Export mesh statistics for use in Richardson Extrapolation for grid sensitivity study
Hi,
Following the post from another user in this thread (http://www.cfdonline.com/Forums/cfx...analysis.html) I want to do a grid sensitivity study using the Richardson extrapolation method. The first step is to define a representative cell, mesh or grid size, . For threedimensional simulations where is the volume of the cell, is the total number of cells used for the computations. My problem is I don't know how to extract the values of from ICEM as ideally I'd like to do the Richardson Extrapolation method in Excel, where I can compare different meshes. In ICEM how do I export mesh statistics such as volume of each cell? Can it be exported as a handy .csv file? I refer you to the paper I am using: http://journaltool.asme.org/Template...umAccuracy.pdf Thank you 
Since you just need the ratio of h(fine)/h(coarse) calculation of an actual value of "h" is not necessary.
How do you want to do the refinement in ICEM? 
Quote:
I will do the refinement in ICEM by applying more nodes in the thermal boundary layer. 
Do you use blocking / hexa meshing or unstructured?

Quote:

Great. Then you have all the numbers...
Do you refine the whole grid by using the mesh>refine utility, or do you change the number of nodes of some relevant edges? Is this 2d? Can you post some picture? 
Quote:
http://i.imgur.com/uRL1727.png Do you want a picture of the mesh? 
How large is your coarsest mesh?
In 2d (and such a simple geometry) it is often affordable to just refine the whole mesh, which means you will end up with a 4 times larger mesh (2 x in "x" and 2 x in "y" direction). Would that be ok for you? 
Quote:
However what I am interested in is the Richardson extrapolation method I mentioned in my original post. 
It's always the same method:
In your case, save your coarse mesh. Then refine the (unstructured) mesh, by clicking on "Edit Mesh > Adjust Mesh Density". Here you can use "Refine All Mesh", method "pure refinement", steps "1". >apply. You will get a mesh, that is 2 times finer in each dimension. Save that mesh. Do the same refinement again and you will end up with a even finer mesh. Now run your simulation on all three meshes. Use the coarse results as interpolation for initializing the other runs. For each simulation you need one single "important" value, such as you heat transfer coefficient or whatever. Using the nomenclature of your pdf, these values are the phi 3, 2 an 1. Since you doubled the number of points in each dimension the value of r21 and r32 is "2". Here we go! 
Thank you! That actually does help.

If you did that, you could post the values here for others to see how it works...

Hello,
I have one additional question regarding the Richardson Interpolation: What is about r21 and r32 if only the total number of cells is doubled (by splitting one direction)? Example: Coarse: 3 Million cells Reference: 6 Million cells Fine: 12 Million cells I then r21=r32=1.25?? Thanks in advance. //Markus 
All times are GMT 4. The time now is 12:21. 