Algebraic models (zero-equation models) are the simplest turbulence models. These models use the Boussinesq eddy viscosity approximation to compute the Reynolds stress tensor as the product of an eddy viscosity and the mean strain-rate tensor. In contrast to the molecular viscosity, which is an intrinsic property of the fluid, the eddy viscosity depends on the flow. Most of them rely on Prandtl’s mixing length hypothesis and are specified by an algebraic relation between eddy viscosity and length scales of the mean flow. Thus, algebraic models are, by definition, incomplete models of turbulence. Although, they have proven to be useful in many engineering fields.

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Subsections

• Prandtl’s mixing length hypothesis