For Reynolds stress models based on the -equation, the dissipation tensor is modeled as

(4–255)

where is an additional "dilatation dissipation" term according to the model by Sarkar  [566]. The turbulent Mach number in this term is defined as

(4–256)

where () is the speed of sound. This compressibility modification is available when the compressible form of the ideal gas law is used.

The scalar dissipation rate, , is computed with a model transport equation similar to that used in the standard - model:

(4–257)

where , , , is evaluated as a function of the local flow direction relative to the gravitational vector, as described in Effects of Buoyancy on Turbulence in the k-ε Models, and is a user-defined source term.

In the case when the Reynolds stress model is coupled with the - or BSL-equation, the dissipation tensor is modeled as

(4–258)

where is defined in the corresponding section of Modeling the Pressure-Strain Term. For the stress-omega model, the specific dissipation rate is computed in the same way as for the standard - model using Equation 4–72, whereas Equation 4–102 from the baseline (BSL) - model is used for the stress-BSL model.