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-   -   how to do a grid independent study (http://www.cfd-online.com/Forums/ansys/81866-how-do-grid-independent-study.html)

xyq102296 November 9, 2010 11:05

how to do a grid independent study
 
Hello everyone

I want to do a grid independent study on my model, the model is only 5mm width, 2D
I add inflation layer on the wall and set the element size in the middle.
what kind of critiria is for the grid independent? After a coarse mesh, decrease the inflation layer and element size by the same ratio?
And for my pc , it can't stand the cell size smaller than 0.08mm. Can I finish the grid independent study on this model?

xyq102296 November 9, 2010 11:07

I have read all the threads about grid independent in this forums, and I also asked my instructors, he has no idea, so please tell me if you know , thank you in advanced.

Jade M November 15, 2010 12:28

Systematically decrease the element size by half and quantify the error, such as the maximum value of the streamfunction. For example, suppose there are two regions in the flow, namely, the bulk of the flow and the boundary layer. Start with the default mesh. In the bulk of the flow, decrease the element size and quantify the error. Repeat until the error is within tolerance. In the boundary layer, repeat the same procedure. That is, keep decreasing the mesh until the solution is independent of the grid.

Good luck!

John222 February 6, 2011 18:27

Quote:

Originally Posted by Jade M (Post 283509)
Systematically decrease the element size by half and quantify the error, such as the maximum value of the streamfunction. For example, suppose there are two regions in the flow, namely, the bulk of the flow and the boundary layer. Start with the default mesh. In the bulk of the flow, decrease the element size and quantify the error. Repeat until the error is within tolerance. In the boundary layer, repeat the same procedure. That is, keep decreasing the mesh until the solution is independent of the grid.

Good luck!

how to know that the solution is independent of the grid?

zxin February 8, 2011 07:19

Untill your result comes to the value within an acceptable error compared to the last one.

myaccount December 24, 2013 07:47

Hi
I have simulated flow over solids.I have applied periodic boundary conditions in GAMBIT.I have run the case in FLUENT and the case got converged.After I change the grid size to finest and most coarser, the values far away from the converged case ,I see the same results .Why is this happening?

KhXeR January 22, 2014 01:13

What tolerance are you setting for your convergance criteria.
Increase it a little bit, say 10e-5 and then see your results.


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