The
Define/Models/Viscous... menu item opens the
Viscous Model panel.
Viscous Model Panel
The
Viscous Model panel allows you to set parameters for inviscid, laminar, and turbulent flow. See Section
12.12 for details about using this panel to set up a turbulent flow calculation.
Controls
Model
contains options for specifying the viscous model.
Inviscid
specifies inviscid flow.
Laminar
specifies laminar flow.
SpalartAllmaras
specifies turbulent flow to be calculated using the SpalartAllmaras model. (See Section
12.3 for details about this model.)
kepsilon
specifies turbulent flow to be calculated using one of three

models. (See Section
12.4 for details about these models.)
komega
specifies turbulent flow to be calculated using one of two

models. (See Section
12.5 for details about these models.)
Reynolds Stress
specifies turbulent flow to be calculated using the RSM. (See Section
12.7 for details about this model.)
Detached Eddy Simulation
specifies turbulent flow to be calculated using the DES. (See Section
12.8 for details about this model.)
Large Eddy Simulation
(3D only) specifies turbulent flow to be calculated using the LES model. (See Section
12.9 for details about this model.)
SpalartAllmaras Options
contains options for the SpalartAllmaras model. This portion of the panel will appear only if
SpalartAllmaras is selected as the
Model.
VorticityBased Production
selects the vorticitybased calculation of the deformation tensor
(Equation
12.38).
Strain/VorticityBased Production
selects the strain/vorticitybased calculation of the deformation tensor
(Equation
12.310).
kepsilon Model
contains options for specifying which of the

models is to be used. This portion of the panel will appear only if
kepsilon is selected as the
Model.
Standard
selects the standard

model, described in Section
12.4.1.
RNG
selects the RNG

model, described in Section
12.4.2.
Realizable
selects the realizable

model, described in Section
12.4.3.
RNG Options
specifies parameters that affect the solution of problems solved with the RNG

model. This portion of the panel will appear only if
RNG is selected as the
kepsilon Model.
Differential Viscosity Model
specifies whether or not the lowReynoldsnumber RNG modifications to turbulent viscosity should be included. By default, this option is turned off. It is likely to have an effect only when the nearwall regions in the domain are well resolved in terms of grid density. See Section
12.19.5 for details.
Swirl Dominated Flow
specifies whether or not the RNG modification to turbulent viscosity for swirling flows should be included. This option is available only in 3D and 2D axisymmetric swirl solvers, and it can yield improved predictions when solving flows with significant swirl. See Section
12.19.6 for details.
komega Model
contains options for specifying which of the

models is to be used. This portion of the panel will appear only if
komega is selected as the
Model.
Standard
selects the standard

model, described in Section
12.5.1.
SST
selects the shearstress transport (SST)

model, described in
Section
12.5.2.
komega Options
specifies parameters that affect the solution of problems solved with the

models. This portion of the panel will appear only if
komega is selected as the
Model.
Transitional Flows
specifies whether or not a lowReynoldsnumber correction to the turbulent viscosity should be included for either of the

models. By default, this option is turned off. See Section
12.19.7 for details.
Compressibility Effects
includes the effects of compressibility in the calculations.
Shear Flow Corrections
specifies whether corrections that improve the accuracy in predicting free shear flows should be included. This option is available only for the standard

model. See Section
12.19.8 for details.
ReynoldsStress Model
specifies the various Reynolds stress models (RSM).
Linear PressureStrain
enables the linear pressurestrain model. See Section
12.7.4 for details.
Quadratic PressureStrain
enables the quadratic pressurestrain model for superior performance in a range of basic shear flows, including plane strain, rotating plane shear, and axisymmetric expansion/contraction. See Section
12.7.4 for details. Note that this option cannot be used with the
Wall Reflection Effects option or the
Enhanced Wall Treatment.
LowRe StressOmega
enables a stresstransport model that is based on the omega equations and LRR model [
403]. This model is ideal for modeling flows over curved surfaces and swirling flows. See Section
12.7.4 for details.
ReynoldsStress Options
specifies parameters that affect the solution of problems solved with the Reynolds stress model. This portion of the panel will appear only if
Reynolds Stress is selected as the
Model.
Wall BC from k Equation
enables the explicit setting of boundary conditions for the Reynolds stresses near the walls, using the values computed with Equation
12.734. See Section
12.19.12 for details. This option is on by default.
Wall Reflection Effects
enables the calculation of the component of the pressure strain term responsible for the redistribution of normal stresses near the wall. See Section
12.19.11 for details. Note that this option is not available if you have enabled the
Quadratic PressureStrain Model.
RANS Model
contains options for the subgridscale model used by the
Detached Eddy Simulation Model. This portion of the panel will appear only if
Detached Eddy Simulation Model is selected as the
Model.
SpalartAllmaras
enables the SpalartAllmaras RANS model. See Section
12.8 for details.
Realizable kepsilon
enables the Realizable

RANS model. See Section
12.8 for details.
SST komega
enables the SST

RANS Model. See Section
12.8 for details.
SubgridScale Model
contains options for the subgridscale model used by the LES model. This portion of the panel will appear only if
Large Eddy Simulation is selected as the
Model.
SmagorinskyLilly
selects the SmagorinskyLilly subgridscale model described in Section
12.9.3.
WALE
selects the WallAdapting local EddyViscosity model described in Section
12.9.3
KineticEnergy Transport
selects the dynamic kinetic energy subgridscale model described in Section
12.9.3.
LES Model Options
contains options for the Large Eddy Simulation model. This portion of the panel will appear only if
Large Eddy Simulation is selected as the
Model.
Dynamic Stress
enables the dynamic stress model. It is available when the LES option
SmagorinskyLilly is enabled.
Dynamic Energy Flux
enables the dynamic energy flux model. It is available when the LES option
KineticEnergy Transport is enabled.
Dynamic Scalar Flux
enables the dynamic computation of turbulent
Sc (
in Equation
15.25). See Section
15.2.1 for details.
NearWall Treatment
specifies the nearwall treatment to be used for modeling turbulence. See Section
12.10 for details about the available methods. This portion of the panel will appear if
kepsilon or
Reynolds Stress is selected as the
Model.
Standard Wall Functions
enables the use of standard wall functions (described in Section
12.10.2).
NonEquilibrium Wall Functions
enables the use of nonequilibrium wall functions (described in Section
12.10.3).
Enhanced Wall Treatment
enables the use of the enhanced wall treatment (described in Section
12.10.4). Note that this option will not appear if you have enabled the
Quadratic PressureStrain Model under
ReynoldsStress Options.
Enhanced Wall Treatment Options
allows you to include pressure gradient or thermal effects in the calculation. See Section
12.10
Pressure Gradient Effects
enables the effect of pressure gradient.
Thermal Effects
enables thermal effects in the calculation. This option appears only if the energy equation is enabled.
Options
contains general options for viscous modeling.
Viscous Heating
(if enabled) includes the viscous dissipation terms in the energy equation. This option is recommended when you are solving a compressible flow. Note that this option is always turned on when one of the densitybased solvers is used; you will not be able to turn it off.
LowPressure Boundary Slip
includes slip boundary conditions for velocity and temperature for modeling fluid flow at very low pressures as in semiconductor fabrication devices. See Section
14.2.2. This option is available only for laminar flows.
Full Buoyancy Effects
enables the inclusion of buoyancy effects on
. See Section
12.19.2 for details. This option will appear if
kepsilon or
Reynolds Stress is selected as the
Modeland a nonzero gravitational acceleration has been specified in the
Operating Conditions panel.
kepsilon Multiphase Model
contains options for multiphase turbulence models. This portion of the panel will appear if
Eulerian is selected as the
Model in the
Multiphase Model panel.
Mixture
specifies the (default) mixture turbulence model.
Dispersed
specifies the dispersed turbulence model.
Per Phase
specifies the calculation of a set of turbulence equations for each phase.
See Section
23.5.10 for details about the available multiphase turbulence models.
Model Constants
contains constants used in the equations for turbulence. See Sections
12.3,
12.4.1,
12.4.2,
12.4.3,
12.7,
12.5.1,
12.5.2, and
12.9 for details about these constants.
Cb1
(only for the SpalartAllmaras model) is the constant
in Equation
12.35.
Cb2
(only for the SpalartAllmaras model) is the constant
in Equation
12.31.
Cv1
(only for the SpalartAllmaras model) is the constant
in Equation
12.33.
Cw2
(only for the SpalartAllmaras model) is the constant
in Equation
12.314.
Cw3
(only for the SpalartAllmaras model) is the constant
in Equation
12.313.
Cprod
(only for the SpalartAllmaras model when the
Strain/VorticityBased Production option is used) is the constant
in Equation
12.310.
Cmu
(only for the standard or RNG

model or the RSM) is the constant
that is used to compute
.
C1Epsilon
(only for the standard or RNG

model or the RSM) is the constant
used in the transport equation for
.
C2Epsilon
(only for the standard, RNG, or realizable

model or the RSM) is the constant
used in the transport equation for
.
C3Epsilon
(only for the dispersed or perphase

multiphase models) is the constant
in Equation
23.5116.
Swirl Factor
sets the value of
in Equation
12.48. This item appears for the RNG

model when the
Swirl Dominated Flow option is turned on.
Alpha*_inf
(only for the standard or SST

model) is the constant
in Equation
12.56.
Alpha_inf
(only for the standard or SST

model) is the constant
in Equation
12.514.
Alpha_0
(only for the standard or SST

model with the
Transitional Flows option enabled) is the constant
in Equation
12.514.
Beta*_inf
(only for the standard or SST

model) is the constant
in Equation
12.519.
Beta_i
(only for the standard

model) is the constant
in Equation
12.527.
R_beta
(only for the standard or SST

model) is the constant
in Equation
12.519.
R_k
(only for the standard or SST

model with the
Transitional Flows option enabled) is the constant
in Equation
12.56.
R_w
(only for the standard or SST

model with the
Transitional Flows option enabled) is the constant
in Equation
12.514.
Zeta*
(only for the standard or SST

model) is the constant
in Equation
12.518.
Mt0
(only for the standard or SST

model) is the constant
in Equation
12.528.
a1
(only for the SST

model) is the constant
in Equation
12.536.
Beta_i (Inner)
(only for the SST

model) is the constant
in
Section
12.5.2.
Beta_i (Outer)
(only for the SST

model) is the constant
in
Section
12.5.2.
Cs
(only for LES) is the Smagorinsky constant
in Equation
12.916.
C1PS
(only for RSM) is the constant
in Equation
12.75.
C2PS
(only for RSM) is the constant
in Equation
12.76.
C1'PS
(only for RSM) is the constant
in Equation
12.77.
C2'PS
(only for RSM) is the constant
in Equation
12.77.
C1SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C1'SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C2SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C3SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C3'SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C4SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
C5SSGPS
(only for RSM with the
Quadratic PressureStrain Model) is the constant
in Equation
12.716.
Prandtl Number
(only for the SpalartAllmaras model) is the constant
in Equation
12.31.
TKE Prandtl Number
(only for the standard or realizable

model, the standard or SST

model, or the RSM) is the effective "Prandtl'' number for transport of turbulence kinetic energy
. This effective Prandtl number defines the ratio of the momentum diffusivity to the diffusivity of turbulence kinetic energy via turbulent transport.
TKE (Inner) Prandtl #
(only for the SST

model) is the effective "Prandtl'' number for the transport of turbulence kinetic energy,
, inside the nearwall region. See Section
12.5.2 for details.
TKE (Outer) Prandtl #
(only for the SST

model) is the effective "Prandtl'' number for the transport of turbulence kinetic energy,
, outside the nearwall region. See Section
12.5.2 for details.
TDR Prandtl Number
is the effective "Prandtl'' number for transport of the turbulent dissipation rate,
, for the standard or realizable

model or the RSM. This effective Prandtl number defines the ratio of the momentum diffusivity to the diffusivity of turbulence dissipation via turbulent transport.
For the standard

model, the
TDR Prandtl Number is the effective "Prandtl'' number for the transport of the specific dissipation rate,
.
SDR (Inner) Prandtl #
(only for the SST

model) is the effective "Prandtl'' number for the transport of the specific dissipation rate,
, inside the nearwall region. See Section
12.5.2 for details.
SDR (Outer) Prandtl #
(only for the SST

model) is the effective "Prandtl'' number for the transport of the specific dissipation rate,
, outside the nearwall region. See Section
12.5.2 for details.
Dispersion Prandtl Number
(only for the

multiphase models) is the effective "Prandtl'' number for the dispersed phase,
. See Section
23.5.10 for details.
Energy Prandtl Number
(for any turbulence model except the RNG

model) is the turbulent Prandtl number for energy, Pr
, in Equation
12.726. (This item will not appear for premixed or partially premixed combustion models.)
Wall Prandtl Number
(for all turbulence models) is the turbulent Prandtl number at the wall, Pr
in Equation
12.105. (This item will not appear for adiabatic premixed combustion or partially premixed combustion models.)
Turb. Schmidt Number
(for turbulent species transport calculations using any turbulence model except the RNG

model) is the turbulent Schmidt number, Sc
, in Equation
14.13.
PDF Schmidt Number
(for nonpremixed or partially premixed combustion calculations using any turbulence model) is the model constant
in Equation
15.25.
UserDefined Functions
allows you to select the userdefined functions for various constants.
Turbulent Viscosity
appears for Spalart Allmaras,

and

models. You can select the userdefined functions for turbulent viscosity in the dropdown list.
Prandtl Numbers
contains a list of relevant Prandtl numbers for which you can select userdefined functions.
TKE Prandtl Number
allows you to select a userdefined function to define the TKE Prandtl number for the standard and realizable

models and the standard

model.
TDR Prandtl Number
allows to select a userdefined function to define the TDR Prandtl number for the standard and realizable

models.
Energy Prandtl Number
allows you to select a userdefined function to define the Energy Prandtl number for the standard and realizable

models and the standard

model when energy is enabled.
Wall Prandtl Number
allows you to select a userdefined function to define the Wall Prandtl number for the standard and realizable

models and the standard

model when energy is enabled.
SDR Prandtl Number
allows you to select a userdefined function to define the SDR Prandtl number for the standard

model.
SubgridScale Turbulent Viscosity
allows you to select a userdefined function for the subgridscale turbulent viscosity for the LES model.