Field Averaging for Steady-State Simulations

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1

I am doing an external automotive flow simulation with the steady-state SIMPLE solver. I am trying to do field averaging over the last 500 iterations. How can I do that in SimScale? I am familiar with OpenFoam which has that ability but I can’t find the option in SimScale for that.

Cheers!

2

Hi! I assume you are looking to measure and average out some quantity of interest (e.g. some sort of area average or forces on a some face) over the last 500 iterations?

If so, you can do this with result controls.

You will be able to download the raw data from the plot on the top right after the simulation finishes running and calculate averages over 500 iterations this way.

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3

Hi Ricardopg,

Thanks for your response, however, that’s not what I am trying to find. I am trying to take the time average of a field variable like velocity U, and pressure P. Like you would do in a transient simulation except for a steady-state simulation. So it’s like to get the field values UMean, and pMean as well as UPrime2Mean, and pPrime2Mean

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4

Hi! If you are looking for field values everywhere in the domain, you could adjust the ‘write interval’ under simulation control to output every result set to the post processor. There are two potential issues that come to mind:

  1. Depending on the size of the mesh, this might result in too much data, leading to the simulation failing due to lack of memory
  2. You will simply have access to all data sets. They won’t be averaged out. Further post-processing might be needed e.g. in ParaView

Going back to my previous point: the result control workflow gives you data for every single iteration on faces of interest. Since it doesn’t have to write all data for the entire volume, it’s usually the way to go if you are looking to average out the last 500 iterations.

Cheers

5

And for a more automatic way of calculating the average of the last 500 (or any qty) of Results Item values, you can use this: Introducing an 'OpenFoam Results Stability Index' (ORSI) that provides a new way to quantify confidence levels of Simulation Convergence

6

I am looking for a functionality similar to openfoams fieldAverage function object. It doesn’t store everytime step, just the temporal average of the fields. If there isnt something like this for steady state simulations in Simscale I would love to have it implemented. I use openFoam in industry and we use the fieldAverage function object for every run. I think it is an important tool to have in SimScale if it’s not already there.

Cheers!

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7

A similar function is available under result controls > Area averages, however it allows only the selection of faces, not volumes. You can also do area integrals instead of averages (e.g. to get flow rates).

Cheers