Flow Optimisation Failed to Converge

[Bradley]

Hi, I am attempting to run an unsteady flow with two lateral weirs, the model completes however it notifies me that the “Flow optimisations failed to converge, Profile1 Initial profile” [This problem also occurs during steady flow analysis].

– My initial condition is blank so it uses the first time step flow in the Flow Hydrograph (Which is 500cfs).
– I have set the max number of iterations (60).
– Optimisation is on for both weirs, and a warm up period is set as 4 hours for the unsteady flow.
– During unsteady flow, a 7 day run period (initial 500cfs, max 3000cfs for 2 days) only the lower weir is flooded (and only by a small amount)

I have attached screenshots of the model and parameters on this link:
https://www.dropbox.com/sh/yavupsudzis2xll/AACPfjizyzPyG4IisjUq4jxCa?dl=0
[Weirs on image of map @ XS 23921 and XS 6093]

I have read a similar thread question but this has not answered my question unfortunately: http://hec-ras-help.1091112.n5.nabble.com/Flow-optimization-failed-to-converge-td84.html

Is there something that can be done to increase the number of iterations / allow it to complete/ Is it a huge problem that it doesn’t complete? Any help would be greatly appreciated, Best, Bradley

[Anonymous]

The flow optimization often fails if there is more than one lateral structure being optimized.

At the end of the warm up period, has the unsteady flow settled down to a stable a answer? If it has, then you probably don’t need to worry about the optimization.

If it hasn’t, you might try a longer warm up period. Or, you might try a longer warm up period with the optimization turned off.

If the model is unstable at the very beginning of the run because of the flow over the lateral structures (and the above tricks do not work), you might have to start out with lower flows and water surfaces in the model so that there is not flow over the lateral structures. Then ramp the flow up to the desired amount before the real part of the model run. If you do this, you might want to look into using a restart file just to save some time.

[Bradley]

Jarvus huge apologies for never replying, I am still having issues with various errors but as you say, multiple lateral structures can cause instability.

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