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Quarterly of Applied Mathematics
  
Online ISSN 1552-4485; Print ISSN 0033-569X
 

Can constitutive relations be represented by non-local equations?


Author: Tommaso Ruggeri
Journal: Quart. Appl. Math. 70 (2012), 597-611
MSC (2010): Primary 54C40, 14E20; Secondary 46E25, 20C20
Published electronically: May 9, 2012
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Abstract: Using the modern theory of extended thermodynamics, it is possible to show that the well-known constitutive equations of continuum mechanics in non-local form with respect to space variables such as Fourier's, Navier-Stokes's, Fick's and Darcy's laws are in reality an approximation of the general balance laws when some suitable relaxation times are neglected. In the present paper we conjecture that this fact is completely general and indeed all the ``real'' constitutive equations of mathematical physics are local in nature and, therefore, the corresponding differential systems of balance equations are hyperbolic rather than parabolic. This does not means that non-local equations are not useful not only because there are situations where non-local equations may be an effective approximation, but also because non-locality permits us to obtain the evaluation of non-observable quantities such as the velocity and the temperature of each constituent of a mixture of fluids. An important consequence is that these equations do not need to satisfy the so-called objectivity principle that on the contrary still continues to be valid only for the constitutive equations. We prove that under suitable assumptions the conditions dictated by the entropy principle in the hyperbolic case guarantee the validity of the entropy principle also in the parabolic limit. Considerations are also made with regard to the formal limit between hyperbolic systems and parabolic ones and from hyperbolic versus hyperbolic, between a system and a subsystem. We end the paper with a discussion of the main analytical properties concerning the global existence of smooth solutions for dissipative hyperbolic systems.


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Additional Information

Tommaso Ruggeri
Affiliation: Department of Mathematics & Research Center of Applied Mathematics, University of Bologna, Via Saragozza 8, 40123 Bologna, Italy
Email: tommaso.ruggeri@unibo.it

DOI: http://dx.doi.org/10.1090/S0033-569X-2012-01314-3
PII: S 0033-569X(2012)01314-3
Keywords: Constitutive equations, objective principle, hyperbolic systems of balance laws
Received by editor(s): January 19, 2012
Published electronically: May 9, 2012
Additional Notes: The author was supported in part by GNFM of INdAM
Dedicated: Dedicated to Constantine Dafermos for his 70th birthday
Article copyright: © Copyright 2012 Brown University



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