Vibration Response Behaviour of a High Solidity, Low Rotational Velocity, Vertical Axis Wind Turbine

Abstract

A series of full scale experimental wind tunnel tests were performed to determine the aerodynamic loading behaviour on the airfoils of a high solidity, low rotational velocity, 3 bladed H-type vertical axis wind turbine. The primary vibration response was resonance excitation of the dominant whirling mode of the turbine. However, for a significant number of test cases, resonance behaviour was also observed in the bending strains of the airfoil support struts, primarily corresponding to higher natural frequencies. Furthermore, under various test conditions, vibration amplitude within the support struts was observed to change dramatically during a single test run, suggesting that the vibration was jumping between sets of airfoil support struts in a complex beating mode. In order to isolate the numerous vibration excitation and response behaviours, tests were performed over a range of flow velocities from 8 m/s to 11 m/s with two different support shaft end conditions.