Tracer diffusion coefficients in a moderately dense granular suspension: Stability analysis and thermal diffusion segregation

The diffusion transport coefficients of a binary granular suspension where one the components is present in tracer concentration are determined from (inelastic) Enskog kinetic equation. effect interstitial gas on solid particles accounted for equation through two different terms: (i) viscous drag force proportional to particle velocity and (ii) stochastic Langevin-like term defined terms background temperature. obtained as solutions set coupled linear integral equations recently derived suspensions with arbitrary [Gómez González et al., “Enskog theory multicomponent suspensions,” Phys. Rev. E 101, 012904 (2020)]. To achieve analytical expressions coefficients, which can be sufficiently accurate highly inelastic collisions and/or disparate values mass diameter rations, above approximately solved by considering so-called second Sonine approximation (two polynomial expansion distribution function). theoretical results coefficient D0 (coefficient connecting flux gradient density particles) compared those numerically solving means direct simulation Monte Carlo method. Although first-Sonine yields, general, good agreement results, we show that second-Sonine leads an improvement over correction, especially when much lighter than gas. here also used applications. First, stability homogeneous steady state discussed. Second, segregation induced thermal studied. As expected, corresponding phase diagrams clearly differ found previous works grains neglected.