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# Perform a volume-based weighted average in post-processing

Hello everyone,

It seems that in NX10, weighted averaging can be done in the post-processing.

I have a collector with elements of various sizes and I want, in my thermal simulation, to evaluate the mean temperature of the related domain. Obviously, an arithmetic average is not relevant (as in the "Identify Results" box) so I wanted to use this new feature but weighting the average with the volume of each element. But I do not know how to use it...

Can anyone help me?

Regards,

Clément

6 REPLIES

## Re: Perform a volume-based weighted average in post-processing

Clement,

Geometry weighted averages of post results are possible with NX 10 Results Probes. It requires geometry based meshes since the weighted average is done based upon geometry selection. You can get the area weighted average of temperatures on a face, the volume weighted average of elements on a body.

1. Create a probe using a results variable to represent your temperature

2. Select a geometry type (edge, face, body) in the Selection and Averaging dialog block

3. Select the appropriate geometry

4. Set the Geometry Value option to Weighted Average

The probe will return a single value for each piece of geometry that you select. You can also combine the results on each piece of geometry to obtain a single value from N geometry inputs.

Regards,

Mark

Mark Lamping

Simulation Product Management

Product Engineering Software

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

mark.lamping@siemens.com

www.siemens.com/plm

## Re: Perform a volume-based weighted average in post-processing

I think I am getting closer to what I want, but I still have an issue doing what you told me to...

When I create a probe, as a "Formula", I simply write "temperature" (without the quotes of course) in the field.

Selection Type : Bodies

I select the body I want to evaluate the mean temperature.

Geometry Value : Weighted Average

As an output, I, choose a Temperature in Celsius.

It all seems to work fine but when I click on Apply, I get the followin error message :

`Probe formula definition does not require entity selection.`

What do you think about that? Is my formula wrong?

Just to remind you, I simply want to evaluate the mean temperature of some bodies, and I can't use the Identify Results tool as the averaging performed there is an arithmetic mean of elements of various sizes, which is not relevant!

Solution
Solution
Accepted by topic author ClementJL
‎08-26-2015 04:32 AM

## Re: Perform a volume-based weighted average in post-processing

Clement,

I believe the problem is with the behavior of the "temperature" variable. It most likely is an expression used somewhere in your model and not retrieving the temperature results that you expect. I had a similar experience with a test model. Avoid the use of "temperature" and define your own results variable with a unique name such as TMP. The Results Variable command is located next to Results Probe on the Results ribbon tab.

Next define your probe's equation as TMP. Repeat all other steps as you did previously. It should work.

The error message "Probe formula definition does not require entity selection" is supposed to be issued when you have a formula that has the selection defined as part of the probe. An example is TEMP("PT1") where TEMP() is the temperature at a point plugin function, and PT1 is the name of a point in your model. Since the formula has a location for the evaluation specified (at PT1), you don't need to select anything. In fact in this case, the probe UI will want you to set the selection to None. I don't know why the error is being issued in your example, but I'm sure it is related to the use of "temperature" in your formula.

Regards,

Mark

## Re: Perform a volume-based weighted average in post-processing

Hi Mark,

I have been able to create a probe through the creation of a result variable. It now appears in the Simulation Navigator.

However, I am not able to evaluate its value. When I right-click on this Result Probe, all I can do is :

- Information

- Edit

- Rename

- Delete

- Properties

I do not have any output type. If it can help you understand, when creating the probe, I had no field next to the "Output Options" parameter to select, just a useless information icon that says : "Information"

Do you have any idea of what I did wrong?

For information, I attach the two operations I performed : Result Variable & Result Probe

Regards,

Clément

## Re: Perform a volume-based weighted average in post-processing

Clement,

The way you defined the probe, you should get a single value back from it - the weighted average of all the temperatures on the body for the first step of the solution. Information on the probe should return the weighted average result. If you specify All for load cases, and you have multiple load cases, then you should be able to generate an XY graph of weighted average temperature across all load cases (1 temperature value per load case).

If Information returns nothing, then I'd have to take a look at your model. Your setup looks good to me. I'm assuming you have a mesh associated to the selected body?

As a test, can you try your approach on a simple (i.e. block) model? Send it to me if you are still having trouble.

Regards,

Mark

mark.lamping@siemens.com

## Re: Perform a volume-based weighted average in post-processing

[ Edited ]

Mark,

Actually, I tried with a very simple model and it worked instantaneously.

I then tried back on my first model and it also worked. The only difference was the time it needed to compute the average (few minutes).