RMS root mean square velocity Fluent

C.C · July 31, 2013, 10:54

Hi all,

I want compare the root mean square velocity from my simulations with results from literature. I'm simulating a turbulent pipe flow with a low Reynolds k-e turbulence model in a steady state. From what i read i can obtain it in fluent if the problem is time dependent. As I'm simulating a steady state flow, can I obtain the RMS directly from Fluent?
Regards

flotus1 · July 31, 2013, 12:07

With the k-epsilon model, the turbulent kinetic energy $k=\frac{1}{2}\left[ \overline{u'u'} + \overline{v'v'} + \overline{w'w'}\right]$ is the only estimator you have for the actual Reynolds stresses in the turbulent flow.

To obtain the individual components of the Reynolds stresses, You have to perform a simulation with a reynolds stress turbulence model or a LES.
Among the transient statistics in fluent for a LES, you have the RMS-values of the fluctuating parts of the velocity components.

Far · July 31, 2013, 19:16

Yes, you can get root mean square velocity (also mean/average) in Fluent unsteady simulation. But you cannot get the different components of Reynolds stresses in RANS simulation.

CFDger · August 29, 2022, 12:14

Quote:

Originally Posted by Far

Yes, you can get root mean square velocity (also mean/average) in Fluent unsteady simulation. But you cannot get the different components of Reynolds stresses in RANS simulation.

Hello Far,

what would be the best way to calculate the rms of the velocity when I got my transient simulation in Fluent?

Thanks!

LuckyTran · August 29, 2022, 21:10

Enable the data sampling for time statistics, just click the box.

July 31, 2013, 10:54	RMS root mean square velocity Fluent	#1
C.C Member CC Join Date: Jun 2011 Posts: 73 Rep Power: 16	Hi all, I want compare the root mean square velocity from my simulations with results from literature. I'm simulating a turbulent pipe flow with a low Reynolds k-e turbulence model in a steady state. From what i read i can obtain it in fluent if the problem is time dependent. As I'm simulating a steady state flow, can I obtain the RMS directly from Fluent? Regards

July 31, 2013, 12:07		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,437 Rep Power: 50	With the k-epsilon model, the turbulent kinetic energy $k=\frac{1}{2}\left[ \overline{u'u'} + \overline{v'v'} + \overline{w'w'}\right]$ is the only estimator you have for the actual Reynolds stresses in the turbulent flow. To obtain the individual components of the Reynolds stresses, You have to perform a simulation with a reynolds stress turbulence model or a LES. Among the transient statistics in fluent for a LES, you have the RMS-values of the fluctuating parts of the velocity components. jzc likes this.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Difficulty in calculating angular velocity of Savonius turbine simulation	alfaruk	CFX	14	March 17, 2017 06:08
root mean square velocity	Far	CFX	12	June 1, 2016 08:58
Prob in rms velocity components, pls help..	sakurabogoda	CFX	5	February 13, 2013 21:30
how to calculate rms velocity fluctuation after runtime	nati	OpenFOAM Post-Processing	6	February 7, 2013 08:42
Can RMS velocity even be smaller than mean velocity?	lgas222	FLUENT	4	May 23, 2012 04:36

July 31, 2013, 19:16		#3
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,564 Blog Entries: 6 Rep Power: 55	Yes, you can get root mean square velocity (also mean/average) in Fluent unsteady simulation. But you cannot get the different components of Reynolds stresses in RANS simulation.

August 29, 2022, 21:10		#5
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,815 Rep Power: 68	Enable the data sampling for time statistics, just click the box.