Closed sluice gate with conintued bypassing flow & no overflow – where is the flow going?

[Anonymous]

Hi

I have an unsteady hydraulic model of an canal, header pond and control gate (sluice) in-between. Along the canal are a number of pump stations; the inflow in to the header pond is equal to the sum of these offtakes.

I am trying to determine the gate opening required to give a particular head in the header pond. To do this, I have the gate opening is defined as a time series -at the start of the run the gate is completely open, at the end of the run it is closed. However, the water depth in the header does not change – even when completely closed. No flow is weiring over the structure. It appears that the flow is effectively bypassing the structure. How can this happen? It seems buggy.

Having inspecting the model reveals that the rating curve of the control gate is entirely negative. However, the flow in the upstream and downstream cross section is positive.

Has anyone experienced anything similar with sluice gates?

Any help would by much appreciated.

Phil.

P.s I have tried running the model with the gate open by a fixed amount. For some opening stages the head changes, for others it does. It does not seem consistent.

[Chris G.]

It’s hard to say what the problem might be over this forum. First make sure you model is stable. When I find a somewhat complex situation with unexplainable results, I’ll usually rebuild my model in stages, starting simple, and adding in one compenent at a time. Checking results in between each change. This usually helps me to pinpoint what the problem is.

In your case, try the model without pumps. Try stabilizing the pool by opening the gate until inflow to the header pond equals outflow through the gates. Then try adding in a pump (one at a time) and adjust the gate settings accordingly.

Hope this helps
Chris G.
@RASModel

[Author]

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