No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Ashok Gopinath. Includes bibliographical references (p. 101-102). Also available online.

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xvi, 219 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 166-169).

Thesis (Ph. D.)--University of Adelaide, Dept. of Applied Mathematics, 1987. / Includes bibliographical references (leaves 184-190).

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 43-45). Also available on the World Wide Web.

Yes / The present study investigates the turbulent hydrodynamics in an open channel flow with an emergent and sparse vegetation patch placed in the middle of the channel. The dimensions of the rigid vegetation patch are 81 cm long and 24 cm wide and it is prepared by a 7× 10 array of uniform acrylic cylinders by maintaining 9 cm and 4 cm spacing between centers of two consecutive cylinders along streamwise and lateral directions respectively. From the leading edge of the patch, the observed nature of time averaged flow velocities along streamwise, lateral and vertical directions is not consistent up to half length of the patch; however the velocity profiles develop a uniform behavior after that length. In the interior of the patch, the magnitude of vertical normal stress is small in comparison to the magnitudes of streamwise and lateral normal stresses. The magnitude of Reynolds shear stress profiles decreases with increasing downstream length from the leading edge of the vegetation patch and the trend continues even in the wake region downstream of the trailing edge. The increased magnitude of turbulent kinetic energy profiles is noticed from leading edge up to a certain length inside the patch; however its value decreases with further increasing downstream distance. A new mathematical model is proposed to predict time averaged streamwise velocity inside the sparse vegetation patch and the proposed model shows good agreement with the experimental data. / Debasish Pal received financial assistance from SRIC Project of IIT Kharagpur (Project code: FVP)

Flow-vegetation interactions are critically important for most hydraulic and sediment processes in streams and rivers and thus need to be accounted for in their management. The central goal of this project therefore was to improve the understanding of flow-vegetation interactions in patchy-vegetated river beds, which are typical in rivers. Based on laboratory experiments covering a range of selected hydraulic and patch mosaic scenarios, the hydraulic resistance mechanisms, turbulence structure, and transport mechanisms were studied. The effects of regular patch mosaic patterns (aligned and staggered) on the bulk hydraulic resistance were investigated first. For the cases in which the relative vegetation coverage BSA in respect to the total flume bed is low (BSA = 0.1), the patches mutual positions do not affect values of the friction factor. When the parameter BSA increases to intermediate values (BSA = 0.3), the spatial distribution of the vegetation patches and their interactions become crucial and lead to a significant increase in the bulk hydraulic resistance. When further increase of the vegetation cover occurs (BSA = 0.6), the effects on hydraulic resistance of patch patterns vanish. To clarify the mechanisms of the revealed patch effects on the overall hydraulic resistance, flow structure was assessed at both scales: individual patch and patch mosaic. The presence of a submerged isolated vegetation patch on the bed introduces a flow diversion which strongly alters the velocity field and turbulence parameters around the patch. Coherent structures, generated at the canopy top due to velocity shear, control the mass and momentum transfer between the layers below and above the vegetation patch. At the patch mosaic scale, a complex three-dimensional flow structure is formed around the patches which depends on the patch spacing and spatial arrangements. For the low surface area blockage factor (BSA = 0.1), the patches are sparsely distributed and the wakes are (nearly) fully developed before they are interrupted by the effects of the downstream patches. At the intermediate surface area blockage factor (BSA = 0.3), significant differences in flow structure between the aligned and staggered patches were observed. For the highest surface area blockage factor investigated (BSA = 0.6) both aligned and staggered patch mosaic configurations showed a similar behaviour. The results on the flow structure are used to provide mechanistic explanation of the observed patch mosaic effects on the bulk hydraulic resistance.

An experimental study on drag reduction by injection of microbubbles was performed in the upper wall of a rectangular channel at Re = 5128. Particle Image Velocimetry measurement technique (PIV) was used to obtain instantaneous velocity fields in the x-y plane. Microbubbles, with an average diameter of 30??m, were produced by electrolysis using platinum wires with a diameter of 76 ??m. They were injected in the buffer layer producing several different values of local void fraction. A maximum drag reduction of 38.45% was attained with a local void fraction of 4.8 %. The pressure drop in the test station was measured by a reluctance pressure transducer. Several parameters such as velocity profile, turbulent intensities, skewness, flatness, joint probability density function (JPDF), enstrophy, one and two-dimensional energy spectra were evaluated. The results indicate that microbubbles reduced the intermittency of the streamwise fluctuating component in the region near the wall. At the same time they destroy or reduce the vortical structures regions (high shear zones) close to the wall. They also redistribute the energy among different eddy sizes. An energy shift from larger wavenumbers to lower wavenumbers is observed in the near wall region (buffer layer). However, outside this region, the opposite trend takes place. The JPDF results indicate that there is a decrease in the correlation between the streamwise and the normal fluctuating velocities, resulting in a reduction of the Reynolds stresses. The results of this study indicate that pursuing drag reduction by injection of microbubbles in the buffer layer could result in great saving of energy and money. The high wavenumber region of the one dimensional wavenumber spectra was evaluated from PIV spatial information, where the maximum wavenumber depends on the streamwise length (for streamwise wavenumber) of the recorded image and the minimum wavenumber depends on the distance between vectors. On the other hand, the low wavenumber region was calculated from the PIV temporal information by assuming Taylor??s frozen hypothesis. This new approach allows obtaining the energy distribution of a wider wavenumber region.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: caustics; turbulence; wave propagation; ultrasonic flow meter. Includes bibliographical references (p. 82-84).