Unsteady Vortex Lattice Techniques Applied To Wake Formation And Performance Of The Statically Thrusting Propeller PDF Download

(Cont.) This test program is aimed at quantifying the steady and unsteady parameters associated with the developed dynamic models. Third, two flow visualization techniques are utilized to visualize, document, and correlate the helical wake characteristics, velocities and forces for both quasi-steady and unsteady propulsor states. A new fluorescent paint flow visualization technique is developed and applied for small, moderate and4 large propulsor azimuth angles, and a laser particle image velocimetry (PIV) technique is adapted for small and moderate propulsor azimuth angles. Finally, a set of comprehensive physics-based models are developed to foster the understanding of the mechanisms associated with the steady and unsteady force dynamics. The quasi-steady models are based upon a combination of momentum-based, blade-element, and vortex wake propeller theories, as applied to an azimuthing podded propulsor. The unsteady force models are based upon unsteady wake or "dynamic inflow" methods. Additionally, an interesting phenomenon associated with the formation of a vortex ring during rapid propeller rate increase is presented and discussed. The steady and unsteady test results, flow visualizations, and theoretical models, are shown to be consistent in terms of the magnitudes and character of the azimuthing maneuvering forces. Limited comparisons of quasi-steady propulsor forces at small, moderate and large azimuth angles are also made with forces predicted by a modified combined blade-element-momentum (BEM) method, as well as the unsteady vortex-lattice propeller code MPUF-3A, with and without modified inflows to account for propulsor pod wake. The results illustrate inherent complexities related to use of existing computational fluid dynamics tools with azimuthing podded propulsors.