On wake dynamics of a propeller operating under nonuniform behind-hull condition

Abstract

The wake dynamics of the benchmark propeller INSEAN E779A operating in the nonuniform wake of a typical ship hull are investigated with large-eddy simulations. The flow features and evolution of vortex structures in the propeller wake are analyzed to evaluate the influences of the nonuniform inflow and to identify the instability mechanisms. Unlike the uniform inflow condition, the azimuthal-variant inflow velocity field results in an asymmetric and faster destabilization of the wake. Local mutual interaction among the neighboring tip vortices in the upper region of the wake, which shows a unique bridging-reconnection mechanism of vortex filaments, initiates the decomposition and destabilization of tip vortices and induces instability in the hub vortex. The power spectrum density (PSD) of kinetic energy is employed to analyze the transition characteristics of the tip vortices quantitatively. The hub vortex core circularity and trajectory envelope are calculated to quantify the long- and short-wave instabilities.