# Turbulent viscosity in Laminar Flow

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 March 24, 2003, 08:45 Turbulent viscosity in Laminar Flow #1 Mike Guest   Posts: n/a Hi, I would like to know if a laminar flow (not potential flow), has got the turbulent or eddy viscosity? If the answer is yes, in which way I can compute it? Thank you Mike

 March 24, 2003, 08:52 Re: Turbulent viscosity in Laminar Flow #2 ag Guest   Posts: n/a No. By definition a laminar flow has no turbulence. Eddy viscosity is a model for how turbulence works, and is computed using turbulence models, developed to simulate turbulent flows.

 March 24, 2003, 08:57 Re: Turbulent viscosity in Laminar Flow #3 Mike Guest   Posts: n/a Thank you! Another question: is the eddy viscosity proportional with an another (non turbulent) quantity? I.e., the kinematic viscosity?

 March 24, 2003, 09:40 Re: Turbulent viscosity in Laminar Flow #4 Steve Guest   Posts: n/a Have a look at pages 6-7 of the following link. ftp://ftp.nist.gov/pub/bfrl/mcgratta...S/techman3.pdf I am sure this can help you. Steve

 April 10, 2010, 17:48 #5 New Member   Santhosh Join Date: Oct 2009 Posts: 14 Rep Power: 16 Steve, th link given by you is nt working anymore. Can you post an updated one.

 April 12, 2010, 08:56 #6 Senior Member   Join Date: Jul 2009 Posts: 357 Rep Power: 18 You do realize that the thread you resurrected is 7 years old, and Steve may not inhabit these fora anymore, don't you?

April 12, 2010, 09:04
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Sydney Miles TEKAM
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Quote:
 Originally Posted by Mike ;23761 Thank you! Another question: is the eddy viscosity proportional with an another (non turbulent) quantity? I.e., the kinematic viscosity?
Steve, eddy and turbulent viscosity are properties of the flow.
Kinematic viscosity is a property of the flui. It remains constant in every area of most common flow.

 April 12, 2010, 09:21 #8 New Member   Santhosh Join Date: Oct 2009 Posts: 14 Rep Power: 16 ooops.. I didnt realize, I thought the qn was still relevant today..!

 April 12, 2010, 11:40 turbulent flows #9 New Member   Patrick Godon Join Date: Apr 2010 Posts: 19 Rep Power: 17 Eventhough the original post is 7 years old... I thought maybe someone might still be interested in that topics.. or for all others who might be interested... In a turbulent flow the size of the Eddies L can be as large as the size of the domain and the velocity of the eddies is as large as the change in the velocity over a distance L, so Vturb ~ V(x+L)-V(x) , such that the viscosity of the turubulence can be written viscosity from tubulence ~ Vturb L Usually supersonic eddies dissipate quickly by shocks such that Vturb < Vsound . In the limit of small L, one can write Vturb = V(x+L)-V(x) = (dV/dx) L such that turbulent viscosity ~ L^2 (dV/dx) the turbulent viscosiity is proportional to the shear dV/dx