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cfrk

PO lines - effect on model results

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Hi,

I am working on a very large model and I am getting some strange effects. The original model runs through OK, and takes about 15-20 hours of computer run time.

I subsequently added a few PO lines to part of the floodplain, which somehow caused some excessive oscillations upstream of my area of interest, sending a large flood wave through the model well after the flood peak.

I wouldn't have thought adding PO lines could cause such a problem, as they merely extract additional data from the model? The only thing I can think that might be happening is that calculations are going astray due to the additional strain on the processor from writing outputs. Is this likely / possible?

Many thanks

Richard

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Hi Richard

Apologies for the slow response. Adding PO lines shouldn't make any difference to your simulation results. Which TUFLOW build are you using?

Cheers

Bill

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Hi Bill,

I'm using 2009-07-AD (not the latest release but I'm keeping things consistent across model runs). The model is quite large (4 separate watercourses, roughly 24 hour run time) and was built by others - we are only interested in a small section of one of the rivers.

We are trying to add proposed developments (in the form of a raised development plateau as well as the conversion of a culverted section of watercourse to open channel) - when I made these changes to the original model it went unstable at a location well away from the development. Rather than start trying to fix problems in the wider model, it seemed simpler to crop the model to our area of interest - hence the addition of PO lines to use as inflows for a cropped version of the model.

So the only change I made was to add PO lines to the original model, which caused the flood wave to occur...? Something to do with rounding up/down when writing outputs maybe?

It's a very large model so will be a bit of pain to try to send unfortunately! I've done a bit of a estimating and interpolation in the meantime to get inflows without the flood wave, so have side-stepped the problem, but would be good to clear up why this is happening...

Cheers

Richard

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Hi Richard

Very strange! If you have them, can you send through the .tlf files for both scenarios (with and without PO lines) to support@tuflow.com and we'll see if there are any clues.

Thanks

Bill

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