eddy viscosity vs dynamic viscosity??

alpharays · August 11, 2014, 04:36

Hi all,

Anyone know whether eddy viscosity and dynamic viscosity are same or not?

Thanks
alpharays

tarjeiba · August 11, 2014, 04:54

No, they are definitely not the same. The dynamic viscosity is a macroscopic fluid property ... you can think of it as what distinguishes honey and water. The "eddy viscosity" is a flow property emerging from the increased momentum transport through the flow field due to turbulent velocity fluctuations.

In many turbulence models, the latter is included as an additional viscosity term and it is calculated from local turbulence properties in the flow field. (E.g. in the ubiquitous k-epsilon model, this is expressed $\mu_t = C_{\mu} \rho \frac{k^2}{\epsilon}$ , which is then added to the viscosity term in the averaged momentum equation.)

August 11, 2014, 04:36	eddy viscosity vs dynamic viscosity??	#1
alpharays New Member shahrul Join Date: Oct 2010 Location: Malaysia Posts: 23 Rep Power: 16	Hi all, Anyone know whether eddy viscosity and dynamic viscosity are same or not? Thanks alpharays

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August 11, 2014, 04:54		#2
tarjeiba New Member Tarjei Join Date: Aug 2013 Posts: 19 Rep Power: 13	No, they are definitely not the same. The dynamic viscosity is a macroscopic fluid property ... you can think of it as what distinguishes honey and water. The "eddy viscosity" is a flow property emerging from the increased momentum transport through the flow field due to turbulent velocity fluctuations. In many turbulence models, the latter is included as an additional viscosity term and it is calculated from local turbulence properties in the flow field. (E.g. in the ubiquitous k-epsilon model, this is expressed $\mu_t = C_{\mu} \rho \frac{k^2}{\epsilon}$ , which is then added to the viscosity term in the averaged momentum equation.)