- Added transition to Physical Definition

Author: rois1995

_docs_v7/Physical-Definition.md

@@ -158,3 +158,27 @@ The following modifications are allowed:
   - Curvature corrections are currently not implemented.
 
 Modifications from each of these three groups can be combined, for example `SST_OPTIONS= V2003m, VORTICITY, SUSTAINING`
+
+## Transition Models ##
+
+| Solver | Version |
+| --- | --- |
+| `*_RANS` | 7.4.0 |
+
+This section describes how to setup transition models for RANS simulations. Transition is activated using the option `KIND_SOLVER= RANS`, or `KIND_SOLVER= INC_RANS`.
+A transition model can then be selected via the option `KIND_TRANS_MODEL`.
+Different submodels and correlations are specified via the different options listed below.
+
+The following modifications are allowed:
+- Versions:
+  - `LM2015` - Correction to include stationary crossflow instabilities. It has to be used only in 3D problems. The RMS of roughness used in this model has to be set through the separate option `HROUGHNESS`.
+- Correlations:
+  - `MALAN` - This is the default correlation when the LM model is coupled with the `SA` turbulence model.
+  - `SULUKSNA` - This should be used only if the `SST` model is used. It requires a formulation of
+  - `KRAUSE` - This correlation should be used for hypersonic flows. Its implementation at the moment is unclear and inconsistent with literature.
+  - `KRAUSE_HYPER` - This correlation should be used for hypersonic flows. Its implementation at the moment is unclear.
+  - `MEDIDA` - Designed for `SA` turbulence model. Has problems when dealing with separation induced transition.
+  - `MEDIDA_BAEDER` - Designed for `SA` turbulence model. Has problems when dealing with separation induced transition.
+  - `MENTER_LANGTRY` - This is the default correlation when the LM model is coupled with the `SST` turbulence model.
+
+  Modifications from each of these three groups can be combined, for example `LM_OPTIONS= LM2015, MENTER_LANGTRY`. Although, at most one correlation should be chosen.