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Numerical Investigation on Offshore wind Turbine Feasibility and Function

Ebrahimi, Alireza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42860 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Abbaspour Tehrani Fard, Madjid
  7. Abstract:
  8. This thesis consists of three main chapters. The first chapter is about describing principles about offshore wind turbine, principal concepts. This chapter also explains about advantages and disadvantages of installing wind turbine at offshore fields, and economical aspect of this kind of wind turbine farms. In the second chapter,anumerical method is used to investigate a SeaStar tension leg platform offshore wind turbine response behavior in parked condition. This code considers nonlinearities due to changes in tension of tethers. Wave forces are calculated adopting the Airy wave theory. Furthermore, shear turbulent wind is exerted on tower, with maximum speed 30 m/s on the hub. Since surge and pitch movements of the TLP platforms are coupled, the off-diagonal components of stiffness, damping and mass matrices are considered to calculate coupling. This code solves nonlinear equation of motion in each time step to calculate pitch, surge, heave and their velocities and accelerations in time domain. In addition, three concepts considered by (Slavounos, 2007) are tested here to find out best response of the concepts. In consideration of its results, response behavior of the prototype in different environmental conditions will be demonstrated.
    And in chapter three, in order to validate numerical analysis, a scaled down model was fabricated in laboratory and tested under similar load conditions to numerical analysis. Linear wave theory was used to simulate Caspian Sea waves on the model. A series of regular waves of 3 cm in heightand a range of 0.45 to 3 m wave length, which can simulate 3 m wave height and 24 to 188 m wave length in real field, were performed to produce the response amplitude operator for heave, pitch and surge movements of the model. Also a wave with 9 cm in height and 2.1 m wave length was exerted to simulate Caspian Sea significant wave on the model. On the other side, these tests were performed on the model in different angles between the wave direction and the forward leg to determine the effects of these angles on the structure response behavior. In order to demonstrate wind effects on the response behavior, a wind generator with a tunnel was used. This wind generator is able to provide 12 m/s at the top of the tower and 6 m/s at the bottom of the tower. The specifications of the blades like weight and center of gravity were considered in calculation, without their fabrication
  9. Keywords:
  10. Numerical Method ; Experimental Method ; Analytical Solution ; Offshore Wind Turbine

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