617 research outputs found
Dust-acoustic waves and stability in the permeating dusty plasma: II. Power-law distributions
The dust-acoustic waves and their stability driven by a flowing dusty plasma
when it cross through a static (target) dusty plasma (the so-called permeating
dusty plasma) are investigated when the components of the dusty plasma obey the
power-law q-distributions in nonextensive statistics. The frequency, the growth
rate and the stability condition of the dust-acoustic waves are derived under
this physical situation, which express the effects of the nonextensivity as
well as the flowing dusty plasma velocity on the dust-acoustic waves in this
dusty plasma. The numerical results illustrate some new characteristics of the
dust-acoustic waves, which are different from those in the permeating dusty
plasma when the plasma components are the Maxwellian distribution. In addition,
we show that the flowing dusty plasma velocity has a significant effect on the
dust-acoustic waves in the permeating dusty plasma with the power-law
q-distribution.Comment: 20 pages, 10 figures, 41 reference
Global solutions to the Nernst-Planck-Euler system on bounded domain
We show that the Nernst-Planck-Euler system, which models ionic
electrodiffusion in fluids, has global strong solutions for arbitrarily large
data in the two dimensional bounded domains. The assumption on species is
either there are two species or the diffusivities and the absolute values of
ionic valences are the same if the species are arbitrarily many. In particular,
the boundary conditions for the ions are allowed to be inhomogeneous. The proof
is based on the energy estimates, integration along the characteristic line and
the regularity theory of elliptic and parabolic equations
Fractional elastoplastic constitutive model for soils based on a novel 3D fractional plastic flow rule
A novel three-dimensional (3D) fractional plastic flow rule that is not limited by the coordinate basis of the differentiable function is proposed based on the fractional derivative and the coordinate transformation. By introducing the 3D fractional plastic flow rule into the characteristic stress space, a 3D fractional elastoplastic model for soil is established for the first time. Only five material parameters with clear physical significance are required in the proposed model. The capability of the model in capturing the strength and deformation behaviour of soils under true 3D stress conditions is verified by comparing model predictions with test results
Dust charging processes in the nonequilibrium dusty plasma with nonextensive power-law distribution
The dust charging processes in the collections of electrons and ions in the
nonequilibrium dusty plasma with power-law distributions are investigated on
the basic of a new q-distribution function theory in nonextensive statistics.
Electrons and ions obey the power-law distributions and are with q-parameters
different from each other. We derive the generalized formulae for the dust
charging currents in which the nonextensive effects play roles. Further we
investigate the dust charging processes taking place in the homogeneous dusty
plasma where only the particle velocities are power-law distributions and in
the dust cloud plasma where the particle velocities and densities are both
power-law distributions. By numerical analyses, we show that the nonextensive
power-law distributions of electrons and ions have significant effects on the
dust charging processes in the nonequilibrium dusty plasma.Comment: 16 pages, 6 figures, 51 reference
A novel transversely isotropic strength criterion for soils based on a mobilized plane approach
The peak shear strength rules of transversely isotropic soils are stress state dependent and dependent on relative orientation between bedding plane and principal stress. Accordingly, the shear strength of transversely isotropic soils exhibits two primary characteristics: (i) the strength curve on the deviatoric plane is asymmetrical with respect to three principal stress axes; (ii) the shear strength changes with the direction angle of the bedding plane when the intermediate principal stress coefficient is a constant. In this paper, the mobilized plane is introduced and used to reveal the failure mechanism of soils. By projecting the microstructure tensor of transversely isotropic soils onto the normal of the mobilized plane, the directionality of the transversely isotropic soils is introduced into the friction rules on the mobilized plane, and a transversely isotropic strength parameter is proposed. The proposed strength parameter can extend isotropic strength criteria into transversely isotropic strength criteria. This mobilized plane approach is used to establish a novel transversely isotropic nonlinear unified strength criterion (TI-NUSC). The difficulty to establish a unified description of the asymmetrical strength curve and its evolution with direction angle is overcome by the established criterion. Comparisons between available test results and the TI-NUSC shows that the TI-NUSC can successfully describe these two primary peak strength characteristics
Dust-acoustic waves and stability in the permeating dusty plasma: I. Maxwellian distribution
The dust-acoustic waves and their stability in the permeating dusty plasma
with the Maxwellian velocity distribution are investigated. We derive the
dust-acoustic wave frequency and instability growth rate in two limiting
physical cases that the thermal velocity of the flowing dusty plasma is (a)
much larger than, and (b) much smaller than the phase velocity of the waves. We
find that the stability of the waves depend strongly on the velocity of the
flowing dusty plasma in the permeating dusty plasma. The numerical analyses are
made based on the example that a cometary plasma tail is passing through the
interplanetary space plasma. We show that, in case (a), the waves are generally
unstable for any flowing velocity, but in case (b), the waves become unstable
only when the wave number is small and the flowing velocity is large. When the
physical conditions are between these two limiting cases, we gain a strong
insight into the dependence of the stability criterions on the physical
conditions in the permeating dusty plasma.Comment: 16 pages, 4 figures, 35 reference
Secondary electron emissions and dust charging currents in the nonequilibrium dusty plasma with power-law distributions
We study the secondary electron emissions induced by the impact of electrons
on dust grains and the resulting dust charging processes in the nonequilibrium
dusty plasma with power-law distributions. We derive new expressions of the
secondary emitted electron flux and the dust charging currents that are
generalized by the power-law q-distributions, where the nonlinear core
functions are numerically studied for the nonextensive parameter q. Our
numerical analyses show that the power-law q-distribution of the primary
electrons has a significant effect on the secondary emitted electron flux as
well as the dust charging currents, and this effect depends strongly on the
ratio of the electrostatic potential energy of the primary electrons at the
dust grain's surface to the thermodynamic energy, implying that a competition
in the dusty plasma between these two energies plays a crucial role in this
novel effect.Comment: 16 pages, 6 figures, 32 reference
Modeling realistic multiphase flows using a non-orthogonal multiple-relaxation-time lattice Boltzmann method
In this paper, we develop a three-dimensional multiple-relaxation-time
lattice Boltzmann method (MRT-LBM) based on a set of non-orthogonal basis
vectors. Compared with the classical MRT-LBM based on a set of orthogonal basis
vectors, the present non-orthogonal MRT-LBM simplifies the transformation
between the discrete velocity space and the moment space, and exhibits better
portability across different lattices. The proposed method is then extended to
multiphase flows at large density ratio with tunable surface tension, and its
numerical stability and accuracy are well demonstrated by some benchmark cases.
Using the proposed method, a practical case of a fuel droplet impacting on a
dry surface at high Reynolds and Weber numbers is simulated and the evolution
of the spreading film diameter agrees well with the experimental data.
Furthermore, another realistic case of a droplet impacting on a
super-hydrophobic wall with a cylindrical obstacle is reproduced, which
confirms the experimental finding of Liu \textit{et al.} [``Symmetry breaking
in drop bouncing on curved surfaces," Nature communications 6, 10034 (2015)]
that the contact time is minimized when the cylinder radius is comparable with
the droplet cylinder.Comment: 19 pages, 11 figure
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