  Segregation induced by a thermal gradient of an impurity in a driven
low-density granular gas is studied. The system is enclosed between two
parallel walls from which we input thermal energy to the gas. We study here
steady states occurring when the inelastic cooling is exactly balanced by some
external energy input (stochastic force or viscous heating), resulting in a
uniform heat flux. A segregation criterion based on Navier-Stokes granular
hydrodynamics is written in terms of the tracer diffusion transport
coefficients, whose dependence on the parameters of the system (masses, sizes
and coefficients of restitution) is explicitly determined from a solution of
the inelastic Boltzmann equation. The theoretical predictions are validated by
means of Monte Carlo and molecular dynamics simulations, showing that
Navier-Stokes hydrodynamics produces accurate segregation criteria even under
strong shearing and/or inelasticity.
