Abstract
Vertical-axis wind turbines (VAWTs) are compact and efficient and have become increasingly popular for wind energy harvesting. This paper mainly focuses on free and forced vibration analysis of two different types of VAWTs, i.e., an H-type VAWT and a new hybrid VAWT. The H-type VAWT has a lower cost, while the hybrid VAWT has a better self-starting capability at a low wind velocity. Both of them can be used for wind energy harvesting. By using the assumed modes method, the two VAWTs are simplified by a single degree-of-freedom (SDOF) model. By utilizing the method of structural mechanics, a multi-degree-of-freedom (MDOF) model is developed for the two VAWTs and the turbines in them are reasonably simplified. Natural frequency analyses for the SDOF and MDOF models of the two VAWTs are conducted. A beam element model (BEM) of the two VAWTs is created to calculate their natural frequencies and mode shapes and to verify natural frequency results from the SDOF and MDOF models. By using the BEM of the two VAWTs, their amplitude-frequency responses are obtained from harmonic response analysis. To analyze forced vibrations of the two VAWTs, aerodynamic loads on the two VAWTs are obtained from computational fluid dynamics (CFD) simulation. By using solid element models of the two VAWTs, forced transient responses of the two VAWTs are calculated by using the aerodynamic loads from CFD simulation. Steady-state forced response amplitudes of the 1 m-mast hybrid VAWT are 23.8% and 20.5% smaller in X- and Y-directions than those of the 1 m-mast H-type VAWT, respectively. Frequency contents of the aerodynamic loads from CFD simulation are calculated, which confirm that they are periodic, and the power efficiency of the H-type VAWT is about 2.6% higher that of the hybrid VAWT.
Highlights
By using solid element models of the two Vertical-axis wind turbines (VAWTs), forced transient responses of the two VAWTs are calculated by using the aerodynamic loads from computational fluid dynamics (CFD) simulation
DOFs increasing, natural frequencies can be more accurately calculated from the beam element model (BEM)
Differences between the first three natural frequencies of the MDOF model of the H-type and hybrid VAWTs and those of their BEM range from 0.13% to 3.54% and from 0.12% to 3.92%, respectively, when the mast height varies from 1 to 4 m, which means that the MDOF model is a useful and reasonably simplified model to analyze free vibrations of the two VAWTs
Summary
[18] used wind tunnel experiments to study the power performance of H-type VAWTs. Research objects of VAWT studies can be classified into five aspects: angle of attack, airfoil section, power efficiency (or coefficient), dynamics and vibration, and VAWT design. Sengupta et al [22] studied effects of different airfoil sections of blades to improve the performance of H-type VAWTs. Yao et al [23], ref. To the best of authors’ knowledge, comparative studies on free and forced vibration analysis of H-type and hybrid VAWTs have not been reported in the literature, which is the objective of the present work. Free vibration results of the two VAWTs from their BEM and SEMs are shown in Sections 5.3 and 5.4, respectively.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
