ON THE THERMODYNAMICS OF GRANULAR MEDIA

A thermodynamic formulation for moving granular material is proposed. The fluctuations due to the constant flux and dissipation of energy are controlled in a ''granular'' ensemble by a pressure rho (''compression'') which is conjugate to a contact volume (''contactopy''). The corresponding response function (''dissipativity'') describes how dissipation increases with rho and should serve to identify the fluidization transition and 1/f noise. In the granular ensemble one can consider the granular medium as a gas of elastically colliding particles and define a ''granular'' temperature and other standard thermodynamic quantities.