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Aeroelastic behavior of square section prisms in uniform flow Wawzonek, Mitchell A.

Abstract

The work presented in this thesis concerns the experimental investigation and analysis of the oscillation behavior of elastically supported square prisms in a uniform flow of air. This is a step in understanding the behavior of structures in flow situations such as in the atmosphere or in water. The principal modes of excitation studied are those due to vortex shedding, and aerodynamic instability known as galloping. The tests showed that when the non-dimensional wind speed U was less than about 2.5, vortex shedding influenced the behavior significantly, so that the quasi-steady theory developed for galloping could not predict the amplitude response. Some of the data in the literature showed that in this wind speed range, measurements of aerodynamic force during forced oscillation could be used to more accurately predict the aeroelastic behavior. The quasi-steady analysis was verified to be valid for U greater than about 2.5 in the present tests, but the measured aerodynamic force behavior on which the analysis depends is in turn dependent on Reynolds number and end conditions. The velocity at which galloping is predicted to occur, U₀, is particularly sensitive to these effects, since the value of the aerodynamic parameter A that defines U₀ is not necessarily constant.

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