Modal analysis of propeller wake dynamics under different inflow conditions

The evolution mechanisms from near to far field of propeller wakes under different inflow conditions were analyzed. Modal decomposition was performed on the propeller wakes calculated by previous numerical simulations [Wang et al., “Propeller wake instabilities under turbulent-inflow conditions,” Phys. Fluids 34, 085108 (2022)]. In particular, the Sparsity-Promoting Dynamic Mode Decomposition (SPDMD) was employed to identify the flow modes that play a dominant role in the inception mechanisms of the propeller wake destabilization. The results showed that the turbulent inflow contributes to the destabilization process of the tip vortex system under the low-turbulence inflow condition, and as a perturbation, it accelerates the interference between adjacent tip-vortex structures, intensifies the instability motion of the tip vortex, and then accelerates the breakdown of the tip vortex system. SPDMD succeeds in selecting a subset of dynamic mode decomposition modes that have the most substantial influence on the quality of approximation of the snapshot sequence. The present study further extends knowledge of propeller wake instability inception mechanisms under different inflow conditions, which can support the development and improvement of next-generation propellers.