The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
J. C. Loraud - One of the best experts on this subject based on the ideXlab platform.
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exact and approximate riemann solvers for Real Gases
Journal of Computational Physics, 1994Co-Authors: R. Saurel, M. Larini, J. C. LoraudAbstract:A procedure is developed for solving the Riemann problem (RP) for the flow of Gases obeying an equation of state (EOS) of the form p = p (�, �). A first method is introduced, producing solutions of the exact RP; the algorithm is validated by applying it to the classical test case of the shock-tube, for a perfect gas. Thereafter, the method is applied to Gases having EOS of the Van der Waals or virial types, with very good resulting accuracy; however, the procedure is somewhat demanding in computer time. Therefore, some simplifying assumptions are introduced into the computation of simple waves, leading to an approximate solution of the RP; in most circumstances, excellent results are obtained, and the computer time is much more competitive. However, under certain extreme flow conditions, it is recommended that a combination of the exact and approximate solvers for the RP be employed.
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An exact Riemann solver for detonation products
Shock Waves, 1992Co-Authors: M. Larini, R. Saurel, J. C. LoraudAbstract:Numerical methods based upon the Riemann Problem are considered for solving the general initial-value problem for the Euler equations applied to Real Gases. Most of such methods use an approximate solution of the Riemann problem when Real Gases are involved. These approximate Riemann solvers do not yield always a good resolution of the flow field, especially for contact surfaces and expansion waves. Moreover, approximate Riemann solvers cannot produce exact solutions for the boundary points. In order to overcome these shortcomings, an exact solution of the Riemann problem is developed, valid for Real Gases. The method is applied to detonation products obeying a 5th order virial equation of state, in the shock-tube test case. Comparisons between our solver, as implemented in Random Choice Method, and finite difference methods, which do not employ a Riemann solver, are given.
Tommaso Ruggeri - One of the best experts on this subject based on the ideXlab platform.
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recent results on nonlinear extended thermodynamics of Real Gases with six fields part i general theory
Ricerche Di Matematica, 2016Co-Authors: Takashi Arima, Tommaso Ruggeri, Masaru Sugiyama, Shigeru TaniguchiAbstract:We review the recently developed theory of extended thermodynamics (ET) of Real Gases with six independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting near-equilibrium approximation. We discuss the polytropic and non-polytropic cases of rarefied polyatomic Gases in detail, including the closure via nonlinear molecular ET.
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non linear extended thermodynamics of Real Gases with 6 fields
International Journal of Non-linear Mechanics, 2015Co-Authors: Takashi Arima, Tommaso Ruggeri, Masaru Sugiyama, Shigeru TaniguchiAbstract:Abstract We establish extended thermodynamics (ET) of Real Gases with 6 independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting the near-equilibrium approximation. We prove its compatibility with the universal principles (the entropy principle, the Galilean invariance and the stability), and obtain the symmetric hyperbolic system with respect to the main field. In near-equilibrium we recover the previous results. The correspondence between the ET 6-field theory and Meixner׳s theory of relaxation processes is discovered. The internal variable and the non-equilibrium temperature in Meixner׳s theory are expressed in terms of the quantities of the ET 6-field theory, in particular, the dynamic pressure. As an example, we present the cases of a rarefied polyatomic gas and study the monatomic-gas limit where the system converges to the Euler system of a perfect fluid.
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Shock Waves in Real Gases
2015Co-Authors: Tommaso RuggeriAbstract:After a brief introduction concerning shock waves and Riemann problem the talk is addressed in non- classical shock waves in comparison with shock waves in ideal gas. The non-classical shock waves are, for example, a rarefaction shock wave (a negative shock wave), a liquefaction shock wave (or more generally, a shock wave accompanied by phase transition), a shock with wave splitting. The organization of the present talk is as follows: (A) A brief and general discussion of Riemann problem and Riemann problem with structure. The admissibility criteria for shocks and the local exceptionality condition. (B) Non-classical shock waves, in a van der Waals gas, which is one of typical Real gas models. (C) A brief and general discussion of shock-induced phase transition. (D) The quantitative classification of Hugoniot types in terms of the thermodynamic quantities of the unperturbed state (the state before a shock wave) and the shock strength is made. Second, the admissibility of shock waves is discussed on th
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extended thermodynamics of Real Gases with dynamic pressure an extension of meixnerʼs theory
Physics Letters A, 2012Co-Authors: Takashi Arima, Tommaso Ruggeri, Shigeru Taniguchi, Masaru SugiyamaAbstract:Abstract Basing on the recent theory of extended thermodynamics of dense Gases, we study a thermodynamic theory of Gases with the energy transfer from molecular translational mode to internal modes as an extension of Meixnerʼs theory. We focus our attention on the simplest case with only one dissipative process due to the dynamic pressure. The dispersion relation for sound derived from the present theory is compared with that from Meixnerʼs theory. Kinetic theoretical basis of the present approach is also discussed.
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Shock Waves in Real Gases
2008Co-Authors: Tommaso RuggeriAbstract:After a brief introduction concerning shock waves and Riemann problem the talk is addressed in non- classical shock waves in comparison with shock waves in ideal gas. The non-classical shock waves are, for example, a rarefaction shock wave (a negative shock wave), a liquefaction shock wave (or more generally, a shock wave accompanied by phase transition), a shock with wave splitting. The organization of the present talk is as follows: (A) A brief and general discussion of Riemann problem and Riemann problem with structure. The admissibility criteria for shocks and the local exceptionality condition. (B) Non-classical shock waves, in a van der Waals gas, which is one of typical Real gas models. (C) A brief and general discussion of shock-induced phase transition. (D) The quantitative classification of Hugoniot types in terms of the thermodynamic quantities of the unperturbed state (the state before a shock wave) and the shock strength is made. Second, the admissibility of shock waves is discussed on the basis of Liu’s condition. The present study is expected to be a basis of the study of shock wave phenomena in more Realistic condensed matters including shock-induced phase transition.
R. Saurel - One of the best experts on this subject based on the ideXlab platform.
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exact and approximate riemann solvers for Real Gases
Journal of Computational Physics, 1994Co-Authors: R. Saurel, M. Larini, J. C. LoraudAbstract:A procedure is developed for solving the Riemann problem (RP) for the flow of Gases obeying an equation of state (EOS) of the form p = p (�, �). A first method is introduced, producing solutions of the exact RP; the algorithm is validated by applying it to the classical test case of the shock-tube, for a perfect gas. Thereafter, the method is applied to Gases having EOS of the Van der Waals or virial types, with very good resulting accuracy; however, the procedure is somewhat demanding in computer time. Therefore, some simplifying assumptions are introduced into the computation of simple waves, leading to an approximate solution of the RP; in most circumstances, excellent results are obtained, and the computer time is much more competitive. However, under certain extreme flow conditions, it is recommended that a combination of the exact and approximate solvers for the RP be employed.
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An exact Riemann solver for detonation products
Shock Waves, 1992Co-Authors: M. Larini, R. Saurel, J. C. LoraudAbstract:Numerical methods based upon the Riemann Problem are considered for solving the general initial-value problem for the Euler equations applied to Real Gases. Most of such methods use an approximate solution of the Riemann problem when Real Gases are involved. These approximate Riemann solvers do not yield always a good resolution of the flow field, especially for contact surfaces and expansion waves. Moreover, approximate Riemann solvers cannot produce exact solutions for the boundary points. In order to overcome these shortcomings, an exact solution of the Riemann problem is developed, valid for Real Gases. The method is applied to detonation products obeying a 5th order virial equation of state, in the shock-tube test case. Comparisons between our solver, as implemented in Random Choice Method, and finite difference methods, which do not employ a Riemann solver, are given.
V. D. Sharma - One of the best experts on this subject based on the ideXlab platform.
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dissipative waves in Real Gases
International Journal of Non-linear Mechanics, 2017Co-Authors: Neelam Gupta, V. D. SharmaAbstract:Abstract In this paper, we characterize a class of solutions to the unsteady 2-dimensional flow of a van der Waals fluid involving shock waves, and derive an asymptotic amplitude equation exhibiting quadratic and cubic nonlinearities including dissipation and diffraction. We exploit the theory of nonclassical symmetry reduction to obtain some exact solutions in the limit of vanishing dissipation. Because of the nonlinearities present in the evolution equation, one expects that the wave profile will eventually encounter distortion and steepening which in the limit of vanishing dissipation culminates into a shock wave; and once shock is formed, it will propagate by separating the portions of the continuous region. Here we have shown how the Real gas effects, which manifest themselves through the van der Waals parameters a and b influence the wave characteristics, namely the shape, strength, and decay behavior of shocks.
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On weak shock diffraction in Real Gases
arXiv: Mathematical Physics, 2014Co-Authors: Neelam Gupta, V. D. SharmaAbstract:Asymptotic solutions are obtained for the two-dimensional Euler system for Real Gases with appropriate boundary conditions which describe the diffraction of a weak shock at a right-angled wedge; the Real gas effects are characterized by a van der Waals type equation of state. The behavior of the flow configuration influenced by the Real gas effects, that includes the local structure near a singular point, is studied in detail.
Shigeru Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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recent results on nonlinear extended thermodynamics of Real Gases with six fields part i general theory
Ricerche Di Matematica, 2016Co-Authors: Takashi Arima, Tommaso Ruggeri, Masaru Sugiyama, Shigeru TaniguchiAbstract:We review the recently developed theory of extended thermodynamics (ET) of Real Gases with six independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting near-equilibrium approximation. We discuss the polytropic and non-polytropic cases of rarefied polyatomic Gases in detail, including the closure via nonlinear molecular ET.
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non linear extended thermodynamics of Real Gases with 6 fields
International Journal of Non-linear Mechanics, 2015Co-Authors: Takashi Arima, Tommaso Ruggeri, Masaru Sugiyama, Shigeru TaniguchiAbstract:Abstract We establish extended thermodynamics (ET) of Real Gases with 6 independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting the near-equilibrium approximation. We prove its compatibility with the universal principles (the entropy principle, the Galilean invariance and the stability), and obtain the symmetric hyperbolic system with respect to the main field. In near-equilibrium we recover the previous results. The correspondence between the ET 6-field theory and Meixner׳s theory of relaxation processes is discovered. The internal variable and the non-equilibrium temperature in Meixner׳s theory are expressed in terms of the quantities of the ET 6-field theory, in particular, the dynamic pressure. As an example, we present the cases of a rarefied polyatomic gas and study the monatomic-gas limit where the system converges to the Euler system of a perfect fluid.
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extended thermodynamics of Real Gases with dynamic pressure an extension of meixnerʼs theory
Physics Letters A, 2012Co-Authors: Takashi Arima, Tommaso Ruggeri, Shigeru Taniguchi, Masaru SugiyamaAbstract:Abstract Basing on the recent theory of extended thermodynamics of dense Gases, we study a thermodynamic theory of Gases with the energy transfer from molecular translational mode to internal modes as an extension of Meixnerʼs theory. We focus our attention on the simplest case with only one dissipative process due to the dynamic pressure. The dispersion relation for sound derived from the present theory is compared with that from Meixnerʼs theory. Kinetic theoretical basis of the present approach is also discussed.
