Hello, I'm working with schemes where there are a number of flows into, and out of, a fully liquid filled header (incompressible system). A typical arrangement would be to have, eg. 2 parallel flows in, with control valves maybe level controlling upstream vessels. All the outlet flows have FCs. In order to satisfy the mass balance, there's a pressure controller on the header, that drives the setpoints of some or all of the outlet flow controllers.
Client is considering a situation where FCs are wanted on all flows into and out of the header. Statically, this arrangement will still work due to the pressure controller. However, a dynamic model with reasonably good models of the hydraulic interactions and control devices indicates that the system is fairly wonky. Disturbances result in persistent, nonlinear oscillations (nonlinear due to the valve characteristics), and adjusting tuning doesn't help a lot.
Does anyone have any practical experience with this situation? Should I believe the model, or is the real world better behaved? TIA