The MultiZone mesh method, which is a patch independent (p. 3) meshing technique, provides automatic decomposition of geometry into mapped (sweepable) regions and free regions. When the MultiZone mesh method is selected, all regions are meshed with a pure hexahedral mesh if possible.
To handle cases in which a pure hex mesh will not be possible, you can adjust your settings so that a swept mesh will be generated in structured regions and a free mesh will be generated in unstructured regions.
For example, using the Sweep mesh method, you would need to slice the part below into five bodies as shown to obtain a pure hex mesh:
Note
This section describes method control settings. See MultiZone Meshing (p. 265) for detailed algorithm and usage information.
Figure 99: Sweep Method Would Require Slicing to Obtain Pure Hex Mesh
In contrast, using the MultiZone mesh method requires no slicing. MultiZone automates the geometry decomposition and generates the pure hex mesh shown in Figure 100: MultiZone Generates Pure Hex Mesh without Slicing (p. 185).
Figure 100: MultiZone Generates Pure Hex Mesh without Slicing
When you choose the MultiZone mesh method, the Details View expands to expose various settings, including several that are unique to MultiZone. For basic usage that involves obtaining a MultiZone mesh, the procedure is to apply a Method Control to one or more bodies, set Method to MultiZone, and accept the default values of the various settings.
For advanced or specialized usage, adjust the settings as needed. The following is a description of each of these settings.
• Mapped Mesh Type - Determines the shape of the elements used to fill structured regions according to the following choices (the default is Hexa):
– Hexa - A mesh of all hexahedral elements is generated for the part the method is scoped to.
– Hexa/Prism - A mesh of hexahedral and prism/wedge elements is generated for the part the method is scoped to. The main difference between the Hexa/Prism option and the other options is that for swept regions, the surface mesh can allow triangles for quality and transitioning. The triangles are later extruded to prisms/wedges.
– Prism - A mesh of all prism elements is generated for the part the method is scoped to. This option is sometimes useful if the source face mesh is being shared with a tet mesh, as pyramids are not required to transition to the tet mesh.
• Surface Mesh Method - Specifying a value for Surface Mesh Method instructs MultiZone to use the Pro-gram Controlled, Uniform, or Pave method to create the surface mesh.
– Program Controlled - Automatically uses a combination of Uniform and Pave mesh methods depending on the mesh sizes set and face properties. This is the default method.
– Uniform - Uses a recursive loop-splitting method which creates a highly uniform mesh. This option is generally good when all edges have the same sizing and the faces being meshed do not have a high degree of curvature. The orthogonality of the mesh from this method is generally very good.
– Pave - Uses a paving mesh method which creates a good quality mesh on faces with high curvature, and also when neighboring edges have a high aspect ratio. This approach is also more reliable to give an all-quad mesh.
Note
The Surface Mesh Method is applicable only to faces that are free meshed. If a face can be mapped meshed, it will be. SeeFace Meshing Control (p. 210) for more information.
Note
Models created in versions of ANSYS older than ANSYS 14.5 that have a MultiZone mesh method defined on them will be resumed in ANSYS 14.5 with the Surface Mesh Method set to Uniform, so that the mesh is similar to what it was in previous versions. You might want to set the Surface Mesh Method to Program Controlled for better results.
• Free Mesh Type - Specifying a value for Free Mesh Type will instruct MultiZone to allow a free mesh if it is not possible (without slicing) to generate a pure hex or hex/prism mesh. The value of Free Mesh Type determines the shape of the elements used to fill unstructured regions according to the following choices (the default is Not Allowed):
– Not Allowed - Choose this option if you require a mapped mesh.
– Tetra – Regions of the model that cannot be meshed with a mapped mesh will be filled with a tetrahedral mesh.Figure 101: Free Mesh Type = Tetra (p. 187) shows a MultiZone mesh that was generated when
Free Mesh Type was set to Tetra. Notice the lower section that was able to be mapped meshed, and the upper section that was free meshed because it could not be map meshed. Refer to Patch Conforming Algorithm for Tetrahedrons Method Control (p. 159) for more information.
Figure 101: Free Mesh Type = Tetra
– Tetra/Pyramid – Regions of the model that cannot be meshed with a mapped mesh will be filled with a tetrahedral mesh with pyramids at the faces.Figure 102: Free Mesh Type = Tetra/Pyramid (p. 188) shows a MultiZone mesh that was generated when Free Mesh Type was set to Tetra/Pyramid. Notice the lower section that was able to be mapped meshed, and the upper section that was free meshed because it could not be map meshed. Refer to Patch Conforming Algorithm for Tetrahedrons Method Control (p. 159) for more information.
Figure 102: Free Mesh Type = Tetra/Pyramid
– Hexa Dominant — Regions of the model that cannot be meshed with a mapped mesh will be filled with a hex dominant mesh.Figure 103: Free Mesh Type = Hexa Dominant (p. 189) shows a MultiZone mesh that was generated when Free Mesh Type was set to Hexa Dominant. Notice the upper section that was able to be mapped meshed, and the lower section that was free meshed because it could not be mapped meshed. Refer to Hex Dominant Method Control (p. 180) for more information.
Figure 103: Free Mesh Type = Hexa Dominant
– Hexa Core - Regions of the model that cannot be meshed with a mapped mesh will be filled with a hexa core mesh. Hexa Core meshes can be generated where the majority of the volume is filled with a Cartesian array of hexahedral elements essentially replacing the tetras. This is connected to the remainder of a
prism/tetra hybrid by automatic creation of pyramids. Hexa Core allows for reduction in number of elements for quicker solver run time and better convergence.Figure 104: Free Mesh Type = Hexa Core (p. 190) shows a MultiZone mesh that was generated when Free Mesh Type was set to Hexa Core. Notice the upper section that was able to be mapped meshed, and the lower section that was free meshed because it could not be mapped meshed.
Figure 104: Free Mesh Type = Hexa Core
• Element Midside Nodes - Refer to Method Controls and Element Midside Nodes Settings (p. 156). The default is Use Global Setting.
• Src/Trg Selection - Defines the source and target selection type according to the following choices (the default is Automatic):
– Automatic - The Automatic option generally works fine for simple sweep configurations, but if there are multiple levels of sweeps it is often best to manually define the source faces.
– Manual Source - You select the faces that will be used as sources (and targets) using the Source Scoping Method you specify. MultiZone treats all sources/targets as sources, as imprinting can occur from either side. For additional details, refer to the description of Source Scoping Method, Source, and Source Named Selection below.
• Source Scoping Method - Defines the method for choosing a source face. Geometry Selection enables you to select sources/targets manually using the Source option. Named Selection enables you to choose one Named Selection as a source/target using the Source Named Selection option.
• Source - Select the faces that need to be imprinted for proper geometry decomposition. This option is available if you select Geometry Selection as your Source Scoping Method. The faces you select can be either “sources” or “targets,” but all of them will be treated as sources by MultiZone, as shown in Fig-ure 105: Source Face Selection for MultiZone (p. 191).
Note
To make source face selection easier, select Annotation Preferences from the Toolbar and then deselect Body Scoping Annotations in the Annotation Preferences option box to toggle the visibility of annotations in the Geometry window. For example, after scoping MultiZone to a body, the body will be displayed using a blue solid annotation.
Turn off the body scoping annotations; then select the source faces. For picking internal faces, the Hide Faces right-click option may help you to see inside a body. For example, you can select external faces in the Geometry window and then use the Hide Faces option to hide the selected faces (making it easier to select the internal faces).
Figure 105: Source Face Selection for MultiZone
• Source Named Selection - Choose an existing Named Selection to select the faces that need to be imprinted for proper geometry decomposition. This option is available if you select Named Selection as your Source Scoping Method.
• Sweep Size Behavior – Enables you to set a Sweep Element Size to define the mesh spacing (default), or to select Sweep Edges to remove edges and prevent them from constraining the source faces.
• Sweep Element Size - Enables you to set an element size to define the mesh spacing along the sweep path from source to target faces. If this control is set to a non-zero value, sizing controls applied to the selected bodies as curvature and proximity refinement and/or local sizing are ignored.
The Sweep Element Size setting is ignored if hard size controls are applied to side edges/faces. If multiple bodies with the same sweep direction have different sizes set for Sweep Element Size, the smallest size is used and the others are ignored.
Clicking the check box adds this setting to the Workbench parameters, enabling you to use element size settings as a variable design point when creating multiple solutions.
• Sweep Edges – This option should be used with an edge sizing control. The edge sizing control defines the distribution along the sweep path, but that sizing control can also affect the source face. Use this option to remove the influence of the edge sizing from the source face mesh. In other words, the edges selected will only influence the sweep path and not the source faces.
• Preserve Boundaries- Preserves only the protected topologies (See Patch Independent (p. 3)) or all features in the model. Protected is the default. If set to All, MultiZone works in a more patch conforming way. If set to All, you can apply boundary conditions, named selections, etc. after meshing. The mesh does not go out of date regardless of what is set by the Patch Independent Topology Checking (p. 123) option.
• Mesh Based Defeaturing - “Filters” edges in/out based on size. Off by default. If set to On, a Defeaturing Tolerance field appears where you may enter a numerical value greater than 0.0. By default, the value of this local Defeaturing Tolerance field is the same as the global Defeaturing Tolerance (p. 96). If you specify a different value here, it will override the global value. Specifying a value of 0.0 here resets the tolerance to its default.
• Minimum Edge Length - Read-only indication of the smallest edge length in the model.
• Write ICEM CFD Files - Sets options for writing ANSYS ICEM CFD files. Refer to Writing ANSYS ICEM CFD Files (p. 64) for details.
Note
For detailed information about MultiZone, refer to MultiZone Meshing (p. 265). For general information on applying MultiZone in combination with other mesh method controls, refer to Meshing: Mesh Control Interaction Tables (p. 349).
Notes on Scoping for the MultiZone Mesh Method
You can use the MultiZone mesh method in combination with other solid mesh methods in a multibody part, and the bodies will be meshed with conformal mesh.
If a multibody part contains some bodies that are scoped to be meshed with MultiZone and other bodies that are not scoped with any mesh method, these other bodies will be meshed with the default mesh method.
Refer to Conformal Meshing Between Parts (p. 5) for information about conformal meshing and mesh method interoperability.