ELFT HÍRADÓ

[Van Peter <vpet AT phyndi.fke.bme.hu>]

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22. Termodinamikai Tea



2003, oktober 13. hetfo, 14.00
BME, Kemiai Fizika Tanszek, F ep. III lcsh. I em., jobbra

Paolo Maria Mariano (University of Roma "La Sapienza", Italy)

"Topological transitions due to transfer of energy from macroscopic to 
substructural level in complex fluids"

Abstract:

In steady-state non-isentropic flows of perfect fluids there is
always thermodynamic generation of vorticity when the difference
between the product of the temperature with the gradient of the
entropy and the gradient of total enthalpy is different from
zero. We note that this property does not hold in general for
complex fluids for which the prominent influence of the material
substructure on the gross motion may cancel t~~he thermodynamic
vorticity. We indicate the explicit condition for this
cancellation (topological transition from vortex sheet to shear
flow)  for general complex fluids described by coarse-grained
order parameters and extended forms of Ginzburg-Landau energies.
As a prominent sample case we treat first Korteweg's fluid, used
commonly as a model of capillary motion or phase transitions
characterized by diffused interfaces. Then we discuss general
complex fluids. We show also that, when the entropy and the total
enthalpy are constant throughout the flow, vorticity may be
generated by the inhomogeneous character of the distribution of
material substructures, and indicate the explicit condition for
such a generation. We discuss also some aspects of unsteady
motion and show that in two-dimensional flows of incompressible
perfect complex fluids the vorticity is in general not conserved,
due to a mechanism of transfer of energy between different
levels.

The results are collected in a paper in press on "J. of Physics
A: Math. & Gen.



Kozreadta: Van Peter
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