Contribution
Acoustic and magnetic signatures of maritime vessels
* Presenting author
Abstract:
Maritime vessels generate various acoustic and magnetic signals as they move through the water, providing information about the characteristics of the object. The interaction between the water flow and the ship's hull creates long wave flows, perceived as a low-frequency background signature. These frequencies are typically in the range of a few hertz to a few tens of hertz and are particularly relevant for large-scale flow analyses. Acoustically prominent is the fundamental frequency of the propeller. In ferromagnetic propellers, however, the rotation generates not only acoustic signals; the movement of the metallic blades also leads to periodic magnetic field disturbances that correspond to the rotor speed and the blade-passing frequency.High-frequency components are generated by cavitation, where vapor bubbles are formed and subsequently implode. This process generates both strong pressure pulses and ionized particles in the water, which locally affect the magnetic field. These ionized particles contribute to the magnetic signature, which becomes particularly detectable at higher frequencies in the kilohertz range.The combination of acoustic and magnetic frequency signatures enables the precise detection and characterization of vessels and provides valuable information for analyzing their movement patterns and specific physical properties.