[example][freeflowchannel] Stokes not Navier Stokes.

examples/freeflowchannel/README.md

@@ -10,7 +10,7 @@ This example contains a stationary free flow of a fluid through two parallel sol
 ## Model description
 The Stokes model without gravitation and without sources or sinks for a stationary, incompressible, laminar, single phase, one-component, isothermal ($`T=10^\circ C`$) flow is considered assuming a Newtonian fluid of constant density $` \varrho = 1~\frac{\text{kg}}{\text{m}^3} `$ and constant kinematic viscosity $` \nu = 1~\frac{\text{m}^2}{\text{s}} `$. The momentum balance
 ```math
-\nabla \cdot (\varrho\boldsymbol{u} \boldsymbol{u}^{\text{T}}) - \nabla\cdot\left(\mu\left(\nabla\boldsymbol{u}+\nabla\boldsymbol{u}^{\text{T}}\right)\right)+ \nabla p = 0
+- \nabla\cdot\left(\mu\left(\nabla\boldsymbol{u}+\nabla\boldsymbol{u}^{\text{T}}\right)\right)+ \nabla p = 0
 ```
 with density  $`\varrho`$, velocity $`\boldsymbol{u}`$, dynamic viscosity  $`\mu=\varrho\nu`$ and pressure $`p`$ and the mass balance
 ```math

examples/freeflowchannel/doc/intro.md

@@ -10,7 +10,7 @@ This example contains a stationary free flow of a fluid through two parallel sol
 ## Model description
 The Stokes model without gravitation and without sources or sinks for a stationary, incompressible, laminar, single phase, one-component, isothermal ($`T=10^\circ C`$) flow is considered assuming a Newtonian fluid of constant density $` \varrho = 1~\frac{\text{kg}}{\text{m}^3} `$ and constant kinematic viscosity $` \nu = 1~\frac{\text{m}^2}{\text{s}} `$. The momentum balance
 ```math
-\nabla \cdot (\varrho\boldsymbol{u} \boldsymbol{u}^{\text{T}}) - \nabla\cdot\left(\mu\left(\nabla\boldsymbol{u}+\nabla\boldsymbol{u}^{\text{T}}\right)\right)+ \nabla p = 0
+- \nabla\cdot\left(\mu\left(\nabla\boldsymbol{u}+\nabla\boldsymbol{u}^{\text{T}}\right)\right)+ \nabla p = 0
 ```
 with density  $`\varrho`$, velocity $`\boldsymbol{u}`$, dynamic viscosity  $`\mu=\varrho\nu`$ and pressure $`p`$ and the mass balance
 ```math