Exporting expression data from *.trn timesteps

smallzilla · January 7, 2015, 21:27

Hi,

I have a few transient simulations running an airfoil at various angles of attack. I have created expressions to determine the Coefficients of Lift, Drag, and Quarter Chord Moment (Cl, Cd, Cm). I have roughly 300 *.trn files that I would like to extract my user defined expressions to do a time dependent average of those coefficients.

One approach I have taken is to create a table and then put my expressions in a table cell.
ex: A1 =Cl, B1 = Cd, C1 = Cm

when changing time steps I see that it the coefficients change slightly. So this is why I want to average them out. Is there a straight forward way that I could have it print all three of these expressions from each *.trn timestep in there respective columns to export? Or is there a much easier process of doing this that I am missing that will automatically average the coefficients for me at the end of a simulation? would averaging the pressure at the airfoil wall then using only that give me the same result I am trying to find, that is; skipping the need to extract each coefficient timestep then average them out?

I am using CFX 15.0

monkey1 · January 8, 2015, 02:52

Maybe just have a look at that thread
http://www.cfd-online.com/Forums/cfx...tml#post385850
I posted there a script file that loads every time step and reads out desired values and prints them in a csv file. In the uploaded example those are the min and max values for x and y. But you could implement any desired cel function

smallzilla · January 8, 2015, 10:15

I just realized you can create a chart using transient data as a series/sequence. This allows you to select user created expression and plot them vs time. Then extract it to a *.csv file.

So, my other question if anyone could clarify for me for future transient cases. If I wanted to save hard drive space, and limit the data that I wanted to save in my *.trn files in CFX-Pre, or even elimnate having any. Would saving the absolute average pressure give me the same result for my Cl, Cd, Cm average of all the timesteps I have been working with?

Basically I would like to save as much hard drive space as I will have many cases to run. Do I even need to output that many *.trn files for my coefficient average.

January 7, 2015, 21:27	*Exporting expression data from .trn timesteps**	#1
smallzilla New Member Join Date: Jun 2014 Posts: 7 Rep Power: 12	Hi, I have a few transient simulations running an airfoil at various angles of attack. I have created expressions to determine the Coefficients of Lift, Drag, and Quarter Chord Moment (Cl, Cd, Cm). I have roughly 300 .trn files that I would like to extract my user defined expressions to do a time dependent average of those coefficients. One approach I have taken is to create a table and then put my expressions in a table cell. ex: A1 =Cl, B1 = Cd, C1 = Cm when changing time steps I see that it the coefficients change slightly. So this is why I want to average them out. Is there a straight forward way that I could have it print all three of these expressions from each .trn timestep in there respective columns to export? Or is there a much easier process of doing this that I am missing that will automatically average the coefficients for me at the end of a simulation? would averaging the pressure at the airfoil wall then using only that give me the same result I am trying to find, that is; skipping the need to extract each coefficient timestep then average them out? I am using CFX 15.0

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January 8, 2015, 02:52		#2
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 15	Maybe just have a look at that thread http://www.cfd-online.com/Forums/cfx...tml#post385850 I posted there a script file that loads every time step and reads out desired values and prints them in a csv file. In the uploaded example those are the min and max values for x and y. But you could implement any desired cel function

January 8, 2015, 10:15		#3
smallzilla New Member Join Date: Jun 2014 Posts: 7 Rep Power: 12	I just realized you can create a chart using transient data as a series/sequence. This allows you to select user created expression and plot them vs time. Then extract it to a .csv file. So, my other question if anyone could clarify for me for future transient cases. If I wanted to save hard drive space, and limit the data that I wanted to save in my .trn files in CFX-Pre, or even elimnate having any. Would saving the absolute average pressure give me the same result for my Cl, Cd, Cm average of all the timesteps I have been working with? Basically I would like to save as much hard drive space as I will have many cases to run. Do I even need to output that many *.trn files for my coefficient average.