How to extract Instantaneous Velocity and RMS velocity from a LES solution?

susovanpal · May 5, 2017, 03:37

I have already run a LES simulation (Fluent) of 2D flow over a Dune and now I want to get urms and vrms. How I can calculate this?

LuckyTran · May 6, 2017, 17:35

Check the box to enable data sampling for time statistics. Unfortunately you have to run it again.

susovanpal · May 7, 2017, 02:33

Thank you for your advice. I have switched on time statistics and run the simulation again. Now many new data for export have appeared but still I am not getting any option for RMS velocity. I am attaching the new Quantities that appeared for exporting after I switched on time statistics.

LuckyTran · May 7, 2017, 15:32

RMSE X velocity and so on are your RMS's of the velocity fluctuations.

It's a common mistake because when people say RMS velocities then actually mean rms of the fluctuations.

Unless you actually want the RMS... then you just add the mean to the RMSE. Btw old versions of Fluent had the RMSE variables incorrectly labeled as RMS. I think newer versions will give you both RMS and RMSE.

May 5, 2017, 03:37	How to extract Instantaneous Velocity and RMS velocity from a LES solution?	#1
susovanpal New Member West Bengal Join Date: Jan 2016 Posts: 3 Rep Power: 10	I have already run a LES simulation (Fluent) of 2D flow over a Dune and now I want to get urms and vrms. How I can calculate this?

May 7, 2017, 15:32		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,679 Rep Power: 66	RMSE X velocity and so on are your RMS's of the velocity fluctuations. It's a common mistake because when people say RMS velocities then actually mean rms of the fluctuations. Unless you actually want the RMS... then you just add the mean to the RMSE. Btw old versions of Fluent had the RMSE variables incorrectly labeled as RMS. I think newer versions will give you both RMS and RMSE. AidealZohary likes this.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
LES and TKE calculations	MST	Main CFD Forum	3	May 30, 2016 06:26
Pressure distribution on a wall	darazsbence	CFX	17	October 6, 2015 10:38
Obtaining RMS of turbulent velocity fluctuations	rks171	Main CFD Forum	0	January 19, 2012 08:45
RMS velocity by DES or LES?	liweif	FLUENT	0	September 20, 2007 04:43
What's wrong with my RMS profile in LES	Jiang Ning	FLUENT	0	March 31, 2005 05:30

May 6, 2017, 17:35		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,679 Rep Power: 66	Check the box to enable data sampling for time statistics. Unfortunately you have to run it again.