14 research outputs found
Uniform shear flow in dissipative gases. Computer simulations of inelastic hard spheres and (frictional) elastic hard spheres
In the preceding paper (cond-mat/0405252), we have conjectured that the main
transport properties of a dilute gas of inelastic hard spheres (IHS) can be
satisfactorily captured by an equivalent gas of elastic hard spheres (EHS),
provided that the latter are under the action of an effective drag force and
their collision rate is reduced by a factor (where is
the constant coefficient of normal restitution). In this paper we test the
above expectation in a paradigmatic nonequilibrium state, namely the simple or
uniform shear flow, by performing Monte Carlo computer simulations of the
Boltzmann equation for both classes of dissipative gases with a dissipation
range and two values of the imposed shear rate .
The distortion of the steady-state velocity distribution from the local
equilibrium state is measured by the shear stress, the normal stress
differences, the cooling rate, the fourth and sixth cumulants, and the shape of
the distribution itself. In particular, the simulation results seem to be
consistent with an exponential overpopulation of the high-velocity tail. The
EHS results are in general hardly distinguishable from the IHS ones if
, so that the distinct signature of the IHS gas (higher
anisotropy and overpopulation) only manifests itself at relatively high
dissipationsComment: 23 pages; 18 figures; Figs. 2 and 9 include new simulations; two new
figures added; few minor changes; accepted for publication in PR
System of elastic hard spheres which mimics the transport properties of a granular gas
The prototype model of a fluidized granular system is a gas of inelastic hard
spheres (IHS) with a constant coefficient of normal restitution . Using
a kinetic theory description we investigate the two basic ingredients that a
model of elastic hard spheres (EHS) must have in order to mimic the most
relevant transport properties of the underlying IHS gas. First, the EHS gas is
assumed to be subject to the action of an effective drag force with a friction
constant equal to half the cooling rate of the IHS gas, the latter being
evaluated in the local equilibrium approximation for simplicity. Second, the
collision rate of the EHS gas is reduced by a factor , relative
to that of the IHS gas. Comparison between the respective Navier-Stokes
transport coefficients shows that the EHS model reproduces almost perfectly the
self-diffusion coefficient and reasonably well the two transport coefficients
defining the heat flux, the shear viscosity being reproduced within a deviation
less than 14% (for ). Moreover, the EHS model is seen to agree
with the fundamental collision integrals of inelastic mixtures and dense gases.
The approximate equivalence between IHS and EHS is used to propose kinetic
models for inelastic collisions as simple extensions of known kinetic models
for elastic collisionsComment: 20 pages; 6 figures; change of title; few minor changes; accepted for
publication in PR
Aging to non-Newtonian hydrodynamics in a granular gas
The evolution to the steady state of a granular gas subject to simple shear
flow is analyzed by means of computer simulations. It is found that, regardless
of its initial preparation, the system reaches (after a transient period
lasting a few collisions per particle) a non-Newtonian (unsteady) hydrodynamic
regime, even at strong dissipation and for states where the time scale
associated with inelastic cooling is shorter than the one associated with the
irreversible fluxes. Comparison with a simplified rheological model shows a
good agreement.Comment: 6 pages, 4 figures; v2: improved version to be published in EP
Transport coefficients for inelastic Maxwell mixtures
The Boltzmann equation for inelastic Maxwell models is used to determine the
Navier-Stokes transport coefficients of a granular binary mixture in
dimensions. The Chapman-Enskog method is applied to solve the Boltzmann
equation for states near the (local) homogeneous cooling state. The mass, heat,
and momentum fluxes are obtained to first order in the spatial gradients of the
hydrodynamic fields, and the corresponding transport coefficients are
identified. There are seven relevant transport coefficients: the mutual
diffusion, the pressure diffusion, the thermal diffusion, the shear viscosity,
the Dufour coefficient, the pressure energy coefficient, and the thermal
conductivity. All these coefficients are {\em exactly} obtained in terms of the
coefficients of restitution and the ratios of mass, concentration, and particle
sizes. The results are compared with known transport coefficients of inelastic
hard spheres obtained analytically in the leading Sonine approximation and by
means of Monte Carlo simulations. The comparison shows a reasonably good
agreement between both interaction models for not too strong dissipation,
especially in the case of the transport coefficients associated with the mass
flux.Comment: 9 figures, to be published in J. Stat. Phy
The Influence of Destination Image and Customer Satisfaction on Revisit Intention of Students in English Village
Based on the background description, the purpose of this study is to analyze the influence of Destination Image and Customer Satisfaction on Revisit Intention of English Village students in the city of Pare Kediri. Where the population in this study were students who took courses in the English village as many as 86 respondents. Data collection methods using questionnaires and interviews. In analyzing the data, the validity and reliability of the instrument were used, hypothesis testing for F and T and the coefficient of determination. From the test results, all questionnaire items are valid and reliable. Destination image and Customer Satisfaction have a significant effect on Revisit Intention either partially or simultaneously. The more destinations that can be visited and give a feeling of satisfaction to consumers, the more they will feel a feeling or encouragement in consumers, the stronger their desire to come back to visit