How do vortices generate noise?
Understanding the fundamental underlying mechanisms of propeller wake vortex sound generation and propagation is very challenging, requiring effective methods able to establish a “cause and effect” relationship between the acoustic perturbation in the far-field and the characteristics of the flow in proximity of the emitting body.
To this end, SATURN partners at CNR-INM developed and successfully implemented an experimental methodology, based on simultaneous measurements of the acoustic perturbation in the far-field, by hydrophones, and in proximity of the noise sources, by detailed flow and pressure fluctuation measurements and filtering techniques, combined with cross-correlation/conditional techniques.
This adopted methodology can be found in full detail in the following publications:
Felli et al. (2014). A novel approach for the isolation of the sound and pseudo-sound contributions from near-field pressure fluctuation measurements: analysis of the hydroacoustic and hydrodynamic perturbation in a propeller-rudder system. Experiments in Fluids.
Felli et al. (2015). Experimental approaches for the diagnostics of hydroacoustic problems in naval propulsion. Ocean Engineering.