I have tried to simulate the examples in the Fluid library using  OpenModelica 1.9.1+dev (r21018) (RML version). The following examples failed to simulate:
Modelica.Fluid.Examples.PumpingSystem
Modelica.Fluid.Examples.Tanks.TanksWithOverflow
Modelica.Fluid.Examples.HeatExchanger.HeatExchangerSimulation
In all cases the simulation process crashed with the message:
simulation terminated by an assertion at initialization
Error: Solving non-linear system failed.

Is there something the user can do to overcome this or is it a matter that the developers have to addres?
I volunteer to help but I will need advice as this is the first time I am using modelica
Thank you.