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Turbulent viscosity in Laminar Flow

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Old   March 24, 2003, 08:45
Default Turbulent viscosity in Laminar Flow
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Mike
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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
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Old   March 24, 2003, 08:52
Default Re: Turbulent viscosity in Laminar Flow
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ag
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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.
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Old   March 24, 2003, 08:57
Default Re: Turbulent viscosity in Laminar Flow
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Mike
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Thank you!

Another question: is the eddy viscosity proportional with an another (non turbulent) quantity? I.e., the kinematic viscosity?
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Old   March 24, 2003, 09:40
Default Re: Turbulent viscosity in Laminar Flow
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Steve
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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
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Old   April 10, 2010, 17:48
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Santhosh
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Steve,

th link given by you is nt working anymore.

Can you post an updated one.
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Old   April 12, 2010, 08:56
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agd
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You do realize that the thread you resurrected is 7 years old, and Steve may not inhabit these fora anymore, don't you?
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Old   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.
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Old   April 12, 2010, 09:21
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Santhosh
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ooops..

I didnt realize, I thought the qn was still relevant today..!
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Old   April 12, 2010, 11:40
Default turbulent flows
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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
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