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How to monitor an expression on a user surface on cfx pre?

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Old   February 20, 2018, 10:33
Default How to monitor an expression on a user surface on cfx pre?
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I need to monitor the average temperature on a user surface. I correctly imported the surface from another cfxpost export file, but when i try to create the monitor it doesnt recognize the surface. Specifically what i did was create an expression called "average temp" as ave(Temperature)@my user surface name, and then create a monitor for that expression. When i create the monitor it gives me the error of the unrecognized name.

I tried with all the different possible name for the surface (the one it originally had in the export file, the one it had on cfx post, etc) and nothing works. I also tried using the probe function as an alternative, but didnīt work either.

How can i make this work?
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Old   February 20, 2018, 10:53
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Use the search tool of this forum.

CFX: Insert custom mesh locators / Use user locations as locators in the expressions
Referencing a User Location for a Monitor point expression in CFX pre

It is not possible to create monitor points at custom locations like User Surfaces. As suggested in the first linked thread, a possible workaround would be to position any interfaces you have at the position you need to monitor. However, that would only work for a few cases, depending on where you try to monitor.
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Old   February 20, 2018, 10:57
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Yes i used the search function and find that exact thread, but that solution doesnt fit me. Is there really no workaround way to do this? My surface is very specific and doesnt involve any interfaces nor interaction between bodies.
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Old   February 20, 2018, 11:02
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Apparently you did not understand what I wrote in the previous threads several times.

In monitoring you can only use mesh locators, meaning things that have been meshed. A user surface is not meshed, so it will not be accepted by Pre. Therefore you need to create an internal surface inside your geometry and mesh it.

In Pre you don't have to set any physics on this internal surface. It just has to be present as mesh locator, so you can refer to it as monitoring object.
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Old   March 1, 2018, 10:31
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Quote:
Originally Posted by Guille1811 View Post
I need to monitor the average temperature on a user surface. I correctly imported the surface from another cfxpost export file, but when i try to create the monitor it doesnt recognize the surface. Specifically what i did was create an expression called "average temp" as ave(Temperature)@my user surface name, and then create a monitor for that expression. When i create the monitor it gives me the error of the unrecognized name.

I tried with all the different possible name for the surface (the one it originally had in the export file, the one it had on cfx post, etc) and nothing works. I also tried using the probe function as an alternative, but didnīt work either.

How can i make this work?
When you load your surface into CFX-Pre, new option appears in Output Control -> Monitor which allows you to setup monitoring of variables on this surface. Monitoring only works for transient simulations (as I remember).
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Old   March 2, 2018, 03:12
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Ok, this changes things. Thanks alot for that hint! I thought it was impossible.

Unfortunately, it does not seem to accept expressions to evaluate and monitor. Too bad since I need that. Anway, should be useful to alot of other people.
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Old   March 2, 2018, 03:58
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Originally Posted by AtoHM View Post
Ok, this changes things. Thanks alot for that hint! I thought it was impossible.

Unfortunately, it does not seem to accept expressions to evaluate and monitor. Too bad since I need that. Anway, should be useful to alot of other people.
You may try to create additional variable, activate it in domain settings and set it to be equal your expression, then select it for monitoring.
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Old   March 2, 2018, 04:02
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Good point. You seem to have used it before, so I have a few more questions:
1) are the monitors shown like all the others in solver manager?
2) are they included in trn output files?

I could try it out I know, but its quite some effort for my case as I need to monitor >200 surfaces and it takes a while to set up.
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Old   March 2, 2018, 04:12
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Originally Posted by AtoHM View Post
Good point. You seem to have used it before, so I have a few more questions:
1) are the monitors shown like all the others in solver manager?
2) are they included in trn output files?

I could try it out I know, but its quite some effort for my case as I need to monitor >200 surfaces and it takes a while to set up.
No. New button will be activated inside solver manager "Launch CFD-Post to monitor run in progress" which opens CFD-Post to monitor variable changes on your surface during solution process. You'll be able to create contour or vector plots on your surface which will be updated automatically or on demand.
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