Fluidization of a two-dimensional granular system: Experimental study and scaling behavior

Digital high speed photography and computer image processing have been used to investigate the fluidization behavior of a two-dimensional model granular material undergoing vertical vibration. Profiles of packing fraction, speed, and velocity distribution functions are measured. The packing fraction is found to be approximately uniform in a narrow region at the base, and a Boltzmann distribution gives a good fit in the upper regions. Values for the granular temperature, as a function of height, are extracted from the distribution functions and an approximately linear decay is found. We also present results for the scaling behavior of the granular temperature and the height of the center of mass. Finally, we describe a simple theoretical analysis to investigate the origin of scaling laws.