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Source: Ansys
When geometries are complex or the range of length scales of the flow is large, a triangular/tetrahedral mesh can be created with far fewer cells than the equivalent mesh consisting of quadrilateral/hexahedral elements. This is because a triangular/tetrahedral mesh allows clustering of cells in selected regions of the flow domain. Structured quadrilateral/hexahedral meshes will generally force cells to be placed in regions where they are not needed. Unstructured quadrilateral/hexahedral meshes offer many of the advantages of triangular/tetrahedral meshes for moderately-complex geometries.
A characteristic of quadrilateral/hexahedral elements that might make them more economical in some situations is that they permit a much larger aspect ratio than triangular/tetrahedral cells. A large aspect ratio in a triangular/tetrahedral cell will invariably affect the skewness of the cell, which is undesirable as it may impede accuracy and convergence. Therefore, if you have a relatively simple geometry in which the flow conforms well to the shape of the geometry, such as a long thin duct, use a mesh of high-aspect-ratio quadrilateral/hexahedral cells. The mesh is likely to have far fewer cells than if you use triangular/tetrahedral cells.
Converting the entire domain of your (tetrahedral) mesh to a polyhedral mesh will result in a lower cell count than your original mesh. Although the result is a coarser mesh, convergence will generally be faster, possibly saving you some computational expense.
In summary, the following practices are generally recommended:
- For simple geometries, use quadrilateral/hexahedral meshes.
- For moderately complex geometries, use unstructured quadrilateral/hexahedral meshes.
- For relatively complex geometries, use triangular/tetrahedral meshes with prism layers.
- For extremely complex geometries, use pure triangular/tetrahedral meshes.
In this tutorial we show the results of a heat transfer simulation using different types of meshes (Tetrahedral mesh vs Hex/Prism vs Polyhedral mesh). You will notice the differences between the number of elements and the results and the computational time.

Ansys Fluent Tutorial | Heatsink
In this tutorial, you will learn how to simulate a Heatsink using Ansys Fluent. In this first video, you will see how to create the geometry and the mesh using DesignModeler, Ansys Meshing and Ansys Fluent.

Ansys Meshing | Inflation
You can set the Use Automatic Inflation control so that inflation boundaries are selected automatically depending on whether or not they are members of Named Selections groups.
Related Articles
Ansys Fluent Tutorial | Heatsink
In this tutorial, you will learn how to simulate a Heatsink using Ansys Fluent. In this first video, you will see how to create the geometry and the mesh using DesignModeler, Ansys Meshing and Ansys Fluent.
Ansys Meshing | Inflation
You can set the Use Automatic Inflation control so that inflation boundaries are selected automatically depending on whether or not they are members of Named Selections groups.
Ansys Meshing – Keyframe Animation
You can make animations based on keyframes. Keyframes define the start and endpoints of each section of animation.
Ansys Meshing – Match Control
In this tutorial, you will learn how to use the Match Control tool in Ansys Meshing. Match Control allows duplicating the mesh in a body. We have two option Match Control Cyclic and Arbitrary.
Ansys Meshing – Body of Influence
The Body of Influence option is available in the Type field if you selected a body and Use Adaptive Sizing is set to No. Using this option, you can set one body as a source of another body
Ansys Meshing – Sphere of Influence
The Sphere of Influence option is available in the Type field after you select an entity such as a body, face, edge, or vertex.
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