Collective wake-mediated interactions in lattice fluids: Effects of strong local force fluctuations stimulated by impurity disorder

Abstract

The perturbation of a medium field (a particle wake) determines the Stokes drag on the particle itself. Besides, it affects the motion of other particles, inducing non-equilibrium correlations between them. We study the induced non-equilibrium correlations and forces, acting on constituent particles of the bunch or cluster of impurities exposed to a gas stream. Such induced correlations exhibit many striking features that are determined by the properties of particle bunch collective scattering in a medium. The characteristics of collective scattering are determined by the structure of the bunch itself, that is associated with scattering on inhomogeneities, i.e., on fluctuations of the number of particles (scatterers) in a correlation volume. This is well-known, e.g., in optics and have been shown for gas scattering in our recent work [1]. In particular, a random cluster of impurities experiences much stronger Stokes drag than a regular one. Inhomogeneity of the cluster also determines the presence of giant local fluctuations of the scattered field inside a cluster, that was shown for gas stream scattering in [1]. This, in turn, should lead to strong local fluctuations of induced gradient forces inside the cluster, which can determine its stability. Moreover, the description of a cluster in terms of effective parameters (penetration index, effective diffusion coefficient, etc.) brakes down due to the presence of such fluctuations.