CFD Online Logo CFD Online URL
Home > Forums

CFD notes

Register Blogs Members List Search Today's Posts Mark Forums Read

OpenFoam, SALOME, all free tools for engineers

note about convergence

Posted March 26, 2013 at 04:39 by skeptik (CFD notes)

Originally Posted by chegdan View Post

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
Posted in Uncategorized
Views 1047 Comments 0 skeptik is offline Edit Tags

Forgotten post about airfoilmesh. Domain shape

Posted March 22, 2013 at 04:00 by skeptik (CFD notes)

First time i tried domain like this

Name:  quad.jpg
Views: 1158
Size:  24.3 KB

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

Name:  p_freestr.jpg
Views: 1117
Size:  15.1 KB

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

Name:  hybrid3.jpg
Views: 1202
Size:  68.0 KB

and only with circular domain i get physically reasonable results.

other figures about mesh i used to

Name:  hybrid_refined.jpg
Views: 1014
Size:  83.7 KB Name:  hybrid1.jpg
Views: 1729
Size:  85.0 KB...
Posted in Uncategorized
Views 1980 Comments 0 skeptik is offline Edit Tags

PISO's last results

Posted March 14, 2013 at 06:39 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.

Name:  kOmega_Piso.jpg
Views: 1132
Size:  43.5 KB
Posted in Uncategorized
Views 1137 Comments 0 skeptik is offline Edit Tags

PISO's strange behavior at different meshes :(

Posted February 25, 2013 at 06:19 by skeptik (CFD notes)

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

Name:  piso_17_hybrid.jpg
Views: 1837
Size:  16.3 KB

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

Name:  piso15_wake.jpg
Views: 1476
Size:  20.6 KB

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
Posted in Uncategorized
Views 1914 Comments 0 skeptik is offline Edit Tags

Good news about airfoil and OpenFoam

Posted February 20, 2013 at 02:42 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...
Attached Thumbnails
Click image for larger version

Name:	kEpsilon_lowRe.png
Views:	963
Size:	36.3 KB
ID:	120  
Posted in Uncategorized
Views 2221 Comments 4 skeptik is offline Edit Tags

All times are GMT -4. The time now is 19:37.