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UBC Theses and Dissertations

A study of nutation dampers with application to wind induced oscillations Welt, François


Energy dissipation due to sloshing liquid in torus shaped nutation dampers is studied using the potential flow model with nonlinear free surface conditions in conjunction with the boundary layer correction. Special consideration is given to the case of resonant interactions which were found to yield interesting damping characteristics. An extensive test program with the dampers undergoing steady-state oscillatory translation is then undertaken to establish the optimal damper parameters. Low liquid heights and large diameter ratios with the system operating at the liquid sloshing resonance are shown to result in increased damping, while low Reynolds numbers and presence of baffles tend to reduce the peak efficiency by restricting the action of the free surface. Tests with two-dimensional as well as three-dimensional models in laminar flow and boundary layer wind tunnels suggest that the dampers can successfully control both the vortex resonance and galloping types of instabilities. Applicability of the concept to vertically oscillating structures such as transmission lines is also demonstrated with dampers undergoing a rotational motion about their horizontal axis.

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