DOCS FIX: Small improvement to nondimensionalization sections for governing equations.

docs/user/governingeqns/elasticity/nondimensionalization.md

@@ -54,7 +54,12 @@ Considering isotropic, linear elasticity we have
 \boldsymbol{\sigma} = \boldsymbol{C} : \boldsymbol{\epsilon} = \boldsymbol{C} : \frac{1}{2}\left(\boldsymbol{\nabla} + \boldsymbol{\nabla}^T \right) \vec{u}.
 \end{equation}
 %
-Substituting in our nondimensional values yields
+We define
+%
+\begin{equation}
+C^* = \frac{C}{\mu_o},
+\end{equation}
+and substituting yields
 %
 \begin{equation}
 \sigma_o \boldsymbol{\sigma}^* = \mu_o \boldsymbol{C}^* : \frac{u_o}{x_o} \frac{1}{2}\left(\boldsymbol{\nabla}^* + \boldsymbol{\nabla}^{*^T}\right) \vec{u}^*.

docs/user/governingeqns/incompressible-elasticity/nondimensionalization.md

@@ -69,7 +69,7 @@ It also separates the stress scale used to nondimensionalize stress, tractions,
 | $u_o$       | Displacement scale  |
 | $\mu_o$     | Rigidity scale      |
 | $t_o$       | Time scale          |
-| $\sigma_o = p_o = \mu_o \frac{u_o}{x_o}$  | Stress scale        |
+| $\sigma_o = p_o = \mu_o \frac{u_o}{x_o}$  | Stress and pressure scale        |
 | $f_o = \frac{\sigma_o}{x_o}$    | Body force scale       |
 | $\rho_o = \mu_o \frac{t_o^2}{x_o^2}$    | Density scale       |
 ```

docs/user/governingeqns/poroelasticity/nondimensionalization.md

@@ -134,7 +134,7 @@ It also separates the stress scale used to nondimensionalize stress, tractions,
 |                             $u_o$                             | Displacement scale |
 |                            $\mu_o$                            | Rigidity scale     |
 | $t_o= \frac{\mu_{f_o}}{\boldsymbol{k}_o} \frac{x_o^2}{\mu_o}$ | Time scale         |
-|           $\sigma_o = p_o = \mu_o \frac{u_o}{x_o}$            | Stress scale       |
+|           $\sigma_o = p_o = \mu_o \frac{u_o}{x_o}$            | Stress and pressure scale       |
 |                 $f_o = \frac{\sigma_o}{x_o}$                  | Body force scale   |
 |             $\rho_o = \mu_o \frac{t_o^2}{x_o^2}$              | Density scale      |
 |                   $q_o = \frac{u_o}{t_o} $                    | Flow scale         |