Parametric hydrodynamic and acoustic performance analysis of toroidal propellers with emphasis on geometric variations and advanced design optimization

Toroidal propellers, defined by their continuous closed-loop blade topology, offer promising potential for marine propulsion but remain insufficiently characterized through systematic geometric parametrization. This paper presents a numerical and experimental study of toroidal propeller hydrodynamics, cavitation, and acoustics. A ten-parameter geometric formulation is simulated in OpenFOAM using RANS–SST k–ω turbulence closure under Moving Reference Frame and Arbitrary Mesh Interface treatments, with discretization uncertainty quantified via the Grid Convergence Index. Two toroidal configurations, fabricated via stereolithography, are validated against the DTMB P4119 benchmark within 2% for thrust coefficient, torque coefficient, and open-water efficiency. The toroidal geometries exhibit higher thrust coefficients and elevated peak efficiencies at greater advance ratios relative to the conventional baseline, with the three-bladed toroidal configuration matching the spanwise loading of a four-bladed conventional propeller. Numerical cavitation predictions indicate suppression of tip-vortex cavitation, with redistribution toward the outer loop junctions at high advance ratios. Acoustic predictions, obtained via a URANS-coupled Ffowcs Williams–Hawkings formulation, indicate consistent tonal and spectral noise attenuation together with a reduced overall sound pressure level across all evaluated receiver locations, relative to the conventional baseline. Parametric sensitivity analysis and Spearman rank correlation establish explicit geometric sensitivity relationships, providing a foundation for future multi-objective optimization of closed-loop marine propulsors.