The limitations of the eddy-viscosity approach are caused by the assumption of equilibrium between the turbulence and the mean strain field, as well as by the independence on system rotation. įlows with boundary layer separation and reattachment.Secondary flows in ducts and in turbomachinery, įlows with rotation and stratification,.įlows with significant streamline curvature,.įlows with sudden change of mean strain rate,.However, there are applications for which the Boussinesq hypothesis is no longer valid (see, e.g., p. Therefore, Boussinesq's approach became the basis for a large variety of first-order turbulence closures. Once we know the eddy viscosity μ T, we can easily extend the Navier-Stokes equations (2.19) or (7.1) to the simulation of turbulent flows by introducing averaged flow variables and by adding μ T to the laminar viscosity. (7.24) or (7.25) is either obtained as a by-product of the turbulence model or is simply omitted). The eddy-viscosity concept of Boussinesq is, at least from the engineering point of view, very attractive since it requires “only” the determination of μ T (the turbulent kinetic energy K needed for the term (2/3)ρ Kδ ij in Eq.
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