From 6d2cdea38a02c04b961b0fe3efaea7f7a02246a4 Mon Sep 17 00:00:00 2001
From: Sebastian Stark <stark.sebastian@gmx.de>
Date: Wed, 15 May 2019 21:18:01 +0200
Subject: [PATCH] Fix bug in tutorial step-46

Fix a bug in step-46, which caused the y-displacements (z in 3d) to be unsymmetric
---
 doc/news/changes/minor/20190515SebastianStark |  3 +++
 examples/step-46/step-46.cc                   | 12 ++++++++----
 2 files changed, 11 insertions(+), 4 deletions(-)
 create mode 100644 doc/news/changes/minor/20190515SebastianStark

diff --git a/doc/news/changes/minor/20190515SebastianStark b/doc/news/changes/minor/20190515SebastianStark
new file mode 100644
index 0000000000..71a7dd9e9b
--- /dev/null
+++ b/doc/news/changes/minor/20190515SebastianStark
@@ -0,0 +1,3 @@
+Fixed: Fix a bug in tutorial step-46, which caused the y-displacement (z-displacement in 3d) to be slightly unsymmetric.
+<br>
+(Sebastian Stark, 2019/05/15)
diff --git a/examples/step-46/step-46.cc b/examples/step-46/step-46.cc
index 58e5d0bf92..12fa63c0c4 100644
--- a/examples/step-46/step-46.cc
+++ b/examples/step-46/step-46.cc
@@ -483,7 +483,7 @@ namespace Step46
                                             common_face_quadrature,
                                             update_JxW_values |
                                               update_normal_vectors |
-                                              update_gradients);
+                                              update_gradients | update_values);
     FEFaceValues<dim>    elasticity_fe_face_values(elasticity_fe,
                                                 common_face_quadrature,
                                                 update_values);
@@ -491,7 +491,8 @@ namespace Step46
                                                   common_face_quadrature,
                                                   update_JxW_values |
                                                     update_normal_vectors |
-                                                    update_gradients);
+                                                    update_gradients |
+                                                    update_values);
     FESubfaceValues<dim> elasticity_fe_subface_values(elasticity_fe,
                                                       common_face_quadrature,
                                                       update_values);
@@ -798,8 +799,11 @@ namespace Step46
           stokes_fe_face_values.normal_vector(q);
 
         for (unsigned int k = 0; k < stokes_fe_face_values.dofs_per_cell; ++k)
-          stokes_symgrad_phi_u[k] =
-            stokes_fe_face_values[velocities].symmetric_gradient(k, q);
+          {
+            stokes_symgrad_phi_u[k] =
+              stokes_fe_face_values[velocities].symmetric_gradient(k, q);
+            stokes_phi_p[k] = stokes_fe_face_values[pressure].value(k, q);
+          }
         for (unsigned int k = 0; k < elasticity_fe_face_values.dofs_per_cell;
              ++k)
           elasticity_phi[k] =
-- 
2.39.5