I just started using Stan for wastewater simulations and see it very promising and relatively easy to use. I create first goods-level and input watervalues as tn/h with 10 % tresholds. I managed to get nice flow even with inner loops and added other layers like nitrogen and sulphur, but while adding phosphorus- level somehow my previous models went broken and even the water-level is not counting anymore to the end of the system. I have used both flow-values and relations and there should not be any contradictions in them. Some of the values are changing, even I would like to keep them constant... How to priorize what is given and what is counted?
not sure if that´s a beginners question.
I would recommend not to use relations extensively, rather use transfer coefficients, where ever possible. Relations are not well documented in your system and, at least, for me it is hard to keep track of them. they are handy in some occasions, but also don´t provide the option to set an St.Dev, as TC.
That you values are changing is probably cased by the Data reconciliation. As soon as your model is overdefined, STAN will try to reconciliate your values. There is, to my knowledge, no option to limited that to certain values or to switch it off.