Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session C6: Computational Physics: Algorithms to Applications |
Hide Abstracts |
Sponsoring Units: DCOMP Chair: Rajiv Kalia, University of Southern California Room: Terrace A-F |
Saturday, April 30, 2011 1:30PM - 1:42PM |
C6.00001: Inverse Problem Involving an Integral Equation in Irrigation Theory Olesya Sarajlic, Alexandra Smirnova The use of Laplace transforms and other computational tools allows to study an elementary inverse problem in hydraulics. Given basic equation $$r(h) = 16 \int_{0}^{h} \sqrt{h-y}\; f(y)\; dy$$ which relates notch shape $f(y)$ and flow rate $r(h)$, we can directly determine the flow rate function $r$ from the notch shape function $f$ through straightforward integration. However, the inverse problem arises from Torricelli's law that is expressed as a particularly simple convolution-type Volterra integral equation of the first kind, which can be solved by Laplace transforms. Unlike the direct problem, the process of solving the inverse problem is unstable in a sense that even a small error in the input data can result in a substantial error at the computed solution. The goal of our research is to develop a regularized numerical algorithm for getting less noisy and more stable outcome of the inverse problem. [Preview Abstract] |
Saturday, April 30, 2011 1:42PM - 1:54PM |
C6.00002: Multigrid Methods Applied to Multigroup Neutron Transport Adnan Rebei A full multigrid algorithm based on the nodal expansion method is used to solve the multigroup neutron transport diffusion equation with discontinuous coefficients. The prolongation and restriction operators between the various meshes are constructed for the surface averaged currents. The fast convergence of the method is demonstrated in a calculation of the criticality of a reactor.\\[4pt] [1] L. Mei, Appl. Math. Comp. 179, 473 (2006).\\[0pt] [2] L. Yu. Zaslavsky, Appl. Math. Comp. 53, 13 (1993). [Preview Abstract] |
Saturday, April 30, 2011 1:54PM - 2:06PM |
C6.00003: CRT: A Numerical Tool for Propagating Ultra-High Energy Cosmic Rays Through Galactic Magnetic Field Models Michael Sutherland, Brian Baughman, James Beatty The deflection of ultra high energy cosmic rays (UHECRs) by cosmic magnetic fields, particularly the Galactic magnetic field (GMF), may be sufficiently large to confuse identification of their sources. Here we present a publicly available numerical tool \textit{CRT}, which can forward- or back-track particles of any type through multiple magnetic field configurations. Trajectories are determined by numerically integrating the relativistic equation of motion. Users may specify magnetic field, source, and particle parameters through an input configuration file. \textit{CRT}'s modular nature allows users to include additional field models and source distributions of their own. The interface is designed to be simple while still allowing the user to manipulate important runtime parameters. Output includes complete simulation information and a full description of each event's initial and final states. The current stage of development (available on the web) will be discussed, as well as plans for future updates. [Preview Abstract] |
Saturday, April 30, 2011 2:06PM - 2:18PM |
C6.00004: Comparing the Random Phase Approximation to Full Configuration-Interaction Calculations of Atomic Structure: Applying Nuclear Techniques to Atomic Problems Micah Schuster, Calvin Johnson We compute the binding energies for helium through neon, comparing the random phase approximation (RPA) against full configuration- interaction diagonalization. RPA gives a reasonable approximation for the full numerical answer and might be useful for efficient determination of basis set parameters. [Preview Abstract] |
Saturday, April 30, 2011 2:18PM - 2:30PM |
C6.00005: Variance Reduced Monte Carlo Simulations of Phonon Transport in Semiconducting Materials Jean-Philippe Peraud, Colin Landon, Nicolas Hadjiconstantinou We present a class of variance reduction methods for drastically reducing the statistical uncertainty associated with Monte Carlo simulations of phonon transport in semiconducting materials. The variance reduction is achieved using a control variate approach, with a nearby equilibrium serving as the control. The resulting simulation methods exhibit drastically reduced statistical uncertainty that is proportional to the deviation from equilibrium; in other words, arbitrarily small signals can be simulated, because, as the signal decreases, the statistical uncertainty also decreases proportionally. The lower statistical uncertainty significantly reduces the cost associated with simulations of systems close to equilibrium (e.g. for calculating thermal conductivity). The computational gains enable efficient and essentially noise-free simulation of three-dimensional problems. Application of our methodology to the investigation of the effect of engineered porosity patterns on the thermal conductivity of silicon as well as the transient response of thin films subject to laser irradiation will be presented and discussed. [Preview Abstract] |
Saturday, April 30, 2011 2:30PM - 2:42PM |
C6.00006: Detonation Initiation by a Temperature Gradient for a Detailed Chemical Reaction Models Michael Liberman, Alexey Kiverin, Alexander Chukalovsky, Mikhail Ivanov The evolution from a temperature gradient to a detonation is investigated using high resolution numerical simulations for combustion mixture whose chemistry is governed by a detailed chemical kinetics. We employ a model representing an initial linear temperature gradient in the fuel. Emphasis is on comparing the results with previous studies that used simple one-step kinetics. It is shown that the evolution to detonation from temperature nonuniformities is considerably different for one-step kinetics models than for chain-branching kinetic models and it is different in different fuels for the same initial conditions. A detailed chemical model has a profound effect on the validity of Zel'dovich's spontaneous wave concept for detonation initiation by a gradient of reactivity. The evolution to detonation from a temperature gradient is considered for hydrogen-air and methane--air mixtures at different initial pressures. The analysis shows that for a detailed chemical kinetics the temperature gradients, which was thought to appear in the form of hot spots and the like, are not satisfy the criteria to initiate detonation, and the gradient mechanism can not be origin of the deflagration-to-detonation transition. [Preview Abstract] |
Saturday, April 30, 2011 2:42PM - 2:54PM |
C6.00007: Large Scale Atomistic Modeling of Scratching Process by a Spherical Tool Behrouz Shiari Large molecular dynamics simulations are performed to investigate the nanoscale scratching process of monocrystalline nickel. The effects of scratching velocities and temperaure of the substrate on the resulting chip formation, scratching forces, dislocation nucleation and propagation, and finally workpiece surface evolution are studied. The results show that the scratching resistance increases with the increase in scratching velocity. The higher scratching velocity results in larger chip volume and closer chip shape with a more amorphous structure. Simulations also show that the scratching force fluctuations can be correlated to nucleation and propagation of dislocations in the substrate. The dislocations nucleated during scratching dissociate into Shockley partial dislocations connected with a band of stacking fault as they propagates along a V-shape pattern. These patterns can be observed as hillock marks on the scratching free surface a short distance from the tool position. The fluctuation of scratching force is affected by the scratching velocity and the drops and rises of the scratching forces disappear at high scratching velocities due to high stain rate. The atomic scale behavior changes with temperature, and the clear drops and rises of the scratching force can not be observed at higher temperatures. [Preview Abstract] |
Saturday, April 30, 2011 2:54PM - 3:06PM |
C6.00008: Calculation of the crystal-melt interfacial free energy for the binary hard-sphere system with the diameter ratio of 0.9 at the azeotrope Majeed Amini, Brian Larid Using the analysis of equilibrium cappillary fluctuations in molecular dynamics simulations,we compute the magnitude and anisotropy of the interfacial free energy $\gamma$ of the crystal-melt interface for the binary hard-sphere system with $\alpha = 0.9$ at the azeotrope. We found $\gamma_{100} = 0.62(2)$, $\gamma_{110} = 0.60(2)$, and $\gamma_{111} = 0.58(2)$. We compare our results with the values of the interfacial free energy of the same system but at points other than azeotrope, as well as with the interfacial free energy of a single hard sphere system. Our results show the relation $\gamma_{100} > \gamma_{110} > \gamma_{111}$ being consistent with the simulation results for various metals, Lennard-Jones (LJ) system, and single hard-sphere system. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700