Appendix B CFX-Mesh ANSYS Meshing Application Introduction ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-1 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Introduction • • • Training Manual CFX-Mesh provides automated mesh generation Unstructured triangular surface mesh generation Volume mesh is created from the surface mesh Tetrahedral/prismatic/pyramidal volume mesh generation Extruded meshes can also be created – If quad faces exist on the extruded face due to inflation, hex elements will be created for those quad elements • Advancing Front and Inflation (AFI) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-2 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Element Types Training Manual • Valid element types for the CFX-Solver include tetrahedra, prisms (wedges), pyramids, and hexes ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-3 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Accessing CFX Mesh Training Manual 1. Launch ANSYS Workbench 2. Double click on Mesh under component systems. 3. This will create a ‘Mesh component’ in the Project Schematic area. 4. Right click on select “Import Geometry” and click on “Browse…” to load a previously created geometry or click “New Geometry” to open Design. Modeler and create a new geometry. 5. Once the geometry is loaded double click on to open the meshing application. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-4 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Accessing CFX Mesh Training Manual • In the Project environment go to Tools > Options… – Select “Geometry Import” – Select Analysis Type as “ 3 D” – Ensure “Solid Bodies” is chosen • Only solid bodies are relevant to CFX Mesh – Check the “Named Selection” box to get Design Modeler defined named selections – Set the filtering prefix (keep the “Filtering Prefixes” box blank to import all named selections regardless of prefix) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-5 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Accessing CFX Mesh • • Training Manual Right-click on Mesh and Insert Method Select the Body of interest Now edit the method and choose CFX Mesh Then right Click on resulting CFX-Mesh Method and Choose Edit in CFX-Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-6 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Accessing CFX Mesh Training Manual • Note that the meshing environment is now modified ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-7 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual • Geometry used for meshing in CFX-Mesh must consist of one or more Solid Bodies • In CFX-Mesh, the body will have the units specified in DM • Surface Bodies and Line Bodies are not supported in CFX-Mesh – On import of certain file formats, Workbench will convert sets of surfaces which fully enclose to a volume into Solid Bodies (see DM documentation for details) • • Solid Bodies must not overlap each other Where Solid Bodies in a multi-body part touch, they must have common faces Bodies which are Frozen in DM will appear in CFX-Mesh and can be meshed To exclude a Solid Body from meshing, you can either suppress/delete it in DM, or suppress it in CFX-Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-8 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual • Example 1: – When Solid Bodies in a multi-body part touch, they must have common faces – If two bodies contact as shown, the face at the end of pipe is not one of the faces of the cylinder, CFX-Mesh will fail in generating mesh if the two bodies are in a single part – How to meet CFX-Mesh topology requirements? wrong ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-9 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual – To make a common face between pipe and cylinder, the cylinder needs to have the cylinder face that touches the pipe split into two: one face is the circular face which matches the end of the pipe, the other face is the remaining annular ring. – This can be done with an Imprint Face body operation in DM. right ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-10 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual • Example 2: – When part of pipe intrudes into the cylinder, part of the side surface is external to the cylinder, while the other part is internal to it. – What should the two bodies look like if they are in a single part? ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-11 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual – Again, the rule to remember is that adjacent solid bodies in a multi-body part must meet at shared faces – If two bodies contact as shown, where the side surface of the pipe is a single face, it does not match up with cylindrical cutout in the bottom cylinder and CFX-Mesh will fail in generating mesh. Single Side Surface Cylindrical Cut-Out wrong ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-12 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Requirements Training Manual – To make sure the pipe and cylinder meet at a shared face, the pipe needs to have its side face segmented into the part that’s external to the bottom cylinder and the part that’s internal to it (via an Imprint Face body operation in DM). External Side Surface Internal Side Surface Cylindrical Cut-Out right ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-13 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Other Geometry Requirements Training Manual • The CFX-Mesh Help provides many useful examples of what can and cannot be handled in CFX-Mesh, and some ways around difficult geometries, including: – – – Bodies Joined by a Common Face Bodies Touching at a Face Body with a Hole Body with an Enclosed Body Bodies with an Enclosed Body and a Hole Body with an Enclosed Body Touching the Face Non-Manifold Geometry Closed Faces (ie. Cylinders) Thin Surface Topology Poorly Parameterized Surfaces Degenerate Geometry ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-14 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Update Training Manual • Geometry Update allows for quick modification of geometry and mesh regeneration. – Updates geometry while retaining most or all CFXMesh settings. – Updates from CAD systems in plug-in mode is faster and cleaner. – If importing in reader mode, then you must save the new geometry into the appropriate file before updating. – Most geometry updates work with the minimum required modification to your mesh settings • Depends on the complexity of the changes made to the geometry, the CAD format and the method of import – Look at status symbols on each entity at the end of the update. If there are problems, you should correct them before regenerating the mesh. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-15 or Right-click on Geometry in Tree View Status Symbols Error OK April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Checking Training Manual • Geometry Checking checks for the presence of certain undesirable features in faces and edges which can cause poor mesh quality or failure of the mesher. • Can be accessed from the Go menu, by rightclicking on Geometry in Tree View, or in the top right toolbar. • Note: the “lock” symbol means the item must remain. • Results of check can be viewed under Errors in Tree View – If a Warning or Error refers to a specific curve or face, it will be highlighted when selected – Last warning gives a summary of the checks ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-16 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Checking Training Manual • Failed check does not necessarily result in poor mesh • Worth checking the mesh on any faces which failed the checks • Doesn’t check for ALL problems which can be present, just a few specific problems: – Sliver Edge Checking – Sliver Face Checking – Parameterization Face Checking • Verify Options determine values which generate errors ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-17 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Sliver Edge Checking Training Manual • Looks for short edges in the geometry • Short edges can produce a mesh which is over-refined in regions near the short edges • To remove short edges, change the default from NO to YES for Remove Short Edges in Fix Options • You can change the tolerance used for the check by using Verify Options ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-18 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Sliver Face Checking Training Manual • Computes a ratio of perimeter length to area for each face • Faces with a high sliver factor can result in a poor quality surface mesh • You can change the limit used for the check by using Verify Options • Default of 25 is usually sensible • Each face identified will be highlighted when the individual warning message is selected ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-19 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Parameterization Face Checking Training Manual • Provides guidance on the parameterization of the surfaces • Each potentially poorly parameterized surface will be highlighted when the individual warning message is selected ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-20 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Training Manual • By Default CFX-Mesh resolves every edge using a minimum of 3 vertices and meshes every face • Results is large mesh when there are many short edges and narrow faces in the CAD data • May not require a fine mesh in these areas for CFD • If proper mesh controls are not used in these areas, the resulting mesh may be of poor quality or the mesher might fail • Virtual Topology allows users to combine faces and edges into Virtual Faces and Virtual Edges. Can be added in CFX-Mesh or the Meshing Application. 78 Surfaces represent car body ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-21 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Training Manual • CFX-Mesh only sees the combined Virtual Face or Virtual Edge • Mesher does not resolve the constituent faces or edges, giving higher quality mesh with the required refinement • Does NOT modify the underlying CAD • Virtual topology will be discussed in more detail later A single virtual surface ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-22 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Geometry Display Training Manual • To change the appearance of your geometry, left-click on Geometry in the Tree View • Transparency (%) – 100% means completely transparent – 0% means completely opaque • Shine (%) Transparency can be very useful for selecting hidden surfaces since there isn’t a wireframe view – Controls how much light is reflected by the faces of the mesh – 0% gives lowest reflection and looks matt – 100% gives highest reflection and looks very bright ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-23 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Composite 2 D Regions Training Manual • You can use 2 D Regions to give meaningful names to parts of the geometry which may comprise many faces • Composite Regions can be used for: – Specifying Locations in CFX-Mesh – Defining Boundary Conditions in CFXPre • Default and additional Regions available – To create a new Region, right-click on Regions and choose Insert>Composite 2 D Region • No primitive 2 D Region can be assigned to more than one Composite 2 D Region ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-24 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Composite 2 D Regions Training Manual • Named Selections are imported from DM as Composite Regions – Select Named Selection under Default Geometry Options on the Project tab before proceeding to CFX-Mesh. – Can be set as default option in the Geometry Import options panel • Composite 2 D Regions can be hidden!! – Removes the constituent faces from the viewer – Hidden faces cannot be selected ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-25 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh 2 D Regions and Faces Training Manual • Where two Solid Bodies meet at a common face: – There is just one face present in the geometry – There are two 2 D Regions • Each meshing feature that requires you to specify a location has its own rules about 2 D Regions on the same face – Ex. Face Spacing: Do not try to apply different Face Spacings to 2 D Regions which are the two sides of a common face (surface mesh is generated on the common face, not 2 D Regions) – Ex. Inflated Boundary: You can have different settings for the two different 2 D Regions which make up a common face ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-26 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh 2 D Regions and Faces Training Manual • Use attached Selection Rectangles to select individual 2 D Regions easily and accurately • CFX-Mesh will not allow you to select locations for meshing features which break the rules given for each feature ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-27 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Saving the Volume Mesh Training Manual • Two formats –. CMDB file • Contains mesh and mesh settings • Larger file which takes longer to generate for large meshes –. GTM file • Suitable for import directly into CFXPRE • Access Options from the Tools Menu • The right panel will show various CFX options. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-28 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Saving the Volume Mesh Training Manual • You may choose to write. cmdb or. gtm or both • User Defined location for. gtm will produce a dialog box to save choose a location when you Generate the Volume Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-29 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Length Scales Training Manual • The process of setting an element length scale for CFX-Mesh can be viewed as a 3 step process – Default Body Spacing – Face Spacing – Other Mesh Controls (Point Spacing, Periodicity, Inflation, etc) • Smallest effecting length scale is chosen ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-30 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Face Spacing Training Manual • Face Spacing can be set to one of 4 types: – Angular resolution - curvature sensitive, discussed next – Relative error - curvature sensitive, discussed next – Constant - constant length scale, overriding the Body Spacing (must be less than Default Body Spacing) – Volume Spacing - uses the same spacing on the face as the Body Maximum Spacing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-33 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Face Spacing Training Manual • Face spacings have a volumetric effect. The region over which they act are determined by the following settings: – Radius of Influence: extent of the Face Spacing influence, after which it will expand according to the Expansion Factor – Expansion Factor: rate of expansion of mesh scale from surface to interior • Location: Faces where the Face Spacing values will be applied – Can be selected from the Model View or Tree View Regions – Unnecessary for Default Face Spacing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-34 April 28, 2009 Inventory #002645
![Appendix B: CFX-Mesh Curvature Sensitive Mesh Training Manual • Angular Resolution [Degrees] – CFX-Mesh](https://present5.com/presentation/f91419277ed9a9560a4e9ad426943851/image-33.jpg "Appendix B: CFX-Mesh Curvature Sensitive Mesh Training Manual • Angular Resolution [Degrees] – CFX-Mesh")
Appendix B: CFX-Mesh Curvature Sensitive Mesh Training Manual • Angular Resolution [Degrees] – CFX-Mesh chooses edge length such that the set angle is subtended at the center of circle with radius equal to smallest radius of curvature – Default is 30 degrees (recommended 5 to 60 degrees) • Relative Error [Δr/r] – Deviation of mesh from surface as a fraction of local radius of curvature • Minimum edge length - lower bound on length scale • Maximum edge length - upper bound on length scale (default same as volume background scale) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-35 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Curvature Sensitive Mesh Training Manual With surface curvature sensitive meshing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Without surface curvature sensitive meshing B-36 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Edge Spacing Training Manual • Edge Spacing specifies the mesh length scale on an edge (or edges) and in the volume adjacent to the selected edges • To create a new Edge Spacing, rightclick on Spacing and choose Insert>Edge Spacing • Parameters and effect on mesh are the same as with Face Spacing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-37 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Edge Spacing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Training Manual B-38 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Controls Training Manual • Mesh Controls are used to refine the surface and volume mesh in specific regions of your model • Location can be defined using any point on the model or by specifying coordinates – Can be located anywhere in the 3 D space of model (inside, outside or on the edge) • 3 types of volumetric Controls are available: – Point – Line – Triangle • Remember: Face Spacing also available for volumetric control ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-39 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Point Spacing Training Manual • Each of the 3 volumetric Controls requires you to specify a Point Spacing for the control at appropriate points. Any number of mesh controls can reference the same point Spacing • Length Scale – For the mesh size where the Point Spacing is applied – Must be less than Body Spacing Max • Radius of Influence – Radial extent of the fixed local length scale influence • Expansion Factor – Geometric rate of increase of local element length scale beyond radius ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-40 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Point Control Training Manual • Point Control controls the mesh spacing in a spherical region • Point – Select either a vertex from the model or coordinates • Spacing – Select a Point Spacing which defines the attributes for the Point Control (Length Scale, Radius of Influence and Expansion Factor) • Figure to right shows a Point Control on a 1 m cube with: – Length Scale=0. 05 m – Radius of Influence=0. 2 m – Expansion Factor=1. 2 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-41 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Line Control Training Manual • Line Control controls the mesh spacing in a region defined by a cylindrical volume between 2 spheres • Point – Select either a vertex from the model or coordinates for both Points • Spacing Definitions – Uniform requires only one Spacing – Non Uniform requires a Spacing for each end • Spacing – Select a Point Spacing which defines the attributes for the Line Control (Length Scale, Radius of Influence and Expansion Factor) • Figure to right shows a Line Control on a 1 m cube with: – Length Scale=0. 05 m – Radius of Influence=0. 2 m – Expansion Factor=1. 2 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-42 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Triangle Control Training Manual • Triangle Control controls the mesh spacing in a region defined by a prismatic volume between 3 spheres • Point – Select either a vertex from the model or coordinates for all 3 Points • Spacing Definitions – Uniform requires only one Spacing – Non Uniform requires a Spacing for each corner of the triangle • Spacing – Select a Point Spacing which defines the attributes for the Triangle Control (Length Scale, Radius of Influence and Expansion Factor) • Figure to right shows a Triangle Control on a 1 m cube with: – Length Scale=0. 05 m – Radius of Influence=0. 2 m – Expansion Factor=1. 2 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-43 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Periodicity Training Manual • Using Periodicity allows you to generate identical meshes for faces that will be specified as part of a periodic boundary condition in ANSYS CFX • The CFX Solver makes more accurate calculations when meshes on periodic pairs are identical (one-to-one) • Periodicity can be either Translation by a fixed vector or Rotation • Rules/Limitations: – Each face in the Location 1 face list must map to an equivalent face in the Location 2 face list – Multiple faces can be selected for each of Location 1 and Location 2, provided each face in the Location 1 face list maps onto a face in the Location 2 face list using the specified transformation – Inflation cannot be applied to a face which is part of a Periodic Pair • See the documentation for further details on Periodicity ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-44 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Periodic Pairs Training Manual • Periodic Pairs create identical meshes on the 2 locations selected • Location – Select face(s) either directly from the Model View or select a Composite 2 D Region from the Tree View – All faces selected must be on the external boundary of the model and must not be included in an Inflated Boundary • Periodic Type – Rotational requires 2 points to define an axis, and possibly an Angle of Rotation • Points can be either a vertex from the model or coordinates – Translational requires no further input ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-45 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Training Manual • Inflation is the generation of prismatic element layers by “inflating” triangular surface elements • Purpose: – Prism elements more effectively and efficiently captures boundary layer effects – Node density near the wall is increased – Velocity profile is captured by the prism layer – Tetrahedral elements efficiently fill the volume region ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-46 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Training Manual • You can control the number, thickness and expansion rate of inflation layers • You can inflate from any surface or boundary condition, except those included in a Periodic Pair • Inflation layers can be viewed within CFX-Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-47 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Training Manual • Number of Inflated Layers – If First Layer Thickness Option is used, this is a maximum number of layers – If Total Thickness Option is used, this is the actual number of layers (unless layers are removed to improve mesh quality) • Expansion Factor – Each layer, moving away from the face, is one Expansion Factor thicker than the previous. • Number of Spreading Iterations – Advanced quality control, see documentation for details • Minimum Internal Angle – Advanced quality control, see documentation for details • Inflation Option – Total Thickness – First Layer Thickness ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-48 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option - Total Thickness Training Manual • Total Thickness – The total thickness of the inflation is controlled by the: • Thickness Multiplier • Local element edge length – Determined by Face Spacing and Controls • Maximum Thickness – Set individually for each Inflated Boundary – Creates a less smooth transition from the inflated prism mesh elements to the tetrahedral mesh elements – The number of inflated layers is more constant, and you have some control over height of layers on face-by face basis ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-49 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option - Total Thickness Training Manual • Process used for creating the layers of prisms when using the Total Thickness option is given below: – CFX-Mesh calculates the total thickness of the inflation layers as follows: • Multiply the Thickness Multiplier by the local element edge length • Where this is less than the specified Maximum Thickness, then this gives the total thickness of the layers • Where this is greater than the specified maximum Thickness, then the Maximum Thickness is taken to be the total thickness of the layers – Use the specified Number of Inflated Layers and Expansion Factor to calculate the height of each layer, given the total thickness that has just been calculated • Inflation thickness will not be constant over the inflated edge if the element edge length changes in the region of the inflation layer ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-50 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option - First Layer Thickness Training Manual • First Layer Thickness – Does not control the overall height of the inflation layers – Prisms based on First Prism Height or y+, Expansion Factor and Number of Inflated Layers – Creates smoother transition from inflated prism mesh elements to the tetrahedral mesh elements – First Prism Height must be less than the Max Spacing under Body Spacing – You should examine the mesh to visualize the extent of the inflation and the quality of the transition from prisms to tetrahedral elements ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-51 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option - First Layer Thickness Training Manual • Define First Layer By y+ – Computes First Prism Height based on user inputs – Desired y+, Flow Reynolds Number and Reference Length Dy = LDy+ 80 Re(-13/14) First Prism Height = Reference Length * (Desired) y+ * 80 * Reynolds Number(-13/14) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-52 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option – Extended Layer Growth Training Manual Process used for creating the layers of prisms when using the First Layer Thickness option is given below • Put a single layer of prisms against the faces of the inflated boundary, of a height equal to the First Prism Height Extended Layer Growth = Yes Extended Layer Growth = No • Check the aspect ratio of the prisms • – If height < base length, add another layer of prisms of height (Previous Height) X (Expansion Factor) – If height ≥ base length, stop adding prisms • Repeat until aspect ratio for all the prisms ≈ 1 or until the Number of Inflated Layers is reached ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Check the aspect ratio of the prisms B-53 – If height ≥ base length keep adding layers of unit aspect ratio until the Number of Inflated Layers is reached April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option – Extended Layer Growth Training Manual Number of Inflated layers = 25 Extended Layer Growth = Yes Extended Layer Growth = No ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-54 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option – Layer Smoothing Training Manual • Available when using First Layer Thickness option • Allows prisms to grow out normal to the surface, i. e. orthogonal to the surface • Layer normals and heights are then progressively smoothed, during the creation of each layer • Maximizes the number of layers obtained • Result in longer mesh generation times ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-55 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflation Option – Layer Smoothing Training Manual Prism growth is orthogonal Layer by Layer Smoothing = No ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Layer by Layer Smoothing = Yes B-56 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Inflated Boundary Training Manual • Creation of an Inflated Boundary is how you specify which faces you want Inflation to apply to • Location – Select face(s) either directly from the Model View or select a Composite 2 D Region from the Tree View – A face cannot be in more than one Inflated Boundary, or in both an Inflated Boundary and a Periodic Pair • Maximum Thickness – The Maximum Thickness for the whole inflation layer, when Inflation Option is set to Total Thickness – Not used if Inflation Option is set to First Layer Thickness ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-57 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Stretch Training Manual • Stretch can be used to expand or contract the mesh elements in a particular direction – The geometry is expanded by the specified factors, meshing takes place, then the geometry is contracted back to its original size – The max and min stretches allowed are 0. 2 and 5 (factors below 0. 6 are not recommended) Before Stretching Stretch in X = 0. 5 Stretch in Y = 1. 0 Stretch in Y = 3. 0 Stretch in Z = 2. 0 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Stretch in X = 1. 0 Stretch in Z = 1. 0 B-58 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Combined Mesh Control and Stretch Training Manual • The effective influence of a Mesh Control, which is treated as a spherical mesh control while meshing takes place, will NOT be modified to elliptical • Therefore, a Point Control will appear to influence an elliptical region when the mesh is examined y z ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. x B-59 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Proximity Training Manual • Proximity settings control automatic refinement of the mesh when edges or faces are near to other edges or faces, but not connected – Edge proximity • ON by default • Adjusts mesh based on mesh size on neighboring edges – Surface proximity • OFF by default • Adjusts mesh based on gap between neighboring surfaces ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-60 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Edge Proximity Training Manual • Edge Proximity is used to automatically modify mesh elements in regions where curves are in close proximity – Bounding curves of surface “sense” nearby curves and increase mesh density locally – Only available when Delaunay Surface Mesher is used (meshers discussed soon) Edge Proximity OFF ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Edge Proximity ON B-61 Edge Proximity ON April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Surface Proximity Training Manual • Surface Proximity is used to automatically reduce the mesh size in regions where surfaces are in close proximity and the original mesh does not resolve the gap sufficiently • Number of Elements Across Gap – Recommend at least 4 – Generates higher quality prismatic and tetrahedral elements in the gap region • Maximum Number of Passes – Number of times the surface mesher will run to try to meet the Number of Elements Across Gap • Available for both Delaunay and Advancing Front Surface Meshers ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-62 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Options – Global Mesh Scaling Training Manual • Allows easy scaling of each length scale for the mesh, except those applied to Face Spacing’s • Decreasing this factor decreases mesh length scales and increases number of elements • Does not affect anything other than mesh length scales (i. e. Radius of Influence is not affected) • Stretch affects all lengths (including Radius of Influence) • Global Mesh Scaling factor is only applied during meshing – Display of size of Controls will show the size as if the factor is 1 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-63 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Options – Surface Meshing Training Manual • Both methods are well recognized and have established track records • Both mesh individual surfaces • Delaunay (default) – works on “closed” surfaces – Delaunay mesh quality is not good on poorly parameterized surfaces • Advancing Front – produces higher quality elements at boundaries – traditionally slower than Delaunay – cannot mesh “closed” surfaces ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-64 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Options – Meshing Strategy Training Manual • Advancing Front and Inflation 3 D – Includes Inflation – Quickly generates a mesh with tetrahedra, prisms and pyramids with low memory usage – New elements created from advancing “front” of triangles – Creates tetrahedral elements by point (node) placement – Identify exposed faces which now form the new “front” • Extruded 2 D Mesh – See next two slides ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-65 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Extruded Meshes Training Manual • When “Extruded 2 D Mesh” is selected, the user is prompted to define the “Extruded Periodic Pair” • Pick the two sets of faces from the model view or the object tree – You can also select composite 2 D regions from the Tree View • Select the “Periodic Type” – Translational or Rotational – If there are no vertices on the selected faces, you will be asked for a translation distance or a rotation angle • Extruded meshes in CFX-Mesh are not as flexible as those that the Swept Mesher can generate – The difference in the Periodic Pair must be a simple translation or rotation – However, the source and target faces can consist of multiple (matching) faces ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-66 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Extruded Meshes Training Manual Extrusion Options • 2 D Extrusion Option – Full = extrude through the full extent of the geometry – Partial = thickness of elements determined automatically such that element quality is high. Will not necessarily fill geometry for a given number of layers • Number of Layers • Distribution – distribution of element heights along the extrusion can be uniform or biased • Expansion Factor – Set the growth rate for the thickness of elements in non-uniform extrusion ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-67 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Options – Volume Meshing Training Manual • This option is only available with the Advancing Front and Inflation 3 D meshing strategy • Advancing Front options is default – Runs as a single process on a single CPU • Parallel Advancing Front – Multiple processes (multiple CPU’s) on the same or different machines – Faster mesh generation for large models – Overcomes memory limitations of a single processor / machine, especially on 32 bit system – Have at least 500, 000 tetrahedral elements per partition. Do not run small models in parallel. – Uses the CFX-Parallel (Solver) licenses if available. Else can be separately licensed. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-68 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Options – Volume Meshing Training Manual • Set the Number of Partitions along the X, Y and Z coordinates – Divides the geometry based on the number of partitions along each coordinate – Each partition is meshed independently and then combined – Combined mesh will be same as that generated by a single process • Parallel Meshing can be: – – Local Parallel, on the same machine Distributed Parallel, on different machines Distributed Parallel requires a Hosts List Refer to CFX-Mesh Help for details on setup and limitations of Distributed Parallel Meshing ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-69 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Preview Training Manual • Allows you to look at the mesh on a particular face or faces before creating the entire surface or volume mesh • Select face(s) for Preview Group either directly from the Model View or select a Composite 2 D Region from the Tree View • Can choose whether to generate mesh on selected faces or all at once • Can view only surface mesh in CFX-Mesh, volume mesh may be viewed in CFX-Post ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-70 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Preview Display Training Manual • Mesh Render Mode – Wire on Face Mesh shows the mesh faces and the mesh lines – Solid Face shows the mesh faces – Wire Mesh shows just the mesh lines • Display Mesh • – Controls how much light is reflected by the faces of the mesh – 0% gives lowest reflection and looks matt – 100% gives highest reflection and looks very bright – Mesh Before Inflation – Mesh After Inflation – Inflated Front shows triangles across the top of the inflated elements – Inflated Mesh shows the inflation layers only • Face Color Mode – Body shows mesh the same colour as body – Uniform allows you to pick a color – Rainbow shows the mesh on each face in a different colour, as different as possible • Transparency (%) – 100% means completely transparent – 0% means completely opaque ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Shine (%) B-71 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Statistics Training Manual • Mesh Statistics – Shows Number of Quads and Triangles (Surface Elements) in the Preview Group • Warning Messages or Errors – Non-fatal warning messages or errors will be shown under the Errors item in the Tree View – Fatal errors produce a pop-up message and are also shown under Errors – Clicking on an Error or Warning highlights the related face or element if appropriate ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-72 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Volume Mesh Training Manual • Generate Volume Mesh – Once mesh is set up, you can generate the Volume Mesh – The Volume Mesh is written to the GTM file for import into CFX-Pre GTM file automatically written when volume mesh is generated – Contains all the mesh and region information – Uses double-precision coordinates – Not viewable in CFX-Mesh, use CFX-Post – Can be repeated after any change to the mesh settings ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-73 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Stopping Mesh Generation Training Manual • To abort surface mesh or volume mesh generation, use the Interrupt or Halt Current Processing button – This button is active only during mesh generation and geometry verification • Limitation: Interrupt takes effect only when underlying process exchanges data with user interface – In some circumstances the mesh process may go on for a long time without exchanging data with the user interface – In these cases, if you want to terminate the process immediately, you can use Task Manager (Windows) or kill command (Unix) to end the following processes. (Use with care) • srfmsh_wb. exe • nsurf 3 d_wb. exe • inflate_wb. exe • nvol 3 d. exe • nvol 2 d_wb. exe ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-74 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Training Manual • By Default CFX-Mesh resolves every edge using a minimum of 3 vertices and meshes every face • Results in a large mesh when there are many short edges and narrow faces in the CAD data • Virtual Topology allows users to combine faces and edges into Virtual Faces and Virtual Edges • CFX-Mesh only sees the combined Virtual Face or Virtual Edge A single virtual surface 78 Surfaces represent car body ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-75 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Creating Virtual Topology Training Manual • Creating Virtual Topology: – Virtual Topology includes Virtual Face and Virtual Edge – Virtual Topology can be created either automatically or manually – Virtual Topology can be created in CFX-Mesh or in the Meshing Application • Automatic Virtual Topology Creation: – CFX-Mesh automatically detect candidate edges and faces that could be merged based on geometric parameters such as contact angle between faces, relative areas of faces, aspect ratios and shared boundary ratio – Once these candidates have been detected, virtual edges and faces are created automatically – Where possible, external edges of Virtual Faces will be automatically merged together to form Virtual Edges • Manual Virtual Topology Creation: – User manually create Virtual Topology by inserting Virtual Faces or Virtual Edges – In the Virtual Face creation, user can turn on and off the option of automatic merging possible external edges of Virtual Faces to from Virtual Edges Manual Virtual Topology creation Automatic Virtual Topology creation ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-76 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Automatic Virtual Topology Training Manual • Automatic Virtual Topology creation: – User controls for this feature are very simple Automatic Merge Strategy controls the aggressiveness of the automatic Virtual Topology algorithm. The Low option merges the worst faces and edges in the model, while the High option attempts to merge much more of the geometry. Select Virtual Topology in the Tree View. Controls are available in the Details View Automatic Merge Option defines whether the automatic Virtual Topology operation should be applied to the whole model (the default) or whether it should only apply to a selection of faces. The face selection can be defined by selecting the faces directly from the graphics window or by selecting a Region name in the tree view. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-77 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Example Training Manual • Automatic Virtual Topology example: – Create a Virtual Face which includes 3 faces at the top – Several ways of doing this automatically Method 1: Generate Virtual Topology on Entire Model Select Automatic merge Option as Entire Model Right Click on Virtual Topology in the Model Tree and select Generate Virtual Topology on Entire Model ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-78 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Example Training Manual Method 2: Generate Virtual Topology on Selected Set Select Automatic Merge Option as Selected Set Select three top faces and apply Right Click on Virtual Topology in the Model Tree and select Generate Virtual Topology on Selected Set ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-79 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Example Training Manual Method 3: Generate Virtual Topology on on a control (Composite 2 D region, inflated boundary, etc) Create a Composite 2 D Region which contains 3 faces at the top Right Click on the created Composite 2 D Region Select Simplify Location using Virtual Topology Virtual Edges Virtual Face Final results for these three methods are the same – One virtual face and two virtual edges will be created. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-80 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Face Example Training Manual • Manually creating a Virtual Face: – – Right Click on Virtual Topology in the Model Tree and Insert a Virtual Face Select the required faces from the graphics window and Apply Can select Composite 2 D regions as well Selected faces must be adjacent • Virtual Face example: Fine mesh due to sliver surface ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. Mesh on Virtual Face Select 3 faces B-81 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Edges Training Manual • Virtual Face … – Where possible, CFX-Mesh will automatically merge external edges to form Virtual Edges. – This behavior can be turned off from the Options panel Single Edge Mesh with auto generation of Virtual Edge turned off. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-82 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Edge Example Training Manual • Creating a Virtual Edge: – Right Click on Virtual Topology in the Model Tree and Insert a Virtual Edge – Select the required edges from the graphics window and Apply – Selected edges must be adjacent • Virtual Edge example: Mesh with Virtual Edge ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-83 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Restrictions Training Manual • Limited to “developable surfaces” – A developable surface has the property that it can be made out of sheet metal – A virtual surface can be created for a group of surfaces that can be unfolded or unrolled into a flat plane • Virtual Faces cannot form a closed region – All six sides of a cube cannot be combined into a Virtual Face ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-84 April 28, 2009 Inventory #002645
Appendix B: CFX-Mesh Virtual Topology Rules Training Manual • Virtual Topology Rules: – Constituent faces of a Virtual Faces will not be available for selection. You can only select the Virtual Face. • Should consider boundary conditions requirements before defining Virtual Faces – Look for the status symbols of features in the Model Tree after creating or deleting virtual entities. • Some features may become invalid or may require verification – Virtual Topology definitions are persistent for geometry updates • If a location or CAD face does not exist after geometry update, the virtual entity will become invalid – You can add more faces/edges to an existing Virtual Face or Virtual Edge – You can include an existing Virtual Face or Edge in a new Virtual Face or Edge ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-85 April 28, 2009 Inventory #002645
Workshop B. 1 Aircraft Engine-Airframe ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-86 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Goals Training Manual This workshop will take you through the process of importing an aircraft engine and airframe model prepared in Design. Modeler, setting the mesh spacings, and generating a surface mesh for a CFD analysis. You will return to this workshop later (Workshop A. 4) and add virtual topology. • Goals: – Import the DM model file. – Define 2 D regions for boundary conditions. – Define mesh spacings ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-87 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Opening the Geometry File Training Manual 1. Copy the file Aircraft_Engine-Airframe. agdb to your working directory 2. Launch ANSYS Workbench 3. Double click on Mesh under component systems. 4. This will create a ‘Mesh component’ in the Project Schematic area. 5. Right click on and “Import Geometry” and click on “Browse…”. 6. Locate and open the file Aircraft_Engine. Airframe. agdb. 7. Once the geometry is loaded double click on to open the meshing application. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-88 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Imported Geometry Training Manual Only half the model will be meshed to take advantage of the symmetry in the flow field ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-89 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Choosing the CFX-Mesh Method Training Manual 8. Right-click on Mesh and select Insert Method • Select the body • Change the Method to CFX-Mesh 9. Right-click on the method in the tree and select Edit Mesh in CFX-Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-90 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Creating Composite Regions Training Manual Now create composite 2 D regions: 10. Right-click on Regions in the Tree View and Insert a Composite 2 D Region called Symmetry on the upper- Y surface 11. Create the remaining 2 D Region's as shown in the right figure Symmetry Inlet Bottom Top Right Outlet ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-91 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Hiding Composite Regions Training Manual Now hide the newly created 2 D Regions: 12. Under Tree View > Regions, right click on Symmetry and select Hide 13. Similarly hide all other 2 D Regions except the Default 2 D Region. You can do them all at once. Note: Hiding the external boundaries makes it easier to see the aircraft surfaces and also makes it easier to pick the surfaces of the aircraft ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-92 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Setting Global Spacings Training Manual Set the Default Body Spacing: 14. Under Tree View > Mesh > Spacing, select Default Body Spacing and set Maximum Spacing to 0. 08 [m] Set the Default Face Spacing: 15. Under Tree View > Mesh > Spacing, select Default Face Spacing and set the parameters as shown Generate surface mesh: 16. Under Tree View >Preview, right click on Default Preview Group and select Generate Surface Meshes ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-93 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe Surface Mesh Preview Training Manual 17. Review the surface mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-94 April 28, 2009 Inventory #002645
WS B. 1: Aircraft Engine-Airframe CAD Model Issues Training Manual – The CAD model has many narrow surfaces which are not significant to the flow analysis – The CAD model has many short edges because of the way the surfaces are constructed – By default CFX-Mesh, resolves these narrow surfaces and short edges, resulting in unnecessary mesh refinement and poor quality elements – We will revisit this geometry in Workshop B. 4 and create virtual faces and virtual edges to remove the unnecessary narrow faces and edges, thereby by reducing the mesh size and improving quality 18. For now, save the CFX-Mesh database (File > Save Project) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-95 April 28, 2009 Inventory #002645
Workshop B. 2 Static Mixer: Basic Settings, Mesh Controls and Inflation ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-96 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Goals Training Manual • This workshop will take you through the process of meshing a Static Mixer geometry with CFX-Mesh. Line mesh controls and inflation layers will be added to better refine the mesh • The basic steps involved in this workshop are: – 1. Start a new instance of the ANSYS Meshing Application and open the geometry file to be meshed – 2. Set the Mesh Method to CFX-Mesh and edit the Method – 3. Define any desired composite regions – 4. Set global mesh spacings (Body Spacing and Face Spacing) – 5. Preview the initial surface mesh – 6. Define Point Spacings and Line Mesh Controls – 7. Define Inflation Boundaries – 8. Generate the Volume Mesh and save the meshing database ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-97 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Starting the Meshing Application Training Manual 1. Copy the file staticmixer. agdb to your working directory 2. Launch ANSYS Workbench 3. Double click on Mesh under component systems. 4. This will create a ‘Mesh component’ in the Project Schematic area. 5. Right click on and “Import Geometry” and click on “Browse…”. 6. Locate and open the file staticmixer. agdb. 7. Once the geometry is loaded double click on to open the meshing application. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-98 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Meshing Options Form Training Manual 8. When the Meshing Application comes up, go to the Meshing Options Panel which appears at the right of the screen • Set the Physics Preference to CFD • Set the Mesh Method to CFX-Mesh • Make sure that Set Meshing Defaults toggle is enabled • Click OK ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-99 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation CFX-Mesh Training Manual 9. Note that the model is now displayed in the CFX meshing environment. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-100 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Making the Model Transparent Training Manual 10. In CFX-Mesh, click on the Geometry entry in the Tree View. 11. In the Details View and move the Transparency slider to 50% to make the model partially transparent • This makes it easier to see hidden faces in the model ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-101 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Defining Composite Region in 1 Training Manual 12. Right-click on Regions in the Tree View and select Insert Composite Region • Create a Composite Region named in 1 at the side pipe inlet as shown ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-102 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Defining Composite Region in 2 Training Manual 13. Create a Composite Region named in 2 at the other side pipe inlet as shown ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-103 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Defining Composite Region out Training Manual 14. Create a Composite Region named out at the bottom pipe outlet as shown ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-104 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Setting the Global Body Spacing Training Manual 15. Click on the + sign next to the Spacing entry in the Tree View to expand it 16. Set the Default Body Spacing to 0. 20 m • Note the mesh size preview icon in the viewport ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-105 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Setting the Global Face Spacing Training Manual 17. Set the Default Face Spacing Option to Angular Resolution with a setting of 18° 18. Set the Minimum Edge Length to 0. 015 m and the Maximum to 0. 20 m • Again note the mesh size preview icon ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-106 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Initial Mesh Preview Training Manual 19. Click on the + sign next to Preview in the Tree View to expand it 20. Right-click on the Default Preview Group and select Generate Surface Meshes ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-107 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Generating a Volume Mesh Training Manual The initial mesh is rather coarse for CFD purposes although it illustrates the basics steps involved in generating a tetrahedral mesh. 21. Right-click the Mesh entry in the Tree View and select Generate Volume Mesh • CFX-Mesh will create the volume mesh • The information panel at the bottom right will display the node and element count for the mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-108 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Mesh Refinement Training Manual • The first part of this tutorial resulted in a rather coarse mesh with no resolution of the boundary layer near walls • Although a better quality mesh for CFD purposes could be generated by defining finer global mesh spacings, the global mesh spacings will be left as they are • Instead, a mesh control will be defined to refine the mesh in the area of the two pipe inlets. Also, an inflation layer will be added to the all walls in the geometry to better resolve the boundary layer ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-109 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Mesh Control: Point Spacing Training Manual 22. In the tree view right click on Controls under the Mesh listing and Insert a Point Spacing 23. In the Details View for the Point Spacing enter the following: • Length Scale = 0. 1 • Radius of Influence = 0. 5 • Expansion Factor = 1. 2 This defines a point spacing which describes the element size and the region of influence over which it will be applied ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-110 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Line Control 1 Training Manual 24. Right-click on Controls in the Tree View, and select Insert > Line Control 25. In the Details View for the Line Control, click on Cancel in the box next to the first Point. Right-click the red bar in the box next to the first Point and select Edit in the pop-up menu 26. In the white text box, clear None and type in 1, -3, -1 • You can hit Enter from the keyboard or click in the model view to finish • Units are entered automatically 27. Similarly set the coordinates of the second Point to 1, -1 28. Leave the Option as Uniform 29. Click in the empty Spacing box and select Point Spacing 1 from the Tree View and then click Apply ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-111 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Line Control 2 and Inflation Training Manual 30. In the Tree View, right-click on Controls under the Mesh listing and Insert another Line Control 31. For Line Control 2: • • • Enter 1, 3 , 1 for the first Point Enter 1, 1 for the second Point Select Point Spacing 1 as the Spacing 32. In the Tree View right-click on Inflation and Insert an Inflated Boundary 33. In the Details View for Inflated Boundary 1, click in the Location box marked None, select Default 2 D Region from the Tree View as the Location and click Apply • This will inflate from all walls in the model 34. Set the Maximum Thickness for the inflated boundary to 0. 2 m ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-112 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Mesh Preview for Refined Mesh Training Manual 35. Right-click on Preview > Default Preview Group and select Generate This Surface Mesh • Notice the finer mesh in the two side pipes • You can modify the Length Scale of Point Spacing 1 to refine the mesh further • Also note the quad faces on the faces normal to the inflated boundary ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-113 April 28, 2009 Inventory #002645
WS B. 2: Static Mixer: Basic Settings, Mesh Controls and Inflation Final Volume Mesh Training Manual You are now ready to create and save the volume mesh: 36. Select Tools > Options > CFX-Mesh Options • Check that Volume Mesh Output is set to Add to CMDB File • Click OK 37. Click on the Generate Volume Mesh icon on the task bar 38. When the process finishes, save your CFX-Mesh database (File > Save) • The volume mesh is now stored in the Meshing Application cmdb file • Note the change in the node and element count in the Information window and the addition of prisms from inflation ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-114 April 28, 2009 Inventory #002645
Workshop B. 3 Extruded Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-115 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Goals Training Manual • This workshop will take you through the process of meshing a simple box geometry with an extruded 2 D mesh. The Full extrusion option will be demonstrated. • The basic steps involved in this workshop are: – 1. Start a new instance of the ANSYS Meshing Application and open the geometry file to be meshed – 2. Set the Mesh Method to CFX-Mesh and edit the Method – 3. In CFX-Mesh, change the mesh options to Extruded 2 D Mesh and set the extrusion options – 4. Define the faces for the 2 D periodic pair – 5. Set global mesh spacings (Body Spacing and Face Spacing) – 6. Define an inflation layer on the side walls – 7. Preview the surface mesh – 8. Generate the Volume Mesh and save the meshing database ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-116 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Starting the Meshing Application Training Manual 1. Copy the file box. agdb to your working directory 2. Launch ANSYS Workbench 3. Double click on Mesh under component systems. 4. This will create a ‘Mesh component’ in the Project Schematic area. 5. Right click on and “Import Geometry” and click on “Browse…”. 6. Locate and open the file box. agdb. 7. Once the geometry is loaded double click on to open the meshing application. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-117 April 28, 2009 Inventory #002645
WS B. 3: Extruded Meshing Options Form Training Manual 8. When the Meshing Application comes up, go to the Meshing Options Panel which appears at the right of the screen • Set the Physics Preference to CFD • Set the Mesh Method to CFX-Mesh • Make sure that Set Meshing Defaults toggle is enabled • Click OK ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-118 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh CFX-Mesh Training Manual 9. The model is now displayed in the CFX meshing environment. 10. Note that there are two faces on either end of the bar. As is, this would not be a general sweepable body in the Meshing Application Swept Mesher. ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-119 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Options Training Manual 11. Click on the Options entry under Mesh in the Tree View 12. In the Details View, set the Meshing Strategy Option to Extruded 2 D Mesh 13. Leave the 2 D Extrusion Option set to Full 14. Change the Number of Layers to 50 with a Uniform distribution ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-120 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Extruded Periodic Pair • Training Manual Note the addition of an Extruded Periodic Pair in the Tree View. This entry has a red X next to it since the faces which comprise it have yet to be defined. 15. Click on the Extruded Periodic Pair entry in the Tree View 16. In the Details View, select the two faces at the high Z end of the box and click Apply in the Location 1 entry box 17. Similarly select the two faces at the other side of the box and click Apply in the Location 2 entry box ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-121 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Setting the Global Body Spacing Training Manual 18. Click on the + sign next to the Spacing entry in the Tree View to expand it 19. Set the Default Body Spacing to 0. 10 in • Note the mesh size preview icon in the viewport ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-122 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Setting the Global Face Spacing Training Manual 20. Set the Default Face Spacing Option to Constant with a setting of 0. 10 in ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-123 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Initial Mesh Preview Training Manual 21. Select Preview > Default Preview Group > Generate Surface Meshes • Note the extrusion in the length direction ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-124 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Adding Inflation Training Manual 22. In the Tree View right-click on Inflation and Insert > Inflated Boundary 23. In the Details View for Inflated Boundary 1, select the four sides of the box from the viewport and click Apply in the Location box. • This will inflate the mesh from the four sides. 24. Set the Maximum Thickness to 0. 20 in ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-125 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Final Mesh Preview Training Manual 25. Right-click on the Default Preview Group and select Generate Surface Meshes • Since there are now quad faces on the ends from the inflated layer, a combination of hex and prism elements will be generated when the mesh is extruded ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-126 April 28, 2009 Inventory #002645
WS B. 3: Extruded Mesh Final Volume Mesh Training Manual You are now ready to create and save the volume mesh: 26. Click on the Generate Volume Mesh icon on the task bar 27. When the process finishes, save your CFX-Mesh database (File > Save). • The volume mesh is now stored in the Meshing Application cmdb file • Note that the Mesh Information Window shows that the volume mesh contains a combination of hexahedral (extruded quads) and prismatic (extruded tris) elements ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-127 April 28, 2009 Inventory #002645
Workshop B. 4 Virtual Topology for Geometry and Mesh ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-128 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Goals Training Manual • This workshop will take you through the process of using virtual topology to create a better quality mesh for the aircraft engine geometry imported in Workshop B. 1 • Goals: – Use Automatic Virtual Topology to improve mesh quality 1. Open the CFX-Mesh database that you saved at the end of Workshop B. 1 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-129 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh CAD Issues and Virtual Topology Training Manual – The CAD model has many narrow surfaces which are not significant to the flow analysis – CAD model has many short edges because of the way the surfaces are constructed – By default CFX-Mesh, resolves these narrow surfaces and short edges, resulting in unnecessary mesh refinement and poor quality elements – We will create virtual faces and virtual edges to remove the unnecessary narrow faces and edges, thereby by reducing the mesh size and improving quality – The automatic method of creating virtual topology will be demonstrated in the workshop ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-130 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Initial Surface Mesh (Before VT) ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-131 Training Manual April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Automatic Virtual Topology Training Manual 2. Select Virtual Topology in the Tree View • Set the Automatic Merge Strategy to Low • Set the Automatic Merge Option to Entire Model 3. Right-click on Virtual Topology and select Generate Virtual Topology on the Entire Model ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-132 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Viewing Virtual Faces Training Manual • You should see that a number of virtual faces and edges have been created • These appear in the Tree View below the Virtual Topology object • You can click on the various virtual faces and edges. They are color coded so that different faces and edges appear differently. • The leading and trailing edge of the wing areas of interest for CFD. You will find that they have been grouped into virtual faces which is not desirable ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-133 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Deleting Virtual Faces Training Manual 4. Find any virtual faces which include the wing leading edge faces and delete them • These are Virtual Face 8 and Virtual Face 11 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-134 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Deleting Virtual Faces Training Manual 5. Find the virtual face which include the wing trailing edge and delete it • This is Virtual Face 7 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-135 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Preview Surface Mesh with VT Training Manual 6. Regenerate the surface mesh to see the effect of adding virtual topology ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-136 April 28, 2009 Inventory #002645
WS B. 4: Virtual Topology for Geometry and Mesh Creating the Volume Mesh Training Manual • You could further modify the mesh by creating virtual faces and edges in selected areas manually to further improve the mesh quality 7. Generate the volume mesh and save the CFX-Mesh database ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. B-137 April 28, 2009 Inventory #002645
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