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Full-Text Articles in Astrophysics and Astronomy

Inverted Velocity Profile In The Cylindrical Couette Flow Of A Rarefied Gas, Alejandro Garcia, K. Aoki, H. Yoshida, T. Nakanishi Jan 2003

Inverted Velocity Profile In The Cylindrical Couette Flow Of A Rarefied Gas, Alejandro Garcia, K. Aoki, H. Yoshida, T. Nakanishi

Faculty Publications

The cylindrical Couette flow of a rarefied gas is investigated, under the diffuse-specular reflection condition of Maxwell’s type on the cylinders, in the case where the inner cylinder is rotating whereas the outer cylinder is at rest. The inverted velocity profile for small accommodation coefficients, pointed out by Tibbs, Baras, and Garcia [Phys. Rev. E 56, 2282 (1997)] on the basis of a Monte Carlo simulation, is investigated extensively by means of a systematic asymptotic analysis for small Knudsen numbers as well as the direct numerical analysis of the Boltzmann equation, and the parameter range in which the phenomenon appears …


A Direct Simulation Monte Carlo Method For The Uehling-Uhlenbeck-Boltzmann Equation, Alejandro Garcia, W. Wagner Jan 2003

A Direct Simulation Monte Carlo Method For The Uehling-Uhlenbeck-Boltzmann Equation, Alejandro Garcia, W. Wagner

Faculty Publications

In this paper we describe a direct simulation Monte Carlo algorithm for the Uehling-Uhlenbeck-Boltzmann equation in terms of Markov processes. This provides a unifying framework for both the classical Boltzmann case as well as the Fermi-Dirac and Bose-Einstein cases. We establish the foundation of the algorithm by demonstrating its link to the kinetic equation. By numerical experiments we study its sensitivity to the number of simulation particles and to the discretization of the velocity space, when approximating the steady-state distribution.


Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss Jan 2003

Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss

Publications

Ground magnetometer measurements of total magnetic field strength from 6 stations at low latitudes were analyzed using power spectrum and Hurst range scaling techniques. The Hurst exponents for most of these time-series were near 0.5, which indicates stochasticity, with the highest latitude stations exhibiting some persistence with Hurst exponents greater than 0.6. Although no definite correlations are evident, the relative increase of the Hurst exponent with latitude suggests the possibility that the underlying dynamics of the magnetosphere change with latitude. This result may help quantify the dynamics of the inner magnetosphere itself without the direct presence of the solar wind …


A Direct Simulation Monte Carlo Method For The Uehling-Uhlenbeck-Boltzmann Equation, Alejandro Garcia, Wolfgang Wagner Jan 2003

A Direct Simulation Monte Carlo Method For The Uehling-Uhlenbeck-Boltzmann Equation, Alejandro Garcia, Wolfgang Wagner

Alejandro Garcia

In this paper we describe a direct simulation Monte Carlo algorithm for the Uehling-Uhlenbeck-Boltzmann equation in terms of Markov processes. This provides a unifying framework for both the classical Boltzmann case as well as the Fermi-Dirac and Bose-Einstein cases. We establish the foundation of the algorithm by demonstrating its link to the kinetic equation. By numerical experiments we study its sensitivity to the number of simulation particles and to the discretization of the velocity space, when approximating the steady-state distribution.


Inverted Velocity Profile In The Cylindrical Couette Flow Of A Rarefied Gas, Alejandro Garcia, K. Aoki, H. Yoshida, T. Nakanishi Jan 2003

Inverted Velocity Profile In The Cylindrical Couette Flow Of A Rarefied Gas, Alejandro Garcia, K. Aoki, H. Yoshida, T. Nakanishi

Alejandro Garcia

The cylindrical Couette flow of a rarefied gas is investigated, under the diffuse-specular reflection condition of Maxwell’s type on the cylinders, in the case where the inner cylinder is rotating whereas the outer cylinder is at rest. The inverted velocity profile for small accommodation coefficients, pointed out by Tibbs, Baras, and Garcia [Phys. Rev. E 56, 2282 (1997)] on the basis of a Monte Carlo simulation, is investigated extensively by means of a systematic asymptotic analysis for small Knudsen numbers as well as the direct numerical analysis of the Boltzmann equation, and the parameter range in which the phenomenon appears …