11,030 research outputs found
Coarse Bifurcation Studies of Bubble Flow Microscopic Simulations
The parametric behavior of regular periodic arrays of rising bubbles is
investigated with the aid of 2-dimensional BGK Lattice-Boltzmann (LB)
simulators. The Recursive Projection Method is implemented and coupled to the
LB simulators, accelerating their convergence towards what we term coarse
steady states. Efficient stability/bifurcation analysis is performed by
computing the leading eigenvalues/eigenvectors of the coarse time stepper. Our
approach constitutes the basis for system-level analysis of processes modeled
through microscopic simulations.Comment: 4 pages, 3 figure
The theory of parametrically amplified electron-phonon superconductivity
The ultrafast optical manipulation of ordered phases in strongly correlated
materials is a topic of significant theoretical, experimental, and
technological interest. Inspired by a recent experiment on light-induced
superconductivity in fullerenes [Mitrano et al., Nature 530, 2016], we develop
a comprehensive theory of light-induced superconductivity in driven
electron-phonon systems with lattice nonlinearities. In analogy with the
operation of parametric amplifiers, we show how the interplay between the
external drive and lattice nonlinearities lead to significantly enhanced
effective electron-phonon couplings. We provide a detailed and unbiased study
of the nonequilibrium dynamics of the driven system using the real-time Green's
function technique. To this end, we develop a Floquet generalization of the
Migdal-Eliashberg theory and derive a numerically tractable set of quantum
Floquet-Boltzmann kinetic equations for the coupled electron-phonon system. We
study the role of parametric phonon generation and electronic heating in
destroying the transient superconducting state. Finally, we predict the
transient formation of electronic Floquet bands in time- and angle-resolved
photo-emission spectroscopy experiments as a consequence of the proposed
mechanism.Comment: 42 pages, 17 figure
Parametric Analysis of Solid Oxide Fuel Cell Using Lattice Boltzmann Method
The present paper deals with a numerical simulation of temperature field inside a solid oxide fuel cell (SOFC) components. The temperature distribution is investigated using a co-flow planar SOFC comprising the air and fuel channel and two-ceramic electrodes, anode and cathode, separated by a dense ceramic electrolyte. The Lattice Boltzmann method (LBM) is used for the numerical simulation of the physical problem. The effects of inlet temperature, anode thermal conductivity and current density on temperature distribution are discussed. It was found that temperature distribution is very sensitive to the inlet temperature and the current density
Drops bouncing off macro-textured superhydrophobic surfaces
Recent experiments with droplets impacting a macro-textured superhydrophobic
surfaces revealed new regimes of bouncing with a remarkable reduction of the
contact time. We present here a comprehensive numerical study that reveals the
physics behind these new bouncing regimes and quantify the role played by
various external and internal forces that effect the dynamics of a drop
impacting a complex surface. For the first time, three-dimensional simulations
involving macro-textured surfaces are performed. Aside from demonstrating that
simulations reproduce experiments in a quantitative manner, the study is
focused on analyzing the flow situations beyond current experiments. We show
that the experimentally observed reduction of contact time extends to higher
Weber numbers, and analyze the role played by the texture density. Moreover, we
report a non-linear behavior of the contact time with the increase of the Weber
number for application relevant imperfectly coated textures, and also study the
impact on tilted surfaces in a wide range of Weber numbers. Finally, we present
novel energy analysis techniques that elaborate and quantify the interplay
between the kinetic and surface energy, and the role played by the dissipation
for various Weber numbers
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