Fluid–Structure Interaction of a Propeller Under a Two-Scale Inflow Field

The interaction between the ship hull and the propeller’s rotational motion causes the propeller to operate under non-uniform inflow conditions. In reality, the ship’s effective wake constitutes a complex nonlinear superposition of multiple wave numbers. However, existing studies often neglect these multi-scale interactions. In this work, Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations with a two-scale inflow model are conducted to investigate the fluid–structure interaction of a propeller under multi-scale inflow. The model introduces large-scale and small-scale Fourier modes together with transverse perturbations, allowing systematic variation of inflow characteristics. The results reveal that large-scale modes amplify unsteady thrust fluctuations and enhance vortex fragmentation, while small-scale modes produce similar but weaker effects, mainly influencing the high-frequency components of unsteady thrust. In contrast, transverse perturbations reduce inflow non-uniformity, effectively suppress single blade thrust fluctuations, and preserve the coherent vortex structures of the wake. This study highlights the importance of multi-scale effects in the unsteady hydrodynamic characteristics of marine propellers and provides useful insights for the optimization of propeller design and energy-saving devices.