Effects of gas interparticle interaction on dissipative wake-mediated forces

Abstract

The effect of concentration-dependent switching of the non-equilibrium depletion interaction between obstacles in a gas flow of interacting Brownian particles is presented. When increasing bath fraction exceeds half-filling, the wake-mediated interaction between obstacles switches from effective attraction to repulsion or vice-versa, depending on the mutual alignment of obstacles with respect to the gas flow. It is shown that for an ensemble of small and widely separated obstacles the dissipative interaction takes the form of induced dipole-dipole interaction governed by an anisotropic screened Coulomb-like potential. This allows one to give a qualitative picture of the interaction between obstacles and explain switching effect as a result of changes of anisotropy direction. The non-linear blockade effect is shown to be essential near closely located obstacles, that manifests itself in additional screening of the gas flow and generation of a pronounced step-like profile of gas density distribution. It is established that behavior of the magnitude of dissipative effective interaction is, generally, non-monotonic in relation to both the bath fraction and the external driving field. It has characteristic peaks corresponding to the situation when the common density "coat" formed around the obstacles is most pronounced. The possibility of the dissipative pairing effect is briefly discussed. All the results are obtained within the classical lattice-gas model.

Nonlinear response and emerging nonequilibrium microstructures for biased diffusion in confined crowded environments

“…This can have important implications for many known phenomena related to the perturbation profile induced by a tracer in a host medium, such as drifting steady-state structures [70], bath-mediated interactions of driven particles [30,71], and "negative" mass transport [72]. Moreover, it would be interesting to check if a change of behavior similar to that observed for discrete lattices between infinite and confined geometries is also found in off-lattice systems, such as colloidal suspensions or granular media.…”

Effects of collectively induced scattering of gas stream by impurity ensembles: Shock-wave enhancement and disorder-stimulated nonlinear screening

“…This can be manifested by formation of common perturbation "coat" around a cloud of scatterers or common wake, localization of gas particles (blockade effects), induced correlations and formation of nonequilibrium (dissipative) structures in the ensemble of impurities. These types of phenomena are intrinsic in various physical systems, including examples from hydrodynamics [1,2], dusty plasmas [3], quantum liquids or Bose condensates [4,5], and can exhibit unusual behavior such as non-Newtonian wake-mediated forces [3,[6][7][8][9][10][11][12] that is characteristic of diffusive or dissipative systems. Spatiotemporal characteristics of medium perturbations are mostly determined by the mechanism of energy losses specific to each particular system and by the properties of medium itself, e.g., nonlinearity of associated field.…”

“…Despite the short range of inter-particle interaction it was shown to give rise to peculiar nonlinear effects essentially manifested at high gas concentrations. These are the dissipative pairing effects [8,17], the wake inversion and switching of wake-mediated interaction [8,18], formation of nonequilibrium structures [19][20][21][22] etc. As will be shown, the nonlinear effects considerably affect collective scattering.…”

“…2 Some properties of this interaction were previously considered for a pair of impurities in [2,6,8]. 3 We exploit the drag force definition f = − S n(r)δn(r) dr, where n(r) is the exterior normal of inclusion surface S at the point r, see [6][7][8]. For single-site inclusions we use discretized version of this expression [17].…”

“…Shock-front stopping criterion can be roughly estimated within the continual approximation [8,18]. Coarse description of the system is given by the Burgers-type equation that admits a kink-like solution.…”