[doc][fluidmatrixinteractions] minor change of the frictionlaws description

doc/doxygen/groups/material.md

@@ -84,7 +84,7 @@ The following laws are implemented:
 
 @defgroup FrictionLaws Friction Laws
 @brief Friction Laws for calculating bottom shear stress
-@details Friction laws calculate the stress between the flow and the bottom,
+@details Friction laws calculate the stress between the flowing fluid and the bottom,
 which is called bottom shear stress. The bottom shear stress is
 needed to calculate on the one hand the loss of momentum due to
 bottom friction and on the other hand the bedload transport rate.

dumux/material/fluidmatrixinteractions/frictionlaws/frictionlaw.hh

@@ -17,7 +17,7 @@ namespace Dumux {
  * \ingroup FrictionLaws
  * \brief Implementation of the abstract base class for friction laws.
  *
- * Friction laws calculate the stress between the flow and the bottom,
+ * Friction laws calculate the stress between the flowing fluid and the bottom,
  * which is called bottom shear stress. The bottom shear stress is
  * needed to calculate on the one hand the loss of momentum due to
  * bottom friction and on the other hand the bedload transport rate.

dumux/material/fluidmatrixinteractions/frictionlaws/manning.hh

@@ -19,7 +19,7 @@ namespace Dumux {
  *
  * ### Manning
  *
- * This friction law calculates the stress between the flow and the bottom,
+ * This friction law calculates the stress between the flowing fluid and the bottom,
  * which is called bottom shear stress, using the Manning friction law.
  * The bottom shear stress is needed to calculate on the one hand the loss of
  * momentum due to bottom friction and on the other hand the bedload transport rate.

dumux/material/fluidmatrixinteractions/frictionlaws/nikuradse.hh

@@ -19,7 +19,7 @@ namespace Dumux {
  *
  * ### Nikuradse
  *
- * This friction law calculates the stress between the flow and the bottom,
+ * This friction law calculates the stress between the flowing fluid and the bottom,
  * which is called bottom shear stress, using the Nikuradse friction law.
  * The bottom shear stress is needed to calculate on the one hand the loss of
  * momentum due to bottom friction and on the other hand the bedload transport rate.

dumux/material/fluidmatrixinteractions/frictionlaws/nofriction.hh

@@ -17,7 +17,7 @@ namespace Dumux {
  *
  * ### No Friction
  *
- * This friction law sets the stress between the flow and the bottom,
+ * This friction law sets the stress between the flowing fluid and the bottom,
  * which is called bottom shear stress, to zero.
  * The bottom shear stress is needed to calculate on the one hand the loss of
  * momentum due to bottom friction and on the other hand the bedload transport rate.