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% Verbal description for system NozzleFlow (NozzleFlow_desc.tex)
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The acausal bond graph of system \textbf{NozzleFlow} is
displayed in Figure \Ref{NozzleFlow_abg} and its label
file is listed in Section \Ref{sec:NozzleFlow_lbl}.
This 5 port component computes the mass flow in a polytropic
convergent nozzle from the formula:
\begin{equation}
\dot m = A p_1 \sqrt{\frac{2n}{n-1}\frac{1}{RT_1}
\left ( \frac{p_2}{p_1} \right )^\frac{2}{n}
\left [ 1- \left ( \frac{p_2}{p_1} \right )^\frac{n-1}{n} \right ] }
\end{equation}
where:
\begin{itemize}
\item $n$ is the coefficient of polytropic expansion and
\item $R$ is the universal gas constant.
\end{itemize}
If the expansion is isentropic
\begin{equation}
n=\gamma=\frac{c_p}{c_v}
\end{equation}
whre $c_p$ and $c_v$ are the spesicfic heats at constant pressure and volume.
Typical values for air are
\begin{equation}
\begin{align}
R &= 287 \text{Nm}\text{kg}^{-1}{K}^{-1}\\
\gamma &= 1.4
\end{align}
\end{equation}