Flow direction in 2D/1D connection

[Yui]

Hello,

I have a 1D/2D HEC-RAS model but I find flow direction at some places are not correct. Water in 2D flows opposite direction of 1D flow. I tried interpolate XS but did not work.

Here are some screenshoot

Do anyone know how to fix this problem?

Thanks in advance.
Yui

[ckatsoulas]

I don’t think it’s incorrect. Your first picture shows some flows escaping the channel as overflows and then re-entering the channel further down.

The second picture which is probably your main concern is showing spilling from the south. It then hits a wall/mound and due to the reverse crossfall of the berm it creates eddies that spill backwords and return to the channel upstream.

You will notice in the second picture that where it hits the wall/mound right on the left of the bend there is splitting of overflows, some go forward and others hit the wall and form eddies and come back.

The same thing is happening in the third picture to the north as it hits that small mound.

I think due to the momentum of the main channel, the overflows are bouncing off the mounds and heading backwards.

[Yui]

I made a new model with whole area 2D and this problem is solved, but I still don’t know why in 1D/2D model water flow was like that.

Another problem after I check the all 2D model is that velocity in channel is very strange when flow increase. After reach a certain flow, the problem disappears. I have tried larger cell size but didn’t solve the problem. Anyone can help?

[Author]

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