Part of an automatic flow-metering system is shown. The main flow goes through a smooth venturi that reduces the area from Am to Av and in which we may assume that all dynamic pressure is fully recovered. The spring-mounted pistons deflect due to the pressure in the main pipe and at the throat. Orifices in the pipes connecting the piston chambers to the main pipe restrict the flows to the pistons to low values. Construct a bond graph for this subsystem, and indicate inertia elements and Bernoulli resistors for the two area change sections of length l. Why should we expect the two pistons to deflect differing amounts? Would the difference between the two deflections serve to measure the main flow?
