Fixed an issue with normal vector not being norm unit, which was causing

reflected particle velocities to increase.

src/modules/mesh/2DCart/moduleMesh2DCart.f90

@@ -193,6 +193,8 @@ MODULE moduleMesh2DCart
       self%normal = (/ self%y(2)-self%y(1), &
                        self%x(2)-self%x(1), &
                        0.D0 /)
+      self%normal = self%normal/NORM2(self%normal)
+
       !Boundary index
       self%boundary => boundary(bt)
       ALLOCATE(self%fboundary(1:nSpecies))