Error- Connecting 1D with Storage area

[Nisha]

Hello,
I’m trying to connect my 1D model with the storage area (as inflow and outflow), but once I connect the 1D network my model become unstable. I tried the connection with lateral structures and without lateral structures, but non of the method work. Following is on of the method I tried. Just wondering any one can share their opinion. Thanks.

[Scott Miller]

Hi Sumedha. Please draw a simple sketch of what you’re trying to do. 1D alignments and a storage area, right? Pencil and paper, if you can scan it.

[Nisha]

Hello Scott,
Thanks for the reply.
My 1D trace and the storage area is like this. I’m simulating the model under unsteady flow condition.
In reality, the storage capacity is inadequate, hence it gives the extrapolation warning. Without the storage, model is running. it becomes unstable once I install the storage. I think the way I connect the inflow and out flow are incorrect.

[Scott Miller]

It looks like attempting a lateral structure to an off line storage area was a good approach. Unless there is a significant lake in line with the system, it makes sense to go with one structure rather than two. You tried the lateral structure with a single reach, right?

In the unsteady flow analysis window, take a look into Options>Calculation Options and Tolerances. There are inline and lateral structure flow stability factors you can turn up. They dampen the calculation of flow over the structure. That can help stability. There is also a number of iterations that can be increased. The default is a single calculation, which may be way off. Try iterating the 1D/2D flow calculation (within each unsteady iteration). There is also a minimum flow tolerance, which allows those iterations to cut off at a reasonably low value. It is different for each model.

Consider how much storage is available in the storage area, and whether the water surface elevation would shoot up rapidly in a single time step. Was the extrapolation warning because the water surface was unreasonable?

[Nisha]

Thanks for the reply Scott. I have already tried changing the calculation options and tolerances. Yet it become unstable. Obviously that storage is under capacity. I have tried with less inflow,yet giving me trouble.
I tried removing the storage and installing a 2D area (in a different location). I made the 1D/2D connection using lateral structure, yet model become unstable.
The issue is I can simulate the 1D model (with extrapolating cross section warnings). But once I connect it with either a storage or a 2D area, it become unstable. Any advice?

[Author]

Posts