CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   ANSYS Meshing & Geometry (https://www.cfd-online.com/Forums/ansys-meshing/)
-   -   Large Valve Flow Analysis - Inflation Problem (https://www.cfd-online.com/Forums/ansys-meshing/73311-large-valve-flow-analysis-inflation-problem.html)

sercan85 March 4, 2010 08:40

Large Valve Flow Analysis - Inflation Problem
 
THE FLOW GEOMETRY IS

http://img41.imageshack.us/img41/505/79616832.jpg


MY AIM:

Creating inflation on pipe and valve walls (~D=0,3m, first layer thickness=0,0001m, about 5 layers)
Also do this by using sweep method for 2 pipe sections.

NOTE: I didn't select very complex small surfaces on valve geometry as can be seen from picture, only major surfaces are selected.




PROBLEM I FACED:

I tried to use sweep method for two pipe sections, automatic method for valve section.

*Inflation couldn't be created on pipe walls by sweeping inflation. (no problem for some surfaces of
valve section walls)

I tried lots of parameters (increased number of sections, growth rate) for inflation but it didn't work.
http://img707.imageshack.us/img707/4531/70145874.jpg


Then I removed sweep method.


Mesher created tetrahedron meshes for pipe geometry.

Inflation created on walls (as seen in the picture below)

but 30-40 of 1 millon mesh elements have very bad aspect ratios, skewness exceeds 0,98 for these 30-40 elements.
This causes epsilon to diverge in k-e turbulent analysis at start.

http://img10.imageshack.us/img10/2274/99821463.jpg

http://img192.imageshack.us/img192/2527/94452193.jpg

http://img641.imageshack.us/img641/8554/31381790.jpg



SUMMARY:
IF SWEEP IS REMOVED, I CAN GET INFLATION, BUT SOME (30-40) CELLS THEN HAVE VERY BAD SKEWNESS.

What can I do? what parameters can I change?

I try to merge some surfaces on valve geometry but it deformates geometry a bit.

My aim is to get inflation without removing sweep method and get good skewness for all cells.

izumi11 June 1, 2010 04:08

Hi have you been able to solve the problem. I've had problems with this for the last 6 months. Have you tried changing the inflation method to post/pre?
Anyways if someone could please explain how to get rid of the highly skewed elements..

sercan85 June 1, 2010 14:02

Yes I have solved it by changing mesh sizing parameters.

From main sizing parameters, three parameters (something like max min tet face size, etc) must be reduced in order to fit the mesh to the geometry.

But the ratio between the three size must remain the same. If the order of magnitude of the one at the top is 1x, then the others should follow like 100x and 200x.


All times are GMT -4. The time now is 10:35.