Start Date

6-29-2016 1:30 PM

End Date

6-29-2016 3:30 PM

Abstract

Air vent systems are designed to protect hydropower penstocks and reservoir outlets under various operating conditions. During an emergency closure of an upstream gate the hydraulic jump that forms downstream of the gate is not stationary and may advance downstream potentially increasing the total air demand. A lab-scale physical model of a general outlet works piping configuration was constructed at Reclamation’s Hydraulics Laboratory in Denver, CO to observe hydraulic jump behavior during emergency gate closures. Parameters including gate discharge, gate closure rate, air vent size, and downstream pipe pressure were tested at two different pipe slopes. Results indicate that the hydraulic jump travel speed is dependent on air vent size as well as gate closure rate, both of which affect the internal pressure in the pipe near the vent connection. For a shallow-sloped pipe, the jump speed remains steady throughout the entire pipe length if the air supply is sufficient. However, if air flow is significantly reduced due to an undersized air vent, unsteady travel speeds and pressure surges were observed. This was not the case for a steep-sloped pipe which produced steady jump speeds for all vent sizes. Once completed, these results are expected to be applicable for prediction of hydraulic jump travel speed and its effects on air demand for vent sizing considerations based on hydraulic operating conditions.

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Jun 29th, 1:30 PM Jun 29th, 3:30 PM

Effects of Hydraulic Jump Motion on Air Entrainment in Closed Conduits

Portland, OR

Air vent systems are designed to protect hydropower penstocks and reservoir outlets under various operating conditions. During an emergency closure of an upstream gate the hydraulic jump that forms downstream of the gate is not stationary and may advance downstream potentially increasing the total air demand. A lab-scale physical model of a general outlet works piping configuration was constructed at Reclamation’s Hydraulics Laboratory in Denver, CO to observe hydraulic jump behavior during emergency gate closures. Parameters including gate discharge, gate closure rate, air vent size, and downstream pipe pressure were tested at two different pipe slopes. Results indicate that the hydraulic jump travel speed is dependent on air vent size as well as gate closure rate, both of which affect the internal pressure in the pipe near the vent connection. For a shallow-sloped pipe, the jump speed remains steady throughout the entire pipe length if the air supply is sufficient. However, if air flow is significantly reduced due to an undersized air vent, unsteady travel speeds and pressure surges were observed. This was not the case for a steep-sloped pipe which produced steady jump speeds for all vent sizes. Once completed, these results are expected to be applicable for prediction of hydraulic jump travel speed and its effects on air demand for vent sizing considerations based on hydraulic operating conditions.