Made ex18 example more consistent with the others in user doc.

examples/ex18.py

@@ -60,7 +60,6 @@ def unit_rotation(v, dv, ddv, w):
     print('phi0 = {} (cf. exact = 1/64 = {})'.format(Psi0, 1/64))
 
     ax = mesh.draw()
-    ax.set_title('stream-lines')
     fig = ax.get_figure()
     ax.tricontour(Triangulation(M.p[0, :], M.p[1, :], M.t.T), Psi)
     ax.axis('off')
@@ -70,7 +69,6 @@ def unit_rotation(v, dv, ddv, w):
     velocity = np.vstack([derivative(Psi, refbasis, refbasis, 1),
                           -derivative(Psi, refbasis, refbasis, 0)])
     ax = mesh.draw()
-    ax.set_title('velocity vectors coloured by buoyancy')
     sparsity_factor = 2**3      # subsample the arrows
     vector_factor = 2**3        # lengthen the arrows
     x = M.p[:, ::sparsity_factor]

examples/ex18.rst

@@ -5,16 +5,16 @@ The stream-function :math:`\psi` for two-dimensional creeping flow is
 governed by the biharmonic equation
 
 .. math::  
-    \nu \Delta^2\psi = \mathop{rot} f
+    \nu \Delta^2\psi = \mathrm{rot}\,f
 
 where :math:`\nu` is the kinematic viscosity (assumed constant),
-:math:`f` the volumetric body-force, and :math:`\mathop{rot} f =
+:math:`f` the volumetric body-force, and :math:`\mathrm{rot}\,f =
 (\partial f/\partial y, -\partial f/\partial x)`.  The boundary
-conditions at a wall are that :math:`\psi` be constant (the wall is
-impermeable) and that the normal component of its gradient vanish (no
+conditions at a wall are that :math:`\psi` is constant (the wall is
+impermeable) and that the normal component of its gradient vanishes (no
 slip).  Thus, the boundary value problem is analogous to that of
 bending a clamped plate, and may be treated with Morley elements as in
-`ex10`.
+`Kirchhoff plate`_ example.
 
 Here we consider a buoyancy force :math:`f = x\hat{j}`, which arises in
 the Boussinesq approximation of natural convection with a horizontal
@@ -30,9 +30,13 @@ polynomial solution with circular stream-lines:
 The resulting stream-lines and velocity vectors are given
 in the following figures:
 
-.. figure:: ../examples/ex18-stream-lines.png
+.. figure:: ../examples/ex18_stream-lines.png
 
-.. figure:: ../examples/ex18-velocity-vectors.png
+	    The stream-lines.
+
+.. figure:: ../examples/ex18_velocity-vectors.png
+
+	    The velocity vectors colored by buoyancy.
 
 The complete source code reads as follows: