  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.

Statistical Mechanics