| Time-accurate solutions of the Reynolds-averaged Navier-Stokes equations are presented, which address through model problems: the response of turbulent propeller-blade boundary layers and wakes subject to external-flow traveling waves; interaction of natural (hull) and forced (propeller) unsteadiness; and resolution of problems with fixed and moving boundaries.;Validation is accomplished through comparisons with the Massachusetts Institute of Technology flapping-foil experiment. The physics of unsteady blade flows are shown to be complex with analogy to Stokes layers and are explicated through analysis of the pressure gradient, which exhibits upstream and downstream traveling waves over the foil and in the wake, respectively, due to an unsteady displacement thickness generated viscous-inviscid interaction. Further studies on the effects of frequency, waveform, and geometry showed the response can be classified in two regimes: long and short wave. The short vertical-combined waves showed results which agree with behavior seen in the flapping-foil experiment. However, as frequency increases, steady/unsteady interaction increases which is manifest as a phase shift in the external-flow waves. The long vertical waves showed a temporal response which agrees with Sears' theory. Flat plate studies in both vertical- and horizontal-combined waves show the viscous-inviscid interaction is directly related to lift and the corresponding wake sheet. Also, in the absence of a mean pressure field, the steady/unsteady interaction and trailing-edge counter-rotating vortices seen in the foil cases are non-existent.;Harmonic forcing of the naturally unsteady wake of a flat plate at incidence using an oscillating body force or trailing-edge flap is studied. The wake is receptive to both the body force and the flap and demonstrates lock-in, quasi-periodic, chaotic, and non lock-in states which are a function of the amplitude and the forced to natural frequency ratio. Chimera domain decomposition is used to resolve the relative motion between the plate and the oscillating flap and shows continuous and single-valued solutions across the overlap regions. The method is shown to be general, robust, and most importantly, capable of future complete ship-propulsor simulations. |
