Turbulent Velocity Flutuations in Natural Riversby Nani G. Bhowmik, Illinois State Water Survey, Champaign, United States,
Renjie Xia, Illinois State Water Survey, Champaign, United States,
Abstract: The longitudinal and transverse components of flow velocity, as well as the normal and tangential stresses, must be expected to fluctuate with time and space when flow at a high Reynolds number moves between fixed boundaries. Although these nonperiodic fluctuations are generally secondary in magnitude compared to the mean motion, they have profound effects on properties of the primary mean motion. Scientists from the Illinois State Water Survey are involved in collecting and analyzing detailed velocity data from the Illinois and Mississippi River using 2-D electromagnetic current meters. The goal of the present research is to understand and evaluate the turbulent structure in natural river systems, especially near the channel border areas. The fluctuations characteristics of flow velocity were analyzed systematically. Flow velocities were measured with time and six different lateral locations and at three different vertical elevations. Analyses of the velocity data included the cross-sectional and vertical distributions of longitudinal and transverse velocity components (u, v), the fluctuating velocity components (u1,v1) and their frequency-distribution curves, turbulent intensities(σx,σy), turbulent shear stress (-ρu1v1), and turbulent kinetic energy.
Subject Headings: Turbulent flow | Velocity distribution | Wave velocity | Fluid velocity | Flow measurement | Rivers and streams | Shear stress | Stress analysis | Flow duration | North America | Illinois | United States | Mississippi River
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