We present an experimental study of the displacement of a light intruder immersed in a vibrated granular
bed. Using high speed video we resolve the motion, during one cycle of oscillation, of a cylindrical object
inside a Plexiglas box partially filled with grains. We report experimental evidence that, in the absence of
convection, at least two forces are behind the intruder’s motion: an air drag force—due to the airflow through
the granular bed—and a buoyancy force produced by an air-mediated granular fluid
