  We analyze the transport properties of a low density ensemble of identical
macroscopic particles immersed in an active fluid. The particles are modeled as
inelastic hard spheres (granular gas). The non-homogeneous active fluid is
modeled by means of a non-uniform stochastic thermostat. The theoretical
results are validated with a numerical solution of the corresponding the
kinetic equation (direct simulation Monte Carlo method). We show a steady flow
in the system that is accurately described by Navier-Stokes (NS) hydrodynamics,
even for high inelasticity. Surprisingly, we find that the deviations from NS
hydrodynamics for this flow are stronger as the inelasticity decreases. The
active fluid action is modeled here with a non-uniform fluctuating volume
force. This is a relevant result given that hydrodynamics of particles in
complex environments, such as biological crowded environments, is still a
question under intense debate.
