Design Improvement of the Small-Scale Vortex-Induced Bladeless Wind Turbine Considering the Characteristic Length of the Oscillating Structure

In this paper, a modification of the mast, which is the main part of a vortex-induced wind generator was considered in order to improve the performance. Numerical simulations were applied to investigate the change in vortex shedding frequency behind an oscillating structure. Considering the identical vortex shedding frequencies throughout the whole mast, an expression for the characteristic length (phi) was defined. The numerical simulations were conducted for an oscillating cylinder at different wind speeds and for different A/D to present a formula for designing of the mast. The FFT was implemented to determine the frequencies. The results showed that for A/D > 0.2, the variations in characteristic length were not significant. It was found that for Re < 2 x 10(4), the variation in phi/D was considerable and was taken into account in the design of the mast. Using these results, an expression for calculation of the diameter of the mast at different heights was generated. Finally, a small mast with a height of 3 m was designed based on this method. For evaluation of the modified mast, a 3D simulation was conducted. Results showed that the vortex shedding frequencies were the same throughout the whole mast, which is desired.