|
In my experience initial conditions play a much more important role in unsteady simulations than in steady ones. I would try to find stable steady situations first for the range of flows you're simulating, so that you can track if the unstabilities are related to particular flow situations, and move to the unsteady version afterwards. Don't forget that friction changes with flow, your Manning's M-s (or n-s) might cause some trouble if you keep them steady while changing flow.
I also experienced that starting with a high flow (and corresponding high water level throughout the reach) is more likely to result in a stable situation, than low flow. Starting with high flow, one can alter Q & h gradually to reach more realistic values (adding artificial series before your real series)
|