20
1 Modeling Systems
x + y + z = 0.
The desired variable after analyzing the aggregate system will be one of the
members of the equation. This equation resembles Kirchhoff’s law for electrical
circuits.
As an example, consider a closed pipeline circuit with a reservoir. The contour
has a section with branching and a pump that starts the circulation of water along the
contour, as illustrated in Fig. 1.11.
It is logical to break this system into components and separately describe each
component. The main components in hydraulic systems are pipes. The variables
connecting the components in this case will be the pressure P and the flow rate Q.
Moreover, the pressure will be a variable of the “contact” type, since the pressure at
the junction of the two pipes must be equal, and the flow rate will be of the “flow”
type to consider the possibility of branching the pipeline; this fluid flow must also
be separated. In order not to overload the model diagram, these variables are usually
combined into one, declaring the record type.
Thus, it is possible to obtain the scheme of the component model, as shown in
Fig. 1.12.
Fig. 1.11 Simple hydraulic
circuit
Fig. 1.12 Component model of the hydraulic circuit