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% Verbal description for system Density (Density_desc.tex)
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The acausal bond graph of system \textbf{Density} is
displayed in Figure \Ref{Density_abg} and its label
file is listed in Section \Ref{sec:Density_lbl}.
This three port component computes the density $\rho$ of substance in
terms of the temperature $T$ and the pressure $P$. At the moment,
there are four forms dependent on the four forms of the component parameter:
\begin{enumerate}
\item \emph{density,incompressible,rho}
\item \emph{specific\_volume,incompressible,rho}
\item \emph{density,ideal\_gas,R}
\item \emph{specific\_volume,ideal\_gas,R}
\end{enumerate}
\begin{equation}
y =
\begin{cases}
\rho & \text{if the parameter is
\emph{density,incompressible,rho}}\\
\frac{1}{\rho} & \text{if the parameter is
\emph{specific\_volume,incompressible,rho}}\\
\frac{P}{RT} & \text{if the parameter is \emph{density,ideal\_gas,R}}\\
\frac{RT}{P} & \text{if the parameter is
\emph{specific\_volume,ideal\_gas,R}}
\end{cases}
\end{equation}
where $\rho$ is the density of the incompressible fluid and $R$ the
universal gas constant of the ideal gas.