Date of Award:

8-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Steven L. Barfuss

Committee

Steven L. Barfuss

Committee

Zachary B. Sharp

Committee

Michael C. Johnson

Abstract

Dams and spillways play a vital role in managing water resources. Many of these hydraulic structures feature a falling jet when discharging downstream. Engineers design plunge pools to receive jets with enough water depth or a protective liner to protect the river bottom so that scour is avoided. Quantifying the pressures at the bottom of the falling jet is a key component to determining the potential for scour and the need for mitigation techniques.

In the laboratory setting, significant discrepancies have been observed between different measurement methods to measure mean and fluctuating pressures of a falling jet intercepting a solid physical boundary. The focus of this research was to evaluate measurable discrepancies between different measurement methods at the impact point on a solid boundary of a falling jet. The laboratory measurements of this study were also compared to numerical modeling and theoretical calculation methods.

A laboratory test fixture was constructed to monitor pressures induced by the falling jet using the following instruments: a flush mounted pressure transducer, a pressure transmitter, and a piezometer. Jet velocity and fall height were the variables associated with this testing. The test fixture conditions were also simulated numerically with computational fluid dynamics and calculated using fundamental equations of momentum. These numerical and theoretical calculation methods simply provided another measurement for comparison.

It was the aim of this study to make conclusions about the appropriate use of different methods of measurement in this scenario. Trends were identified that give insight into the pressures resulting from the various measurement methods. The flush mounted transducer, pressure transmitter, and piezometer produced similar results at the 2-ft and 5-ft fall heights. At the 10-ft fall height, the resulting pressure from the flush mounted transducer was notably different from pressures recorded using the pressure transmitter and the piezometer. This paper discusses conclusions that have been made regarding the most acceptable methods for measuring pressure at the impact point of a falling jet in a laboratory setting.

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