eddy viscosity

eddy viscosity

[‚ed·ē vi′skäs·əd·ē]
(fluid mechanics)
The turbulent transfer of momentum by eddies giving rise to an internal fluid friction, in a manner analogous to the action of molecular viscosity in laminar flow, but taking place on a much larger scale.
References in periodicals archive ?
The k - [epsilon] model, like the zero equation model, is based on the eddy viscosity concept, so that:
The turbulence modeling community has responded by developing model equations of ever increasing complexity, ranging from the nonlinear eddy viscosity models where the Reynolds stress is nonlinearly related to the mean rate of strain, to the full Reynolds-stress transport models where each component of the Reynolds stress is governed by its own transport equation (able to resolve secondary flows).
The eddy viscosity hypothesis assumes that Reynolds stresses can be related to mean velocity gradients and eddy (turbulent) viscosity by the gradient diffusion hypothesis in a manner analogous to the relationship between stress and strain tensors in laminar Newtonian flow:
Attempts have been made to overcome the inconsistency between the recorded data and Ekman theory by using numerical modelling including the depth-varying eddy viscosity (Madsen 1977; Huang 1979) and by complementing the physical background of the Ekman layer description with dynamic processes like the buoyancy flux, Stokes drift, etc.
Thus, it was not very surprising to see the good performance of these eddy viscosity models.
The k - [epsilon] turbulence model is an eddy--viscosity model in which the Reynolds stresses are assumed to be proportional to the mean velocity gradients, with the constant of proportionality being the turbulent eddy viscosity.
The third type of models to solve the boundary layer problems are eddy viscosity based models together with the equation of motion
For situations where a protective film was present the diffusion coefficient and eddy viscosity were modified by employing a film diffusion coefficient and film eddy viscosity:
KAYA, Numerical analysis of a subgrid scale eddy viscosity method for higher reynolds number flow problem, University of Pittsburgh, Technical report, (2002).
The tidal BCs and bottom roughness opted in the first calibration were used for the second calibration in which wind stress coefficient and eddy viscosity were determined once simulated and measured residual flow matched well.
In addition, FLUENT makes available a large suite of turbulence models ranging from one-equation eddy viscosity models through full second-moment closures.