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scott

1D/2D Instability

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Hi,

I think I am having trouble with the transition between 1D/2D boundaries in an open channel. In the attached files I was previously getting a similar problem as seen in the 2nd picture upstream of the bridge. I extended the width of the 1D area by a marginal amount and this helped solve the problem at this region, however, I am now getting the same problem upstream of the culvert. I have played around with width of the 1D region with little luck. Has anyone come across this problem? The model appears to be stable in the timestep procreeding the problem and therefore it doesn't appear to a problem with backwater effects (the water levels being reported at the problem area are in the order of 500m well above the DEM of 28m). Any suggestions would be appreciated.

Cheers

post-2457-1263543393_thumb.jpg

post-2457-1263543403_thumb.jpg

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Hi Scott,

I had what sounds like similar problems recently in a model and found that by increasing the Shallow Depth Stability Factor that the instabilities were overcome in the model.

To do this add the following line to the TCF file

Shallow Depth Stability Factor == 3

The default value for this is 3 and as such you may want to try increasing it. I believe the range of values you can use are 0 - 10.

I don't know how this affects accuracy but we achieved results we believe to be realistic.

Hope this helps

Andy

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Thanks Andy, I have tried the shallow depth stability factor without a lot of luck. I have tried the suggested range (0-10), the model becomes unstable at the same location. The only difference for the range of values being different mass errors and the time at which the model becomes unstable. Any other suggestions?

Thanks

Scott

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Hi Scott

If you're still having stability problems, can you please contact support@tuflow.com and we'll arrange to get a copy of the model as it will be much easier if we can see how you've set things up. If the model is not too large, make a copy of it using the -c option (ie. run TUFLOW.exe -c my_model.tcf), zip up the folder created and email through. If too large we'll arrange for an ftp site to upload.

Cheers

Bill

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