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Full-Text Articles in Physics

Three-Body Recombination In One Dimension, Nirav P. Mehta, B D. Esry, Chris H. Greene Aug 2007

Three-Body Recombination In One Dimension, Nirav P. Mehta, B D. Esry, Chris H. Greene

Physics and Astronomy Faculty Research

We study the three-body problem in one dimension for both zero- and finite-range interactions using the adiabatic hyperspherical approach. Particular emphasis is placed on the threshold laws for recombination, which are derived for all combinations of the parity and exchange symmetries. For bosons, we provide a numerical demonstration of several universal features that appear in the three-body system, and discuss how certain universal features in three dimensions are different in one dimension. We show that the probability for inelastic processes vanishes as the range of the pairwise interaction is taken to zero and demonstrate numerically that the recombination threshold law …


Numerical Hydrodynamics Of Relativistic Extragalactic Jets, Eunwoo Choi May 2007

Numerical Hydrodynamics Of Relativistic Extragalactic Jets, Eunwoo Choi

Physics and Astronomy Dissertations

This dissertation describes a multidimensional relativistic hydrodynamic code which solves the special relativistic hydrodynamic equations as a hyperbolic system of conservation laws based on the total variation diminishing (TVD) scheme. Several standard tests and test simulations are presented to demonstrate the accuracy, robustness and flexibility of the code. Using this code we have studied three-dimensional hydrodynamic interactions of relativistic extragalactic jets with two-phase ambient media. The deflection angle of the jet is influenced more by the density contrast of the cloud than by the beam Mach number of the jet, and a relativistic jet with low relativistic beam Mach number …


Numerical Methods For The Stochastic Landau-Lifshitz Navier-Stokes Equations, Alejandro Garcia, John B. Bell, Sarah Williams Jan 2007

Numerical Methods For The Stochastic Landau-Lifshitz Navier-Stokes Equations, Alejandro Garcia, John B. Bell, Sarah Williams

Alejandro Garcia

The Landau-Lifshitz Navier-Stokes (LLNS) equations incorporate thermal fluctuations into macroscopic hydrodynamics by using stochastic fluxes. This paper examines explicit Eulerian discretizations of the full LLNS equations. Several computational fluid dynamics approaches are considered (including MacCormack’s two-step Lax-Wendroff scheme and the piecewise parabolic method) and are found to give good results for the variance of momentum fluctuations. However, neither of these schemes accurately reproduces the fluctuations in energy or density. We introduce a conservative centered scheme with a third-order Runge-Kutta temporal integrator that does accurately produce fluctuations in density, energy, and momentum. A variety of numerical tests, including the random walk …


Numerical Methods For The Stochastic Landau-Lifshitz Navier-Stokes Equations, Alejandro Garcia, J. B. Bell, S. Williams Jan 2007

Numerical Methods For The Stochastic Landau-Lifshitz Navier-Stokes Equations, Alejandro Garcia, J. B. Bell, S. Williams

Faculty Publications

The Landau-Lifshitz Navier-Stokes (LLNS) equations incorporate thermal fluctuations into macroscopic hydrodynamics by using stochastic fluxes. This paper examines explicit Eulerian discretizations of the full LLNS equations. Several computational fluid dynamics approaches are considered (including MacCormack’s two-step Lax-Wendroff scheme and the piecewise parabolic method) and are found to give good results for the variance of momentum fluctuations. However, neither of these schemes accurately reproduces the fluctuations in energy or density. We introduce a conservative centered scheme with a third-order Runge-Kutta temporal integrator that does accurately produce fluctuations in density, energy, and momentum. A variety of numerical tests, including the random walk …