Large-eddy simulation of a ducted propeller in crashback

Large-eddy simulation (LES) using an unstructured overset numerical method is performed to study the flow around a ducted marine propeller for highly unsteady off-design condition called crashback. Known as one of most challenging states analyse, rotates in reverse direction yield negative thrust while vehicle still forward motion. The LES results David Taylor Model Basin 4381 with neutrally loaded duct are validated against experiments, showing good agreement. simulations at Reynolds number 561 000 and advance ratio $J=-0.82$ . field different components (duct, rotor blades stator blades) their impact on loading examined. side-force coefficient $K_S$ mostly generated from surface, consistent experiments. majority torque coefficients $K_T$ $K_Q$ arise blades. A prominent contribution also produced Tip-leakage between blade tips surface shown play major role local loads duct. physical mechanisms responsible overall large production identified globally, vortex ring locally, leading-edge separation well tip-leakage which forms blade-local recirculation zones.