Civil Engineering ETDs

Jungseok Ho

Publication Date

11-28-2006

Abstract

The primary objective of this study is to develop and use physical and numerical modeling techniques to predict the hydraulic impact on the Rio Grande induced by the Albuquerque diversion structure and its operation. A 1:24 scale distorted movable bed model, constructed and tested to investigate the hydraulic performance of the diversion structure, provided measurements for validating the numerical models developed in this study. Crushed coal was substituted for the prototype sediment particles and a 6.5 times steeper channel bed slope were employed to obtain sediment transport model similitude.

The diversion structure consists of an overshot gate system that can control the water surface elevation of the upstream pool over various river flow rate conditions. With the diversion gates in operation, up to 93.1 m3/s (3,288 ft3/s) of river flow rate can be maintained at the design water surface elevation of 1,522.5 m (4,995 ft). Flow patterns due to three different gate opening scenarios (left side gate opening, right side gate opening, and evenly-distributed gate opening) were compared with the full gate opening scenario, which assumed river flow with no diversion gates. A two-dimensional hydrodynamic model was simulated and verified with the physical model measurements. More gates must be opened opposite the intake structure to achieve the same water surface elevation as fewer gates opened near the intake structure. However, velocity and turbulence increases when the gates near the intake structure are opened (the left side gate opening scenario), resulting in more sediment transport to the intake structure. The evenly distributed gate opening scenario results in minimizing the impacts to river flow while spreading those impacts across the river.

As with other diversion structures, sediment exclusion and fish passage were of great importance. After a total of 13 different design alternatives and 24 tests conducted using the physical model, as well as a three-dimensional computational fluid dynamic model, independent submerged vanes were recommended for the sediment exclusion system. A 45° rotated intake channel worked well with the sediment exclusion vanes and was able to effectively divert the river flow. A porous media numerical scheme was used for modeling the fish screen material at the intake channel, showing very positive agreement with the physical model measurements. Different screen types with different ratios of sweeping to approach velocities were tested in both the physical and numerical models. A wedged wire type of screen with a 10:1 velocity ratio was shown to be the most effective in guiding the fish out of the intake channel while the desired flow rate could reach the pumping station for future treatment.

This study presented a numerical prediction method for determining the impacts on a river of a proposed hydraulic structure. Geographic Information Systems were used to generate contour maps of the prospective impacted regions for the flow properties of flow velocity, water depth, water surface elevation, and channel bed shear stress. The pools upstream of the gates were predicted to be the regions with the most water depth impacts. The channel bed around the opened gates and the islands located at the upstream of the diversion structure are shown to be the regions with the most channel instability.

This type of study provides valuable information for the proposed hydraulic structure design as well as provides reliable data for a structure operation and maintenance after calibration \vith prototype measurements. The numerical modeling techniques developed in this work can be utilized in similar situations where the impacts of a diversion structure on a river are to be determined.

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Julie Coonrod

Second Committee Member

Brett Mefford

Third Committee Member

Grant Meyer

Fourth Committee Member

Bruce Thomson

Fifth Committee Member

Timothy Ward

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