Sheared and vibrated granular gas in microgravity

We present two experimental studies on the flow of model granular media made of nearly elastic spherical particles. Experiments are performed in microgravity conditions inside an airplane undergoing parabolic flights. We first investigate the rheological behaviour of the medium in a cylindrical Couette geometry. The curves, shear stress versus shear rate, are presented and the quadratic dependence on the shear rate is clearly shown. The second series of experiments investigate the behaviour of a vibrated monolayer of spherical particles. A high speed camera is used to record the motion of particles. With an image analysis tracking technique we determine the velocities of the particles from which we retrieve the temperature. The density profiles show the persistence of clusters of particles at the centre of the cell which coexist with a gas phase at the edges of the cell. We conclude by comparing experiments performed in microgravity and in normal gravity.