adapt 3D tests to at least do something

test/stokes/stokes_3d_dg_quadrilateral.mini

@@ -11,5 +11,3 @@ extension = vtu
 
 [formcompiler]
 numerical_jacobian = 0, 1 | expand num
-exact_solution_expression = g
-compare_l2errorsquared = 5e-7

test/stokes/stokes_3d_dg_quadrilateral.ufl

 cell = hexahedron
 
 x = SpatialCoordinate(cell)
-g_v = as_vector((4*x[1]*(1.-x[1]), 0.0, 0.0))
-g_p = 8*(1.-x[0])
-g = (g_v, g_p)
+g_v = as_vector((16.*x[1]*(1.-x[1])*x[2]*(1.-x[2]), 0.0, 0.0))
 bctype = conditional(x[0] < 1. - 1e-8, 1, 0)
 
 P2 = VectorElement("DG", cell, 2)

test/stokes/stokes_3d_quadrilateral.mini

@@ -12,5 +12,3 @@ extension = vtu
 
 [formcompiler]
 numerical_jacobian = 1, 0 | expand num
-exact_solution_expression = g
-compare_l2errorsquared = 1e-10

test/stokes/stokes_3d_quadrilateral.ufl

@@ -2,11 +2,9 @@ cell = hexahedron
 
 x = SpatialCoordinate(cell)
 v_bctype = conditional(x[0] < 1. - 1e-8, 1, 0)
-g_v = as_vector((4.*x[1]*(1.-x[1]), 0.0, 0.0))
-g_p = 8.*(1.-x[0])
-g = (g_v, g_p)
+g_v = as_vector((16.*x[1]*(1.-x[1])*x[2]*(1.-x[2]), 0.0, 0.0))
 
-P2 = VectorElement("Lagrange", cell, 2, dirichlet_constraints=v_bctype, dirichlet_expression=g_v)
+P2 = VectorElement("Lagrange", cell, 2)
 P1 = FiniteElement("Lagrange", cell, 1)
 TH = P2 * P1
 
@@ -16,3 +14,5 @@ u, p = TrialFunctions(TH)
 r = (inner(grad(v), grad(u)) - div(v)*p - q*div(u))*dx
 
 forms = [r]
+is_dirichlet = v_bctype, v_bctype, v_bctype, 0
+dirichlet_expression = g_v, None