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Hi,

I am working on a large coastal model where I prescribed water levels on two open boundaries. While the model has reproduced the water level fairly well throughout, I am having some problems getting the current direction to match.

Looking at the surface water level near the open boundary, I noted that the general flow direction takes 4-5 hours to change when the tide changes from ebb to flood (and vice versa). I have attached two figures here showing the surface water level and current vector over a period of 8 hours when the tide switched. As shown on the figure, the flow continues to exit the open boundary for several hours even though the water level at the boundary is higher.

Does anyone have any suggestion on what I can try to have the flow direction responding better with changes in water level?

Thanks.

Edwin

Hello,

Would it be possible that your two levels on either side are not zeroying to the same datum. If you had a slight difference, your signals could create a residual flow from the higher level to the lower which might be harder to overcome.

Friction and bathymetry of course would have to be looked closely otherwise.

Hope this helps,
Sébastien.

Thanks Sébastien.

I was using the 'pseudo' water levels which were based on the predicted water levels at the boundaries in addition to observed surge effects from nearby stations. When I applied just the predicted water levels at the boundaries, I got much better flow vector results.

Edwin

Your are welcomed.

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