Wake field characteristics of a toroidal propeller under different advance coefficients

This study employs Improved Delayed Detached Eddy Simulation to investigate the open-water wake characteristics of a novel toroidal propeller. Following validation against cavitation tunnel data, numerical simulations were conducted at advance coefficients of J = 0.4, 0.8, and 1.2 to analyze the wake field, focusing on vortex evolution and topology. Dynamic Mode Decomposition was subsequently applied to extract coherent spatiotemporal modes from the downstream flow. The results reveal that the closed-loop tip induces strong shear, generating symmetric alternating high- and low-velocity axial streaks at the slipstream boundary. Notably, the tip vortex manifests as a distinct double-layer anti-phase pulsation at the Blade Passage Frequency. As the advance coefficient increases, the hydrodynamic load shifts toward the tip. Consequently, at a low advance coefficient (J = 0.4), secondary vortices formed by the merging of blade wakes surround and destabilize the main tip vortex. Conversely, at a high advance coefficient (J = 1.2), extended blade vortices interact with the hub vortex, inducing significant instability in the hub region.