Hi all,

I'm working on a very simple Fluid model to learn Modelica (with Dymola) and the MSL.

First I have connected a full OpenTank pouring water in an empty OpenTank thanks to a ControlledPump (see Fig 1). I used a ControlledPump because I wanted a constant flow of 0.1kg/min. My example on fig 1 works well and the DestTanks progressively collects water from the SourceTank.

Now I'd like to be able to switch on and switch off the pump during simulation, controlling it with a Pulse block. I changed the parameter of the pump "use_m_flow_set" to true in order to add a "m_flow" input pin. I plugged on this pin a pulse sending infinitely 0.1 between 10sec and 0.0 then (fig 2). I set "flow reversal" to false in order to avoid problems. By this way I thought that my pump would be on during 10 sec, then off during 10 sec, and so on...

The new model compiles well but unfortunately during simulation the simulator says that the jacobian is too hard to solve because of a zero pivot.

I think I'm not using the right way to switch on and off the pump. How would you do to do that?
Thanks