Abstractto be a function of yaw angle and is anticipated to alter at higher yaw angles as the inlet angle of the shroud is close to the maximum yaw angle investigated. This study addresses the fact why the reported augmentation factors for diffuser augmented wind turbines in the literature has a broad range from -36% to 760% which shows disagreements between researchers.iii Acknowledgement

The novel features of the Havriliak-Negami model for dynamic description of viscoelastic material behavior along with the Donnell theory of shell motion are applied to study free vibrational and damping characteristics of an infinitely long viscoelastic thin circular cylindrical shell submerged in and filled with acoustic fluids. The analytical results are illustrated with numerical examples in which two fluid-filled shells of distinctive viscoelastic material properties are undergoing free vibrations in a surrounding ideal fluid medium. The natural frequencies and the associated modal loss factors as a function of the circumferential mode number at selected axial wave lengths and submergence conditions are numerically evaluated and discussed. The numerical results reveal the imperative influence of dynamic viscoelastic properties on the vibrational characteristics of the fluid-coupled system. They demonstrate an interesting correlation between the modal loss factor and the material loss factor in the vicinity of the calculated natural frequency. In particular, the modal loss factor (natural frequency) is found to be highly dependent on (fairly insensitive to) the frequency dependence of the loss factor in the viscoelastic material. A limiting case involving a thin elastic steel shell submerged in water is considered and fair agreement with a well-known solution is established.

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Dataset includes power and thrust coefficients of a 19.8 cm diameter horizontal axis hydrokinetic model turbine measured experimentally in a water tunnel. Tests are done at 0.7, 0.9, and 1.1 m/s water speeds for three turbine configurations: turbine blade alone and then with two shrouds. Output power of the turbine and its thrust force are measured experimentally. Results are corrected using a theoretical model that accounts for free surface proximity and blockage effects of the water tunnel.