I have been having some issues with a dynamic fluid network, where when the structure of the fluid network is updated (e.g. connectors have been deleted or created between objects connected to pipes), the successors of any fluid sources (e.g. a storage tank) re-assesses its inflow rate without reseting the inflow rate to 0 first.
For example, if a source produced 5l/s into a tank, and we delete a connector somewhere else in the network, the inflow rate of the tank increases by 5l/s (on top of its current flow rate). Multiple changes in this way stack this effect as well.
What is the cause of this, and is there a way I can work around this?
To me it is quite unusual to dynamically create/delete connectors.
The way we usually manage a fluid network, is by opening and closing objects (EntranceLocked, ExitLocked, PipeOpened). This works well so far.
I agree that for pre-defined systems, using the entrance and exit lock is an easier way to control the flow, however in this system we need to create parts of the network through the simulation, as they are not known at initialisation.
I have attached a model that demonstrates the issue. If you click the button to enable or disable the extra tank, you will see the inflow rate of the first tank increase each time. Note that this is only a concern when there is no open set of pipes from the change to the original source.
When I run your model I do not see any violation of flow rate constraints, using v18.104.22.1688. Maybe you use an outdated version?
Anyway, I still do not get the need for the dynamic model creation, as you seem to know the possible "maximum" network beforehand.
Apologies - I may not have made it clear of what the model is supposed to show. Do not try to run the model (it is saved partially through a run), simply click the 'Extra Tank' checkbox, and you will see the 'inflowRate' variable increase (this is the inflow rate for the 'Tank' object. The issue is that creating and deleting the connecters (done by the checkbox) increase the inflow rate.
As for why this could be needed - it is in precisely the situation where we do not know the 'maximum' network beforehand as the entire system can populate it from scratch with as few bounds as possible (e.g. number of storage tanks etc).
Sorry for any confusion!
No, the inflowRate variable does not increase on my system.
But still, to me it does not really make sense to change the structure itself in a running simulation. I would always do a reset between different structures. The fluid functions require a bit more network calculation compared to discrete material flow, hence a reset is safer.
There was a bug in the version 14.0.0 and 14.0.1 which has increased the inflow rate. Please use the actual maintenance pack which was already mentioned from Gerd Nomden