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note about convergence

Posted March 26, 2013 at 05:39 by skeptik (CFD notes)

Quote:
Originally Posted by chegdan View Post
Nick,

There are some strategies that I would try to get these residuals down to something you would like.
  1. Lower your pressure relTol by an order of magnitude compared to U i.e. relTol = 0.001 for P and relTol = 0.01 for U.
  2. Without knowing the mesh you are using you may need to increase the nonorthogonal corrector by 1 or 2. if you are using a tet mesh...then there are many things you can do.
  3. Use first order schemes to start with (you will move to higher order ones
...
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Old

Forgotten post about airfoilmesh. Domain shape

Posted March 22, 2013 at 05:00 by skeptik (CFD notes)

First time i tried domain like this

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And i got no good results cause pressure distribution shown problems with BC

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I tried to make a circular domain like in this work shown in the next figure

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and only with circular domain i get physically reasonable results.

other figures about mesh i used to

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Old

PISO's last results

Posted March 14, 2013 at 07:39 by skeptik (CFD notes)

SIMPLE showed better results.

May be it was caused by mesh. Tetra mesh with lower y+ shows similar results. Quad+tri 3D extruded mesh did not demonstrate good Cx, Cy.

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Old

PISO's strange behavior at different meshes :(

Posted February 25, 2013 at 07:19 by skeptik (CFD notes)

1. mesh quad+tri+3D extruded. at 17 grad most flow around airfoil is laminar

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2. mesh only tri+3D extruded. at 15 grad flow behind foil is completely turbulent

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so this pictures shows that we cannot get proper results for Cx, Cy due to bad prediction of the flow detachment.

try to find a solution, may be OF 2.1 will show better results
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Old

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:

NACA23012
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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