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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Synchronization and phase dynamics of oscillating foils

Unknown Date (has links)
In this work, a two-dimensional model representing the vortices that animals produce, when they are flying/swimming, was constructed. A D{shaped cylinder and an oscillating airfoil were used to mimic these body{shed and wing{generated vortices, respectively. The parameters chosen are based on the Reynolds numbers similar to that which is observed in nature (104). In order to imitate the motion of ying/swimming, the entire system was suspended into a water channel from frictionless air{bearings. The position of the apparatus in the channel was regulated with a linear, closed loop PI controller. Thrust/drag forces were measured with strain gauges and particle image velocimetry (PIV) was used to examine the wake structure that develops. The Strouhal number of the oscillating airfoil was compared to the values observed in nature as the system transitions between the accelerated and steady states... As suggested by previous work, this self-regulation is a result of a limit cycle process that stems from nonlinear periodic oscillations. The limit cycles were used to examine the synchronous conditions due to the coupling of the foil and wake vortices. Noise is a factor that can mask details of the synchronization. In order to control its effect, we study the locking conditions using an analytic technique that only considers the phases.. The results suggest that Strouhal number selection in steady forward natural swimming and flying is the result of a limit cycle process and not actively controlled by an organism. An implication of this is that only relatively simple sensory and control hardware may be necessary to control the steady forward motion of man-made biomimetically propelled vehicles. / by Cyndee L. Finkel. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
92

Determination of Average Lift of a Rapidly Pitching Airfoil

Linn, Anthony Blane 12 May 2000 (has links)
Dynamic stall characteristics of an NACA-0012 airfoil were investigated to assess the possibility of augmented lift during sinusoidal angle of attack motion. Tests were conducted over a range of Reynolds numbers from 2.0x10^5 to 5.0x10^5 and reduced frequencies from 0.02 to 0.3. The data were recorded and plotted in a series of lift coefficient vs. angle of attack diagrams. These diagrams exhibited a hysteresis curve for the dynamic stall cycle similar to the results of previous investigators but without a large peak at high angles of attack. The data were also plotted with lift coefficient vs. angular cycle position. The average lift coefficient was computed for each set of test conditions and plotted with average lift coefficient vs. reduced frequency for each value of Reynolds number. The summary data indicate an increase of average lift coefficient with reduced frequency, and increased Reynolds number, althought the increase was not monotonic.
93

The production of sound by moving objects

Munro, David Herbert January 1980 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 346-350. / by David Herbert Munro. / Ph.D.
94

Unsteady airfoil pressures induced by perturbation of the trailing edge flow

Lorber, Peter Frederick January 1981 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO. / Includes bibliographical references. / by Peter Frederick Lorber. / M.S.
95

Modeling dynamic stall of SC-1095 airfoil at high mach number

Clark, Brian 26 January 2010 (has links)
In this thesis, the Leishman-Beddoes method of determining airloads for an airfoil undergoing dynamic stall is studied over a range of Mach numbers. To validate the method for conditions where little experimental data is available, a computational fluid dynamics solver is utilized to provide airload predictions for comparison to the Leishman-Beddoes results. It is found that even for high Mach numbers the Leishman-Beddoes method provides reliable predictions for lift coefficient. However, at the higher Mach numbers pitching moment is sometimes overpredicted at high angle of attack. This is seemingly due to an inability to accurately determine the center of pressure in the high speed unsteady flow environment.
96

The prediction of viscous flow round multiple-section aerofoils.

Seebohm, Thomas January 1972 (has links)
No description available.
97

Experiments on a low aspect ratio wing at low Reynolds numbers /

Morse, Daniel R. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 120-123). Also available on the World Wide Web.
98

Optimization techniques exploiting problem structure : applications to aerodynamic design /

Shenoy, Ajit R., January 1997 (has links)
Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1997. / Vita. Abstract. Includes bibliographical references (leaves 185-198). Issued also in computer file.
99

An experimental study of flow control using blowing for a low-pressure turbine airfoil /

McAuliffe, Brian January 1900 (has links)
Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 221-230). Also available in electronic format on the Internet.
100

Particle image velocimentry measurements of an airfoil-vortex interaction event in a two-dimensional wind tunnel /

Burwash, Wesley, M. January 1900 (has links)
Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 102-106). Also available in electronic format on the Internet.

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