Civil Engineering

 

Date of this Version

Summer 7-2013

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of the Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor David Admiraal. Lincoln, Nebraska: July 2013

Copyright 2013 Mohamed M. Jalloh

Abstract

The South Florida Water Management District (SFWMD) uses G304 control structures to manage flow into and out of a large storm-water treatment area (STA). These structures consist of a lateral unsuppressed weir, a sluice gate and a corrugated culvert for flow control and transfer through an embankment. For better flow control in the STAs, it is imperative to accurately measure the discharge through the G304 control structures and to determine the approach velocity over the weir for different field scenarios.

Flow behavior of the G304 structure was examined in a prototype during two days of testing for two canal headwater elevations. The complexity of the inflow over the weir and the difficulty and cost of varying flow in the field made it desirable to use a model to further investigate the structure. Thus, a 1:6.26 Froude-based physical model was used to simulate additional flow conditions over the weir.

Large-Scale Particle Tracking Velocimetry (LPTV) was used to determine surface velocity contours for both the prototype and the model. By applying standard assumptions about the velocity profiles in the flow, the mean velocity and discharge were calculated from the surface velocity measurements. These measurements were compared with discharge measurements using an Acoustic Doppler Flow Meter (ADFM) and an array of Acoustic Doppler Velocimeters (ADVs) in the prototype and a weigh tank in the model.

For the prototype tests, the LPTV discharge measurements upstream of the weir were in close agreement with the discharge measured using ADFM and ADV devices. The results also showed that LPTV discharge measurements directly above the weir were very low. Laboratory results confirmed that LPTV is a good method for estimating discharge over this type of structure, especially when the discharge is measured well-upstream of the weir where the velocity distributions approach uniform flow behavior. It was also observed that wind and side abutments had a significant influence on the measured surface velocity and the distribution of flow over the weir.

Advisor: David Admiraal

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