Facet and vertex value
 

Hi guys:

What is the difference between Facet maximum and vertex maximum? When you take facet maximum, does it give you the maximum value of a varibale in that face, i mean in case of minimum does it consider the wall value (where velocity is zero)? Thanks guys. Munni

Re: Facet and vertex value
 

Fluent is a cell centered solver, so it stores data based on the cell centered values. The only exception is boundary conditions. Boundary conditions are stored in the facet centers. So if you're looking at Facet values on a boundary condition, then you're looking at stored data... if you're looking at node values, then you're looking at interpolated data (again, that's only for on BCs... within the volume, facet and node values are both interpolated).

So if you do facet maximum on a BC, it will look for the maximum stored value. If you're looking at vertex maximum then it's going to interpolate the data to the nodes and look for the maximum values.

Hope this helps, Jason

Re: Facet and vertex value (FOR JASON)
 

Thanks Jason. But my question was not at the BC. Lets say I am simulating fluid flow in a pipe. Now I would like to know the pressure at different planes in that pipe. So we have to make some iso surface based on the grid value. Then we can get the average values there from surface integrals. Now when you go to surface integral panel from REPORT, you will find there is option to take facet maxm, minm, or vertex maxm, minm etc. I found some strange values for this caes. Thats why I would like to understand what are they represent. Could you please elaborate a bit more about these values. Thanks again. Munni

Re: Facet and vertex value (FOR JASON)
 

Within the volume, all of the data is stored at volume element centers, so everything you're looking at is interpolated data (this is true when looking at contours or vectors on the plane as well). When you're creating a surface, then you're not slicing perfectly along faces, so Fluent will create kind of pseudo-geometry. Wherever your plane slices through a volume element will create a face... wherever your plane slices through a face you will create an edge, and wherever it intersects an edges you will create a vertex. Because of the way the elements are, the interpolation becomes a little hairy. If you look at the grid (instead of "Features", plot "All") and you'll see how much of a mess the mesh looks like along this slice. Even so, the values should be reasonable (a little more error than if you were cutting along a perfect mesh plane, but still pretty reasonable). If you plot the contours on this plane you will be able to locate where the problem is (turn off "Node Values" to see the "Facet Values" on a surface).

Hope this helps, Jason