1,266 research outputs found
Geothermal studies - Yellowstone National Park /test site 11/, Wyoming
Summary report of diamond drilling in thermal areas of Yellowstone National Park, and method for determining heat flow in thermal area
Solitary and compact-like shear waves in the bulk of solids
We show that a model proposed by Rubin, Rosenau, and Gottlieb [J. Appl. Phys.
77 (1995) 4054], for dispersion caused by an inherent material characteristic
length, belongs to the class of simple materials. Therefore, it is possible to
generalize the idea of Rubin, Rosenau, and Gottlieb to include a wide range of
material models, from nonlinear elasticity to turbulence. Using this insight,
we are able to fine-tune nonlinear and dispersive effects in the theory of
nonlinear elasticity in order to generate pulse solitary waves and also bulk
travelling waves with compact support
Scale separation in granular packings: stress plateaus and fluctuations
It is demonstrated, by numerical simulations of a 2D assembly of polydisperse
disks, that there exists a range (plateau) of coarse graining scales for which
the stress tensor field in a granular solid is nearly resolution independent,
thereby enabling an `objective' definition of this field. Expectedly, it is not
the mere size of the the system but the (related) magnitudes of the gradients
that determine the widths of the plateaus. Ensemble averaging (even over
`small' ensembles) extends the widths of the plateaus to sub-particle scales.
The fluctuations within the ensemble are studied as well. Both the response to
homogeneous forcing and to an external compressive localized load (and gravity)
are studied. Implications to small solid systems and constitutive relations are
briefly discussed.Comment: 4 pages, 4 figures, RevTeX 4, Minor corrections to match the
published versio
Comment on the calculation of forces for multibody interatomic potentials
The system of particles interacting via multibody interatomic potential of
general form is considered. Possible variants of partition of the total force
acting on a single particle into pair contributions are discussed. Two
definitions for the force acting between a pair of particles are compared. The
forces coincide only if the particles interact via pair or embedded-atom
potentials. However in literature both definitions are used in order to
determine Cauchy stress tensor. A simplest example of the linear pure shear of
perfect square lattice is analyzed. It is shown that, Hardy's definition for
the stress tensor gives different results depending on the radius of
localization function. The differences strongly depend on the way of the force
definition.Comment: 9 pages, 2 figure
Prediction of strong shock structure using the bimodal distribution function
A modified Mott-Smith method for predicting the one-dimensional shock wave
solution at very high Mach numbers is constructed by developing a system of
fluid dynamic equations. The predicted shock solutions in a gas of Maxwell
molecules, a hard sphere gas and in argon using the newly proposed formalism
are compared with the experimental data, direct-simulation Monte Carlo (DSMC)
solution and other solutions computed from some existing theories for Mach
numbers M<50. In the limit of an infinitely large Mach number, the predicted
shock profiles are also compared with the DSMC solution. The density,
temperature and heat flux profiles calculated at different Mach numbers have
been shown to have good agreement with the experimental and DSMC solutionsComment: 22 pages, 9 figures, Accepted for publication in Physical Review
On the 3D steady flow of a second grade fluid past an obstacle
We study steady flow of a second grade fluid past an obstacle in three space
dimensions. We prove existence of solution in weighted Lebesgue spaces with
anisotropic weights and thus existence of the wake region behind the obstacle.
We use properties of the fundamental Oseen tensor together with results
achieved in \cite{Koch} and properties of solutions to steady transport
equation to get up to arbitrarily small \ep the same decay as the Oseen
fundamental solution
Stretching and folding versus cutting and shuffling: An illustrated perspective on mixing and deformations of continua
We compare and contrast two types of deformations inspired by mixing
applications -- one from the mixing of fluids (stretching and folding), the
other from the mixing of granular matter (cutting and shuffling). The
connection between mechanics and dynamical systems is discussed in the context
of the kinematics of deformation, emphasizing the equivalence between stretches
and Lyapunov exponents. The stretching and folding motion exemplified by the
baker's map is shown to give rise to a dynamical system with a positive
Lyapunov exponent, the hallmark of chaotic mixing. On the other hand, cutting
and shuffling does not stretch. When an interval exchange transformation is
used as the basis for cutting and shuffling, we establish that all of the map's
Lyapunov exponents are zero. Mixing, as quantified by the interfacial area per
unit volume, is shown to be exponentially fast when there is stretching and
folding, but linear when there is only cutting and shuffling. We also discuss
how a simple computational approach can discern stretching in discrete data.Comment: REVTeX 4.1, 9 pages, 3 figures; v2 corrects some misprints. The
following article appeared in the American Journal of Physics and may be
found at http://ajp.aapt.org/resource/1/ajpias/v79/i4/p359_s1 . Copyright
2011 American Association of Physics Teachers. This article may be downloaded
for personal use only. Any other use requires prior permission of the author
and the AAP
Power-law velocity distributions in granular gases
We report a general class of steady and transient states of granular gases.
We find that the kinetic theory of inelastic gases admits stationary solutions
with a power-law velocity distribution, f(v) ~ v^(-sigma). The exponent sigma
is found analytically and depends on the spatial dimension, the degree of
inelasticity, and the homogeneity degree of the collision rate. Driven
steady-states, with the same power-law tail and a cut-off can be maintained by
injecting energy at a large velocity scale, which then cascades to smaller
velocities where it is dissipated. Associated with these steady-states are
freely cooling time-dependent states for which the cut-off decreases and the
velocity distribution is self-similar.Comment: 11 pages, 9 figure
Third and fourth degree collisional moments for inelastic Maxwell models
The third and fourth degree collisional moments for -dimensional inelastic
Maxwell models are exactly evaluated in terms of the velocity moments, with
explicit expressions for the associated eigenvalues and cross coefficients as
functions of the coefficient of normal restitution. The results are applied to
the analysis of the time evolution of the moments (scaled with the thermal
speed) in the free cooling problem. It is observed that the characteristic
relaxation time toward the homogeneous cooling state decreases as the
anisotropy of the corresponding moment increases. In particular, in contrast to
what happens in the one-dimensional case, all the anisotropic moments of degree
equal to or less than four vanish in the homogeneous cooling state for .Comment: 15 pages, 3 figures; v2: addition of two new reference
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