 B d th d i ti f N li d

p

actual cell

2. Based on the deviation from a Normalized Angle deviation:

• Skewness = ⎥⎦

⎤⎢⎣

⎡ −− mineemax ,180

maxθθθ

θθθ

θ

maxθcircumsphere

Where is the equiangular face/cell (60 for tets and tris, and 90 for quads and hexas)• Applies to all cell and face shapes

⎥⎦

⎢⎣ − ee

,180 θθ minθ

eθ

0 1



pp p• Used for prisms and pyramids 0 1

Perfect Worst


Training ManualMesh Quality Metrics

Aspect Ratio

• Aspect for generic triangles and quads is a• Aspect for generic triangles and quads is a function of the ratio of longest side to the shortest side of the reconstructed quadrangles (see User Guide for details)E l t 1 (id l) f il t l t i l

aspect ratio = 1 high-aspect-ratio quad• Equal to 1 (ideal) for an equilateral triangle

or a square

aspect ratio = 1 high-aspect-ratio triangle




Training ManualMesh Quality Statistics in ANSYS Meshing• The min, max, averaged and standard

deviation for the selected mesh metric are shown for the surface mesh (after Preview Surface Mesh generation) and g )for the volume mesh (after Preview Inflation layer or Generate Meshgeneration)

• The worst elements can be highlighted using the Show Worst Elements under the Mesh object in the Tree Outline




Training ManualMesh Quality Considerations for FLUENT

• FLUENT requires high quality mesh to avoid numerical diffusion• Several Mesh Quality Metrics are involved in order to quantify the quality,

however the skewness is the primary metrichowever the skewness is the primary metric• The aspect ratio and cell size change mesh metrics are also very

important I t i d d di th l d (d it b d• In worst scenarios and depending on the solver used (density based or pressure based) FLUENT can tolerate poor mesh quality. However some applications may require higher mesh quality, resolution and good mesh distributiondistribution

• The location of poor quality elements helps determine their effect• Some overall mesh quality metrics may be obtained in Ansys Meshing

d th St ti ti bj tunder the Statistics object• Additional mesh quality metrics may be retrieved in FLUENT GUI under

Mesh/Info/Quality from the menu, or using the TUI commands ‘ h/ lit ’



‘mesh/quality’


Training ManualMesh Quality Requirements for FLUENT

• The most important mesh metrics for Fluent are:– Skewness– Aspect RatioAspect Ratio– Cell Size Change (not implemented in Ansys

Meshing)For all/most applications:

• Poor mesh quality may lead to inaccurateFor all/most applications:

• For Skewness:– For Hexa, Tri and Quad: it should be less than 0.8

For tetrahedra: it should be less than 0 9

lead to inaccurate solution and/or slow convergence

– For tetrahedra: it should be less than 0.9• For Aspect Ratio:

– It should be less than 40, but this depends onthe flow characteristics

• Some applications may require even lower skewness than the suggested valuethe flow characteristics

– More than 50 may be tolerated at the inflation layers

• For Cell Size Change:

suggested value



• For Cell Size Change:– It should be between 1 and 2.


Training ManualSkewness and the Fluent Solver

• High skewness values are not recommended• Generally try to keep maximum skewness of volume mesh < 0.95.

However this value is strongly related to type of physics and the locationHowever this value is strongly related to type of physics and the location of the cell

• FLUENT reports negative cell volumes if volume mesh contains degenerate cells.degenerate cells.

• Classification of the mesh quality metrics based on skewness:

0 0 25 0 25 0 50 0 50 0 80 0 80 0 95 0 95 0 98 0 98 1 00*

•

0-0.25 0.25-0.50 0.50-0.80 0.80-0.95 0.95-0.98 0.98-1.00*

Excellent very good good acceptable bad Inacceptable*

* In some circumstances the pressure based solver in Fluent can handle meshes containing a small percentage of cells with skewness ~0.98.




Training ManualImpact of the Mesh Quality on the Solution

(max,avg)CSKEW=(0.912,0.291) (max,avg)CAR=(62.731,7.402)Example

VzMIN≈-90ft/min Vz ≈600ft/min

Mes

h 1

VzMAX≈600ft/min

Large cell size change

(max,avg)CSKEW=(0.801,0.287) (max,avg)CAR=(8.153,1.298)

2

VzMIN≈-100ft/min VzMAX≈400ft/min

Mes

h 2



VzMAX 400ft/min


Training ManualMesh Quality Considerations for CFX

• Mesh quality requirements are somewhat different for the CFXsolver than for the FLUENT solver due to the difference in thesolver structure for the two codes

– Fluent uses a a cell-centered scheme, in which the fluid flow variables are allocated at the center of the computational cell, and the mesh-element is the same as the solver-element

– CFX employs a vertex-centered scheme for which the fluid flow variables are stored at the cell vertex, and the solver-element or control volume is a “dual” of the mesh-element. This means that the vertex of the mesh-element is the center of the solver-elementelement is the center of the solver element




Training ManualMesh Quality Considerations for CFX• The CFX solver calculates 3 important measures of mesh

quality at the start of a run and updates them each time themesh is deformed

– Mesh Orthogonality– Aspect Ratio– Expansion Factor

+--------------------------------------------------------------------+| Mesh Statistics |+--------------------------------------------------------------------+Domain Name: Air Duct

Mi i O th lit A l [d ] 20 4 k

Good(OK)Minimum Orthogonality Angle [degrees] = 20.4 ok

Maximum Aspect Ratio = 13.5 OKMaximum Mesh Expansion Factor = 700.4 !

Domain Name: Water PipeMinimum Orthogonality Angle [degrees] = 32.8 okMaximum Aspect Ratio = 6.4 OK

(OK)

Acceptable(ok)

Maximum Mesh Expansion Factor = 73.5 !Global Mesh Quality Statistics :

Minimum Orthogonality Angle [degrees] = 20.4 okMaximum Aspect Ratio = 13.5 OKMaximum Mesh Expansion Factor = 700.4 !

( )

Questionable(!)




Training ManualMesh Orthogonality in CFX

•Orthogonality measures alignment of:• ip-face normal vector, n, &• node-to-node vector, s.

• Orthogonality Factor = n·s, >1/3 desirable• Orthogonality Angle = 90º-acos(n·s), >20º desirableOrthogonality Angle 90 acos(n s), >20 desirable• Are these different than Max/Min Face Angles in CFD Post? YES!

– Face angles correspond to angles between edges– One can have an acceptable Face Angle and an unacceptable Orthogonality

Angle if an element is skewed in two directions…




Training ManualMesh Expansion Factor in CFX

Expansion factor measures how poorly the nodal position corresponds p y p pto the control volume centroid

• Mesh Expansion Factor ≈ ratio of largest to smallest elementvolumes surrounding a nodevolumes surrounding a node,<20 is desirable

• The Mesh Expansion Factor is essentially identical to the Element Volume Ratio in CFD Post




Training ManualMesh Aspect Ratio in CFX

Aspect ratio measures how stretched a control volume is

• Aspect Ratio = maximum of the ratio of largest to smallest ip-areas for each element surrounding a node,

100 i d i bl<100 is desirable• The Aspect Ratio is very similar to the Edge Length Ratio in CFD Post




Training ManualSignificance of Mesh Quality in CFX

• Sources of discretisation error

Why is geometrical mesh quality important?

• Sources of discretisation error– non-orthogonality introduces errors in flux approximations– large mesh expansion introduces errors in storage and source

approximationsapproximations• Amplification of discretisation error

– corrections to reduce errors caused by non-orthogonality can create unphysical influencesunphysical influences

• Difficulties solving linearised equations– large aspect ratios require use of more significant digits

(i e use of double precision solver)(i.e. use of double precision solver)




Training ManualFactors Affecting Mesh Quality• CAD Issues

– Small edges, sharp edges and faces– Small gaps/passages between edges and faces– Unconnected geometry entities

CAD i d tCAD issues need to be fixed to avoid this




Training ManualFactors Affecting Mesh Quality• Mesh Resolution

and Distribution– Geometry with

abrupt changes, discontinuities and/or small gaps may require more resolution, and

– Mesh distribution where appropriate to be able to predict pphysical conditions

Inappropriate resolution and di t ib ti l ddistribution may lead to large cell size change, aspect ratio and/or skewness




Training ManualFactors Affecting Mesh Quality• Type of Size Function

– Inappropriate usage (or no usage at all) of Advanced Size FunctionsAdvanced Size Functions (ASF) may lead to poor mesh quality

– Use Curvature ASF for geometries ithgeometries with dominant curvature features

– Use Proximity ASF for geometries with gaps or narrow components

– Use Curvature and Proximity ASF in geometries having a combination of these features ASF may be used to

avoid this !




Training ManualFactors Affecting the Mesh Quality• Meshing Method

– Inappropriate usage of Meshing Method (Automatic, Tetrahedrons, Sweep, MultiZone and CFX-Mesh) may lead to large skewness

– The selection of the Meshing Method depends on the geometry and application– It is a good practice to use Show the Sweepable Bodies under the Mesh object in the

Tree Outline– Many applications may take advantage of Patch Conforming and Sweep Meshing MethodMany applications may take advantage of Patch Conforming and Sweep Meshing Method

A relatively “good” mesh in terms of ma ske nessterms of max skewness, however the average and standard deviation are large




Training ManualFactors Affecting Mesh Quality• Inflation

Inappropriate:– Surface mesh

quality– Choice of the

inflation surfaces– Inflation Optionp– Inflation algorithm

(layer compression or stair-stepping)Inflation– Inflation parameters

– Advanced Inflation Options Affected Inflation

may lead to poor

mesh quality!




Training ManualStrategies to Improve Mesh Quality

• CAD cleanupUse CAD or DM to:

– Simplify the geometry

After split edge/Project edge/merge face in DM

Simplify the geometry– Merge small edges– Merge the faces in

order to reduce the n mber of facesnumber of faces

– Avoid narrow faces– Keep volume gaps only

where important– Decompose the

geometry– Remove unnecessary

geometriesgeometries– Add geometries– Repair the geometry





• Virtual topologyUse VT in order to simplify details at

After virtual merging of narrow face with wide face

simplify details at geometry level in AM

Can be added under Model object in the Tree Outline

Mesh may be improved by creating virtual edges/facesvirtual edges/faces

If the resulting surface mesh is distorted consider fixing the geometry issue in DM or CAD




Training ManualStrategies to Improve Mesh Quality• Pinch Controls

– Allow to remove small features (small edges or narrow faces) at the mesh level

Pinch locations are detected automatically with Pinch Controls under

Mesh object in the Tree Outline

– Intended for Patch-Conforming Tetrahedral Method– When it is defined the small features are “pinched-

out” from the mesh when pinch criteria are met





• Sensible Mesh Sizings and Inflation Settings

The minimal size decreased 2X in order toThe minimal size decreased 2X in order to fit the narrow geometry. As a result the mesh quality has been improved. Local face sizing may also be used





• General Recommendations– A volume mesh may be considered inacceptable if it satisfies one or more theA volume mesh may be considered inacceptable if it satisfies one or more the

following conditions:• Very high skewness for FLUENT meshes(> 0.98)• Degenerate cells (skewness ~ 1)

Hi h t ti ll• High aspect ratio cells • Negative volumes

– Cell Quality can be improved by:I i f h lit• Improving surface mesh quality

• Moving mesh nodes• CAD to fix geometric problems such as sharp angles, small edges, merge faces unite

and/or decompose the geometries• Clean-up tools in DM to simplify the geometries and their entities• Different methods, global and local sizings and parameters in the ANSYS Meshing

Application• Pinch Controls in the ANSYS Meshing Application to avoid small features



• Virtual topology in the ANSYS Meshing Application in order to simplify the geometry


Training ManualMiscellaneous

• If the model contains multiple parts or bodies the mesh metric information can be shown by highlighting them under the Geometry object in the Tree Outline

• The Body of Influence (BOI) technique may be used also to control the mesh quality and appropriate local resolution

• More advanced mesh statistics including histograms can be exhibited by FE Modeler Mesh Metrics in FEM

• Different mesh quality metricscan also be viewed in CFD Post



Workshop A.1

Virtual Topology for anAuto Manifold

p

Auto Manifold




Training ManualGoalsThis workshop uses the manifold geometry from workshop 5.2. Recall that this geometry contains many problematic small faces and sharp angles.

In workshop 5.2, the Patch Independent method was used to produce a good quality mesh without modifying the geometry. In this workshop Virtual Topology will be used to “remove” the problematic geometry and then the



p gy p g ydefault Patch Conforming meshing method will be used.


Training ManualStarting the Project1. Launch ANSYS 12.0 Workbench2. Click on Component Systems in the Toolbox on the LHS of the main panel 3. Double click the Mesh option to add it to the Project Schematic3. Double click the Mesh option to add it to the Project Schematic4. In the Project Schematic right-click on Geometry and select Import

Geometry > Browse. Select the file Auto-Manifold.agdb




Training ManualNamed Selections5. Next, make sure that Named Selections will be brought into Meshing:6. Right-click on cell A2 and then select Properties7. Ensure Named Selections is checked, and the Named Selection Key is7. Ensure Named Selections is checked, and the Named Selection Key is

blank8. Close the Properties window




Training ManualEdit the Mesh9. Edit the Mesh (cell A3)

– The Meshing window will open10.Start by suppressing the fluid region and meshing the solid:y pp g g g

• Select the Body selection icon from the toolbar

• Select the inner fluid region, sothat it is highlighted in green, andthen right-click and selectS B dSuppress Body




Training ManualMesh Settings11.Select Mesh from the Outline tree12. In the Details view set the Physics Preference to CFD

• The assumption here is that heat transfer will be solved in the solid region p gusing a CFD solver

13.Expand the Sizing section in the Details view and set:Details view and set:• Span Angle Center = Medium• Min Size = 1.0 mm

Ma Face Si e 10 0 mm• Max Face Size = 10.0 mm• Max Tet Size = 10.0 mm

14.Right-click on Mesh in the Outlinet d l t P i S ftree and select Preview Surface Mesh• Since the body is not sweepable, the

Patch Conforming method will be



Patch Conforming method will be applied by default


Training ManualExamine the Mesh• The Patch Conforming method meshes each individual surface. This

produces a poor quality mesh on some surfaces in this geometry. Examine the surface mesh and look for regions of poor mesh quality. By

G O fswitching between Geometry and Mesh in the Outline tree relate regions of poor mesh quality to the underlying surface geometry. Some examples are shown here:




Training ManualAdding Virtual Topology• Virtual Topology allows you to merge adjacent surfaces, removing

undesirable surface geometry feature and producing a higher quality mesh

15. Right-click on Model (A3) in the Outline tree and select Insert > Virtual Topology

• A Virtual Topology entry is added to the Outline tree• In the Details view note that the Behaviour is set to Low

16 Right click on Virtual Topology in the Outline tree and select Generate16.Right-click on Virtual Topology in the Outline tree and select Generate Virtual Cells• This automatically creates virtual cells using a “Low” merging strategy.

“Medium” and “High” strategies are likely to result in more faces being



Medium and High strategies are likely to result in more faces being merged into virtual cells


Training ManualVirtual Topology• When Virtual Topology is selected in the Outline tree the viewer shows

all virtual cells that have been created• Examine the new surface geometry and note that most of the

problematic faces have been merged to produce a cleaner surface geometry

17. In the Details view change the Behaviour to Medium• Right-click on Virtual Topology in the Outline tree and select Generate

Virtual Cells• Note that more faces have been merged

into virtual cells18.Try generating virtual cells using the High

option for Behaviour• This does not work as well for this

geometry as shown to the right19.Switch back to the Medium option and



generate the virtual cells again


Training ManualExamine Improved Mesh20.Re-create the surface mesh and examine the regions that previously

showed poor mesh quality• You should find that the surface mesh has been greatly improved

21.There are still some regions where the mesh quality could be improved. The arrows below shows one of these locations.• If you zoom in and examine the geometry here you will find a kink at the

edge of the surface




Training ManualAdding Virtual Cells Manually22.You can manually add Virtual Cells to improve the mesh further

• Pick the Face selection icon from the toolbar

• Orient the view approximately as shown below (note the X-Y axes)• Check that Virtual Topology is selected from the Outline tree• Select the four faces shown below, then right-click and select Insert > Virtual

Cell

1 2

3



4


Training ManualExamining Improved Mesh23.Re-create the surface mesh and examine the region again

• You should find an improved surface mesh• You can continue adding Virtual Cells as necessaryg y• In some cases the automatic virtual cell creation may merge faces that

you do not want to merge. You can delete individual virtual cells by selecting the Virtual Face from below the Virtual Topology entry in the g p gy yOutline tree and right-clicking to delete.

24 Right-click on Mesh and select Generate Mesh to create the final solid



24.Right-click on Mesh and select Generate Mesh to create the final solid mesh


Training ManualViewing the Fluid Body• The next step is to create the mesh for

the fluid region25. In the Outline tree expand the Geometry

> Part section

• Right-click on the first solid and select gHide Body to hide the solid region

• Right-click on the suppressed (second) solid and select Unsuppress Body

• With the second solid selected, in the D t il i d th G hi lDetails view expand the Graphical Properties section and set the Transparency to 1




Training ManualAdding Inflation26.Select Virtual Topology from the Outline tree

• Virtual Cells have already been created on the fluid region from earlier27.Check that the automatic virtual cells look reasonable

• There should be no small surfaces remaining in the model28.The next step is to add inflation to the fluid walls

• Right-click on Mesh and select Insert > InflationRight click on Mesh and select Insert Inflation• In the Geometry field you need to select the solid body corresponding to the

fluid region from the Viewer then click Apply• Once this has been selected click on No Selection in the Boundary field so y

that the Apply / Cancel buttons appear




Training ManualCreating the Fluid Mesh• Now select one of the faces from the

model that is not an inlet or outlet• Select Extend to Limits from the

t lb htoolbar as shown:– All the fluid walls should now be

selected• Click Apply in the Boundary field in• Click Apply in the Boundary field in

the Details view

29 To generate the final mesh right-click29.To generate the final mesh right-click on Mesh and select Generate Mesh




Training ManualChecking the Mesh Quality30.Expand the Statistics entry and set the

Mesh Metric to Skewness. Note that theMax Skewness is within the acceptable rangeffor the FLUENT solver.

31. If you had generate the mesh without VT, theM Sk ld h b id blMax Skewness would have been considerablyhigher

Without Virtual Cells



Without Virtual Cells


Training ManualFluid Region Mesh

NO VT

VT



Workshop A.2

FLUENT and CFX Mesh Quality Metrics

p

Quality Metrics




Training ManualGoals

• This hands on tutorial will demonstrate how the Meshing Application in ANSYS is used to generate a CFD mesh for an internal flow domain

• The geometry represents portions of an aerospace valve region,The geometry represents portions of an aerospace valve region, decomposed into 3 bodies

• The goal is to produce a conformal hybrid CFD mesh including hex, pyramid, prism and tetrahedral elements including pinch controls and topyramid, prism and tetrahedral elements including pinch controls and to examine mesh quality metrics for the Fluent and CFX solver preferences




Training ManualCreating a Meshing System

1. Launch ANSYS Workbench from the START menu

2 Click on Component Systems in the Toolbox on the LHS of the WB2. Click on Component Systems in the Toolbox on the LHS of the WB main panel

3 Double click the Mesh3. Double click the Meshoption




Training ManualImporting the Geometry

4. Right click (RMB) on the Geometry button and select Import Geometry (the question mark on the button goes away once a geometry file is imported)

5. Import the Aero-Valve.agdb file from the tutorial folder6. Double click on the Mesh button in the Project Schematic to launch the Meshing

Application




Training ManualGeometry7. The original geometry is a Solid part and the Fluid region was extracted

out in DesignModeler (DM). Other operations performed in DM;• A parameter was defined for the position of the valve• Some outlet ports were closed• One multi-body part was created and a given the name “Fluid” and the material “Fluid”• Individual bodies were re-named and Named Selection was used to define the Inlet

and Outletand Outlet• Fillets were added to some

sharp corners to improvemesh quality




Training ManualMeshing Options

8. In the Meshing Options panel select the following meshing options:• Physics Preference

– CFDCFD• Mesh Method

– Automatic• Click OK after youClick OK after you

make the selection

• In Units, make sure the setting is mm




Training ManualGlobal Mesh Parameters9. Set global “Mesh” control parameters:

• Click on Mesh to change settings• Verify Defaults

– Physics Preference • CFD

– Solver Preference• Fluent or CFX• Fluent or CFX

– Fluent is used initially, but results for the CFXsetting are also presented

• Set Sizing parametersg p– Set Use Advanced Size Function

• On: Curvature– Set Curvature Normal Angle to 15°

S Mi Si 0 20– Set Min Size to 0.20 mm– Maintain all other defaults




Training Manual

10 S t I fl ti tInflation and Pinch Parameters

10.Set Inflation parameters• Click drop-list for Use Automatic Tet Inflation and select Program

Controlled, leave all others as default

Note: Program Controlled Inflation will add inflation on all boundaries that doNote: Program Controlled Inflation will add inflation on all boundaries that do not have assigned Name Selection. It does not add inflation to Fluid-Fluid interfacesNote: Smooth Transition provides a transition between the inflation layers and the tetrahedral mesh following the specified Growth Rate

• Set Maximum Layers to 4• Activate View Advanced Options

Note: Layer Compression is the default Collision Avoidance for Fluent and Stair Stepping is default for CFX

11.Set Pinch controlfor Fluent and Stair Stepping is default for CFX

Note: When edge length or distance between vertices is less than the pinch tolerance software will ignore the edge or remove extra vertex during meshing

• Set Pinch Tolerance = 0.15 mm• Activate Generate on Refresh

tolerance, software will ignore the edge or remove extra vertex during meshing

Note: Pinch Tolerance should be



12.Set Mesh Metrics to Skewness ( for Fluent)smaller than Size Function Min Size


Training ManualPinch Controls

13.Create Pinch control :• Right-Mouse-Button -click in the Tree (RMB (Tree))• Select Create Pinch ControlsSelect Create Pinch Controls

– 10 Pinch Controls are created (Expand the Mesh button to list the pinch controls)




Training ManualViewing Pinch Controls14.View the Pinch Controls

• Ctrl Left-Mouse-Button – Select the Pinch controls, these will be highlighted in the viewing window




Training ManualSweep Method

15.Assign Sweep Method to the inlet and outlet bodies:• Select Mesh button in Tree• Select the bodies (as shown below)( )

– Set the Cursor Mode to Body Selection– Left-Mouse-Button click (Select) one sweepable body– Hold Ctrl key and select the second body

• Insert Method– Right-Mouse-Button -click in the graphics window (RMB (Window))– Insert - Method

• The “Automatic Method” form appears• The Automatic Method form appears

• In the Automatic Method form– Select Sweep from the – pull-down menupull down menu




Training ManualSweep Method Settings

16.Set Sweep Method controls• Src/Trg Selection;

– Select Manual Source– Click on the Source Selection Field

• This will activate the face pickerHold the Ctrl key and pick both the Inlet

Outlet

– Hold the Ctrl key and pick both the Inletand the Outlet face

– Apply the Selection

Inlet

• Additional Settings– Set Free Face Mesh Type; All Quad– Set Sweep Num Divs; 20– Set Sweep Bias Type; _ __ ___ __ _– Set Sweep Bias; 4




Training ManualInflating the Sweep17.2D-Inflation on swept bodies:

• Pick Faces; – Set the Cursor Mode to Face Selection– Select the Inlet and Outlet faces (green)– RMB (Window) Insert-Inflation

• Pick Edges– Set the Cursor Mode to Edge selection– Select four edges surrounding the

inlet and outlet faces (marked in red)– Apply the selectionApply the selection

• Inflation Settings– Set Maximum Thickness:

• 3.0 mm– Maintain all other options




Training ManualInitial Surface Mesh18.Surface-mesh the model:

• Right-click on Mesh and select Preview Surface Mesh– This will provide us with feedback about mesh quality and density

Th Ad d Si F ti t fi h i th t b di



– The Advanced Size Function creates a very fine mesh in the swept bodies, • We can reduce the size by specifying the edge intervals on the Inlet and Outlet


Training ManualEdge Sizing19.Scoped edge mesh on swept bodies:

• Insert Scoped Edge Size ;– Activate edge picker– Pick the four edges

surrounding the inlet and outlet faces

– Right-clickRight click – Insert ->Sizing

• Set ParametersCh th T– Change the Type• Number of Divisions; 20

– Change Behavior; Hard




Training ManualPreview Inflation20.Check the inflation layer: (Optional)

• Right-click on Mesh and select Preview Inflation– View the mesh Statistics, mesh size and max skew is around 310000

and 0.92 respectively– We are ready for volume meshing

.




Training ManualVolume Mesh with Fluent Settings21.Mesh the model:

• RMB (Tree) select Generate Mesh– Again, check the Statistics for the total element count and Max Skewness

which will be around 926000 and 0.92 respectively

.




Training ManualUsing a Section Plane to View Internal Mesh22.Create a Section Plane:

• Click on the Z-Axis at the lower right corner to orient the model

• Click the Selection Plane icon• Press and hold the left mouse

button while moving along the i di t d d thindicated red arrow then release

• The position of the Section Plane can be adjusted byPlane can be adjusted by moving the slider bar

• Click on “Show Whole Element”



• Reselect the rotation button to adjust the view


Training ManualViewing the Worst Elements23.Rotate the geometry to view the mesh

• RMB (Tree) Show Worst Elements– Note the location; far from the main flow field

Tip: Select ‘Wireframe’ from theTip: Select ‘Wireframe’ from the ‘View’ menu to help see the element




Training ManualCFX Solver Preference

24.Using CFX Solver Preference (optional)• Change Solver Preference: CFX• RMB (Tree) select Generate MeshRMB (Tree) select Generate Mesh

– Note the higher Max Skewness for the CFX Solver settings




Training ManualChecking the Quality in FEModeler25.Check quality in FEModeler (optional)

• Meshing application– RMB (Tree) Update– Close Meshing Application

• Workbench 2– Drag-and-Drop FE Modeler on

t f M h i th P j t S h titop of Mesh in the Project Schematic– Double click on Model

• FEModeler– RMB (Tree) Insert Mesh Metrics– RMB (Tree) Insert Mesh Metrics– Mesh Metrics - Valve – 4 Node

Linear Tetrahedron– Set Mesh Metric Type: Aspect Ratio

– Max aspect ratio is less than 50

.




Training ManualSaving the Project

26.The mesh is now complete

• Select File > Close to close FEModeler

• In the WB panel select UpdateIn the WB panel select Update• In the WB panel select File > Save Project As… and give the project a

name

• Exit from ANSYS Workbench by selecting File > Exit



am 12 appendix a

Documents

fluid flow

virtual topology

mesh quality

poor mesh

mesh quality

improve mesh

select insert

select generate