combined 1D-2D

[JensPK]

Hello everyone,

I have a problem with combined 1D-2D modelling. As you can see in the pictures I tried different ways for the same terrain (flow direction E-W).
At first I developed an only 2D model with a Land Cover layer and Break Lines around the zones of one roughness (https://drive.google.com/file/d/0B_zwXaohkABJS2JJTnk2QVpNbUU/view?pref=2&pli=1).
Afterwards I combined 1D and 2D modelling with the same Land Cover and Break Lines (https://drive.google.com/file/d/0B_zwXaohkABJSUpwRnFRRTdaTVk/view?pref=2&pli=1).
I attached graphs of the water surface elevations as well (https://drive.google.com/file/d/0B_zwXaohkABJdWFPUkFCb1JyQWc/view?pref=2&pli=1 ; red measured in reality, yellow 2D, green combined model).
So now the problem: There is a tailback in the 2D section of the combined model, while the 1D sections are close to the measured data (or at least parallel to it). The calculated elevations in 2D fit quite good with a deviation of only a few cm.
Has anyone an explanation for this?

Thanks!

[PaoloP]

Jens,

in my opinion the width of flow between 2D and 1D model happen only on the width of XS -1700 (the first of 1D model) instead in the fully 2D model this width is much larger. Are you sure there is no flow in that part?

In case there is flow you should add a lateral weir to connect 2D with the downstream XSs

Paolo

[JensPK]

Hi Paolo,

yes I´m sure that there is no flow outside the river channel. You can find a railroad embankment north of XS -1700 and -3351 and I used the mean water flow for the calculations. Even high tides shouldn´t overflow the embankment.

I created another 2D net for mean water flow that only overdraws the river channel. So it has an even smaller width but it gave good results.

[PaoloP]

Hi Jens,

in your completely 2D mesh you don’t have a breakline on embankment so you don’t have cell faces on the top of embankment. I’m not sure that the embankment is well represented. Are you sure in the 2D results there is no flow across the embankment?

Paolo

[Author]

Posts