This section describes the theory behind the Standard, BSL, and SST 
-
models. Information is presented in the following sections:
For details about using the models in Ansys Fluent, see Modeling Turbulence and Setting Up the k-ω Model in the User's Guide.
This section presents the standard [708], baseline (BSL) [428], and shear-stress transport (SST) [428]
-
models. All three models have similar forms, with transport equations for
and 
. The major ways in which the BSL and SST models [432]
differ from the standard model are as follows:
gradual change from the standard
-
model in the inner region of the boundary layer to a high-Reynolds number
version of the 
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model in the outer part of the boundary layer (BSL, SST)modified turbulent viscosity formulation to account for the transport effects of the principal turbulent shear stress (SST only)
The transport equations, methods of calculating turbulent viscosity, and methods of calculating model constants and other terms are presented separately for each model.
Low Reynolds number modifications have been proposed by Wilcox for the k-
model and are available in Ansys Fluent. It is important to note that all
k-
models can be integrated through the viscous sublayer without these terms. The
terms were mainly added to reproduce the peak in the turbulence kinetic energy observed in DNS
data very close to the wall. In addition, these terms affect the laminar-turbulent transition
process. The low-Reynolds number terms can produce a delayed onset of the turbulent wall boundary
layer and constitute therefore a very simple model for laminar-turbulent transition. In general,
the use of the low-Reynolds number terms in the k-
models is not recommended, and it is advised to use the more sophisticated, and
more widely calibrated, models for laminar-turbulent transition instead.