Vibrationally driven particle formations in fluid systems with bimodal thermal inhomogeneities

This study builds on and extends an earlier investigation [Santhosh and Lappa, “On the relationship between solid particle attractors and thermal inhomogeneities in vibrationally-driven fluid-particle systems,” Phys. Fluids 35(10), 103316 (2023)]. As the predecessor work, it can be placed in a wider theoretical context, that is, a line of inquiry started a decade ago [Lappa, “The patterning behavior and accumulation of spherical particles in a vibrated non-isothermal liquid,” Phys. Fluids 26(9), 093301 (2014)] about the surprising ability of high-frequency vibrations imposed on a non-isothermal fluid containing dispersed solid particles to support the self-emergence of ordered particle structures. Here, the non-trivial relationship between the number and shape of the particle formations and the nature of the thermal conditions along the boundary of the fluid container is further explored by probing in detail the role of thermal spot multiplicity. The problem is approached in the framework of a hybrid Eulerian–Lagrangian numerical approach. The results indicate that completely new morphologies become accessible, which are not possible when only two walls are thermally active. Moreover, on increasing the angle ϕ formed by vibrations with the direction perpendicular to the adiabatic walls of the cavity, the compact surfaces formed by particles for ϕ = 0° are taken over by more complex formations, which give the observer the illusion of a flexible fabric formed by the intersection of many independent filamentary structures.