Estimating velocity fluctuation's component based on Reynolds stress

Mariusz · August 23, 2014, 06:59

Hi,

Can I estimate the value of velocity fluctuation's component based on Reynolds stress tensor?

For example, if I have a simulation that is:
-steady state (simpleFoam)
-constant density
-turbulence is modeled using LRR RSM

and at the end of this simulation I'd like to estimate the values of velocity fluctuation's components in this way (example for z-direction fluctuation):

Code:

so

Code:

Is that correct?

Or are in simpleFoam the Reynolds stress tensor components already divided by density? In case of which it is already:

Code:

Is any of this correct?

huangxianbei · September 12, 2014, 22:19

I don't think so. You'd better use u-umean, considering your simulation is steady, it's impossible to estimate the fluctuation (my opinion)

August 23, 2014, 06:59	Estimating velocity fluctuation's component based on Reynolds stress	#1
Mariusz New Member MP Join Date: Jun 2011 Posts: 4 Rep Power: 14	Hi, Can I estimate the value of velocity fluctuation's component based on Reynolds stress tensor? For example, if I have a simulation that is: -steady state (simpleFoam) -constant density -turbulence is modeled using LRR RSM and at the end of this simulation I'd like to estimate the values of velocity fluctuation's components in this way (example for z-direction fluctuation): Code: $R_{zz}=\rho\overline{u'_z u'_z}=\rho\overline{(u')^2_z}$ so Code: $\overline{u'_z}=\frac{\sqrt{R_{zz}}}{\rho}$ Is that correct? Or are in simpleFoam the Reynolds stress tensor components already divided by density? In case of which it is already: Code: $\overline{u'_z}=\sqrt{R_{zz}}$ Is any of this correct?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Error message: Insufficient Catalogue Size	Paresh Jain	CFX	32	February 3, 2021 03:37
Howe to get swirl velocity component in 2D axisymtric swirl modeling	Perra	Fluent UDF and Scheme Programming	2	March 6, 2018 02:14
Superficial velocity component and velocity component?	zcesd47	CFX	0	July 20, 2011 05:31
Reynolds transport, turbulence model, etc	Beginner	Main CFD Forum	1	January 7, 2009 05:36
is there any method give node based velocity BC?	daniel	FLUENT	2	July 18, 2006 21:21

September 12, 2014, 22:19		#2
huangxianbei Senior Member Huang Xianbei Join Date: Sep 2013 Location: Yangzhou,China Posts: 302 Rep Power: 13	I don't think so. You'd better use u-umean, considering your simulation is steady, it's impossible to estimate the fluctuation (my opinion)