ANSYS Meshing

ANSYS Meshing provides multiple methods to generate a pure hex or hex dominant mesh. Depending on the model complexity, desired mesh quality and type, and how much time a user is able to spend meshing, a user has a scalable solution to generate a quick automatic hex or hex dominant mesh, or a highly controlled hex mesh for optimal solution efficiency and accuracy.

Hex mesh of brake assembly using a combination of hex meshing methods including sweep, thin sweep, MultiZone and hex dominant

Automated hex meshing using new MultiZone mesh method which automatically decomposes a geometry to create an all hex or hex dominant mesh

Hexhedral Meshing Approaches include:

• Automated Sweep Meshing
  • Sweepable bodies are automatically detected and meshed with hex mesh when possible
  • Edge increment assignment and side matching/mapping is done automatically
  • Sweep paths found automatically for all regions/bodies in a multibody part
  • Defined inflation is swept through connected swept bodies
  • User can add sizing controls, mapped controls , and select source faces to modify and take control over the automated sweeping
  • Adding/Modifying geometry slices/decomposition to the model also greatly aids in the automation of getting a pure hex mesh

• Thin Solid Sweep meshing
  • This mesh method quickly generates a hex mesh for thin solid parts that have multiple faces as source and target.
  • Can be used in conjunction with other mesh methods
  • User can add sizing controls, mapped controls, and select source faces to modify and take control over the automated sweeping

• MultiZone Sweep meshing
  • This advanced sweeping approach uses automated topology decomposition behind the scenes to attempt to automatically create a pure hex or mostly hex mesh on complicated geometries
  • Decomposed topology is meshed with a mapped mesh or a swept mesh if possible. A user has the option to allow for free mesh in sub-topologies that can’t be mapped or swept.
  • Supports multiple source/target selection
  • Defined inflation is swept through connected swept bodies
  • User can add sizing controls, mapped controls and select source faces to modify and take control over the automated meshing

• Hex-dominant meshing
  • This mesh method uses an unstructured meshing approach to generate a quad dominant surface mesh and then fill it with a hex dominant mesh
  • This approach generally gives nice hex elements on the boundary of a chunky part with a hybrid hex, prism, pyramid, tet mesh internally

The combination of robust and automated surface, inflation and tet meshing using default physics controls to ensure a high-quality mesh suitable for the defined simulation allows for push-button meshing. Local control for sizing, matching, mapping, virtual topology, pinch and other controls provide additional flexibility, if needed.

Automated CFD meshing including inflation layers for complicated geometries such as this drill bit model

2-D planar model with inflation layers defined at the boundary of the model

Meshing methods include:

• Patch conforming mesh method:
  • Bottom-up approach (creates surface mesh, then volume mesh)
  • Multiple triangular surface meshing algorithms are employed behind the scenes to ensure a high quality surface mesh is generated, the first time
  • From that inflation layers can be grown using several techniques
  • The remaining volume is meshed with a Delaunay-Advancing Front approach which combines the speed of a Delaunay approach with the smooth-transitioned mesh of an advancing front approach
  • Throughout this meshing process are advanced size functions that maintain control over the refinement, smoothness and quality of the mesh

• Patch independent mesh method:
  • Top-down approach (creates volume mesh and extracts surface mesh from boundaries)
  • Many common problems with meshing occur from bad geometry, if the bad geometry is used as the basis to create the surface mesh, the mesh will often be bad (bad quality, connectivity, etc.) The patch independent method uses the geometry only to associate the boundary faces of the mesh to the regions of interest thereby ignoring gaps, overlaps and other issues that give other meshing tools countless problems.
  • Inflation is done as a post step into the volume mesh. Since the volume mesh already exists, collisions and other common problems for inflation are known ahead of time.

Note: For volume meshing, a tetrahedral mesh generally provides a more automatic solution with the ability to add mesh controls to improve the accuracy in critical regions. On the contrary, a hexahedral mesh generally provides a more accurate solution, but is more difficult to generate.

For 2-D planar (axisymmetric), shell and beam models, ANSYS Meshing provides efficient tools for quickly generating a high quality mesh to accurately simplify the physics.

Beam model of an electrical tower

Mesh using standard size function

Mesh Methods for shell models include:

• Default surface meshing
  • Multiple surface meshing engines are used behind the scenes to provide a robust, automated surface mesh consisting of all quad, quad dominant or all tri surface mesh.
  • User can add sizing controls, and mapped controls to modify and take control over the automated meshing

• Uniform surface meshing
  • Orthogonal, uniform meshing algorithm that attempts to force an all quad or quad dominant surface mesh that ignores small features to provide optimum control over the edge length

Advanced Size Functions
ANSYS Meshing provides two types of size functions to provide appropriate mesh sizing for different physics. The default size function for Mechanical applications is designed to accurately capture the geometry while minimizing the number of elements in the model. The Advanced size function is the default for Fluids applications and is designed to accurately capture the geometry while maintaining a smooth growth rate between the regions of curvature and/or proximity.

Mesh using advanced size function

Using a body as a body of influence will use the selected body to control the mesh spacing without a mesh being generated for that body

Flexible Sizing Controls
ANSYS Meshing will automatically set default mesh size controls on the geometry. If the user wants more control over certain areas of the model, global, body, face, edge or vertex sizing controls can be inserted.

Using body, face, edge or vertex controls a user can locally control the mesh sizing

In addition, a sphere of influence, and/or a body of influence can be used to further control the mesh sizing.

Using an arbitrary match mesh control you can match two similar topology faces using coordinate systems to define the orientation

Match Mesh Controls
Periodic models will automatically be meshed with matched mesh at the periodic faces. In addition, the user can insert match controls to specifically define which faces should be matched.

Mapped mesh controls have advanced options to control how a face is “sub-mapped”, or broken into multiple mapped regions. Using side, corner or end controls you can force the mesher to sub-map the face as desired.

Mapped Mesh Controls
ANSYS Meshing allows a user to specify which face(s) to force a mapped mesh on. The user can also specify options on how the face should be sub mapped if it is more than 4 sided. Faces marked with a mapped mesh control that cannot be mapped will be meshed with a free mesh and the software will notify the user. This is convenient as the user can mark all faces to be mapped meshed to try to force more orthogonal meshing. For solid parts being meshed with a tet mesh, the quads will be split into triangles.

Mapped mesh controls have advanced options to control how a face is “sub-mapped”, or broken into multiple mapped regions. Using side, corner or end controls you can force the mesher to sub-map the face as desired.

ANSYS Meshing allows for geometry and mesh based defeaturing in a variety of ways. In Patch Independent and MultiZone meshing defeaturing is integrated into the meshing process and driven by a tolerance. Virtual topologies are used to merge faces and edges together prior to meshing so that the mesher ignores the individual faces and edges. Pinch controls are used to merge mesh nodes in close proximity together after meshing using a given tolerance. Each of the above approaches has some unique strengths.

Virtual topologies can be created manually or automatically to do geometry based defeaturing

Pinch controls can be created manually or automatically to do mesh based defeaturing