Measurements of Multi-Blade Wind Turbine Wakes in an Open-Jet Wind Tunnel

Abstract

In this study the wake characteristics of two-blade three-blade and four-blade wind turbines were investigated experimentally The experiments were carried out in an open-jet wind tunnel under a uniform incoming flow condition Hot-wire and Cobra-probe anemometers were used to measure the mean and fluctuating quantities of turbulent flows at different locations with downwind distance The blade element momentum (BEM) theory is used to model the streamwise velocity distribution in the near wake region and the results from the BEM theory were compared with the measurements by using a hot-wire anemometer We carried out the wake measurements with turbines in two conditions: (a) in different yaw angles (0° and 30°) by using hot-wire anemometer and (b) in non-yaw condition by different anemometers (hot-wire and Cobra probe) The measurement results indicate that: (a) The yawed turbines wake have an obvious shifting phenomena and the ‘wake-region width‘ as well as wake characteristics are smaller than normal turbines; (b) The hot-wire and Cobra-probe anemometers are consistent with turbulent characteristics except the vertical velocity The power spectrum analysis demonstrates that the turbulence dissipation rate from both anemometers measurements follows as the slope of -5/3 in the inertial subrange The reliability of the data can be confirmed by the consistency with the first harmonic peak in the spectra plots and rotating speed from the laser tachometer

Date of Award	2017 Jul 20
Original language	English
Supervisor	Yu-Ting Wu (Supervisor)