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-   -   Extracting Raw Data from STARCCM+ (http://www.cfd-online.com/Forums/star-ccm/95706-extracting-raw-data-starccm.html)

rks171 December 29, 2011 10:57

Extracting Raw Data from STARCCM+
 
I need to get some raw data from the mesh and I can't figure out the best way to do it. I need the raw data at specific points of the flow region so that I can compare it to experimental data. I specifically want the velocity vector components (u,v,w) as well as the fluctuating velocity (u',v',w') at specific points in the flow region. I have an excel file with the (x,y,z) values of the locations that I need the measurments at. So I'm thinking there is some way I can make a .csv file of the (x,y,z) values and use that in STARCCM+ to collect the velocity information at those locations. However, I'm not sure of the best way to get the fluctuating components of the velocity. I assume I will need to run a transient solution of like 3-5 seconds and export the velocity information at every single time step so that I can later do some data analysis to calculate the average (u,v,w) values as well as the rms values of (u'-u,v'-v,w'-w). Can anybody help me with the specifics of how to do what I'm requesting and/or give me a better method for getting this information out of STARCCM+? I'm completely new to CFD as well as STARCCM+.

rks171 December 29, 2011 13:26

Okay, so I figured out that post-processing won't be necessary to obtain the RMS of the fluctuating velocity components. It is simpler to create field variance monitors and then select the i, j, and k components of velocity as the function. This will create corresponding field functions under the 'tools' menu. An internal xyz report can then be created and the variance field functions can be selected as the scalars. This will automatically calculate the RMS of the fluctuating velocity over the transient and eliminates a lot of unnecessary raw data. I can export this table after the simulation is finished running and import the data into excel.

The xyz table can be produced for a part. Currently, I have selected a derived part, which is a performance grid. So the xyz table will extract data at those points on the performance grid plane. However, I'd much rather supply STARCCM+ with a table from file that lists the exact experimental locations that measurements were taken at because it will greatly reduce the amount of data I need to export from STARCCM+ and later reduce. However, I have not yet figured out if it is possible to specify the points at which you want raw data extracted from by using a file instead of some derived part. Or perhaps there is a way to create a derived part from file...

Ladnam December 30, 2011 17:13

I have not tried this before but I think it should work to make an STL file with your coordinates and use an arbitrary grid as the derived part.

Another way I can think of is to use a java macro that makes a point probe of all your coordinates.

rks171 December 30, 2011 18:10

Thanks, I actually figured that out yesterday. Except that I made a .vtk file instead of a .stl file. I created a mean field monitor and a variance field monitor for each of the three velocity components (6 field monitors in total). I set the trigger to time-step so that I can get time-averaged velocity and it's standard deviation to represent the turbulence. Then I created a table for the arbitrary probe that I created and chose my 6 monitors. This way, I can export the data for use in excel.


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