Modeling Tide Gate with HydroCAD Version 9

[login67]

I read from "HydroCAD tips" that in HydroCAD version 9.0 and below, gates can sometimes be modeled using "pump" outlet. I am looking for help on how to setup data in the pump window so the pump understands I am only modeling a gate and not a pump per se. What I have is a 48-inches RCP pipe fitted with a tideflex valve at the end and the tidlex closes at high tide and opens at low tide to discharge roadway drainage flows. Any help is highly appreciated. Thanks in advance for your help.

 

[psmart]

All HydroCAD outlet devices behave as if they had a 1-way value attached. They permit flow only in the direction of the outflow arrow. If the tailwater exceeds the headwater you will get zero discharge until the tailwater drops below the headwater. You will never get any flow in the reverse direction, as if your valve has closed.

In your case, a culvert outlet will give the behavior you're looking for. You don't need to do anything else.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[login67]

Thank you very much Mr. Smart. I did follow your suggestion about the tide gate modeling but I get three warnings:
1- Pond XXX Qout>Qin may require Finer Routing or smaller dt
2- Pond XXX Oscillations may require Finer Routing or smaller dt
3- Downstream Pond exceeded upstream Pond by XXX.

The online help suggests that all three warnings may be resolved by increasing the finer routing value, reducing the time increment, or increase the available storage. I did set my finer routing to 3, reduce my time increament to 0.01 hrs and have no catch basin flood elevation exceedance. I am using the SBUH and the Dyn-Stor-Ind reach routing method to route flows through connected storm sewers which eventually discharge to a tidal creek. Any suggestion on how to overcome these warning messages? Thanks again for your support.

 

[psmart]

A reverse-head warning is to be expected at the valve: This indicates the reverse-head when the valve is closed. However, the oscillations need to be resolved. I suggest you set the finer routing to 1 and the time step to 0.01 while you locate the source of the problem. Since oscillations will propagate through the entire model, make sure you review all the warning messages. If you have further questions please post the HydroCAD project file or send it to HydroCAD support.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[login67]

Mr. Smart. Still no success with my model. Please see attachment for my model setup. Thanks.

 

[psmart]

The oscillations seem to occur at the very end of the storm, and can be avoided if you reduce the calculation time span to 0-20 hours. (NOT the rainfall duration, just the calculation span)

You appear to have unrouted grate overflows on most of the CB's. These must be routed somewhere or the overflow will "disappear" from the model.

I believe the remaining reverse-head messages are the expected result of the tidal tailwater. You can disconnect the tailwater link to see how the system behaves with free discharge.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[login67]

Thank you very much for your support. It works when I reduce the calculation time span. Suppose the oscillations occur at or near the peak of the storm this approach will not work. Correct? In that case, what other options are worth exploring? As always, your support is highly appreciated. Thanks again.

 

[psmart]

Actually, your high tide and storm peak are both near 12 hours, and the oscillations are at 20+ hours, so they don't really compromise the primary analysis.

Peter Smart
HydroCAD Software

http://www.hydrocad.net