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Good news about airfoil and OpenFoam

Posted February 20, 2013 at 03:42 by skeptik (CFD notes)

So, at the end of the testing OpenFOAM/simpleFoam, i get:

U=21.3, Re=0.44e6,

LowRe case, LaunderSharmaKE:
1. OF 1.7 cannot solve the case with kEpsilon on hex+tetra 2D mesh. It just crashes.

2. There are a lots of details when you use LowRe LSkEps model, you need lots of iteration, lots of interpolation data to provide better accuracy.

3. People invented k-omega for different flows near the walls. And better one - kOmega...
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Hey, Dude, be careful with liftDir/dragDir in controlDict

Posted February 19, 2013 at 05:41 by skeptik (CFD notes)

When U is changed due to angle of attack you should change controlDict in libForces section.

So, what can you get when you have proper controlDict

U=56.4, Re=1.6e6

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The mesh was refined so it was OK after checkMesh

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not bad) the next - recalculate LowRe K-eps, just for fun.
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TUI commands for running a Transient simulation in ANSYS FLUENT

Posted February 18, 2013 at 11:22 by diamondx

The TUI command solve/iterate 100 just iterates 100 more iterations. This is used for running steady simulations.

Use the following commands for running a transient simulation:

solve/set/time-step 1e-2 ( for setting the time step size)

solve/dual-time-iterate 100 40 ( 100 is the number of time steps and 40 is the iterations per time steps)
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Hexa dominant meshing

Posted February 11, 2013 at 20:36 by diamondx

Originally Posted by PSYMN View Post
Hex Dominant doesn't really play well with the other methods. You will also have a hard time when you try to merge it with the Hexa method, so you will need to do things in the right order...

Hex Dominant is also really more of an FEA method. It starts from the quad surface mesh and grows into the middle. If you don't have a quad surface mesh, it surface meshes everything first and then starts. It doesn't do the material point flood fill that the octree tetra mesher does. It
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Turbine blade with filleting and tip clearance

Posted February 10, 2013 at 22:06 by diamondx

The periodicity (set under Mesh (tab) => Global Parameters) is to ensure that your mesh on one side matches the mesh on the other side... Once you see the DEZ (data entry zone), you will understand what you need to fill in. Periodicity is set on the geometry so that the generated mesh comes out periodic, so if you go back to set it, you must regenerate.

Even if you are copying your mesh around to create an annulus instead of a periodic section, it will be easier if you have...
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