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Vertex Average solution

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Old   September 3, 2007, 09:18
Default Vertex Average solution
  #1
Omer
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Some of you already know that I have been working on both FLUENT and CFX for my thesis. And you have always been a great help to me .

Well, I have one more querry.

In FLUENT it is easier to create a monitor point to see how a transient result changes w.r.t time. And trying to extract the result in Postprocessing w.r.t time is not as easy as it can be done in CFX.

While creating the monitor points we have several options to plot a particle variable w.r.t time. Vertex minimum, maximum, average, integral, facet minimum, maximum...etc.

So we need to choose one such option, say Vertex Average, in my case.

But in CFX post, when we plot a variable w.r.t time, we don't have an option of such kind. Is there a way to specify this? If there is no way to do it. What is the default in CFX Post, does it take average values , minimum or maximum?

Thanking in advance!

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Old   September 4, 2007, 16:26
Default Re: Vertex Average solution
  #2
Stumpy
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Perhaps I've misunderstood, but if you plot a variable versus time then all you get is it's value at a series of points in time. The only way to get minimum, maximum, average etc values is to look at some range of time and then calculate the min, max, average over that time period. So in CFX-Post when you plot a variable versus time that is exactly what you get, there should be no ambiguity.
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Old   September 4, 2007, 16:45
Default Re: Vertex Average solution
  #3
CycLone
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Hi Omer,

Easier is relative; it depends on what you already know.

You're looking in the wrong place. When you set this up in Fluent, you are doing so before the run; you must do the same in CFX-Pre. If you want CFX to calculate average values, add these in the Output Control object under "Transient Statistics". When the run is complete, the transient statistics are available as variable fields in your results file.

-CycLone
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Old   September 6, 2007, 10:27
Default Re: Vertex Average solution
  #4
Omer
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Thanx Stumpy and Cyclone!

yes Stumpy. I didn't mean average over time. I was referring to monitor point variable values in FLUENT. When you use this option you can choose from Vertex Average, Minimum, Max, Facet Average......etc. This has to do with finite volume results itself for each elemental volume.

Yes, Cyclone I can choose the monitor points and the variable to monitor when I set up the Pre-case itself. But the point is I only pick the option "Pressure", from there I don't have options for Vertex Average, vertex minimum...etc.

I hope I am more clearer this time around. I cannot seem to explain it in a proper way.

Thanx

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Old   September 6, 2007, 14:19
Default Re: Vertex Average solution
  #5
CycLone
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I see. Right now there is no way to average the monitor point data, but you can right click on the plot and export the data to a .csv file, which you can then load into your favorite spreadsheet application to get your statistics.

-CycLone
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Old   September 7, 2007, 22:27
Default Re: Vertex Average solution
  #6
TB
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Hi... If you are only interested in post processing your transient results, it can be done relatively easy in CFX. Just create the points & variables on the spot that you are interested, and then create a new variable to get a max, min, mean value etc of all these points from post. You can plot this new variable vs time straight away. The procedure sounds tedious, but Post has a very good programming tool attached with it. What you have described here can be done automatically by creating a perl program in CFX Post. Graphical interface is usually for begineer only. Don't jump into conclusion too fast, if you're only played with it a few times only.

However, you maybe right if you're talking about Solver. So far as I know, you can't create a mean value vs time while you are solving the transient problem. I'm not sure if CFX has added new feature in the latest version. I only got it up to Version 10. Can Fluent do that anyway?
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Old   September 9, 2007, 17:31
Default Re: Vertex Average solution
  #7
Omer
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Thanx Everyone!

But I guess I am not really clear at all. I know how to use post processing in CFX, I can hold my own on that I guess. Atleast that is not the problem.

The point is when I monitor points for pressure in FLUENT I can use a whole range of options for say, vertex averaged, minimum, maximum, facet average,facet minimum , integral.....etc etc. That is the pressure would be either a vertex average value (if I choose that option) for each sub-timestep. Not an average over the whole simulation time!

CFX doesn't have that options, or does it? If there is , how to activate it. If there is no such option, what is the default? I mean, the pressure value that we read for each timstep, is it an vertex average, minima, integral.....etc.

Thanks again!

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