| The basic laws of thermodynamics are the universal laws of nature, whichcan be applied to any macroscopic material system. However thermodynamics isnot time-dependent, can be applied to systems at the equilibrium only. In orderto depict the system state changing a long time, it’s necessary to developnon-equilibrium thermodynamics. So far, main influential genres ofnon-equilibrium thermodynamics includes classical irreversiblethermodynamics (CIT), rational thermodynamics (RT), internal variablethermodynamics (IVT) and extended irreversible thermodynamics (EIT).Thisarticle introduces the non-equilibrium thermodynamics genres in the lineageof classical irreversible thermodynamics.Granular flow is usually divided into three kinds of flow pattern, namelyquasi static flow, slow flow, and rapid flow. The core issue of the researchis the constitutive relation. A series of constitutive relations ofapplication value have been received up to now, however, the study on principaltheory is insufficient. Granular flow has an emergent mesoscopic structure,such as force chain network and vortex, involving complex irreversibleprocesses. This paper studies its mesoscopic structure and principalcharacters, introduces the concept of two granular temperatures of thegranular flow to characterize the degree of chaotic motion and disorderedconfiguration evolution, sets them as the non-equilibrium variables toconstitute the thermodynamic state variables set for granular flow with theclassical irreversible thermodynamic variables, also determines the granularflow law of energy conversion and the entropy production rate, etc., anddevelops the two granular temperatures (TGT) model. Taking the simple shearquasi-static granular flow in a constant volume as example, and combining itwith the discrete element method (DEM), this work confirms the materialparameters needed for the TGT model, and analyzes the law of developing periodand the effective coefficient of friction of steady period of granular flow. |
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