Modeling of a Floating Outlet (Flout by Rissy Plastics) in HydroCAD 9

[dnrandall]

I am attempting to model a floating outlet within a tank in HydroCAD 9. This outlet device does not operate like a skimmer. It has an air chamber that causes the end of the arm to float until the high water level is reach, where the float losses its buoyancy. It then begins to discharge at 0.2 cfs until low water level is reached and the discharge arm is horizontal. When the low water level is reached, the air chamber becomes buoyant again, and the floating outlet arm rises with the water level (with no discharge) until high water level is reached. Then the cycle is repeated. This unit basically creates dosing of the discharge. I have attached a PDF of the manufactures drawing of the unit to help with visualization of the operation.

Any ideas on modeling this would be greatly appreciated.

 

[psmart]

The challenge in modeling this device is the hysteresis in the stage-discharge curve. In other words, at a given elevation the discharge could be zero or 0.2 CFS, depending on whether the pond is filling up from empty (zero flow) or emptying from the trip point (0.2 CFS).

What you need is a way to define the trip points where the float loses and then regains buoyancy. I suspect this could be achieved by using the "pump" outlet option, with the "on" and "off" elevations set to the upper and lower trip points. For the pump rating curve, you would just set the 0.2 CFS discharge for any head.

I would have to give it a try to know for sure, but I think this would solve your problem.

BTW, your need to select the DSI routing procedure in order to allow for hysteresis and enable the on and off fields on the pump screen.



Peter Smart
HydroCAD Software

http://www.hydrocad.net