13,159 research outputs found
Discrete Boltzmann modeling of multiphase flows: hydrodynamic and thermodynamic non-equilibrium effects
A discrete Boltzmann model (DBM) is developed to investigate the hydrodynamic
and thermodynamic non-equilibrium (TNE) effects in phase separation processes.
The interparticle force drives changes and the gradient force, induced by
gradients of macroscopic quantities, opposes them. In this paper, we
investigate the interplay between them by providing detailed inspection of
various non-equilibrium observables. Based on the TNE features, we define a TNE
strength which roughly estimates the deviation amplitude from the thermodynamic
equilibrium. The time evolution of the TNE intensity provides a convenient and
efficient physical criterion to discriminate the stages of the spinodal
decomposition and domain growth. Via the DBM simulation and this criterion, we
quantitatively study the effects of latent heat and surface tension on phase
separation. It is found that, the TNE strength attains its maximum at the end
of the spinodal decomposition stage, and it decreases when the latent heat
increases from zero. The surface tension effects are threefold, to prolong the
duration of the spinodal decomposition stage, decrease the maximum TNE
intensity, and accelerate the speed of the domain growth stage.Comment: 10 pages, 10 figure
Lattice BGK kinetic model for high speed compressible flows: hydrodynamic and nonequilibrium behaviors
We present a simple and general approach to formulate the lattice BGK model
for high speed compressible flows. The main point consists of two parts: an
appropriate discrete equilibrium distribution function (DEDF)
and a discrete velocity model with flexible velocity size. The DEDF is obtained
by , where is a set of
moment of the Maxwellian distribution function, and is the matrix
connecting the DEDF and the moments. The numerical components of
are determined by the discrete velocity model. The calculation of
is based on the analytic solution which is a function of the
parameter controlling the sizes of discrete velocity. The choosing of discrete
velocity model has a high flexibility. The specific heat ratio of the system
can be flexible. The approach works for the one-, two- and three-dimensional
model constructions. As an example, we compose a new lattice BGK kinetic model
which works not only for recovering the Navier-Stokes equations in the
continuum limit but also for measuring the departure of system from its
thermodynamic equilibrium. Via adjusting the sizes of the discrete velocities
the stably simulated Mach number can be significantly increased up to 30 or
even higher. The model is verified and validated by well-known benchmark tests.
Some macroscopic behaviors of the system due to deviating from thermodynamic
equilibrium around the shock wave interfaces are shown.Comment: accepted for publication in EP
First Personal Nineties R&B Soul EP
For this project, the artist Gan Xu made the first personal EP with 5 tracks including four full-length tracks and an outro. The purpose of this EP was to express the artist’s emotion and stories throughout this year in Spain, with its main theme of love, pain and growth. The genres focused on R&B, Soul, and Ballad. This EP would also be a brand new chapter and meaningful journey for the artist Gan Xu transforming from a physicist to a musician.https://remix.berklee.edu/graduate-studies-production-technology/1198/thumbnail.jp
FFT-LB modeling of thermal liquid-vapor systems
We further develop a thermal LB model for multiphase flows. In the improved
model, we propose to use the FFT scheme to calculate both the convection term
and external force term. The usage of FFT scheme is detailed and analyzed. By
using the FFT algorithm spatiotemporal discretization errors are decreased
dramatically and the conservation of total energy is much better preserved. A
direct consequence of the improvement is that the unphysical spurious
velocities at the interfacial regions can be damped to neglectable scale.
Together with the better conservation of total energy, the more accurate flow
velocities lead to the more accurate temperature field which determines the
dynamical and final states of the system. With the new model, the phase diagram
of the liquid-vapor system obtained from simulation is more consistent with
that from theoretical calculation. Very sharp interfaces can be achieved. The
accuracy of simulation results are also verified by the Laplace law. The FFT
scheme can be easily applied to other models for multiphase flows.Comment: 34 pages, 21 figure
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