Investigation of rotor-rotor and rotor-structure interactions on multi-rotor wind turbine systems

Abstract

Multi-rotor wind turbine systems (MRS) are an innovative alternative to conventional single-rotor (SR) wind turbines. This paper investigates the rotor interactions of three 20 MW floating offshore MRS designs with 12, 27 and 48 rotors respectively. Similar to the interaction between the tower of an SR and the blades, there is a rotor-structure interaction with the space frame members due to a reduction in wind speed in front of the space frame members. There are also rotor-rotor interactions based on changes in local wind conditions when the blades tips of two neighboring rotos pass each other. The blade root edgewise and flapwise bending moments Mx and My, and their change in damage-equivalent loads (DEL) based on both kinds of rotor interactions are investigated. Low fidelity simulations based on blade element momentum (BEM) theory are used as well as scaling of loads in the post processing.