Fluid–structure interaction in downstream wind turbine: Spacing-dependent structural loads and responses to upstream wake

• Multiple wind turbines are analyzed using a novel FSI model. • The loads and responses of rigid and flexible wind turbines under wake conditions are explored. • The equivalent fatigue loads of downstream wind turbines are evaluated. • The loads and responses of downstream wind turbines under the influence of inflow conditions and wind turbine spacing are considered. As wind turbines continue to grow in size, the aeroelastic phenomenon in multi-turbine configurations becomes crucial for the safety of downstream turbines subject to wake interactions. This study utilizes the Large Eddy Simulation (LES) turbulence model and introduces a novel Fluid–Structure Interaction (FSI) method to analyze the structural loads and responses of downstream turbines under varied wind conditions, turbine spacings, and structural-flexibility scenarios. This study offers an in-depth examination of load time histories and displacement responses at key locations on downstream turbines. It evaluates time-series loads, statistical properties, exceedance probability curves, and equivalent fatigue load (EFL) and power spectral density (PSD) curves across various scenarios. The results indicate that the presence of upstream wake reduces loads on the downstream turbine, while loads gradually increase as turbine spacing increases; this phenomenon is most pronounced under Atmospheric Boundary Layer (ABL) conditions. At 4D spacing, F x at the blade root and F x and M z at the tower bottom increase by 14.1%, 14.7%, and 19.5%, respectively, compared with 2D spacing under turbulent inflow. Scenarios that account for turbine flexibility exhibit higher EFL, and increasing turbine spacing further amplifies EFL in the downstream turbine. Compared with the 2D spacing, the EFL calculated from the three types of loads increased by 16.7%, 11.5%, and 17.8% under the 4D spacing.