For anyone with experience with Simulink...

Bit of preamble here, question is at the end. I'm assisting a colleague who
is following the instructions in an old report he's unearthed, to model a
noncompressible flow network (liquids in pipes and valves) using Simulink.
The method involves introducing 'artificial' compressibility at the network
nodes, so that the pressure balance can be calculated using ODEs, ie.

PressureAtNode = integral (flow in - flow out).

The model is taking forever to run, presumably because the amount of compressible material is kept small so that nonexistent dynamics isn't added to the model, this means that the equations are very stiff, and the solver needs to work with extremely small time increments.

My own approach in this situation is simply to calculate the system pressures and flows statically, that's usually pretty easy, just a nonlinear version of ohms law. The resultant models are efficient, and run very fast.

Is there something in Simulink that makes solving the flow network using background integrators the preferred approach? Or would one normally do something a bit more (IMHO) sensible, and do a static solution?

Bit of preamble here, question is at the end. I'm assisting a colleague who

PressureAtNode = integral (flow in - flow out).

The model is taking forever to run, presumably because the amount of compressible material is kept small so that nonexistent dynamics isn't added to the model, this means that the equations are very stiff, and the solver needs to work with extremely small time increments.

My own approach in this situation is simply to calculate the system pressures and flows statically, that's usually pretty easy, just a nonlinear version of ohms law. The resultant models are efficient, and run very fast.

Is there something in Simulink that makes solving the flow network using background integrators the preferred approach? Or would one normally do something a bit more (IMHO) sensible, and do a static solution?