How to create an average of an average?

Guille1811 · February 8, 2018, 13:52

Im running a transient simulation of 300 seconds. For the thread purposes, lets say the simulation is just a giant cube of air with heat exchange. My coordinate system is so that Y is the vertical axis, and X and Z the horizontal axises.

I need to get the value of the average temperature along the line [z=a,z=b] located at plane X=0 and at height y=1 [mt], along all the simulation. In other words, get the average temperature across that line each second, and then average all those 300 values.

What could be a good/efficient way of doing this?

PD: no extreme precision is needed for the results nor the method.

ghorrocks · February 8, 2018, 18:38

This should be reasonably straight forward in CFD-Post. Use a session file to automate the generation of the line and line averaged temperatures. Then you could use the session file to put them all in a spreadsheet tab and average them there, or if that does not work export it and use an external package like matlab/python/excel/whatever to average them all.

Guille1811 · February 9, 2018, 18:34

Yeah the thing i forgot to mention is that the lenght of the line, ie the value of "b" is a result of the simulation deduced by doing some analisis in cfx post, so i don´t know it before hand. Because of this, doing a session file for that line lenght doesnt seem possible.

Back to the original problem, basically what i need is, given a manually created line in cfx post, get an excel or txt with 2 columns: one being the average temperature of that line in that given time or timestep, and the other column being the corresponding time or timestep.

With function calculator for average temp on that line this could theoretically be done manually, but i have to do this for 20 simulations, 300 seconds each so this is not really an option...

ghorrocks · February 10, 2018, 06:12

Why don't you include the generation of the line in the CFD-Post session file?

Quote:

but i have to do this for 20 simulations, 300 seconds each so this is not really an option...

? That is exactly the situation where you would use a session file. If you are doing the same thing on lots of simulations over lots of time steps a session file can do this.

February 8, 2018, 13:52	How to create an average of an average?	#1
Guille1811 Member Join Date: Oct 2017 Posts: 89 Rep Power: 8	Im running a transient simulation of 300 seconds. For the thread purposes, lets say the simulation is just a giant cube of air with heat exchange. My coordinate system is so that Y is the vertical axis, and X and Z the horizontal axises. I need to get the value of the average temperature along the line [z=a,z=b] located at plane X=0 and at height y=1 [mt], along all the simulation. In other words, get the average temperature across that line each second, and then average all those 300 values. What could be a good/efficient way of doing this? PD: no extreme precision is needed for the results nor the method.

February 8, 2018, 18:38		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This should be reasonably straight forward in CFD-Post. Use a session file to automate the generation of the line and line averaged temperatures. Then you could use the session file to put them all in a spreadsheet tab and average them there, or if that does not work export it and use an external package like matlab/python/excel/whatever to average them all. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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February 9, 2018, 18:34		#3
Guille1811 Member Join Date: Oct 2017 Posts: 89 Rep Power: 8	Yeah the thing i forgot to mention is that the lenght of the line, ie the value of "b" is a result of the simulation deduced by doing some analisis in cfx post, so i don´t know it before hand. Because of this, doing a session file for that line lenght doesnt seem possible. Back to the original problem, basically what i need is, given a manually created line in cfx post, get an excel or txt with 2 columns: one being the average temperature of that line in that given time or timestep, and the other column being the corresponding time or timestep. With function calculator for average temp on that line this could theoretically be done manually, but i have to do this for 20 simulations, 300 seconds each so this is not really an option...