No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 92-93). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1953. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 97-99).

Inaug.-diss.--Marburg. / Lebenslauf.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Unlike conventional propellers, flapping wings may generate large amplitude oscillating forces, which can make them difficult to incorporate into a craft design. This is particularly true for a single, vertically oscillating hydrofoil, as part of a surface water craft where the cyclic lift of the hydrofoil disrupts the craft stability. This thesis begins by reviewing the history of human-powered watercraft with a focus on those having flapping foil propellers. This review combined with a review of the literature provides a balanced overview on how flapping wing propellers are currently designed. Current literature shows that although the mean performance of an oscillating foil has been determined in terms of the Strouhal number and the angle of attack, relatively little describes performance directly in terms of the foil motion. Hence, predicting temporal hydrodynamic forces acting on an oscillating foil is difficult. This provides motivation for research investigating the temporal performance of an oscillating foil directly in terms of its motion. In this thesis, experimental equipment designed to measure the hydrodynamic forces on a heaving object is presented. Key features of the equipment are analysed to show how measurement accuracy is maintained. Experimental measurements of unsteady hydrodynamic forces acting on a heaving cylinder, flat plate, symmetrical foil, and an asymmetrical foil are analysed with respect to the heaving motion. Firstly, the object motion is limited to one degree of freedom; pure heaving with zero forward velocity, to investigate the start-up conditions of the oscillating hydrofoil propeller. Secondly, these results are expanded on by adding a steady forward velocity component to the object motion to investigate how the hydrodynamic forces on the object are affected by the cross-flow. Experimental temporal hydrodynamic force measurements presented in this thesis show how the relative composition of hydrodynamic drag and inertia forces change with oscillating frequency, and forward velocity, affecting the phase, magnitude, and profile of the force cycles. This composition is also influenced by the cross-section of the oscillating object and the presence of a free surface. Current marine engineering equations for unsteady hydrodynamic forces on an object in an oscillating flow are validated for a cylinder. However, they are found to contain significant error when predicting the unsteady hydrodynamic forces on an oscillating hydrofoil. Contributions of this thesis link oscillating foil propulsion research to common marine engineering equations with the intent of making flapping wing propeller design more accessible to the general engineering community.

A análise harmônica e o ramo da matemática que estuda a representação de funções ou sinais como a sobreposição de ondas base. Ela investiga e generaliza as noções das séries de Fourier e da transformação de Fourier. Neste trabalho, investigou-se um teorema de restrição da transformada de Fourier devido a Mitsis e Mockenhaupt (uma generalização do teorema de Stein-Tomas). Foram realizados estudos analíticos sobre o método para operadores integrais oscilatórios, baseado na fase estacionária. Os resultados permitem deduzir o teorema de restrição no plano (em seu caso geral) e o teorema de Carleson-Sjölin. / Harmonic analysis is the mathematical branch that studies the function or signals representation as a base wave overlay. It investigates and generalizes the notions of Fourier series and of the Fourier transform. In this work, was investigated a restriction theorem of the Fourier transform due to Mitsis and Mockenhaupt (a generalization of Stein-Tomas theorem) . Were performed analytic studies on the method for oscillating integral operators, based in the stationary phase. The results allow deducing the restriction theorem on the plane (in the general case) and the Carleson-Sjölin theorem.

The present thesis is examining the forced vibrations of a circular cylinder in the low Reynolds number flow of 200. A numerical study is performed that employs an already existing algorithm developed by (Breuer 1998) and enhanced with the characteristic of the cylinder's motion by (MadaniKermani 2014) who employed the moving frame of reference method of (L. Li, Sherwin et al. 2002). The algorithm was extensively assessed for the benchmark studies of flow around a stationary circular cylinder. A new observation was made on the effect of the aspect ratio of the computational cells in the mid region of the wake. The studies so far are emphasizing on the characteristic of a dense mesh, with a small aspect ratio, in the high divergence areas in the near region of the cylinder surface, neglecting the effect of the regions away from the surface. The present study on a stationary circular cylinder flow, proved that the aspect ratio of the distant cells has a significant effect on the St number and the force coefficients. The main study of the thesis emphasizes on the lock-in region where the wake oscillates in unison with the harmonic motion of the cylinder. The study makes a new observation on the qualitative and quantitative description of the lock-in conditions. In particular, it reveals two regions of resonance and non-resonance lock-in. Despite the fact that the lock-in is achieved, when the frequency ratio is in the first part of the region away from the unity ratio, the forces are not greatly magnified. As the ratio approaches the unity the forces experience a resonance that reaches the highest value after the unity. Furthermore, the adaptation time of the flow to the motion of the cylinder is examined and extends the results of (Anagnostopoulos 2000) to the full extent of the lock-in and the non-lock-in regions. More precisely the flow strives to reach a steady state when it is in the lock-in region rather in the non-lock in cases it reaches the steady state faster. It is postulated that the adaptation time depends on both the numerical and the physical adaptation. Moreover, the force coefficients characteristic of sinusoidal behaviour in the lock-in region is attempted to be approximated by a Newton polynomial that is built by making use of the divided differences method. The amplitude of the forces is approximated by a third degree Netwon polynomial built from the results of the present thesis simulations. The use of an approximation is providing faster results ignoring the need for a full resolution of the Navier-Stokes equation.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Ekaterinaris, John A. ; Platzer, Max. "September 1990." Description based on title screen as viewed on December 21, 2009. DTIC Identifier(s): Dynamics, leading edges, airfoils, dynamic stall, oscillating airfoil, pitching airfoil, leading edge geometry, pressure gradient, theses. Author(s) subject terms: Dynamic stall, oscillating airfoil, pitching airfoil, leading edge geometry, pressure gradient. Includes bibliographical references (p. 111-112). Also available in print.