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Eddy viscosity is a model viscosity. It is used to account for the effects lost in averaging the turbulent effects in a CFD simulation. More specifically, it models the transport and dissipation of energy that was neglected as a result of turbulence modeling. These turbulence models are abstract fundamental equations that predict the mathematical development of turbulent flows
Eddy viscosity is the proportionality factor describing the turbulent transfer of energy as a result of moving eddies, giving rise to tangential stresses.
It is also referred to as turbulent viscosity and doesn’t have any physical existence.
One can, thus, express the effective viscosity of the fluid flow as:
where,
Hence, it wouldn’t be inaccurate to say that the difference between different turbulence models is the difference in calculating turbulent viscosity.
In Computational Fluid Dynamics, turbulence models where eddies of all scales are completely modeled, for e.g. RANS (Reynolds Averaged Navier Stokes) models like
Hence, for sub-grid scale models equation (1) becomes
Where,
SimScale allows its users to define dynamic turbulent viscosity
Since,
the value for
References
Last updated: January 12th, 2025
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