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This dissertation investigates the effect of airfoil steady loading on the sound generated by the interaction of an isolated, zero-thickness airfoil with a high-frequency convected disturbance. The analysis is based on a linearization of the inviscid equations of motion about a nonuniform mean flow. The mean flow is assumed to be two-dimensional and subsonic. Throughout most of the dissertation, we assume that the Mach number is 0(1), though in one section we concentrate on the leading-edge region and study the behavior of the sound field as the Mach number tends to zero. The small parameter representing the amount of airfoil camber and incidence angle, and the large parameter representing the ratio of airfoil chord to disturbance wavelength, are utilized in a singular perturbation analysis. The analysis shows that essentially all of the sound is generated at the leading and trailing edges, in regions the size of the disturbance wavelength. The solution in the local-leading-edge region reveals several sound-generating mechanisms which do not exist for an airfoil with no mean loading. These mechanisms are not present at the trailing edge; the trailing edge is important only as a scatterer of the sound produced at the leading edge. The propagation of sound away from the airfoil edges is described by geometric acoustics, with the amplitude varying on the scale of the airfoil chord and the phase varying on the much smaller scale of the disturbance wavelength. In addition, a diffraction-type transition region exists downstream of the airfoil. Calculations of radiated acoustic power show that the sound field depends strongly on Mach number, gust characteristics, and airfoil steady loading. Small changes in these properties can produce large changes in radiated power levels. Most importantly, we find that the amount of power radiated correlates very well with the strength of the mean flow around the leading edge.

Geometric modification as the most effective passive flow control method has recently received wide attention due to its enormous potential in enhancing performance characteristics of airfoils or hydrofoils without expensive manufacturing and maintenance cost. Two primary passive flow control modifications, known as leading-edge tubercles and internal slots and their applications in airfoils/hydrofoils have been investigated in this dissertation. For the hydrofoil, since free surface effects cannot be neglected, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil has been studied as well. In the theoretical approach aspect, an empirically-based model based on an iteration scheme has been proposed for predicting the lift coefficients of twisted airfoils with leading-edge tubercles by using experimental data for untwisted airfoils. With both numerical and experimental investigations, this dissertation has discussed the application of a custom optimized-design internal slot on a NACA 634-021 airfoil blade to allow ventilation of flow through the slot from the pressure side to the suction side of the blade, in support of delaying flow separation, and stall. The combined effect of an internal slot in an airfoil and transverse leading-edge tubercles on its performance has been further studied both numerically and experimentally. Moreover, performance of a NACA 634-021 hydrofoil in motion under and in close proximity of a free surface for a large range of AoAs has been studied. Lift and drag coefficients of the hydrofoil at different submergence depths are investigated both numerically and experimentally. The results of the numerical study are in good agreement with the experimental results. The agreement confirms the new finding that for a submerged hydrofoil operating at high AoAs close to a free surface, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil results in mitigation of the flow separation characteristics on the suction side of the foil and delay in stall, and improvement in hydrofoil performance. A similarly submerged hydrofoil with a custom-designed internal slot has further been studied. The performance characteristics of the slotted hydrofoil in the presence of the free surface are investigated both numerically and experimentally. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Knox Millsaps. Includes bibliographical references (p. 69-72). Also available online.

An effective method, based on hodograph theory, has been developed for the aerodynamic design of subcritical and shock-free supercritical airfoil sections. In addition to the free-stream conditions, the input to the design procedure includes a prescription of the subsonic part of a target pressure distribution and, for supercritical airfoils, of a presumed stream function on the sonic line. A computer program carries out a number of sequential steps that result in an airfoil with a pressure distribution close to that desired at little computational cost. Thus, the airfoil designer can alter the input if design goals are not met and quickly produce another candidate airfoil. This is aided by appropriate graphic display of the airfoil and its pressure distribution.

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Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 26, 2008) Includes bibliographical references (p. 102-104).

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jagoda, Jechiel; Committee Co-Chair: Jacobs, Laurence; Committee Member: Seitzman, Jerry. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 355-359). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on Nov. 16, 2009. "September 2009." "In partial fulfillment of the requirements for the degree [of] Master of Science in Aerospace Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: David D. Marshall, Ph.D. Includes bibliographical references (p. 85-87).