Analysis of time-frequency characteristics and the impact of advanced coefficients on electromagnetic wakes generated by rotating propellers

In the marine environment, the rotation of propellers induces charged ion movement in the wake, generating an electromagnetic field influenced by the ambient geomagnetic field. This electromagnetic signal is crucial for non-acoustic underwater target detection. However, the complex interactions among hydrodynamics, ion motion, and electromagnetic fields in the formation of the propeller's electromagnetic wake have not been systematically explored. To investigate the evolution and time-frequency characteristics of this wake, we developed a theoretical model that integrates propeller wake dynamics, seawater ion movement, and electromagnetic fields through a multiphysics coupling approach. High-fidelity numerical simulations replicated the hydrodynamic and electromagnetic wake evolution induced by propeller rotation. The study provides a comprehensive analysis of the wake's evolution and spatial distribution, with an in-depth examination of frequency domain characteristics at various distances behind the propeller. Additionally, we assessed the impact of the propeller's advance coefficient on the electromagnetic wake. The results indicate that a low advance coefficient amplifies vortex and turbulence effects, leading to greater fluctuations in the induced magnetic field, while a high advance coefficient reduces turbulence, producing a more stable magnetic signal with blade-passing frequency characteristics that persist over longer distances. These findings enhance our understanding of electromagnetic wakes, potentially advancing future efforts in underwater target detection and tracking.