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parkesa

negative QT

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I have been given output from a drainage model with flows at a number of surcharged manholes which I want to add into a 2D TuFlow model. I have configured the data as 2D_QT boundaries and linked to the model. Several of the manholes start with negative flow (very minor) which causes model instability, is there an easy way to get TuFlow to ignore -'ve QT flows? I'd rather not manually remove the -'ve values as there are a lot of manholes!

Thanks

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Hi

No, there isn't an easy way other than if you can write a macro/program or use Excel/UltraEdit to some how globally remove them from the input files. It's an interesting idea so have added to the list putting in an option/flag for TUFLOW to do this, however, you want to make sure that this isn't unacceptably changing the volume of water entering the model. As you say, they are very small so in this case is probably fine.

Cheers

Bill

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I have been looking at a model which has negative flows in a QT boundary after the main inflow has passed. These show as 'Q vol Out' in the _mb.csv file, but not as 'HX V out' in the _2dmb.csv file and as a result a mass balance error is generated in the 1d (and overall) components reported on the console/tlf file. (Some -dvol is generated but not enough to match the -ve Q).

So, my question is firstly, should -ve flows in QT boundaries work, or would there be a better way of them doing it (if actually needed)? If they should work, why is there an anomaly in the mb files?

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