User Forum of Software BASEMENT

chri_and

User

Registered: 2017-07-27

Posts: 34

Sediment pilling up at Inner_boundary type weir

Hello

For my 2D simulation I'm using an Inner_boundary of type weir under Morphology/bedload to manipulate the amount of sediment released downstream of the weir. To do this I have created a file with weir height that changes over time. Following the behaviour of the discharge hydrograph, at time 0 the weir is high as the river bed bottom, it increases, remains stable for the middle pahse of the hydropraph and then decreases until the end of the simualtion.  When I tried this I get right from the beginning  sediment pilling up at the side of the weir. This effect vanishes gradually by setting a weir height higher than the river bed bottom at the beginning of the simulation. If the weir height is equal the high of the lateral banks at the beginning of the simulation, then this effect disapperar. How can I get sediment over a weir for weir height lower than the banks?

PS: I'm using gravtitational transport

Cheers

Matthias Bürgler

Developer

From: Zürich

Registered: 2019-04-04

Posts: 150

Re: Sediment pilling up at Inner_boundary type weir

Hi chri_and

From your description i don't fully understand where the problem lies in your case.

The inner boundary type "weir" for sediments results in sediment transport over an edge if the average bed level of the edge is higher than the weir level (z_edge > z_weir). In this case, the entire sediment volume of the adjacent cell that is higher than the weir level is transport downstream. Therefore, the bed level cannot get above the weir crest elevation. On the opposite, this boundary acts like a "wall" when the average bed level of the boundary edge is below the weir level (z_edge <= z_weir), i.e. no sediment is transported downstream.

I hope this helps.

Best regards
Matthias