Vortical structures are regarded as the dominant organized patterns in wall turbulence. They play a key role in physical phenomena of practical importance such as energy and momentum transport, combustion, mixing, and noise and drag production. Considerable investigations have been performed in drag and noise phenomena studies, with a main purpose of controlling and reducing them. Various techniques to control the drag reduction have been studied for over last five decades; however, the detailed understanding of the drag reduction mechanism is still lacking. Vortices play an important role in turbulence structure. Nevertheless, the identification of vortices is still unclear, not even a universal definition of a vortex is accepted. In the present study, several vortex feature extraction schemes are implemented. The methods are applied to analyze instantaneous two-dimensional velocity fields obtained by particle tracking Velocimetry (PTV) measurements of a turbulent channel flow with and without microbubble injection within the boundary layer. Microbubble injection is one of the drag reduction techniques, first studied in early 1970s, that has undergone extensive research in past years, and the generated information has aided into drag reduction understanding. As a general rule, vortex extraction methods can be either a simple visualization scheme or more sophisticated identification tools. The Reynolds decomposition and its variants are suitable due to their capacity to mark vortices advecting at different velocities. In the case of identification techniques, which yield a scalar field calculated from either the velocity vector field or the velocity gradient tensor, both the modified swirling strength Λci or the λ2 criteria were found to be well suited for vortex identification.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Ashok Gopinath. Includes bibliographical references (p. 39-40). Also available online.

Thesis (M.S.)--University of Kentucky, 2004. / Title from document title page (viewed June 21, 2004). Document formatted into pages; contains xii, 117 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 113-116).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 208-218).

Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, December 2003. / Thesis advisor(s): D.L. Walters, D.K. Miller. Includes bibliographical references (p. 35-36). Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 66-69). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 130-141).

A demand for methods that can be used in the numerical analysis of three dimensional air flow in large buildings has developed as more buildings are being designed with large atriums using a solar loading that leads to complex flow. The flow in such buildings is almost always turbulent which means that turbulence models that are accurate but which do not require undue computer resources have to be selected. As a result, a numerical study of natural convective heat transfer and turbulent flows in large atria, specifically part of the Atria in the EV building at Concordia University, has been completed. Experimental work on turbulence modeling and atria design has been studied and compared with the numerical results obtained here to gain confidence in the modeling techniques used in the study. The flow has been assumed to be steady, and the Boussinesq approximation has been used. The governing equations have been numerically solved using the CFD solver FLUENT. The three-dimensional air flow in the Concordia-like atria used the following parameters: forced flow vent inlet angle; forced flow vent velocity; date and time (for solar radiation purposes). The case with adiabatic floor and ceiling conditions was examined and compared to the case with isothermal floor and ceiling conditions. Several models were studied to compare the effect of turbulent modeling in the atria, including the following: (1) K-Epsilon; (2) K-Omega; (3) Detached Eddy Simulation (DES) model; (4) Large Eddy Simulation (LES) model. Further study was completed after it was noted the flow was completely based on natural convection when the velocity of the inlet flow was set to zero. In addition, experimental results were available and this situation was modeled using similar parameters to the work explained above. Comparing these results supported the accuracy of the work done on the Concordia Atrium. Experimental work on the Annex 26 Atrium in Yokohama Japan was also compared to numerical results to gain confidence in techniques used in the present study and results were obtained that were in good agreement. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-05-21 16:21:27.82

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