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-   -   plotting/monitoring maximum Mach number (http://www.cfd-online.com/Forums/cfx/103704-plotting-monitoring-maximum-mach-number.html)

alpha754293 June 24, 2012 10:08

plotting/monitoring maximum Mach number
 
Is there a way to plot/monitor the maximum Mach number during the course of a run?

(And not at a specific point, but for the entire fluid domain volume).

I'm getting a maximum Mach number message showing up in the output file, and I was just wondering if there's a way to plot/track/monitor that.

Help would be greatly appreciated.

Notes about the run:
It is a transient run. Timesteps are now 1e-7 [s]. Total time I think only works out to be for like 9e-3 [s] or something like that (although right now, it's not even getting past 2e-5 [s]), so I'm using the Mach number to try and help me debug the run.

Thanks.

ghorrocks June 24, 2012 19:29

Use a monitor point, set to max(Mach Number)@domain or something like that.

alpha754293 June 24, 2012 21:55

Quote:

Originally Posted by ghorrocks (Post 368063)
Use a monitor point, set to max(Mach Number)@domain or something like that.

If I got multiple domains, that would mean that I would have to use:

max(max(Mach Number)@domain1,max(Mach Number)@domain2,max(Mach Number)@domain3))?

alpha754293 June 25, 2012 19:16

Quote:

Originally Posted by ghorrocks (Post 368063)
Use a monitor point, set to max(Mach Number)@domain or something like that.

ERROR
The following unrecognised name was referenced: max.

ghorrocks June 25, 2012 19:24

Sorry, the command is maxVal()@domain. Look at the CFX Reference guide for full variable and function list

alpha754293 June 25, 2012 19:37

Quote:

Originally Posted by ghorrocks (Post 368278)
Sorry, the command is maxVal()@domain. Look at the CFX Reference guide for full variable and function list

Thanks. That's kind of interesting that they have different commands to get the maximum values.

ghorrocks June 25, 2012 20:36

Yes, it is confusing. But there is a bit of logic in there - the max() function returns the max of the arguement values, but maxVal looks at the mesh object referenced and returns the max value from that. The max function is a simple function equivalent to most languages, the maxVal function is known as a CFX callback (not sure why, they just are) function which works on mesh objects.

alpha754293 June 25, 2012 20:40

Quote:

Originally Posted by ghorrocks (Post 368288)
Yes, it is confusing. But there is a bit of logic in there - the max() function returns the max of the arguement values, but maxVal looks at the mesh object referenced and returns the max value from that. The max function is a simple function equivalent to most languages, the maxVal function is known as a CFX callback (not sure why, they just are) function which works on mesh objects.

:) Good to know.

So if I want to probe/query a parameter/value in the run, I would need to use maxVal, but if I want to find the maximum (between two things), I would use max().

Also it's interesting that it doesn't allow more than two arguments (so say...I have three domains, I can't ask it to compare and find the max values out of all three; I have to do them two at a time, and then find the max between the two pairs).

It would be nice if max() would be intelligent enough to be able to tell whether you're looking at a value, or as a comparison. But either way, it works. It takes a few more expressions to get there, but it works.


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