Fix for Saturation Equation

diff --git a/examples/step-21/doc/intro.dox b/examples/step-21/doc/intro.dox
index 4c1f2c8d9611a2368b46ee34f0e153675f732ddb..d1e082b7004a310e71d3d27a22e2a6f604c5c7fb 100644 (file)
--- a/examples/step-21/doc/intro.dox
+++ b/examples/step-21/doc/intro.dox
@@ -108,7 +108,7 @@ In summary, what we get are the following two equations:
   - \nabla \cdot (\mathbf{K}\lambda(S) \nabla p) &=& q
   \qquad \textrm{in}\ \Omega\times[0,T],
   \\
-  S_{t} + \mathbf{u} \cdot \nabla F(S) &=& 0
+  S_{t} + \nabla (F(S) \cdot \mathbf{u}) &=& 0
   \qquad \textrm{in}\ \Omega\times[0,T].
 @f}
 Here, $p=p(\mathbf x, t), S=S(\mathbf x, t)$ are now time dependent