scholarly journals Relativistic Extended Thermodynamics of Polyatomic Gases with Rotational and Vibrational Modes

2021 ◽  
Vol 2 (3) ◽  
pp. 187-201
Author(s):  
Sebastiano Pennisi

In a recent article an infinite set of balance equations has been proposed to modelize polyatomic gases with rotational and vibrational modes in the non-relativistic context. To obtain particular cases, it has been truncated to obtain a model with 7 or 15 moments. Here the following objectives are pursued: 1) to obtain the relativistic counterpart of this model which, at the non-relativistic limit, gives the same balance equations as in the known classical case; 2) to obtain the previous result for the model with an arbitrary but fixed number of moments, 3) to obtain the closure of the resulting relativistic model so that all the functions appearing in the balance equations are expressed in terms of the independent variables. To achieve these goals, the following methods are used: 1) The Entropy Principle is imposed. As a result is obtained that the closure is determined up to a single 4-vectorial function usually called 4-potential. 2) To determine this last function, a more restrictive principle is imposed, namely the Maximum Entropy Principle (MEP). 3) Since all the functions involved must be expressed in the covariant form, so as not to depend on the observer, the Representation Theorems are used. Findings of this article are exactly the goals outlined earlier. They are clearly novelty because they had never been achieved before. They can be considered also improvements because, if the aforementioned arbitrary number of moments is restricted to 16, the present work coincide with that already known in literature. Doi: 10.28991/HIJ-2021-02-03-04 Full Text: PDF

2021 ◽  
Vol 1 (2) ◽  
pp. 12-21
Author(s):  
Sebastiano Pennisi

In this article the known models are considered for relativistic polyatomic gases with an arbitrary number of moments, in the framework of Extended Thermodynamics. These models have the downside of being hyperbolic only in a narrow domain around equilibrium, called "hyperbolicity zone". Here it is shown how to overcome this drawback by presenting a new model which satisfies the hyperbolicity requirement for every value of the independent variables and without restrictions. The basic idea behind this new model is that hyperbolicity is limited in previous models by the approximations made there. It is here shown that hyperbolicity isn't limited also for an approximated model if terms of the same order are consistently considered, in a new way never used before in literature. To design and complete this new model, well accepted principles are used such as the "Entropy Principle" and the "Maximum Entropy Principle". Finally, new trends are analized and these considerations may require a modification of the results published so far; as a bonus, more manageable balance equations are obtained. This allows to obtain more stringent results than those so far known. For example, we will have a single quantity (the energy e) expressed by an integral and all the other constitutive functions will be expressed in terms of it and its derivatives with respect to temperature. Another useful consequence is its easier applicability to the case of diatomic and ultrarelativistic gases which are useful, at least for testing the model in simple cases.


Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 62
Author(s):  
Takashi Arima ◽  
Tommaso Ruggeri

The aim of this paper is to construct the molecular extended thermodynamics for classical rarefied polyatomic gases with a new hierarchy, which is absent in the previous procedures of moment equations. The new hierarchy is deduced recently from the classical limit of the relativistic theory of moments associated with the Boltzmann–Chernikov equation. The field equations for 15 moments of the distribution function, in which the internal degrees of freedom of a molecule are taken into account, are closed with the maximum entropy principle. It is shown that the theory contains, as a principal subsystem, the previously polyatomic 14 fields theory, and in the monatomic limit, in which the dynamical pressure vanishes, the differential system converges, instead of to the Grad 13-moment system, to the Kremer 14-moment system.


2012 ◽  
Vol 700 ◽  
pp. 187-213 ◽  
Author(s):  
Bernd R. Noack ◽  
Robert K. Niven

AbstractA statistical closure is proposed for a Galerkin model of an incompressible periodic cylinder wake. This closure employs Jaynes’ maximum entropy principle to infer the probability distribution for mode amplitudes using exact statistical balance equations as side constraints. The analysis predicts mean amplitude values and modal energy levels in good agreement with direct Navier–Stokes simulation. In addition, it provides an analytical equation for the modal energy distribution.


VLSI Design ◽  
2000 ◽  
Vol 10 (4) ◽  
pp. 335-354 ◽  
Author(s):  
A. M. Anile ◽  
O. Muscato ◽  
V. Romano

Balance equations based on the moment method for the transport of electrons in silicon semiconductors are presented. The energy band is assumed to be described by the Kane dispersion relation. The closure relations have been obtained by employing the maximum entropy principle.The validity of the constitutive equations for fluxes and production terms of the balance equations has been checked with a comparison to detailed Monte Carlo simulations in the case of bulk silicon.


2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Maria Cristina Carrisi ◽  
Rita Enoh Tchame ◽  
Marcel Obounou ◽  
Sebastiano Pennisi

A new model for Polyatomic Gases with an arbitrary but fixed number of moments has been recently proposed and investigated in the framework of Extended Thermodynamics; the arbitrariness of the number of moments is linked to a numberNand the resulting model is called anN-Model. This model has been elaborated in order to take into account the entropy principle, the Galilean relativity principle, and some symmetry conditions. It has been proved that the solution for all these conditions exists, but it has not been written explicitly because hard notation is necessary; it has only been shown how the theory is self-generating in the sense that if we know the closure of theN-Model, then we will be able to find that of(N+1)-Model. Up to now only a single particular solution has been found in this regard. Instead of this, we find here a numberable set of exact solutions which hold for every fixed numberN.


Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 43
Author(s):  
Takashi Arima ◽  
Maria Cristina Carrisi ◽  
Sebastiano Pennisi ◽  
Tommaso Ruggeri

A relativistic version of the rational extended thermodynamics of polyatomic gases based on a new hierarchy of moments that takes into account the total energy composed by the rest energy and the energy of the molecular internal mode is proposed. The moment equations associated with the Boltzmann–Chernikov equation are derived, and the system for the first 15 equations is closed by the procedure of the maximum entropy principle and by using an appropriate BGK model for the collisional term. The entropy principle with a convex entropy density is proved in a neighborhood of equilibrium state, and, as a consequence, the system is symmetric hyperbolic and the Cauchy problem is well-posed. The ultra-relativistic and classical limits are also studied. The theories with 14 and 6 moments are deduced as principal subsystems. Particularly interesting is the subsystem with 6 fields in which the dissipation is only due to the dynamical pressure. This simplified model can be very useful when bulk viscosity is dominant and might be important in cosmological problems. Using the Maxwellian iteration, we obtain the parabolic limit, and the heat conductivity, shear viscosity, and bulk viscosity are deduced and plotted.


1986 ◽  
Vol 108 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Guy Jumarie

The problem of estimating the state of a continuous markovian process in the presence of nonlinear observation (nonlinear filtering) may be considered as being completely solved on a theoretical standpoint. All the difficulties arise in the practical applications which require new ways of investigation: search for special approaches related to special problems, and search for improvement of the numerical techniques which are now available. In fact, nonlinear filtering is basically an infinite dimensional problem, and any approximation should work in a finite dimensional space. The paper proposes an approach without using stochastic differential equations. The continuous markovian process is defined by its transition moments only and therefore one can derive the equation of state moments. When the transition moments are polynomials, the state moments are then given by an infinite set of linear differential equations. Likewise when the observation is polynomial, an infinite set of linear equations provides estimates of the state moments in terms of the observation moments. Given the estimates of the state moments, and using the maximum entropy principle we will obtain the corresponding probability density, and therefore the estimate of the state. When the nonlinear functions are not polynomials, it will be possible to apply the method above, using a polynomial approximation.


1990 ◽  
Vol 27 (2) ◽  
pp. 303-313 ◽  
Author(s):  
Claudine Robert

The maximum entropy principle is used to model uncertainty by a maximum entropy distribution, subject to some appropriate linear constraints. We give an entropy concentration theorem (whose demonstration is based on large deviation techniques) which is a mathematical justification of this statistical modelling principle. Then we indicate how it can be used in artificial intelligence, and how relevant prior knowledge is provided by some classical descriptive statistical methods. It appears furthermore that the maximum entropy principle yields to a natural binding between descriptive methods and some statistical structures.


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