CFD Online Discussion Forums

CFD Online Discussion Forums (
-   Siemens (
-   -   Plotting iso-surface cells (

usker October 16, 2008 06:00

Plotting iso-surface cells
Here is my question:

In pro-Star post-processing I can plot iso-surface of some scalar by specifying a certain value. I want to select all the cells on the surface of this iso-surface. Then I want to plot any other scalar only on those selected cells.

Please advise how I can do it.


James October 16, 2008 07:59

Re: Plotting iso-surface cells
If you just want the cells why not do a CSET with the PRANGE option, that will provide all the cells within a specified set of values.

This is not identical to your wish but it may be close enough.

usker October 16, 2008 08:24

Re: Plotting iso-surface cells
Thank you James for your advice.

But when I use CSET PRANGE option I cannot get all the cells in that particular range. In other words, if I plot iso-surface it gives me the closed surface within the value I specify, but with CSET PRANGE it gives me only a few cells. This is because I need a very narrow range of values, for example from 0.0589 to 0.0652, (maximum scalar value 0.2) but a cell usually contains several scalar values, even out of my range. That is why when I plot iso-surface I could just select all the cells on the surface knowing that these cells are in the range I need.

If you have any other ideas please let me know


Balduin Bankerotti October 16, 2008 09:50

Re: Plotting iso-surface cells
create shells at the isosurface (pscreate isos) and later use "pmap" to map other quantities onto that shell.

usker October 17, 2008 06:30

Re: Plotting iso-surface cells

Thank you very much. I have solved my problem with your help. I really appreciate it.

And for those who are interested in iso-surface mapping, shell mapping, and any other matters regarding post-processing, there is a good information source on


James October 17, 2008 07:54

Re: Plotting iso-surface cells
One thing to be careful of is that what you are using is an iterpolation on an interpolation (using an isosurface based on vertex data).

The reason the CSET 'fails' is that the data does not exist. The values you want are at a point between one cell center and its neighbour.

Putting in an iso-surface does not create the data, although it is probably the best and only thing possible.

Just make sure that what you are doing is valid. For example the PMAPPED data if done from cell data will be from the cell and not the surface of the isosurface. This may work OK for general field data, i.e. pressure/velocity, but for scalar species interlinked by heavily non linear reaction mechanisms this may not be true/consistent/consevative/...

You will need to convince yourself of the validity of the asumptions you are making.

usker October 17, 2008 09:56

Re: Plotting iso-surface cells
Thank you James for your valuable comments. This is what I have actually been doing now: Validating the results I got; whether they are resonable and accurate.

Really appreciate your help

All times are GMT -4. The time now is 03:14.