ICEM CFD
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ANSYS ICEM CFD is a popular software package used for CAD and mesh generation.
It can create structured, unstructured, multi-block, and hybrid grids with different cell geometries.
Contents |
[edit] Tutorials
[edit] basic viewport interaction
- use the left mouse button and drag to rotate the view
- use the middle mouse button to pan the view
[edit] importing data
Once the aerofoil coordinates have been imported into ICEM, they must be connected with splines. ICEM can handle up to 15 points per curve:
[edit] Grid Types
C-Type: O-Type:
[edit] creating a C-grid
A C-grid is normally used for structured grids, and true to its name looks like a letter 'C'.
[edit] creating a structured grid
The first thing to do when creating a structured grid is to create the geometry or a .tin file in ICEM. You can do this by manually creating it in ICEM or importing data into ICEM, for example 3-dimensional point data from a .txt file.
The tools available are specified under the geometry tab. There are quite a number of tools and they can be quite useful. However, it is suggested that some planning is done before beginning to make a geometry. There are tools specifically for curves.
- curves can be split or joined to other curves.
- Points can be created at cross-sections of curves.
- Surfaces can be created from curves.
All of this gives extra flexibility in the methods of designing a grid.
| Tip |
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| A tip that is quite useful is the use of the F9 key to "pause" the tool being used so the grid can be moved or zoomed in to. |
Also, different parts of the grid can be saved under a part name which can be switched off or on if you want certain things to be invisible like points or curves or certain surfaces. You can also copy an entire set of geometry by selecting the parts you want and translating it to a specified point using the translation tool. This is useful, especially when creating a symmetrical object such as a wing, where the aerofoil can be copied to another location and then joined up to the original aerofoil with curves.
Once the geometry is created, the next step is to create the actual grid. Note that the tolerances of the geometry plays an important role in the accuracy of the grid. So make sure that depending on what you want, the tolerances are high enough. Using the blocking tab, a block can be created around the entire geometry and then split up into sections. The mesh is created by specifying the distribution of points along the edges of the blocks. Therefore the more blocks you have, the more flexibility you have in changing the distribution of points along the edges. The edges and vertices of the blocks must be assosciated with the geomery curves and points.
Once the blocks have been created and all the required points and curves assosciated, the number of points and the distribution can be set along each edge. In somecases, you want the density of cells to be high, for example at the boundary layer of an object, whereas to save time, you may want the cells further away to be large. There are various types of distribution such as linear, geometrical and exponential variation that can be used. The premesh tool can then be used to view the meshing. There is also a quality check tool, where one can specify how you want to check the quality of the blocking. For example, one can check the variation in volume size to see if it varies smoothly, or if there are any negative volumes, which would suggest that the grid crosses into solid surfaces.
The blocking is saved as a .blk file. When all is done, the mesh can be made readable by a solver by specfying what type of solver is to be used in the "output tab".
[edit] creating an unstructured grid
Once the curves and surfaces have been created, click the mesh tab -> surface mesh and define the mesh density on the surfaces.
The surface menu is shown on the right, and to select surfaces, click the button next to it and start selecting surfaces, using middle-click when done. Then select a mesh density (0.05 in this case, but will vary with each case) and check remesh selected surfaces if needed, and click ok.
Then, click volume mesh, and select the method (tetra for tetragonal unstructured meshes) to generate the unstructured grid, press 'ok' and wait for the grid to be generated and review the result.
