[FXC-1921] Added example for roughness height to the Wall docstring (#1674)

Author: piotrkluba

flow360/component/simulation/models/surface_models.py

@@ -317,6 +317,7 @@ class WallRotation(Flow360BaseModel):
 class Wall(BoundaryBase):
     """
     :class:`Wall` class defines the wall boundary condition based on the inputs.
+    Refer  :ref:`here <wall_formulations>` for formulation details.
 
     Example
     -------
@@ -365,6 +366,14 @@ class Wall(BoundaryBase):
       ...     ),
       ... )
 
+    - Define roughness height on entities
+      with the naming pattern :code:`"fluid/Roughness-*"`:
+
+      >>> fl.Wall(
+      ...     entities=volume_mesh["fluid/Roughness-*"],
+      ...     roughness_height=0.1 * fl.u.mm,
+      ... )
+
     ====
     """