Vineela – Have you turned on iterations for 1D/2D flow computation?
Unsteady Flow Analysis Plan – Options > Computation Options and Tolerances > 1D/2D Options tab. The default maximum iterations between 1D and 2D is 0. It does not iterate unless to tell it to. Even if there is a difference in water surface elevation over a lateral structure, the simulation holds each solution moving into the next time step. In a single time step, for the entire model, 1D/2D water surface elevation can iterate up to 20 times. Iteration of 1D/2D water surface elevations within a single time step can help the difference you see converge.
On the General tab – 1D2D Unsteady Flow Options you can also adjust the lateral structure flow stability factor. Also look into setting flow tolerances. In a 1D/2D model with multiple lateral structures, I believe it may be helpful to equalize the flow through each (more or less), such that the flow through one does not control all the iteration.
Unsteady Flow Analysis Plan – Options > Computation Options and Tolerances > View Computation Log File. Verify that the Volume Accounting is reasonable.
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