Tutorial on 2d Hybrid Meshing in ICEM CFD for 2d Airfoil

Tutorial on 2d hybrid meshing in ICEM CFD for 2d airfoil

1. Objective: To make the hybrid mesh in ICEM CFD for an airfoil. 2. Learning objectives:  To make the hexa mesh in vicinity of airfoil  Tetra mesh (patch dependent) in outer domain with conformal mesh at boundary  Merging of two meshes. Here two methods are given for better understand of process.  Exporting mesh and importing in Fluent and sample solution

3. Importing geometry Geometry is available in formatted .dat format

   

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Then I added smaller far field boundary (interface between hexa and tetra mesh, called interfacecurves) and scaled it to get the outer most boundary (called far field) . Faces were also made and after that I run build topology to segment surfaces automatically. I have also deleted inner most surface(inside airfoil). Fairfield  

inner domain – meshing  with hexa blocking 

Airfoil 

Pressure  outlet 

Interface  boundary Outer domain –  meshing with tetra  

.

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Set these parameters in part mesh setup

After that 2d planner block is created as shown in Fig. After usual processing C-type blocking was made and mesh was converted to unstructured mesh

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Now update mesh sizes for blocking and specially at boundary of inner mesh which will be used for the outer mesh.

Now create pre-mesh and check the mesh for any error.

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Mesh will look like as follows.

Convert to unstructured mesh

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Now hide inner domain from model tree. Also turn on surfaces so that we can pick outer surface/domain while meshing. This tetra mesh will be merged with previously created hexa mesh. Method selected is patch dependent mesh and All Tri. Also check Respect line elements. This is necessary since at interface we need same mesh on both sides.

Since we have already defined mesh sizes for all parts (surfaces and curves). Now go to compute mesh panel (surface mesh, first option from left) and choose visible option for input.

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Mesh looks like as shown in following Fig.

Now turn-on the inner mesh also (Hexa one)

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You can notice two colors for mesh inside and outside. This is due to fact that both meshes are in different part. First step in merging 2d meshes is to make single part for both meshes. For this right click on outer part model tree,

Now you see both meshes are combined together. But if you export mesh without doing this you will get wall between both domains (inner and outer).

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Method one defining interior boundary condition for interfacecurves and output mesh.

Farfield 

Interface  curves 

int is added by ICEM 

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When I simulated this case in Fluent, results are not different than the case without the interior boundary.

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Method two Deleting line elements in interface zone. There are two methods to do this a) delete the interface part (assuming you have separate part for the interfacecurves, which we have). Go to Geometry > delete curves and choose part which contains the interfacecurves

No export mesh from ICEM and import into Fluent

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Results are :

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Method three Deleting interface elements when you have not defined separate part for interfacecurves In this case disable all other elements type and only leave the line elements.

Line elements are selected in  interface region.  

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Summary: 1. We have learned how to tackle the hybrid 2d mesh in ICEM CFD. 2. It should be noted that the hybrid meshing for 3d cases is different than 2d. I will show it in separate tutorial. 3. We have discussed three methods to make hybrid mesh. 4. All files at each stage are also included in package.

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