Aeroelastic Load Analysis of a Co-Rotating Quad-Rotor Wind Turbine

An aeroelastic analysis is carried out to assess the loads on a selected quad-rotor wind turbine vis-a-vis those on an equivalent rated single-rotor turbine, with a specific focus on a comparison of support structure loads (e.g., tower root, yaw-bearing, and boom loads). A quad-rotor wind turbine with combined rated power of 6 MW and a single-rotor with equivalent machine rating are modeled in SIMAPCK coupled with AerodynV15 (including turbulent wind input from TurbSim) to calculate the aerodynamic loads. A correction for tower/boom shadow is implemented in Matlab to account for reduction in (axial) incoming wind due to the presence of support structures that carry the rotors. The performance of the quad-rotor wind turbine, with the single-rotor as baseline, is carried out for load cases selected from wind turbine certification standard (IEC-61400-1) covering the following: nominal loads under normal wind speed profile, fatigue loads under normal turbulence, and ultimate loads under extreme turbulence. Results show that, comparing the quad-rotor tower root loads to those of the single-rotor turbine under extreme turbulence, the side-side force is up to 31% higher, the force-aft bending moment is up to 15% higher, and the normal force is up to 46% higher due to additional boom/nacelle inertial loads.