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Canonical fluid thermodynamicsThe space-time integral of the thermodynamic pressure plays in a certain sense the role of the thermodynamic potential for compressible adiabatic flow. The stability criterion can be converted into a variational minimum principle by requiring the molar free-enthalpy and temperature to be generalized velocities. In the fluid context, the definition of proper-time differentiation involves the fluid velocity expressed in terms of three particle identity parameters. The pressure function is then converted into a functional which is the Lagrangian density of the variational principle. Being also a minimum principle, the variational principle provides a means for comparing the relative stability of different flows. For boundary conditions with a high degree of symmetry, as in the case of a uniformly expanding spherical gas box, the most stable flow is a rectilinear flow for which the world-trajectory of each particle is a straight line. Since the behavior of the interior of a freely expanding cosmic cloud may be expected to be similar to that of the fluid in the spherical box of gas, this suggests that the cosmic principle is a consequence of the laws of thermodynamics, rather than just an ad hoc postulate.
Document ID
19750049750
Acquisition Source
Legacy CDMS
Document Type
Other - Collected Works
Authors
Schmid, L. A.
(NASA Goddard Space Flight Center Theoretical Studies Branch, Greenbelt, Md., United States)
Date Acquired
August 8, 2013
Publication Date
January 1, 1974
Subject Category
Thermodynamics And Statistical Physics
Accession Number
75A33822
Distribution Limits
Public
Copyright
Other

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