18,596 research outputs found
Modelling of the coupling hydrodynamic transfer for a gas-liquid countercurrent flow on a wavy surface
This paper concerns laminar countercurrent gas–liquid flow over a wavy wall column, in the case of a falling liquid film. The modelling concerns the coupling of hydrodynamic and heat and mass transfer for an absorption as an example of application. The falling liquid film interacts, through the free interface, with the gas phase. The wavy surface generates particular hydrodynamic conditions with the presence of a vortex in both phases. The consequence of these vortices is an increase of transfers compared to the smooth wall
Poisson Brackets Scheme for Vortex Dynamics in Superfluids and Superconductors and Effect of Band Structure of Crystal
Poisson brackets for the Hamiltonian dynamics of vortices are discussed for 3
regimes, in which the dissipation can be neglected and the vortex dynamics is
reversible: (i) The superclean regime when the spectral flow is suppressed.
(ii) The regime when the fermions are pinned by crystal lattice. This includes
also the regime of the extreme spectral flow of fermions in the vortex core:
these fermions are effectively pinned by the normal component. (iii) The case
when the vortices are strongly pinned by the normal component. All these limits
are described by the single parameter , which physical meaning is
discussed for superconductors containing several bands of electrons and holes.
The effect of the Fermi-surface topology on the vortex dynamics is also
discussed.Comment: LaTeX file, 11 pages, no figures, version accepted in JETP Letter
Theory of Double-Sided Flux Decorations
A novel two-sided Bitter decoration technique was recently employed by Yao et
al. to study the structure of the magnetic vortex array in high-temperature
superconductors. Here we discuss the analysis of such experiments. We show that
two-sided decorations can be used to infer {\it quantitative} information about
the bulk properties of flux arrays, and discuss how a least squares analysis of
the local density differences can be used to bring the two sides into registry.
Information about the tilt, compressional and shear moduli of bulk vortex
configurations can be extracted from these measurements.Comment: 17 pages, 3 figures not included (to request send email to
[email protected]
Enhancement of absorption efficiency for a laminar film flow by hydrodynamic conditions generated by a new type of column wall
Anumerical model is developed to quantify the effects of hydrodynamics on heat and mass transfer during an absorption, for a laminar film flowing over awavywall column. First of all, the modelling is written for a singlewave of thewall shape. Then, an experimental set up, composed of aCCDvideo camera, validates this model. Finally, the model is extended to an entire column. The results include a comparison with the simulation of a smooth column having the same geometrical and operating conditions. Thewavy column dissipates more heat through the
wall (43%) due to the presence of a vortex in the furrows. This leads to an increase of the absorptionrate at the interface (10%). Moreover, the wavy column reaches equilibrium more rapidly in spite of a lower mean film temperature
Hydrodynamic Coupling of Particle Inclusions Embedded in Curved Lipid Bilayer Membranes
We develop theory and computational methods to investigate particle
inclusions embedded within curved lipid bilayer membranes. We consider the case
of spherical lipid vesicles where inclusion particles are coupled through (i)
intramembrane hydrodynamics, (ii) traction stresses with the external and
trapped solvent fluid, and (iii) intermonolayer slip between the two leaflets
of the bilayer. We investigate relative to flat membranes how the membrane
curvature and topology augment hydrodynamic responses. We show how both the
translational and rotational mobility of protein inclusions are effected by the
membrane curvature, ratio of intramembrane viscosity to solvent viscosity, and
inter-monolayer slip. For general investigations of many-particle dynamics, we
also discuss how our approaches can be used to treat the collective diffusion
and hydrodynamic coupling within spherical bilayers.Comment: 32 pages, double-column format, 15 figure
Translational Correlations in the Vortex Array at the Surface of a Type-II Superconductor
We discuss the statistical mechanics of magnetic flux lines in a
finite-thickness slab of type-II superconductor. The long wavelength properties
of a flux-line liquid in a slab geometry are described by a hydrodynamic free
energy that incorporates the boundary conditions on the flux lines at the
sample's surface as a surface contribution to the free energy. Bulk and surface
weak disorder are modeled via Gaussian impurity potentials. This free energy is
used to evaluate the two-dimensional structure factor of the flux-line tips at
the sample surface. We find that surface interaction always dominates in
determining the decay of translational correlations in the asymptotic
long-wavelength limit. On the other hand, such large length scales have not
been probed by the decoration experiments. Our results indicate that the
translational correlations extracted from the analysis of the Bitter patterns
are indeed representative of behavior of flux lines in the bulk.Comment: 23 pages, 1 figure (not included), harvmac.tex macro needed (e-mail
requests to [email protected] SU-CM-92-01
Quantized superfluid vortex dynamics on cylindrical surfaces and planar annuli
Superfluid vortex dynamics on an infinite cylinder differs significantly from
that on a plane. The requirement that a condensate wave function be single
valued upon once encircling the cylinder means that such a single vortex cannot
remain stationary. Instead, it acquires one of a series of quantized
translational velocities around the circumference, the simplest being , with the mass of the superfluid particles and the radius
of the cylinder. A generalization to a finite cylinder automatically includes
these quantum-mechanical effects through the pairing of the single vortex and
its image in either the top or bottom end of the surface. The dynamics of a
single vortex on this surface provides a hydrodynamic analog of Laughlin
pumping. The interaction energy for two vortices on an infinite cylinder is
proportional to the classical stream function , and it
crosses over from logarithmic to linear when the intervortex separation becomes larger than the cylinder radius. An Appendix summarizes the
connection to an earlier study of Ho and Huang for one or more vortices on an
infinite cylinder. A second Appendix reviews the topologically equivalent
planar annulus, where such quantized vortex motion has no offset, but Laughlin
pumping may be more accessible to experimental observation.Comment: 16 pages, 7 figures; published version, with thoroughly revised
Appendice
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