Automatic control (2D)
Tank. Add to your 2D drawing panel a tank filled of a blue fluid. Model of a level variable in automatic control. It accumulates a flow, representing its integral.
Pipe. Draw a pipe. It represents a flow of a liquid, or in Automatic Control, a flow of any variable in a wide sense. It shows how flow is moved from one place to another.
Valve. Draw a valve. It represents the abstraction of the control over a flow, ignoring therefore its internal delays or non-linearities. Its value is given as the value of the passing flow, with a negative value meaning a flow with inverse direction of the one shown.
Pump.? Add a pump to the drawing panel.
Line. Include a control line.