Merge pull request #75 from su2code/turbulence_update

SST and SA options

Author: pcarruscag

_docs_v7/Physical-Definition.md

@@ -18,12 +18,15 @@ SU2 offers different ways of setting and computing this definition. This documen
 - [Flow Condition (Incompressible)](#flow-condition-incompressible)
   - [Thermodynamic and Gauge Pressure](#thermodynamic-and-gauge-pressure)
   - [Initial State and Non-Dimensionalization](#initial-state-and-non-dimensionalization)
+- [Turbulence Models](#turbulence-models)
+  - [Spalart-Allmaras (SA)](#spalart-allmaras-model)
+  - [Shear Stress Transport (SST)](#shear-stress-transport)
 
 ---
 
 ## Reference Values ##
 
-| Solver | Version | 
+| Solver | Version |
 | --- | --- |
 | `EULER`, `NAVIER_STOKES`, `RANS`, `INC_EULER`, `INC_NAVIER_STOKES`, `INC_RANS`, `FEM_EULER`, `FEM_NAVIER_STOKES` | 7.0.0 |
 
@@ -47,7 +50,7 @@ The following table depicts the reference values used by most of the solvers in
 
 ## Free-Stream Definition (Compressible) ##
 
-| Solver | Version | 
+| Solver | Version |
 | --- | --- |
 | `EULER`, `NAVIER_STOKES`, `RANS`,`FEM_EULER`, `FEM_NAVIER_STOKES` | 7.0.0 |
 
@@ -79,7 +82,7 @@ For all schemes, as reference values for the density and temperature the free-st
 
 ## Flow Condition (Incompressible) ##
 
-| Solver | Version | 
+| Solver | Version |
 | --- | --- |
 | `INC_EULER`, `INC_NAVIER_STOKES`, `INC_RANS` | 7.0.0 |
 
@@ -97,3 +100,61 @@ The reference values $$\rho_{ref}, T_{ref}, v_{ref}$$ equal the initial state va
 
 **Note:** The initial state is also used as boundary conditions for `MARKER_FAR`.
 
+## Turbulence Models ##
+
+| Solver | Version |
+| --- | --- |
+| `*_RANS` | 7.4.0 |
+
+This section describes how to setup turbulence models for RANS simulations. Turbulence is activated using the option `KIND_SOLVER= RANS`, or `KIND_SOLVER= INC_RANS`
+A turbulence model can then be selected via the option `KIND_TURB_MODEL`
+Different submodels and parameters are specified via the different options listed below.
+The turbulent Prandtl number can be modified with the option `PRANDTL_TURB` (the default is 0.9).
+
+### Spalart-Allmaras (SA) ###
+
+SU2 implements several versions and corrections of the SA model.
+The model is selected using `KIND_TURB_MODEL= SA` and the modifications via the `SA_OPTIONS` list. If this list is empty, then SU2 defaults to `SA-noft2`.
+The freestream and inlet conditions are specified via the option `FREESTREAM_NU_FACTOR= 3` (ratio of SA variable to freestream kinematic viscosity).
+
+The following modifications are allowed (refer to [NASA's TMR](https://turbmodels.larc.nasa.gov/spalart.html) for further info):
+- Versions:
+  - `NEGATIVE` - Negative SA model.
+  - `EDWARDS` - Edwards modification.
+  - `BCM` - BCM transitional model.
+  - `WITHFT2` - SA model **with** ft2 term, note that by default we omit this term.
+- Corrections:
+  - `QCR2000` - Quadratic contitutive relation used in the stress tensor.
+  - `COMPRESSIBILITY` - Mixing layer compressibility correction.
+  - `ROTATION` - Dacles-Mariani et al. rotation correction.
+
+All the modifications can be combined with each other expect `NEGATIVE` and `EDWARDS`.
+For example, to specify `SA-neg-R-comp-QCR2000` use `SA_OPTIONS= NEGATIVE, WITHFT2, ROTATION, COMPRESSIBILITY, QCR2000`.
+**However, some combinations are not considered standard**, e.g. `SA-neg` should have the ft2 term, whereas `SA-noft2-Edwards` and `SA-noft2-BCM` should not have the ft2 term, and they are usually not combined with other corrections (see TMR for more details). To use non-standard combinations it is necessary to add `EXPERIMENTAL` to the option list, e.g. `SA_OPTIONS= NEGATIVE, BCM, EXPERIMENTAL`.
+
+The rough wall correction is implicitly turned on by specifying roughness values for wall markers via the `WALL_ROUGHNESS` option.
+
+### Shear Stress Transport (SST) ###
+
+SU2 implements the "Standard" (1994) and 2003 versions of the SST model along with several modifications.
+
+**Note:** Currently all versions are "modified" i.e. the turbulence kinetic energy (TKE) is not included in the viscous stress tensor.
+
+The main model is selected using `KIND_TURB_MODEL= SST` and the version and modifications via the `SST_OPTIONS` list. If this list is empty SU2 defaults to the baseline 1994 model, `V1994m` (see warning below). The options allow for a version and a set of modifiers to the version. 
+The freestream and inlet conditions are specified via the options `FREESTREAM_TURBULENCEINTENSITY= 0.05` (5%) and `FREESTREAM_TURB2LAMVISCRATIO= 10` (ratio of turbulent to laminar viscosity).
+
+**Note:** The default values for these options are suitable for internal flows but may be too high for external aerodynamics problems.
+
+The following modifications are allowed:
+- Versions:
+  - `V1994m` - SSTm **WARNING:** Our implementation has a small [inconsistency with the literature](https://github.com/su2code/SU2/issues/1551), which will be resolved in the next major SU2 update (i.e. version 8).
+  - `V2003m` - SST-2003m (no known inconsistencies).
+- Production modifications:
+  - `VORTICITY` - Uses vorticity to compute the source term instead of strain-rate magnitude.
+  - `KATO_LAUNDER` - Uses the Kato-Launder modification (vorticity times strain-rate).
+  - `UQ` - Production is computed using a modified stress tensor for [uncertainty quantification](https://su2code.github.io/tutorials/UQ_NACA0012/). **Note** with this modification TKE is always included in the stress tensor.
+- Corrections:
+  - `SUSTAINING` - SST with controlled decay.
+  - Curvature corrections are currently not implemented.
+
+Modifications from each of these three groups can be combined, for example `SST_OPTIONS= V2003m, VORTICITY, SUSTAINING`

_docs_v7/Theory.md

@@ -164,9 +164,10 @@ Within the `INC_EULER` solver, we discretize the equations in space using a fini
 
 # Turbulence Modeling #
 
-The Shear Stress Transport (SST) model of Menter and the Spalart-Allmaras (S-A) model are two of the most common and widely used turbulence models. The S-A and SST standard models, along with several variants, are implemented in SU2. The reader is referred to the [NASA Turbulence Modeling Resource](https://turbmodels.larc.nasa.gov/index.html) (TMR) for the details of each specific model, as the versions in SU2 are implemented according to the well-described formulations found there.
+SU2 implements several variants of the SST and SA turbulence models, for specifics of the models please see the [NASA Turbulence Modeling Resource](https://turbmodels.larc.nasa.gov/index.html) (TMR).
+For information on how to use turbulence models in SU2 see the [users guide](https://su2code.github.io/docs_v7/Physical-Definition/).
 
-Within the turbulence solvers, we discretize the equations in space using a finite volume method (FVM) with a standard edge-based data structure on a dual grid with vertex-based schemes. The convective and viscous fluxes are evaluated at the midpoint of an edge.
+The edge-based finite volume discretization of flow solvers is also used in turbulence solvers. Convective fluxes are evaluated using a scalar upwind scheme (1st or 2nd order).
 
 ---
 

_tutorials/compressible_flow/Transitional_Flat_Plate/Transitional_Flat_Plate.md

@@ -62,17 +62,17 @@ Several of the key configuration file options for this simulation are highlighte
 %                               LINEAR_ELASTICITY, POISSON_EQUATION)
 SOLVER= INC_RANS
 %
-% Specify turbulent model (NONE, SA, SA_NEG, SST)
+% Specify turbulent model (NONE, SA, SST)
 KIND_TURB_MODEL= SA
 %
-% Specify transition model (NONE, BC)
-KIND_TRANS_MODEL= BC
+% Specify transition model
+SA_OPTIONS= BCM
 %
 % Specify Turbulence Intensity (%)
 FREESTREAM_TURBULENCEINTENSITY = 0.18
 ```
 
-The governing equations are RANS with the Spalart-Allmaras (`SA`) turbulence model. By entering `KIND_TRANS_MODEL= BC`, the Bas-Cakmakcioglu Algebraic Transition Model is activated. This model requires freestream turbulence intensity that is to be used in the transition correlation, thus the `FREESTREAM_TURBULENCEINTENSITY` option is also used. The BC model achieves its purpose by modifying the production term of the 1-equation SA turbulence model. The production term of the SA model is damped until a considerable amount of turbulent viscosity is generated, and after that point, the damping effect on the transition model is disabled. Thus, a transition from laminar to turbulent flow is obtained.
+The governing equations are RANS with the Spalart-Allmaras (`SA`) turbulence model. By entering `SA_OPTIONS= BCM`, the Bas-Cakmakcioglu Algebraic Transition Model is activated. This model requires freestream turbulence intensity that is to be used in the transition correlation, thus the `FREESTREAM_TURBULENCEINTENSITY` option is also used. The BC model achieves its purpose by modifying the production term of the 1-equation SA turbulence model. The production term of the SA model is damped until a considerable amount of turbulent viscosity is generated, and after that point, the damping effect on the transition model is disabled. Thus, a transition from laminar to turbulent flow is obtained.
 
 The incompressible freestream properties are specified as follows. (Please see "Notes" for freestream properties of other transitional flat plate test cases).