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32.3.4 Define/Models/Viscous...

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.

figure

Controls

Model   contains options for specifying the viscous model.

Inviscid   specifies inviscid flow.

Laminar   specifies laminar flow.

Spalart-Allmaras   specifies turbulent flow to be calculated using the Spalart-Allmaras model. (See Section  12.3 for details about this model.)

k-epsilon   specifies turbulent flow to be calculated using one of three $k$- $\epsilon$ models. (See Section  12.4 for details about these models.)

k-omega   specifies turbulent flow to be calculated using one of two $k$- $\omega$ 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.)

Spalart-Allmaras Options   contains options for the Spalart-Allmaras model. This portion of the panel will appear only if Spalart-Allmaras is selected as the Model.

Vorticity-Based Production   selects the vorticity-based calculation of the deformation tensor $S$ (Equation  12.3-8).

Strain/Vorticity-Based Production   selects the strain/vorticity-based calculation of the deformation tensor $S$ (Equation  12.3-10).

k-epsilon Model   contains options for specifying which of the $k$- $\epsilon$ models is to be used. This portion of the panel will appear only if k-epsilon is selected as the Model.

Standard   selects the standard $k$- $\epsilon$ model, described in Section  12.4.1.

RNG   selects the RNG $k$- $\epsilon$ model, described in Section  12.4.2.

Realizable   selects the realizable $k$- $\epsilon$ model, described in Section  12.4.3.

RNG Options   specifies parameters that affect the solution of problems solved with the RNG $k$- $\epsilon$ model. This portion of the panel will appear only if RNG is selected as the k-epsilon Model.

Differential Viscosity Model   specifies whether or not the low-Reynolds-number 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 near-wall 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.

k-omega Model   contains options for specifying which of the $k$- $\omega$ models is to be used. This portion of the panel will appear only if k-omega is selected as the Model.

Standard   selects the standard $k$- $\omega$ model, described in Section  12.5.1.

SST   selects the shear-stress transport (SST) $k$- $\epsilon$ model, described in
Section  12.5.2.

k-omega Options   specifies parameters that affect the solution of problems solved with the $k$- $\omega$ models. This portion of the panel will appear only if k-omega is selected as the Model.

Transitional Flows   specifies whether or not a low-Reynolds-number correction to the turbulent viscosity should be included for either of the $k$- $\omega$ 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 $k$- $\omega$ model. See Section  12.19.8 for details.

Reynolds-Stress Model   specifies the various Reynolds stress models (RSM).
Linear Pressure-Strain   enables the linear pressure-strain model. See Section  12.7.4 for details.

Quadratic Pressure-Strain   enables the quadratic pressure-strain 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.

Low-Re Stress-Omega   enables a stress-transport 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.

Reynolds-Stress 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  12.7-34. 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 Pressure-Strain Model.

RANS Model   contains options for the subgrid-scale 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.
Spalart-Allmaras   enables the Spalart-Allmaras RANS model. See Section  12.8 for details.

Realizable k-epsilon   enables the Realizable $k$- $\epsilon$ RANS model. See Section  12.8 for details.

SST k-omega   enables the SST $k$- $\omega$ RANS Model. See Section  12.8 for details.

Subgrid-Scale Model   contains options for the subgrid-scale model used by the LES model. This portion of the panel will appear only if Large Eddy Simulation is selected as the Model.

Smagorinsky-Lilly   selects the Smagorinsky-Lilly subgrid-scale model described in Section  12.9.3.

WALE   selects the Wall-Adapting local Eddy-Viscosity model described in Section  12.9.3

Kinetic-Energy Transport   selects the dynamic kinetic energy subgrid-scale 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 Smagorinsky-Lilly is enabled.

Dynamic Energy Flux   enables the dynamic energy flux model. It is available when the LES option Kinetic-Energy Transport is enabled.

Dynamic Scalar Flux   enables the dynamic computation of turbulent Sc ( $\sigma_t$ in Equation  15.2-5). See Section  15.2.1 for details.

Near-Wall Treatment   specifies the near-wall 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 k-epsilon or Reynolds Stress is selected as the Model.

Standard Wall Functions   enables the use of standard wall functions (described in Section  12.10.2).

Non-Equilibrium Wall Functions   enables the use of non-equilibrium 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 Pressure-Strain Model under Reynolds-Stress 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 density-based solvers is used; you will not be able to turn it off.

Low-Pressure 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 $\epsilon$. See Section  12.19.2 for details. This option will appear if k-epsilon or Reynolds Stress is selected as the Model and a non-zero gravitational acceleration has been specified in the Operating Conditions panel.

k-epsilon 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 Spalart-Allmaras model) is the constant $C_{b1}$ in Equation  12.3-5.

Cb2   (only for the Spalart-Allmaras model) is the constant $C_{b2}$ in Equation  12.3-1.

Cv1   (only for the Spalart-Allmaras model) is the constant $C_{v1}$ in Equation  12.3-3.

Cw2   (only for the Spalart-Allmaras model) is the constant $C_{w2}$ in Equation  12.3-14.

Cw3   (only for the Spalart-Allmaras model) is the constant $C_{w3}$ in Equation  12.3-13.

Cprod   (only for the Spalart-Allmaras model when the Strain/Vorticity-Based Production option is used) is the constant $C_{\rm prod}$ in Equation  12.3-10.

Cmu   (only for the standard or RNG $k$- $\epsilon$ model or the RSM) is the constant $C_{\mu}$ that is used to compute $\mu_t$.

C1-Epsilon   (only for the standard or RNG $k$- $\epsilon$ model or the RSM) is the constant $C_{1\epsilon}$ used in the transport equation for $\epsilon$.

C2-Epsilon   (only for the standard, RNG, or realizable $k$- $\epsilon$ model or the RSM) is the constant $C_{2\epsilon}$ used in the transport equation for $\epsilon$.

C3-Epsilon   (only for the dispersed or per-phase $k$- $\epsilon$ multiphase models) is the constant $C_{3\epsilon}$ in Equation  23.5-116.

Swirl Factor   sets the value of $\alpha_s$ in Equation  12.4-8. This item appears for the RNG $k$- $\epsilon$ model when the Swirl Dominated Flow option is turned on.

Alpha*_inf   (only for the standard or SST $k$- $\omega$ model) is the constant $\alpha^*_\infty$ in Equation  12.5-6.

Alpha_inf   (only for the standard or SST $k$- $\omega$ model) is the constant $\alpha_\infty$ in Equation  12.5-14.

Alpha_0   (only for the standard or SST $k$- $\omega$ model with the Transitional Flows option enabled) is the constant $\alpha_0$ in Equation  12.5-14.

Beta*_inf   (only for the standard or SST $k$- $\omega$ model) is the constant $\beta^*_\infty$ in Equation  12.5-19.

Beta_i   (only for the standard $k$- $\omega$ model) is the constant $\beta_i$ in Equation  12.5-27.

R_beta   (only for the standard or SST $k$- $\omega$ model) is the constant $R_\beta$ in Equation  12.5-19.

R_k   (only for the standard or SST $k$- $\omega$ model with the Transitional Flows option enabled) is the constant $R_k$ in Equation  12.5-6.

R_w   (only for the standard or SST $k$- $\omega$ model with the Transitional Flows option enabled) is the constant $R_\omega$ in Equation  12.5-14.

Zeta*   (only for the standard or SST $k$- $\omega$ model) is the constant $\zeta^*$ in Equation  12.5-18.

Mt0   (only for the standard or SST $k$- $\omega$ model) is the constant ${\rm M}_{t0}$ in Equation  12.5-28.

a1   (only for the SST $k$- $\omega$ model) is the constant $a_1$ in Equation  12.5-36.

Beta_i (Inner)   (only for the SST $k$- $\omega$ model) is the constant $\beta_{i,1}$ in
Section  12.5.2.

Beta_i (Outer)   (only for the SST $k$- $\omega$ model) is the constant $\beta_{i,2}$ in
Section  12.5.2.

Cs   (only for LES) is the Smagorinsky constant $C_s$ in Equation  12.9-16.

C1-PS   (only for RSM) is the constant $C_1$ in Equation  12.7-5.

C2-PS   (only for RSM) is the constant $C_2$ in Equation  12.7-6.

C1'-PS   (only for RSM) is the constant $C'_1$ in Equation  12.7-7.

C2'-PS   (only for RSM) is the constant $C'_2$ in Equation  12.7-7.

C1-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_1$ in Equation  12.7-16.

C1'-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_1^*$ in Equation  12.7-16.

C2-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_2$ in Equation  12.7-16.

C3-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_3$ in Equation  12.7-16.

C3'-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_3^*$ in Equation  12.7-16.

C4-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_4$ in Equation  12.7-16.

C5-SSG-PS   (only for RSM with the Quadratic Pressure-Strain Model) is the constant $C_5$ in Equation  12.7-16.

Prandtl Number   (only for the Spalart-Allmaras model) is the constant $\sigma_{\tilde{\nu}}$ in Equation  12.3-1.

TKE Prandtl Number   (only for the standard or realizable $k$- $\epsilon$ model, the standard or SST $k$- $\omega$ model, or the RSM) is the effective "Prandtl'' number for transport of turbulence kinetic energy $\sigma_k$. 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 $k$- $\omega$ model) is the effective "Prandtl'' number for the transport of turbulence kinetic energy, $\sigma_{k,1}$, inside the near-wall region. See Section  12.5.2 for details.

TKE (Outer) Prandtl #   (only for the SST $k$- $\omega$ model) is the effective "Prandtl'' number for the transport of turbulence kinetic energy, $\sigma_{k,2}$, outside the near-wall region. See Section  12.5.2 for details.

TDR Prandtl Number   is the effective "Prandtl'' number for transport of the turbulent dissipation rate, $\sigma_{\epsilon}$, for the standard or realizable $k$- $\epsilon$ 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 $k$- $\omega$ model, the TDR Prandtl Number is the effective "Prandtl'' number for the transport of the specific dissipation rate, $\sigma_{\omega}$.

SDR (Inner) Prandtl #   (only for the SST $k$- $\omega$ model) is the effective "Prandtl'' number for the transport of the specific dissipation rate, $\sigma_{\omega,1}$, inside the near-wall region. See Section  12.5.2 for details.

SDR (Outer) Prandtl #   (only for the SST $k$- $\omega$ model) is the effective "Prandtl'' number for the transport of the specific dissipation rate, $\sigma_{\omega,2}$, outside the near-wall region. See Section  12.5.2 for details.

Dispersion Prandtl Number   (only for the $k$- $\epsilon$ multiphase models) is the effective "Prandtl'' number for the dispersed phase, $\sigma_{pq}$. See Section  23.5.10 for details.

Energy Prandtl Number   (for any turbulence model except the RNG $k$- $\epsilon$ model) is the turbulent Prandtl number for energy, Pr $_t$, in Equation  12.7-26. (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 $_t$ in Equation  12.10-5. (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 $k$- $\epsilon$ model) is the turbulent Schmidt number, Sc $_t$, in Equation  14.1-3.

PDF Schmidt Number   (for non-premixed or partially premixed combustion calculations using any turbulence model) is the model constant $\sigma_t$ in Equation  15.2-5.

User-Defined Functions   allows you to select the user-defined functions for various constants.

Turbulent Viscosity   appears for Spalart Allmaras, $k$- $\epsilon$ and $k$- $\omega$ models. You can select the user-defined functions for turbulent viscosity in the drop-down list.

Prandtl Numbers   contains a list of relevant Prandtl numbers for which you can select user-defined functions.

TKE Prandtl Number   allows you to select a user-defined function to define the TKE Prandtl number for the standard and realizable $k$- $\epsilon$ models and the standard $k$- $\omega$ model.

TDR Prandtl Number   allows to select a user-defined function to define the TDR Prandtl number for the standard and realizable $k$- $\epsilon$ models.

Energy Prandtl Number   allows you to select a user-defined function to define the Energy Prandtl number for the standard and realizable $k$- $\epsilon$ models and the standard $k$- $\omega$ model when energy is enabled.

Wall Prandtl Number   allows you to select a user-defined function to define the Wall Prandtl number for the standard and realizable $k$- $\epsilon$ models and the standard $k$- $\omega$ model when energy is enabled.

SDR Prandtl Number   allows you to select a user-defined function to define the SDR Prandtl number for the standard $k$- $\omega$ model.

Subgrid-Scale Turbulent Viscosity   allows you to select a user-defined function for the subgrid-scale turbulent viscosity for the LES model.


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