Propeller–duct interaction on the wake dynamics of a ducted propeller

The propeller–duct interaction on the wake dynamics of a ducted propeller is numerically investigated via detached eddy simulations. The blade–blade interference and blade–duct interaction are analyzed through different configurations under non-ducted and ducted conditions. It is found that the blade–blade interference benefits the loading stability, and the duct leads to a faster efficiency decrease in a single blade with the increasing blade number. The short-wave instability dominates the wake as the unstable secondary vortices accelerates the vortex evolution. The multi-induction effect stabilizes the two tip vortices system in a two-bladed configuration, while the tip vortex grouping occurs early in a four-bladed propeller due to the combined effect of the duct retardation and smaller spiral-to-spiral distance. Additionally, the enhanced wake instability leads to the fast decline of the power spectral density peaks of kinetic energy at blade passing frequency and shaft frequency harmonics toward the far field under ducted conditions.