NewTest

\begin{equation}\tag{176} k_b = 0.062 \left[ 1-0.9 \tanh \left( 0.25\frac{u_{*w}}{W_s} \right) \right] \end{equation}

\begin{equation} \begin{align}

 & {{{\vec{F}}}_{a}}=c\ \vec{u}+c\ w\ {{{\vec{e}}}_{z}} \\
 & {{{\vec{F}}}_{s}}=-c\ {{W}_{s}}\ {{{\vec{e}}}_{z}} \tag{117} \\ 
 & {{{\vec{F}}}_{d}}=-{{\varepsilon }_{h}}\ \overrightarrow{\text{gra}{{\text{d}}_{\text{h}}}}\left( c \right)-{{\varepsilon }_{\nu }}\frac{\partial c}{\partial z}{{{\vec{e}}}_{z}} \\
 \end{align}

\end{equation}