An experimental study on the strain responses of blades and struts of a 5MW semi-submersible floating vertical-axis wind turbine

Abstract

A blade and strut strain sensing system is utilized in this study for a floating vertical-axis wind turbine (VAWT) to monitor and measure dynamic strains in the wave basin model test. The floating VAWT concept consists of a 5MW H-type rotor with three straight blades and a semi-submersible platform. The strain sensing system combines the advantages of Fiber Bragg Grating (FBG) sensors and a fiber optic rotary joint (FORJ). Subsequently, a series of model tests are carried out to investigate the strain response characteristics of blades and struts under various environmental conditions. The results show that the strains on blades and struts are affected by wave, wind, and rotor rotational speed, among which the influence of waves is minor. Under combined wind, rotational speed, with/without wave conditions, the increasing wind speed and rotational speed can lead to increases in mean values and oscillations of blade and strut strains, as well as nP (n times per revolution) components. Besides, blade strain is primarily influenced by the 1P (once-per-revolution) component, while strut strain is mainly affected by the 2P (twice-per-revolution) component for the present FBG sensors arrangement. In summary, this study offers valuable insights into the dynamic strain characteristics of blades and struts of floating VAWT under different environmental conditions, contributing to the advancement of floating VAWT model test technology and the validation of future numerical models.