Thursday, February 16, 2012

1202.3169 (S. Kokou Dadzie et al.)

On the thermodynamics of volume/mass diffusion in fluids    [PDF]

S. Kokou Dadzie, Jason M. Reese
In reference (Dadzie and Reese, PhysicaA, 2008), a kinetic equation for gas
flows was proposed that leads to a set of four macroscopic conservation
equations, rather than the traditional set of three equations. The additional
equation arises due to local spatial random molecular behavior, which has been
described as a volume or mass diffusion process. In this present paper, we
describe a procedure to construct a Gibbs-type equation and a second-law
associated with these kinetic and continuum models. We also point out the close
link between the kinetic equation in (Dadzie and Reese, PhysicaA, 2008) and
that proposed previously by Klimontovich, and we discuss some of their
compatibilities with classical mechanical principles. Finally, a dimensional
analysis highlights the nature of volume/mass diffusion: it is a
non-conventional diffusive process, with some similarities to the `ghost
effect', which cannot be obtained from a fluid mechanical derivation that
neglects non-local-equilibrium structures, as the conventional
Navier-Stokes-Fourier model does.
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