# turbulence model equation

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 December 28, 2009, 08:49 turbulence model equation #1 Member   Yi-Lang Chen Join Date: May 2009 Posts: 58 Rep Power: 17 Dear experts: Turbulence model have one equation(turbulent energy model) that have dissipation term.Another, two equation(k-e model) that e was turbulence disspation transport equation. And, what about different on dissipation term and turbulence dissipation transport equation. I studied paper. Everyone usually use one equation(turbulent energy model) to calculate turbulent energy dissipation budget. And FLOW-3D can output turbulence dissipation. But it seems different between on dissipation term and FLOW-3D output turbulence dissipation. Thanks your help!

December 31, 2009, 19:50
#2
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michael barkhudarov
Join Date: Mar 2009
Location: Sante Fe, New Mexico, USA
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Quote:
 Originally Posted by Andy Chen Dear experts: Turbulence model have one equation(turbulent energy model) that have dissipation term.Another, two equation(k-e model) that e was turbulence disspation transport equation. And, what about different on dissipation term and turbulence dissipation transport equation. I studied paper. Everyone usually use one equation(turbulent energy model) to calculate turbulent energy dissipation budget. And FLOW-3D can output turbulence dissipation. But it seems different between on dissipation term and FLOW-3D output turbulence dissipation. Thanks your help!
Hi,

What difference do you see between dissipation term in the turbulent energy equation and turbulent dissipation? They are the same, aint they?

January 1, 2010, 03:27
#3
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Yi-Lang Chen
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Quote:
 Originally Posted by mike@flow3d.com Hi, What difference do you see between dissipation term in the turbulent energy equation and turbulent dissipation? They are the same, aint they?
I think that difference on unit. Beacuse the unit of dissipation term in one equation (turbulent energy equation) is [m^2/s^3] and the unit of turbulent transport dissipation (two eauations) is [kg/m/s^2]. Are they the same?

January 1, 2010, 17:55
#4
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michael barkhudarov
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Quote:
 Originally Posted by Andy Chen I think that difference on unit. Beacuse the unit of dissipation term in one equation (turbulent energy equation) is [m^2/s^3] and the unit of turbulent transport dissipation (two eauations) is [kg/m/s^2]. Are they the same? Thanks your reply mike!
The difference in your units is just density. Divide your turbulent transport dissipation by density and you have the same units. In any case, the two dissipations are the same quantities. In FLOW-3D turbulent dissipation has units of m^2/s^3.

January 1, 2010, 21:45
#5
Member

Yi-Lang Chen
Join Date: May 2009
Posts: 58
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Quote:
 Originally Posted by mike@flow3d.com The difference in your units is just density. Divide your turbulent transport dissipation by density and you have the same units. In any case, the two dissipations are the same quantities. In FLOW-3D turbulent dissipation has units of m^2/s^3.
Ok, I see. Thanks your help, Mike.