Wind tunnel test of rotor aerodynamic interference characteristics in complex low-altitude wind fields

The low-altitude environment for rotorcraft is characterized by complex wind fields resulting from the combined effects of terrain and wind conditions. This study investigates the aerodynamic interference mechanisms of three typical low-altitude wind fields on a rotor system, generated in a wind tunnel, including obstacle wake, spatial constraints, and random turbulence. Unsteady aerodynamic forces and moments acting on the rotor were measured using a six-component force balance. The influence of varying wind conditions and interference locations on rotor aerodynamic characteristics was assessed through time-frequency analysis. Furthermore, a disturbance wind field simulation method based on Detached Eddy Simulation (DES) is proposed. Numerical simulation results were then used to analyze the characteristics of the rotor-environment coupled flow field in various scenarios. The results reveal that rotor wake recirculation induced by spatial constraints decreases rotor thrust, and the reduction is exacerbated by increased confinement. The large-scale periodic vortex shedding within the obstacle wake region results in low-frequency aerodynamic perturbations. Increasing the rotor height above ground and the horizontal distance from the obstacle increases high-frequency fluctuations within the flow field, leading to a migration of the rotor thrust power spectrum peak towards higher frequencies. Random turbulence exhibits energy concentration in the high-frequency band, exhibiting a comparatively small effect on the low-frequency sensitive region associated with pilot workload. This research reveals the inherent relationship between energy distribution and rotor aerodynamic response characteristics in various scenarios, providing the theoretical basis for the design of turbulence suppression in rotorcraft.