Date of Award

7-31-2018

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

Erin E. Hackett

Second Advisor

Roi Gurka

Third Advisor

Diane Fribance

Abstract

Turbulent boundary layers are influential in numerous applications (e.g. naval architecture, ocean engineering, sediment transport, etc.), yet considerable knowledge gaps still exist. Boundary layers are regions where transfer of mass, momentum, energy, and heat occur within the interface between a fluid and a solid, or between two fluids. Utilization of optical flow measurement techniques to measure the velocity field with high spatial resolution enables non-intrusive investigation of the complex fluid dynamics of boundary layers. In this study two-dimensional Particle Image Velocimetry was employed to investigate, primarily, the overlap layer of a turbulent boundary layer developed in the recirculating flume facility located in the Environmental Fluids Laboratory at Coastal Carolina University. Three locations in the streamwise direction and two locations in the spanwise direction were investigated covering a range of Reynolds numbers, 〖Re〗_D = 32,432 - 65,586. The overarching goal of this research was to i) investigate the flow characteristics of turbulent boundary layers in open channel flow and ii) provide benchmark results for future studies conducted in this facility. We calculated from the two measured velocity components (streamwise and vertical) over two spatial dimensions (streamwise and vertical) various mean flow and turbulent quantities. Results for the facility indicated: i) a distinct overlap layer existed between ~100 < y+< ~400, ii) a shape-factor characteristic of a zero-pressure gradient boundary layer, iii) turbulent intensity is relatively constant over the range of 〖Re〗_D (4-10%), iv) peak of TKE production occurred at the lower limit of the overlap layer and iv) free-surface effects influenced flow up to 20% of the water depth below the surface. Based on results and findings in this study, users should conduct experiments along the channel middle to avoid the influence of sidewalls, between 40-80% of the water height to perform measurements in the region of lowest turbulence intensity, and between 0-40% of the water height to perform turbulent boundary layer measurements.

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