For steady free-stream, zero and favorable pressure gradient turbulent boundary layers, the unsteadiness in the form of turbulent fluctuations was investigated. Phase ensemble-averaged flow characteristics of a large amplitude periodic unsteady turbulent boundary layer was also investigated at a reduced frequency k = 0.61 based on the length of the converging and diverging test section with amplitude to mean velocity ratio of 0.8. In steady flow cases, both zero and favorable pressure gradient flows show good two-dimensional flow characteristics and mean flow characteristics are compared with other researchers’ data. Measured power spectral data show good agreement with those of Klebanoff, Ueda and Hinze, Perry, Lim and Henbest for the zero pressure gradient flows and Jones and Launder for the favorable pressure gradient flow. The power spectral data measured in the turbulent wall region of the zero pressure gradient flow closely follow the model equation proposed by Perry, Lim and Henbest. Convective wave speed also show good agreement with those of Favre, Gaviglio and Dumas and Sternberg within the experimental uncertainties. In the inner region of the boundary layer where y+ < 40, convective wave speed is higher than local mean velocity at all eddy scales as observed by Kline, Reynolds, Schraub and Runstadler. In the unsteady flow case, in the absence of flow reversal, the flow behaves in a quasi-steady manner and can be described by the steady flow structure as in the case of moderate amplitude flows. The Ludwieg·Tillmann skin friction equation and the Perry-Schofield universal velocity defect law hold at these phases. Except the laminariscent velocity profile observed during the acceleration phases, the large amplitude unsteady flow shows basically the same flow characteristics as the moderate amplitude flows. / Master of Science

<p> This thesis is an experimental study of the effects of injecting dilute polymer solutions into a turbulent boundary layer developed on a flat plate submerged in water.</p> <p> A flat plate having a plexiglass surface together with a separate leading edge piece were specially designed for observing the boundary layer phenomena. Aqueous polymer solutions were introduced into the boundary layer through a slit situated in the leading edge piece. Hot-film anemometer technique was employed in the measurements of velocity profiles, turbulence intensities and lateral correlation coefficients at several locations on the plate. The investigation was carried out for two Reynolds Numbers, based on the length of the plate, of 2.4 x 10^5 and 6.4 x 10^5. The variation in the drag force with respect to the polymer concentrations and the injection rates was assessed based on the velocity profile data. It was found that the momentum diffusivity was smaller than for pure water, and that the presence of the polymer molecules seemed to promote a more uniform distribution of the sizes of the turbulence eddies.</p> / Thesis / Master of Engineering (MEngr)

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