Equation

The turbulence model is based on a standard k-e model, with buoyancy extension, see e.g. Rodi (1980). This model uses transport equations for the turbulent kinetic energy (TKE), k, and the dissipation of TKE, e, to describe the turbulence.

In the k-e closure model, the Prandtl number, which appears in the transport equations for k and e, can be modified explicitly following the empirical expression of Munk and Anderson (1948). This correction will introduce a damping of the buoyancy production in case of stable stratification. This damping is included by default.

Empirical constants

Four empirical constants can be specified for the standard k-e model: c1e, c2e, c3e are related to the equation for the dissipation of TKE and the Prandtl number (s_T) is used in the buoyancy production term. Cmy (c_m ) is an empiri­cal constant used in the expression for determination of the eddy viscosity (see Eddy Viscosity).

Several carefully calibrated empirical coefficients enter the k-e turbulence model. Therefore great care should be taken if you decide to alter any of these coefficients. The empirical constants are listed in Table 7.1.

Maximum and minimum values

Here you specify maximum and minimum values for the TKE, k, and the dis­sipation of TKE, e.