On the variety of particle accumulation structures under the effect of g-jitters

Lappa, Marcello (2013) On the variety of particle accumulation structures under the effect of g-jitters. Journal of Fluid Mechanics, 726. pp. 160-195. ISSN 0022-1120 (https://doi.org/10.1017/jfm.2013.203)

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The present analysis extends the author's earlier work (Lappa, Phys. Fluids, vol. 25, 2003, 012101; Lappa, Chaos, vol. 23, 2003, 013105) on the properties of patterns formed by the spontaneous accumulation and ordering of solid particles in certain types of flow (with a toroidal structure and a travelling wave propagating in the azimuthal direction) by considering the potential impact of 'vibrations' (g-jitters) on such dynamics. It is shown that a kaleidoscope of possible variants exist whose nature and variety calls for a concerted analysis using the tools of computational fluid dynamics in synergy with dimensional arguments and existing theories on the effect of periodic accelerations on fluid systems. A possible categorization of the observed phenomena is introduced according to the type and scale of 'defects' displayed by the emerging particle aggregates with respect to unperturbed (vibration-less) conditions. It is shown that the resulting degree of 'turbulence' depends essentially on the direction (φ), amplitude (γ) and frequency (π{variant}) of the applied inertial disturbance. A range of amplitudes and frequencies exist where the formation of recognizable particle structures is prevented. A quantitative map (in the γ-π{variant}) for their occurrence is derived with the express intent of supporting the optimization of future experiments to be performed in space.