  Buoyancy-driven (thermal) convection in dilute granular media, fluidized by a
vibrating base, is known to appear without the need of lateral boundaries in a
restricted region of parameters (inelasticity, gravity, intensity of energy
injection). We have recently discovered a second buoyancy-driven convection
effect which occurs at any value of the parameters, provided that the impact of
particles with the lateral walls is inelastic (Pontuale et al., Phys. Rev.
Lett. 117, 098006 (2016)). It is understood that this novel convection effect
is strictly correlated to the existence of perpendicular energy fluxes: a
vertical one, induced by both bulk and wall inelasticity, and a horizontal one,
induced only by dissipation at the walls. Here we first review those previous
results, and then present new experimental and numerical data concerning the
variations of box geometry, intensity of energy injection, number of particles
and width of the box.
