From: Omotayo Omosebi <dr.omosebi@gmail.com>
Date: Mon, 19 Aug 2019 18:06:10 +0000 (-0400)
Subject: Explains formulation of the saturation equation
X-Git-Tag: v9.2.0-rc1~1222^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6bde00c1257b84adea686ee34533e2ec6b8b15f8;p=dealii.git

Explains formulation of the saturation equation
---

diff --git a/doc/news/changes/minor/20190807Omosebi b/doc/news/changes/minor/20190807Omosebi
new file mode 100644
index 0000000000..bd9cca8ea1
--- /dev/null
+++ b/doc/news/changes/minor/20190807Omosebi
@@ -0,0 +1,4 @@
+Changed: The saturation equation in step-21 is explained further for 
+consistency with literatures in porous media transport.
+<br>
+(Omotayo Omosebi, 2019/08/07)
diff --git a/examples/step-21/doc/intro.dox b/examples/step-21/doc/intro.dox
index 543c69f6a7..4fa98411d9 100644
--- a/examples/step-21/doc/intro.dox
+++ b/examples/step-21/doc/intro.dox
@@ -79,13 +79,13 @@ of course is going to change as the fluids move around.
 The second part of the equations is the description of the
 dynamics of the saturation. The saturation equation for the displacing fluid (water) is:
 @f{eqnarray*}
-  S_{t} + \nabla \cdot (F(S) \mathbf{u}) = \{q}_{w},
+  S_{t} + \nabla \cdot (F(S) \mathbf{u}) = q_{w},
   \\
-  S_{t} + F(S) \nabla \mathbf{u} + \mathbf{u} \cdot \nabla F(S) = S_{t} + F(S) * \q + \mathbf{u} \cdot \nabla F(S) = \{q}_{w}.
+  S_{t} + F(S) \nabla \mathbf{u} + \mathbf{u} \cdot \nabla F(S) = S_{t} + F(S) * q + \mathbf{u} \cdot \nabla F(S) = q_{w}.
 @f}
-where $\{q}_{w}$ is the flow rate of the displacing fluid (water) and is related to the fractional flow F(S) through:
+where $q_{w}$ is the flow rate of the displacing fluid (water) and is related to the fractional flow F(S) through:
 @f[
-  \{q}_{w} = F(S) * \q,
+  q_{w} = F(S) * q,
   \\
   F(S)
   =