Quantification of shear stress in a meandering native topographic channel using a physical hydraulic model
Date
2011
Authors
Ursic, Michael E., author
Thornton, Christopher I., advisor
Abt, Steven R., committee member
Williams, John D., committee member
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Abstract
Current guidelines for predicting increases in shear stress in open-channel bends were developed from investigations that were primarily prismatic in cross section. This study provides possible increases in shear stress relative to approach flow conditions resulting from planimetric and topographic geometric features. Boundary shear stress estimates were determined by several methods utilizing acoustic Doppler velocimeter (ADV) and Preston tube data in a physical model of a full meander representing native topographic features found in the Middle Rio Grande. Methods examined include: the law of the wall, Preston tube, turbulent Reynolds stress approximations, and a turbulent kinetic energy (TKE) proportionality constant approach. Results from each method were compared by magnitude and distribution and limitations were noted. Measured boundary shear stresses in the bend were, in some instances, nearly thirteen times the approach shear stress. Relationships were determined for the expected increase that may provide practical application. Measured bend velocities were four times greater than approach velocities and relationships were determined between velocity and bend geometry. Multipliers for shear stress and velocities were determined for one-dimensional model results.
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Subject
shear stress
physical model
native topography
meandering bend
Rio Grande