Extend Actuator Disk documentation

adflow/pyADflow.py

@@ -888,17 +888,19 @@ def addActuatorRegion(
         coordXfer=None,
     ):
         """
-        Add an actuator disk zone defined by the supplied closed
-        surface in the plot3d file "fileName". This surface defines the
-        physical extent of the region over which to apply the source terms.
-        Internally, we find all of the CFD volume cells that are inside
-        this closed surface and apply the source terms over these cells.
-        This surface is only used with the original mesh coordinates to
-        mark the internal CFD cells, and we keep using these cells even
-        if the geometric design and the mesh coordinates change. For
-        example, the marked cells can lie outside of the original
-        closed surface after a large design change, but we will still
-        use the cells that were inside the surface with the baseline design.
+        Add an actuator disk zone defined by the supplied closed surface in the
+        plot3d file "fileName". This surface defines the physical extent of the
+        region over which to apply the source terms. The plot3d file may be
+        multi-block but all the surface normals must point outside and no
+        additional surfaces can be inside. Internally, we find all of the CFD
+        volume cells that have their center inside this closed surface and
+        apply the source terms over these cells. This surface is only used with
+        the original mesh coordinates to mark the internal CFD cells, and we
+        keep using these cells even if the geometric design and the mesh
+        coordinates change. For example, the marked cells can lie outside of
+        the original closed surface after a large design change, but we will
+        still use the cells that were inside the surface with the baseline
+        design.
 
         axis1 and axis2 define the vector that we use to determine the
         direction of the thrust addition. Internally, we compute a