Integrated Numerical and Experimental Study of Cavitating Flow and Underwater Noise in Tug Vessels With Ducted Propellers

Abstract In marine/offshore engineering, the environmental and operational implications of underwater radiated noise from marine vessels are becoming increasingly critical. This paper aims to understand these concerns through an integrated study of the hydrodynamic and hydroacoustic dynamics of ducted propeller systems on tugboats. Specifically, we examine the wakefield and noise characteristics of a tugboat equipped with a Kaplan 4-70 propeller in a 19a nozzle via large-eddy simulation and homogeneous mixture theory-based cavitation modeling. Noise propagation is analyzed using the Ffowcs-Williams-Hawkings acoustic model. Results reveal that aft-field flow non-uniformity creates a disordered pressure distribution on the propeller surface, with hydrodynamic coefficient pulsations exhibiting periodicity. Sea trials confirm that tugboats can produce underwater noise levels up to 180 dB, with experimental data capturing fixed-frequency mechanical noise, high-frequency oceanic background noise, and propeller-induced hydrodynamic noise. The nozzle extrusion suppresses blade tip vortex shedding and associated cavitation, while upstream hull-induced flow perturbation enhances turbulence and broadband noise. Numerical simulations align well with experimental results in the low-frequency range, primarily corresponding to blade passage behavior. These findings provide valuable insights into noise mitigation strategies and sustainable tugboat design, addressing both environmental and operational challenges.