Semester of Graduation
Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
The Lower Mississippi River Physical Model (LMRPM) is a distorted, movable-bed physical model that replicates the hydraulics and bedload (sand) transport of the lower 195 miles of the Mississippi River. One year of flow and sediment transport on the prototype can be modeled in approximately one hour. With the ability to simulate long periods of time on the Lower Mississippi River in such a short time frame, the model can provide unique insight into subjects such as the potential effects from relative sea level rise on the lower river’s hydraulics and sediment transport. Quantifying discharge on the LMRPM is an important step in understanding these mechanics. This research involves a series of experiments on the model in which the OSS-PC1 Miniature Current Meter was evaluated for its ability to measure velocity that could then be used to calculate discharge. First, dye tests were performed to ensure the presence of the current meter was not causing significant flow separation at the point of measurement. Then, constant discharges were run without sediment on the model to determine the optimal measurement time interval for the current meter and variation in velocity when the meter was moved vertically and horizontally within several cross-sections throughout the channel. Next, surface velocities were measured and compared to the measured current meter velocities. Then, a series of historical hydrographs were run with sediment on the model to quantify the variation in velocity with respect to headbox discharge during a typical experiment on the LMRPM. Finally, velocity measurements along with calculated cross-sectional areas were used to calculate discharge with the continuity equation. Results showed that the current meter measured point velocities approximately equal to surface velocities which were typically much higher than cross-sectional average velocities. In addition to this, results indicated that due to the mobile bed, during the same headbox flows there were significant differences in measured velocities at most locations, and as a result, a large range in calculated discharge. Therefore, while the methods used in this research are not sufficient for studying processes such as overbank flow, they can potentially be used for quickly measuring surface velocities on the model. With some suggested improvements to these methods as well as the addition of a second current meter or a combination of the current meter and surface velocity tests, results would likely yield much smaller deviations in velocity and more accurate discharge calculations.
Cagle, Taylor S., "Quantifying Discharge on the Lower Mississippi River Physical Model" (2021). LSU Master's Theses. 5358.