Driven granular gases with gravity - art. no. 011301

We study fluidized granular gases in a stationary state determined by the b alance between external driving and bulk dissipation. The two considered si tuations are inspired by recent experiments, where gravity plays a major ro le as a driving mechanism: in the first case, gravity acts only in one dire ction and the bottom wall is vibrated: in the second case, gravity acts in both directions and no vibrating walls are present. Simulations performed u nder the molecular chaos assumption show averaged profiles of density, velo city, and granular temperature that are in good agreement with the experime nts. Moreover. we measure velocity distributions that show strong non-Gauss ian behavior, as experiments pointed out, but also density correlations acc ounting for clustering, at odds with the experimental results. The hydrodyn amics of the first model is discussed and an exact solution is found for th e density and granular temperature as functions of the distance from the vi brating wall. The limitations of such a solution, in particular in a broad layer near the wall injecting energy, are discussed.