The strategy undertaken in the author's earlier work [M. Lappa, "The patterning behaviour and accumulation of spherical particles in a vibrated non-isothermal liquid," Phys. Fluids 26(9), 093301 (2014) and M. Lappa, "On the multiplicity and symmetry of particle attractors in confined non-isothermal fluids subjected to inclined vibrations," Int. J. Multiphase Flow 93, 71-83 (2017)] based on the use of polarized (purely translational) vibrations for achieving the segregation or accumulation of solid particles in specific regions of an initially dilute dispersion is further pursued by allowing the direction of vibrations to change in time with respect to the applied temperature difference. In particular, the potential of the considered approach in separating the particles from the liquid is explored under the assumption that the angular velocity by which the vibrations axis rotates about a fixed axis is of the same order of magnitude or smaller (one or two orders of magnitude) than the frequency of shaking. A new family of particle coherent structures is identified in the physical space, which can be distinguished from the companion category of particle attractors for fixed vibration direction due to its increased symmetry properties. It is shown how the average nonlinear effects produced by the rotation of the vibration axis, together with those induced by the finite size of the enclosure, accumulate over time leading to the observed fascinating variety of symmetrical patterns.
- particle segregation and accumulation
- thermovibrational flow
- angular velocity
- vibrations axis