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querdynamik June 4, 2010 09:43

Problem: tetrahedral mesh and interFoam = bad results ?

i'm using the interFoam-solver (OF 1.6) to simulate a drop/wall-collision.

Because it is much more comfortable and time efficient (compared to blockMesh), i create the geometry and mesh with Salome. In Salome i use the "Netgen(1D,2D,3D)"-mesher to create a tetrahedral mesh.

From previous (and through experiments already validated) works, i pretty much know how the fluid-flow of the drop-impact - at least in the early phase of the simulation - should look like. In this case : The spreading wave-front has to be quiet smooth and spread nearly symmetrically in radial direction from the first point of contact between drop and wall.

When using a hexahedral mesh, the results of the simulation match the experiments pretty good.
Using a tetrahedral mesh (with approx. the same amount of cells and geometry as before) however, i get completely different and inappropriate results. The wave-front "splashes" immediatly and brakes into many little fragments.

For a better clearness, i add these two pictures from topview (both show a quarter of a droplet shortly after it touches the wall and starting to spread) :

With hexahedral mesh:

With tetrahedral mesh:

My questions are : Has someone an explanation for this discrepancy ? Is the interFoam-solver predestined for the use of hexahedral meshes ?
What could be the reasons for this numerical error?

Thanks in advance !

Best regards

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