Tip vortex merging dynamics governing wake coherence evolution in marine propellers through advance coefficient modulation

Using an improved delayed detached Eddy simulation method on a grid consisting of 79.99 × 106 cells, this study investigates the wake topology and flow field characteristics of a marine propeller under different operating conditions. The focus is on the evolution of vortex structures and their relationship with the turbulence characteristics in the wake, effectively evaluating the specific impact of momentum transfer and instability development in the wake. Furthermore, the study provides a detailed analysis of the flow characteristics at the tip vortex core and reveals the influence mechanism of inflow conditions on the vortex dynamics of the wake system and turbulence development. The results show that, with increasing propeller load conditions, the mutual inductance between vortex structures intensifies, promoting the generation of turbulence and the instability of coherent structures. The instability of the wake is triggered more rapidly, leading to a quick loss of coherence. The anisotropy of the wake, which is dominated by turbulent fluctuations in the radial velocity component, disappears. The complete breakdown of tip vortex coherence manifests as turbulence gradually approaching an isotropic state, which is attributed to the strong mixing between the external free stream and the internal wake, resulting in momentum recovery.