Still playing around with tank filling. This time my inflow hydrograph starts with zero flow and ends with zero flow over a period of 120 min (first graph). Unless I have overlooked something the calculated depth in the tank should also start at zero (no inflow) and end at zero (tank depleted i.e. no out flow) but instead although the solve block ODE shows that the depth in the tank is trending downwards but it never gets to zero depth (second graph) or zero outflow (third graph). This appears to be physically incorrect as I think all would agree. But why is the solve block returning answers that don't go to zero when as you can see by the hydrograph the inflow is zero at 120 minutes. Something is wrong but I don't know what it is can someone explain.
Kind regards, Mark