Design and analysis of pumpjet propulsors using CFD-based optimization

A Study on the Wake Evolution of a Set of RIM-Driven Thrusters

“…To the same aim, two different thresholds on Q are employed as a way of distinguishing the strength of the vortical structures shed by the propulsors. As already observed in similar calculations [31], the tip leakage vortex is easily recognizable inside the nozzle. As discussed in the description of the reference ducted propeller characteristics and geometry, tip leakage vortices are the most relevant vortical structures shed by the blade tips.…”

“…The rolling up and wrapping process between tip leakage vortices and secondary duct-induced vortices promote these secondary structures that realize the "tip-duct mutual inductance instability" described in [26]. Disturbed by the presence of helical vortices (tip or tip leakage from the blades), the shear layer formed on the nozzle surface and shed in the wake is distorted and reorganized into the secondary vortices between the tip and As already observed in similar calculations [31], the tip leakage vortex is easily recognizable inside the nozzle. As discussed in the description of the reference ducted propeller characteristics and geometry, tip leakage vortices are the most relevant vortical structures shed by the blade tips.…”

“…In the case of RIM-driven thrusters, these analyses are almost non-existent. Specific destabilization mechanisms have been highlighted recently in the case of ducted propellers through dedicated numerical calculations [28] and also pumpjets underwent detailed numerical analyses aimed at characterizing the rotor/stator (or vice versa) wakes' interaction [26,27,31]. These propulsors are rather similar to RIM-driven, at least for the presence and the influence of the nozzle and its shear layer, but their leakage tip vortex plays a completely different role, suggesting the relevance of accurate investigations dedicated to "tip-less" propulsors.…”

“…Some characteristics of the vortical wakes of RIM-driven thrusters were evidenced in the case of the optimal geometries designed in [12], but only RANSE calculations and simplified steady cases using Moving Reference Frames were employed for those analyses. None of the theoretical [18,19], experimental [20,21], or numerical studies [22][23][24][25][26][27][28][29][30][31] available for conventional and tip-loaded propellers, as well as for ducted propulsors and pumpjets, were repeated for RIM-driven thrusters with the same systematic approach.…”

Pre-Swirl Ducts, Pre-Swirl Fins and Wake-Equalizing Ducts for the DTC Hull: Design and Scale Effects

“…These methods evidenced several limitations in the description of the function and in the design of these devices (pre-swirl fins in particular) that are often required to operate under very high angles of attack and in heavily nonuniform inflows, which are clearly out of the assumptions of inviscid/potential methods. Simulation-based design optimization (SBDO) approaches, on the contrary, represent a valid and solid design alternative to be exploited, similar to what has already been already proposed for unconventional propulsors' [28,29] and hulls' design [30].…”