A RATE-DEPENDENT THERMODYNAMICAL MODEL FOR RAPID GRANULAR FLOWS

The averaged equations of balance and the Clausius-Duhem inequality for the rapid granular flows are considered and the thermodynamics of the mean motion is studied. On the basis of the averaged entropy inequality, constitutive equations including a rate-dependent one for the stress tensor are formulated. For spherical nearly elastic particles, the material coefficients are evaluated. The special case of a simple shear flow is analyzed in detail. The predicted stresses are compared with the available digital simulation data for a range of solid volume fractions and reasonable agreement is observed. It is shown that the rate-dependent model properly predicts the observed normal stress effects for rapid granular flows in simple shear. © 1990.