Numerical investigation of propeller excitation force and wake dynamics under harmonic-modulated non-uniform inflow

In underwater vehicle propulsion systems, propeller vibration and noise induced by non-uniform inflow are ubiquitous and have attracted widespread attention. Understanding the response mechanism of propeller excitation forces under non-uniform inflow conditions is of great significance for propulsor optimization and noise control. In this study, three non-uniform inflow conditions are constructed based on the nominal wake of SUBOFF by modulating the amplitude of the seventh-order harmonic component. The improved delayed detached eddy simulation is employed to simulate the excitation forces and wake characteristics of a seven-bladed propeller under design conditions. The results show that, for the seven-bladed propeller, when the amplitude of the seventh-order harmonic component in the non-uniform inflow is increased to five and ten times its original value, the amplitude of the axial excitation force at the blade-passing frequency (BPF = 70 Hz) increases by factors of 4.19 and 8.19, respectively, exhibiting a clear linear relationship with the imposed harmonic amplitude. In contrast, the amplitudes of the transverse and vertical excitation forces remain nearly unchanged. Furthermore, flow field analysis indicates that the characteristics of the non-uniform inflow are preserved in the propeller wake. As the amplitude of the seventh-order harmonic increases, the energy of the BPF mode is enhanced, accompanied by increased velocity fluctuations in the wake.