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9,500 | Jets from Collapsing Bubbles | physics.flu-dyn | When an asymmetric bubble collapses it generally produces a well defined high
velocity jet. This is remarkable because one might expect such a collapse to
produce a complex or chaotic flow rather than an ordered one. I present a
dimensional argument for the ubiquity of jets from collapsing bubbles, and
model the aspher... | physics |
9,501 | Boundary-layer control by electric fields: A feasibility study | physics.flu-dyn | A problem of great concern in aviation and submarine propulsion is the
control of the boundary layer and, in particular, the methods to extend the
laminar region as a means to decrease noise and fuel consumption. In this paper
we study the flow of air along an airfoil when a layer of ionized gas and a
longitudinal elec... | physics |
9,502 | An instability criterion for a finite amplitude localized disturbance in a shear flow of electrically conducting fluids | physics.flu-dyn | The stability of shear flows of electrically conducting fluids, with respect
to finite amplitude three-dimensional localized disturbances is considered. The
time evolution of the fluid impulse integral, characterizing such disturbances,
for the case of low magnetic Reynolds number is obtained by integrating
analyticall... | physics |
9,503 | A two-dimensional network simulator for two-phase flow in porous media | physics.flu-dyn | We investigate a two-dimensional network simulator capable of modeling
different time dependencies in two-phase drainage displacements. In particular,
we focus on the temporal evolution of the pressure due to capillary and viscous
forces and the time dependence of the interface between the two liquids. The
dynamics of ... | physics |
9,504 | Dispersion Relation of a Ferrofluid Layer of Any Thickness and Viscosity in a Normal Magnetic Field; Asymptotic Regimes | physics.flu-dyn | We have calculated the general dispersion relationship for surface waves on a
ferrofluid layer of any thickness and viscosity, under the influence of a
uniform vertical magnetic field. The amplification of these waves can induce an
instability called peaks instability (Rosensweig instability). The expression
of the dis... | physics |
9,505 | Averaging theory for the structure of hydraulic jumps and separation in laminar free-surface flows | physics.flu-dyn | We present a simple viscous theory of free-surface flows in boundary layers,
which can accommodate regions of separated flow. In particular this yields the
structure of stationary hydraulic jumps, both in their circular and linear
versions, as well as structures moving with a constant speed. Finally we show
how the fun... | physics |
9,506 | Nonuniqueness and Turbulence | physics.flu-dyn | The possibility is considered that turbulence is described by differential
equations for which uniqueness fails maximally, at least in some limit. The
inviscid Burgers equation, in the context of Onsager's suggestion that
turbulence should be described by a negative absolute temperature, is such a
limit. In this pictur... | physics |
9,507 | On the absence of dissipative instability of negative energy waves in hydrodynamic shear flows | physics.flu-dyn | Stability criterion for the surface gravity capillary waves in a flowing
two-layered fluid system with viscous dissipation is investigated. It is seen
that the dissipative instability of negative energy waves is absent,- contrary
to what earlier authors have concluded. Their error is identified to arise from
an erroneo... | physics |
9,508 | Odd Viscosity | physics.flu-dyn | When time reversal is broken the viscosity tensor can have a non vanishing
odd part. In two dimensions, and only then, such odd viscosity is compatible
with isotropy. Elementary and basic features of odd viscosity are examined by
considering solutions of the wave and Navier-Stokes equations for hypothetical
fluids wher... | physics |
9,509 | Progressive internal gravity waves with bounded upper surface climbing a triangular obstacle | physics.flu-dyn | In this paper we discuss a theoretical model for the interfacial profiles of
progressive non-linear waves which result from introducing a triangular
obstacle, of finite height, attached to the bottom below the flow of a
stratified, ideal, two layer fluid, bounded from above by a rigid boundary. The
derived equations ar... | physics |
9,510 | Models of low-speed flow for near-critical fluids with gravitational and capillary effects | physics.flu-dyn | We study low-speed flows of a highly compressible, single-phase fluid in the
presence of gravity, for example in a regime appropriate for modeling recent
space-shuttle experiments on fluids near the liquid-vapor critical point. In
the equations of motion, we include forces due to capillary stresses that arise
from a co... | physics |
9,511 | Investigation of renormalization group methods for the numerical simulation of isotropic turbulence | physics.flu-dyn | Renormalization group has enjoyed successes in other areas of statistical
physics. However, its application to turbulence faces several technical
difficulties, which have had to be circumvented by uncontrolled approximations.
Indeed, in view of the deterministic nature of the Navier-Stokes equations, it
is clear that t... | physics |
9,512 | Explict-scales projections of the partitioned non-linear term in direct numerical simulation of the Navier-Stokes equation | physics.flu-dyn | In this paper we consider the properties of the internal partitions of the
nonlinear term, obtained when a filter with a sharp cutoff is introduced in
wavenumber space. We see what appears to be some degree of independence of the
choice of the position of the cutoff wavenumber for both instantaneous and
time-integrated... | physics |
9,513 | A necessary and sufficient instability condition for inviscid shear flow | physics.flu-dyn | The linear stability of inviscid, incompressible, two-dimensional, plane
parallel, shear flow was considered over a century ago by Rayleigh, Kelvin, and
others. A principal result on the subject is Rayleigh's celebrated inflection
point theorem {R80}, which states that for an equilibrium flow to be unstable,
the equili... | physics |
9,514 | Influence of the second viscosity on the flow propagation | physics.flu-dyn | We found the energetic stability criteria of non-equilibrium gase plain
flows. | physics |
9,515 | Drag and lift forces for the thin body in the supersonic flow of the non-equilibrium gas | physics.flu-dyn | The classical problem of the fluid mechanics is the problem of a supersonic
motion around a thin body was generalized to the case of non-equilibrium gas.
The drag and lift force coefficients were founded. It is shown that the drag
and lift force coefficients in the acoustically active supersonic flow are both
decreased | physics |
9,516 | Interfacial tension in water at solid surfaces | physics.flu-dyn | A model for the formation of cavitation nuclei in liquids has recently been
presented with basis in interfacial liquid tension at non-planar solid surfaces
of concave form. In the present paper investigations of water-solid interfaces
by atomic force microscopy are reported to illuminate experimentally effects of
inter... | physics |
9,517 | Convection and heat transfer in liquid under low gravity conditions and thermocapillary effects | physics.flu-dyn | The two-dimensional flow of viscous incompressible liquid in a square cavity
with a free boundary and differentially heated vertical sides is considered in
the present work. The influence of gravitational and thermocapillary convection
on temperature and velocity fields is studied in large range of dimensionless
parame... | physics |
9,518 | The Two Fluid Drop Snap-off Problem: Experiments and Theory | physics.flu-dyn | We address the dynamics of a drop with viscosity $\lambda \eta$ breaking up
inside another fluid of viscosity $\eta$. For $\lambda=1$, a scaling theory
predicts the time evolution of the drop shape near the point of snap-off which
is in excellent agreement with experiment and previous simulations of Lister
and Stone. W... | physics |
9,519 | Coalescence of Liquid Drops | physics.flu-dyn | When two drops of radius $R$ touch, surface tension drives an initially
singular motion which joins them into a bigger drop with smaller surface area.
This motion is always viscously dominated at early times. We focus on the
early-time behavior of the radius $\rmn$ of the small bridge between the two
drops. The flow is... | physics |
9,520 | On some dynamical problems related to boundary layer turbulence | physics.flu-dyn | A number of simplified dynamical problems is studied in an attempt to clarify
some of the mechanisms leading to turbulence and the existing proposals to
control this transition. A simplified set of boundary layer equations displays
a solution that corresponds to the rolls and streaks instability and exhibits
its stream... | physics |
9,521 | Computation of Mean Velocity Distribution in a Turbulent Flow | physics.flu-dyn | An approximate method to compute mean velocity profiles in turbulent flows is
developed. This approach is based on the equation connecting the Reynolds
stress and mean velocity. By using the measured values of pressure drop and
average (bulk) flow velocity, such characteristics of a turbulent flow as the
mean velocity ... | physics |
9,522 | Vorticity statistics in the two-dimensional enstrophy cascade | physics.flu-dyn | We report the first extensive experimental observation of the two-dimensional
enstrophy cascade, along with the determination of the high order vorticity
statistics. The energy spectra we obtain are remarkably close to the Kraichnan
Batchelor expectation. The distributions of the vorticity increments, in the
inertial r... | physics |
9,523 | Low-dimensional dynamics embedded in a plane Poiseuille flow turbulence : Traveling-wave solution is a saddle point ? | physics.flu-dyn | The instability of a streak and its nonlinear evolution are investigated by
direct numerical simulation (DNS) for plane Poiseuille flow at Re=3000. It is
suggested that there exists a traveling-wave solution (TWS). The TWS is
localized around one of the two walls and notably resemble to the coherent
structures observed... | physics |
9,524 | Drag Reduction over Dolphin Skin via the Pondermotive Forcing of Vortex Filaments | physics.flu-dyn | The skin of Tursiops Truncatus is corrugated with small, quasi-periodic
ridges running circumferentially about the torso. These ridges extend into the
turbulent boundary layer and affect the evolution of coherent structures. The
development and evolution of coherent structures over a surface is described by
the formati... | physics |
9,525 | New features in non-coalescense of tanget liquid bulks | physics.flu-dyn | We had observed a couple of new phenomena in which, two liquid bulks in
contact with each other do not coalesce. The main reason seems to be the motion
of the surface in the place of contact, which forms an air film between the
bulk boundaries. The surface velocities is also estimated and showed to be near
each other a... | physics |
9,526 | A Phase Transistion in the Water Coupled to a Local External Perturbation | physics.flu-dyn | A flux of ideal fluid coupled to perturbation is investigated by
nonperturbative methods of the quantum field theory. Asymptotic behavior of the
flux coupled to perturbation turns out to be similiar to that of superfluids. | physics |
9,527 | Critical Behavior of the Water Coupled to a Local External Perturbation | physics.flu-dyn | The response of inviscid incompressible unbounded fluid subject to a
localized external perturbation is studed. The physically relevant hypotheses
on the mode coupling mechanisma is justified by renormalization group method.
The scaling laws for the scalar and vector velocity potentials are derived. The
spectrum of ene... | physics |
9,528 | On the Viscosity of Emulsions | physics.flu-dyn | Combining direct computations with invariance arguments, Taylor's
constitutive equation for an emulsion can be extrapolated to high shear rates.
We show that the resulting expression is consistent with the rigorous limits of
small drop deformation and that it bears a strong similarity to an a priori
unrelated rheologic... | physics |
9,529 | Spinning jets | physics.flu-dyn | A fluid jet with a finite angular velocity is subject to centripetal forces
in addition to surface tension forces. At fixed angular momentum, centripetal
forces become large when the radius of the jet goes to zero. We study the
possible importance of this observation for the pinching of a jet within a
slender jet model... | physics |
9,530 | Differential criterion of a bubble collapse in viscous liquids | physics.flu-dyn | The present work is devoted to a model of bubble collapse in a Newtonian
viscous liquid caused by an initial bubble wall motion. The obtained bubble
dynamics described by an analytic solution significantly depends on the liquid
and bubble parameters. The theory gives two types of bubble behavior: collapse
and viscous d... | physics |
9,531 | Interaction of a vortex ring with the free surface of ideal fluid | physics.flu-dyn | The interaction of a small vortex ring with the free surface of a perfect
fluid is considered. In the frame of the point ring approximation the
asymptotic expression for the Fourier-components of radiated surface waves is
obtained in the case when the vortex ring comes from infinity and has both
horizontal and vertical... | physics |
9,532 | The decay of multiscale signals - deterministic model of the Burgers turbulence | physics.flu-dyn | This work is devoted to the study of the decay of multiscale deterministic
solutions of the unforced Burgers' equation in the limit of vanishing
viscosity.
A deterministic model of turbulence-like evolution is considered. We con-
struct the initial perturbation as a piecewise linear analog of the Weierstrass
function... | physics |
9,533 | Wavelet Cross-Correlation Analysis of Turbulent Mixing from Large-Eddy-Simulations | physics.flu-dyn | The complex interactions existing between turbulence and mixing in a
bluff-body stabilised flame configuration is investigated by means of a wavelet
cross-correlation analysis on Large Eddy Simulations. The combined approach
allows to better point out typical features of unsteady turbulent flows with
mixing through the... | physics |
9,534 | Statistical mechanics of the shallow water system | physics.flu-dyn | We extend the formalism of the statistical theory developed for the 2D Euler
equation to the case of shallow water system. Relaxation equations towards the
maximum entropy state are proposed, which provide a parametrization of sub-grid
scale eddies in 2D compressible turbulence. | physics |
9,535 | Surface waves at the interface between two viscous fluids | physics.flu-dyn | The Surface Green Function Matching analysis (SGFM) is used to study the
normal modes of the interface oscillations between two non-mixed fluids by
considering the difference in their densities and viscosities. The limiting
case of viscous-inviscid system is used for comparison. The role of the
viscosity and the densit... | physics |
9,536 | The modifications of customary filtrational equation | physics.flu-dyn | The usable limits of the customary and relaxational filtrational theories are
considered. The questions of applicable the locality and local thermodynamical
equilibrium principles to depict the nonstationary flows are discussed. The
experimental procedures are proposed to determine the filtrational flows
relaxation tim... | physics |
9,537 | Scaling properties of an inviscid mean-motion fluid model | physics.flu-dyn | An inviscid two-dimensional fluid model with nonlinear dispersion that arises
simultaneously in coarse-grained descriptions of the dynamics of the Euler
equation and in the description of non-Newtonian fluids of second grade is
considered. The scaling of the equilibrium states of this model for conserved
energy and ens... | physics |
9,538 | Solitary coherent structures in viscoelastic shear flow: computation and mechanism | physics.flu-dyn | Starting from stationary bifurcations in Couette-Dean flow, we compute
nontrivial stationary solutions in inertialess viscoelastic circular Couette
flow. These solutions are strongly localized vortex pairs, exist at arbitrarily
large wavelengths, and show hysteresis in the Weissenberg number, similar to
experimentally ... | physics |
9,539 | Radial Viscous Flow between Two Parallel Annular Plates | physics.flu-dyn | An analytic solution to the linearized Navier-Stokes equation is given that
describes the radial flow of an incompressible, viscous fluid between two
parallel, concentric annular plates. | physics |
9,540 | New complex variables for equations of ideal barotropic fluid | physics.flu-dyn | We propose new construction of dependent variables for equations of an ideal
barotropic fluid. This construction is based on a direct generalization of the
known connection between Schroedinger equation and a system of Euler-type
equations. The system for two complex-valued functions is derived that is
equivalent to Eu... | physics |
9,541 | Breaking of vortex lines - a new mechanism of collapse in hydrodynamics | physics.flu-dyn | A new mechanism of the collapse in hydrodynamics is suggested, due to
breaking of continuously distributed vortex lines. Collapse results in
formation of the point singularities of the vorticity field $|{\bf\Omega}|$. At
the collapse point, the value of the vorticity blows up as $(t_0-t)^{-1}$ where
$t_0$ is a collapse... | physics |
9,542 | Single-bubble sonoluminescence: Shape stability analysis of collapse dynamics in a semianalytical approach | physics.flu-dyn | This paper theoretically analyzes the hydrodynamic shape stability problem
for sonoluminescing bubbles. We present a semianalytical approach to describe
the evolution of shape perturbations in the strongly nonlinear regime of
violent collapse. The proposed approximation estimating the damping rate
produced by liquid vi... | physics |
9,543 | A path-integral approach to the collisional Boltzmann gas | physics.flu-dyn | Collisional effects are included in the path-integral formulation that was
proposed in one of our previous paper for the collisionless Boltzmann gas. In
calculating the number of molecules entering a six-dimensional phase volume
element due to collisions, both the colliding molecules and the scattered
molecules are all... | physics |
9,544 | The decay of plane wave pulses with complex structure in a nonlinear dissipative medium | physics.flu-dyn | Nonlinear plane acoustic waves propagating through a fluid are studied using
Burgers' equation with finite viscosity. The evolution of a simple N-pulse with
regular and random initial amplitude and of pulses with monochromatic and noise
carrier is considered. In the latter case the initial pulses are characterized
by t... | physics |
9,545 | Vortex tubes in velocity fields of laboratory isotropic turbulence | physics.flu-dyn | The streamwise and transverse velocities are measured simultaneously in grid
turbulence at Reynolds numbers 100-300. We extract typical intermittency
patterns, which are consistent with velocity profiles of Burgers and Lamb-Oseen
vortices. The radii of these vortex tubes are estimated to be several of the
Kolmogorov le... | physics |
9,546 | Fluid Particle Accelerations in Fully Developed Turbulence | physics.flu-dyn | The motion of fluid particles as they are pushed along erratic trajectories
by fluctuating pressure gradients is fundamental to transport and mixing in
turbulence. It is essential in cloud formation and atmospheric transport,
processes in stirred chemical reactors and combustion systems, and in the
industrial productio... | physics |
9,547 | Air entrainment through free-surface cusps | physics.flu-dyn | In many industrial processes, such as pouring a liquid or coating a rotating
cylinder, air bubbles are entrapped inside the liquid. We propose a novel
mechanism for this phenomenon, based on the instability of cusp singularities
that generically form on free surfaces. The air being drawn into the narrow
space inside th... | physics |
9,548 | The Numerical Solution of Nekrasov's Equation in the Boundary Layer near the Crest, for Waves near the Maximum Height | physics.flu-dyn | Nekrasov's integral equation describing water waves of permanent form,
determines the angle phi that the wave surface makes with the horizontal. The
independent variable s is a suitably scaled velocity potential, evaluated at
the free surface, with the origin corresponding to the crest of the wave. For
all waves, excep... | physics |
9,549 | Finite time singularities in a class of hydrodynamic models | physics.flu-dyn | Models of inviscid incompressible fluid are considered, with the kinetic
energy (i.e., the Lagrangian functional) taking the form ${\cal L}\sim\int
k^\alpha|{\bf v_k}|^2d^3{\bf k}$ in 3D Fourier representation, where $\alpha$
is a constant, $0<\alpha< 1$. Unlike the case $\alpha=0$ (the usual Eulerian
hydrodynamics), a... | physics |
9,550 | Anomalous scaling in homogeneous isotropic turbulence | physics.flu-dyn | The anomalous scaling exponents $\zeta_{n}$ of the longitudinal structure
functions $S_{n}$ for homogeneous isotropic turbulence are derived from the
Navier-Stokes equations by using field theoretic methods to develop a low
energy approximation in which the Kolmogorov theory is shown to act effectively
as a mean field ... | physics |
9,551 | Global stability of systems related to the Navier-Stokes equations | physics.flu-dyn | A generalized Lyapunov method is outlined which predicts global stability of
a broad class of dissipative dynamical systems. The method is applied to the
complex Lorenz model and to the Navier-Stokes equations. In both cases one
finds compact domains in phase space which contain the omega sets of all
trajectories, in p... | physics |
9,552 | Remarks on unsolved basic problems of the Navier-Stokes equations | physics.flu-dyn | There is renewed interest in the question of whether the Navier-Stokes
equations (NSE), one of the fundamental models of classical physics and widely
used in engineering applications, are actually self-consistent. After recalling
the essential physical assumptions inherent in the NSE, the notion of weak
solutions, poss... | physics |
9,553 | Some closed form solutions to the Navier Stokes equations | physics.flu-dyn | An algorithm for generating a class of closed form solutions to the
Navier-Stokes equations is suggested, with examples. Of particular interest are
those exact solutions that exhibit intermittency, tertiary Hopf bifurcations,
flow reversal, and hysteresis. | physics |
9,554 | Topology and Turbulence | physics.flu-dyn | Over a given regular domain of independent variables {x,y,z,t}, every
covariant vector field of flow can be constructed in terms a differential
1-form of Action. The associated Cartan topology permits the definition of four
basic topological equivalence classes of flows based on the Pfaff dimension of
the 1-form of Act... | physics |
9,555 | Instability patterns, wakes and topological limnit sets | physics.flu-dyn | Many hydrodynamic instability patterns can be put into correspondence with a
subset of characteristic surfaces of tangential discontinuities. These
topological limits sets to systems of hyperbolic PDE's are locally unstable,
but a certain subset associated with minimal surfaces are globally stabilized,
persistent and n... | physics |
9,556 | On the thermocapillary motion of deformable droplets | physics.flu-dyn | In studies on Marangoni type motion of particles the surface tension is often
approximated as a linear function of temperature. For deformable particles in a
linear external temperature gradient far from the reference point this
approximation yields a negative surface tension which is physically
unrealistic. It is show... | physics |
9,557 | Mathematics of Structure-Function Equations of All Orders | physics.flu-dyn | Exact equations are derived that relate velocity structure functions of
arbitrary order with other statistics. "Exact" means that no approximations are
used except that the Navier-Stokes equation and incompressibility condition are
assumed to be accurate. The exact equations are used to determine the
structure-function... | physics |
9,558 | Alternative to R_lambda-scaling of Small-Scale Turbulence Statistics | physics.flu-dyn | Traditionally, trends of universal turbulence statistics are presented versus
R-lambda, which is the Reynolds number based on Taylor's scale, lambda, and the
root-mean-squared (rms) velocity component, u'. Taylor's scale and u', and
hence R-lambda, do not have the attribute of universality. The ratio of rms
fluid-parti... | physics |
9,559 | Equations relating structure functions of all orders | physics.flu-dyn | The hierarchy of exact equations is given that relates two-spatial-point
velocity structure functions of arbitrary order with other statistics. Because
no assumption is used, the exact statistical equations can apply to any flow
for which the Navier-Stokes equations are accurate, and they apply no matter
how small the ... | physics |
9,560 | Interaction of two deformable viscous drops under external temperature gradient | physics.flu-dyn | The axisymmetric deformation and motion of interacting droplets in an imposed
temperature gradient is considered using boundary-integral techniques for slow
viscous motion. Results showing temporal drop motion, deformations and
separation are presented for equal-viscosity fluids. The focus is on cases when
the drops ar... | physics |
9,561 | The Inverse Energy Cascade of Two-Dimensional Turbulence | physics.flu-dyn | This thesis presents an experimental study of the inverse energy cascade as
it occurs in an electromagnetically forced soap film. It focuses on
characterizing important features of the inverse cascade such as it's range,
how energy is distributed over the range and how energy flows through the
range. The thesis also pr... | physics |
9,562 | Time resolved tracking of a sound scatterer in a turbulent flow: non-stationary signal analysis and applications | physics.flu-dyn | It is known that ultrasound techniques yield non-intrusive measurements of
hydrodynamic flows. For example, the study of the echoes produced by a large
number of particle insonified by pulsed wavetrains has led to a now standard
velocimetry technique. In this paper, we propose to extend the method to the
continuous tra... | physics |
9,563 | Quasiperiodic waves at the onset of zero Prandtl number convection with rotation | physics.flu-dyn | We show the possibility of quasiperiodic waves at the onset of thermal
convection in a thin horizontal layer of slowly rotating zero-Prandtl number
Boussinesq fluid confined between stress-free conducting boundaries. Two
independent frequencies emerge due to an interaction between a stationary
instability and a self-tu... | physics |
9,564 | Anomalous self-similarity in two-dimensional turbulence | physics.flu-dyn | Our velocity measurements on a quasi-two-dimensional turbulent flow in a
rapidly rotating annulus yield an inverse cascade with E(k)~k^{-2} rather than
the expected E(k)~k^{-5/3}. The probability distribution functions for
longitudinal velocity differences, \delta_v(r)=v(x+r)-v(x), are self-similar
(scale independent) ... | physics |
9,565 | Gap Size Effects for the Kelvin-Helmholtz Instability in a Hele-Shaw Cell | physics.flu-dyn | We report experimental results for the Kelvin-Helmholtz instability between
two immiscible fluids in parallel flow in a Hele-Shaw cell. We focus our
interest on the influence of the gap size between the walls on the instability
characteristics. Experimental results show that the instability threshold, the
critical wave... | physics |
9,566 | Three-Dimensional Morphology of Vortex Interfaces Driven by Rayleigh-Taylor or Richtmyer-Meshkov Instability | physics.flu-dyn | We study the 3D topology of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM)
single-modes, which includes bubbles, jets and saddle points. We present an
analytic description of the interface as a whole, for arbitrary time-dependant
acceleration g(t). The dependance of morphology on the lattice - Hexagonal,
square or tri... | physics |
9,567 | Dynamic Model for LES Without Test Filtering: Quantifying the Accuracy of Taylor Series Approximations | physics.flu-dyn | The dynamic model for large-eddy simulation (LES) of turbulent flows requires
test filtering the resolved velocity fields in order to determine model
coefficients. However, test filtering is costly to perform in large-eddy
simulation of complex geometry flows, especially on unstructured grids. The
objective of this wor... | physics |
9,568 | Passive scalar anisotropy in a heated turbulent wake: new observations and implications for LES | physics.flu-dyn | The effects of passive scalar anisotropy on subgrid-scale (SGS) physics and
modeling for Large-Eddy Simulations are studied experimentally. Measurements
are performed across a moderate Reynolds number wake flow generated by a heated
cylinder, using an array of four X-wire and four cold-wire probes. By varying
the separ... | physics |
9,569 | The statistical dynamics of thin vortex line | physics.flu-dyn | We discuss the statistical properties of a single vortex line in a perfect
fluid. The partition function is calculated up to the end in the thin vortex
approximation. It turns out that corresponding theory is renormalizable, and
the renormalization law for the core size of the vortex is found. The direction
of renormal... | physics |
9,570 | Nonlinear equation for curved stationary flames | physics.flu-dyn | A nonlinear equation describing curved stationary flames with arbitrary gas
expansion $\theta = \rho_{{\rm fuel}}/\rho_{{\rm burnt}}$, subject to the
Landau-Darrieus instability, is obtained in a closed form without an assumption
of weak nonlinearity. It is proved that in the scope of the asymptotic
expansion for $\the... | physics |
9,571 | Non-Newtonian effects in the peristaltic flow of a Maxwell fluid | physics.flu-dyn | We analyzed the effect of viscoelasticity on the dynamics of fluids in porous
media by studying the flow of a Maxwell fluid in a circular tube, in which the
flow is induced by a wave traveling on the tube wall. The present study
investigates novelties brought about into the classic peristaltic mechanism by
inclusion of... | physics |
9,572 | Self Gravitating Instability of a Compressible Fluid Cylinder | physics.flu-dyn | The self-gravitating instability of a compressible-inviscid fluid cylinder
immersed into a self-gravitating tenuous medium of negligible motion is
developed. The stability criterion is derived based on the linear perturbation
technique. Some previous reported works are recovered. The effect of different
factors on the ... | physics |
9,573 | On the universality of small scale turbulence | physics.flu-dyn | The proposed universality of small scale turbulence is investigated for a set
of measurements in a cryogenic free jet with a variation of the Reynolds number
(Re) from 8500 to 10^6. The traditional analysis of the statistics of velocity
increments by means of structure functions or probability density functions is
repl... | physics |
9,574 | Matrix Fluid Dynamics | physics.flu-dyn | The paper reports the recent results on application and extension of the
matrix formulation of lagrangian hydrodynamic equations. The matrix approach is
based on the notion of continuous deformation of infinitesimal material
elements and treats the Jacobi matrix of their derivatives with respect to
lagrangian variables... | physics |
9,575 | About linear threshold of instability Of faraday waves in fluid covered by thin film | physics.flu-dyn | The solution was found from Navier-Stokes equation and boundary conditions
with interfacial tension as function of the film substance concentration. Here
the method of Chen&Vinals is used. It was found that adding to coefficient
leads to growth of critical value of the driving acceleration. | physics |
9,576 | Measurement of Particle Accelerations in Fully Developed Turbulence | physics.flu-dyn | We use silicon strip detectors (originally developed for the CLEO III high
energy particle physics experiment) to measure fluid particle trajectories in
turbulence with temporal resolution of up to 70,000 frames per second. This
high frame rate allows the Kolmogorov time scale of a turbulent water flow to
be fully reso... | physics |
9,577 | Turbulent Drag Reduction of polyelectrolyte (DNA) solutions: relation with the elongational viscosity | physics.flu-dyn | We report measurements of turbulent drag reduction of two different
polyelectrolyte solutions: DNA and hydrolyzed Polyacrylamide. Changing the salt
concentration in the solutions allows us to change the flexibility of the
polymer chains. For both polymers the amount of drag reduction was found to
increase with the flex... | physics |
9,578 | Drop Formation in a One-Dimensional Approximation of the Navier-Stokes Equation | physics.flu-dyn | We consider the viscous motion of a thin, axisymmetric column of fluid with a
free surface. A one-dimensional equation of motion for the velocity and the
radius is derived from the Navier-Stokes equation. We compare with recent
experiments on the breakup of a liquid jet and on the bifurcation of a drop
suspended from a... | physics |
9,579 | Hydrodynamic Singularities | physics.flu-dyn | We give a brief overview of the physical significance of singularities in
fluid mechanics. | physics |
9,580 | Theory of Drop Formation | physics.flu-dyn | We consider the motion of an axisymmetric column of Navier-Stokes fluid with
a free surface. Due to surface tension, the thickness of the fluid neck goes to
zero in finite time. After the singularity, the fluid consists of two halves,
which constitute a unique continuation of the Navier-Stokes equation through
the sing... | physics |
9,581 | Wavelet Analysis of Vortex Tubes in Experimental Turbulence | physics.flu-dyn | This report proposes a new method to study vortex tubes in one-dimensional
velocity data of experimental turbulence. Vortex tubes are detected as local
maxima on the scale-space plot of wavelet transforms of the velocity data. Then
it is possible to extract a typical velocity pattern. The result for data
obtained in a ... | physics |
9,582 | Scaling of acceleration in locally isotropic turbulence | physics.flu-dyn | The variances of the fluid-particle acceleration and of the pressure-gradient
and viscous force are given. The scaling parameters for these variances are
velocity statistics measureable with a single-wire anemometer. For both high
and low Reynolds numbers, asymptotic scaling formulas are given; these agree
quantitative... | physics |
9,583 | Scaling dependence on the fluid viscosity ratio in the selective withdrawal transition | physics.flu-dyn | In the selective withdrawal experiment fluid is withdrawn through a tube with
its tip suspended a distance S above a two-fluid interface. At sufficiently low
withdrawal rates, Q, the interface forms a steady state hump and only the upper
fluid is withdrawn. When Q is increased (or S decreased), the interface
undergoes ... | physics |
9,584 | The Stationary Statistics of a Turbulent Environment as an Attractor | physics.flu-dyn | A proposal for a calculational program in fluid turbulence is presented. It
is proposed that the fluid probability density functional has an attractor for
its time-evolution, just as the dynamical system itself has. The evolution of
the fluid's statistics can be set up as a space-time path integral. Fluid
space-time co... | physics |
9,585 | Probability density function of turbulent velocity fluctuation | physics.flu-dyn | The probability density function (PDF) of velocity fluctuations is studied
experimentally for grid turbulence in a systematical manner. At small distances
from the grid, where the turbulence is still developing, the PDF is
sub-Gaussian. At intermediate distances, where the turbulence is fully
developed, the PDF is Gaus... | physics |
9,586 | Non-premixed Flame-Turbulence Interaction in Compressible Turbulent Flow | physics.flu-dyn | Nonpremixed turbulent reacting flows are intrinsically difficult to model due
to the strong coupling between turbulent motions and reaction. The large amount
of heat released by a typical hydrocarbon flame leads to significant
modifications of the thermodynamic variables and the molecular transport
coefficients and thu... | physics |
9,587 | Two dimensional incompressible ideal flow around a small obstacle | physics.flu-dyn | In this article we study the asymptotic behavior of incompressible, ideal,
time-dependent two dimensional flow in the exterior of a single smooth obstacle
when the size of the obstacle becomes very small. Our main purpose is to
identify the equation satisfied by the limit flow. We will see that the
asymptotic behavior ... | physics |
9,588 | Velocity and Pressure Fields Induced by Spheres in an Unbounded Fluid | physics.flu-dyn | We propose a procedure for the determination of the time-dependent velocity
and pressure fields of an unbounded incompressible viscous fluid in an external
force field induced by an arbitrary number of spheres moving and rotating in it
as well as the forces and torques exerted by the fluid on the particles. Within
the ... | physics |
9,589 | Towards a sufficient criterion for collapse in 3D Euler equations | physics.flu-dyn | A sufficient integral criterion for a blow-up solution of the Hopf equations
(the Euler equations with zero pressure) is found. This criterion shows that a
certain positive integral quantity blows up in a finite time under specific
initial conditions. Blow-up of this quantity means that solution of the Hopf
equation in... | physics |
9,590 | The alpha effect and its saturation in a turbulent swirling flow generated in the VKS experiment | physics.flu-dyn | We report the experimental observation of the alpha-effect. It consists in
the generation of a current parallel to a magnetic field B0 applied to a
turbulent swirling flow of liquid sodium. At low magnetic Reynolds number, Rm,
we show that the magnitude of the alpha-effect increases like Rm2 and that its
sign is determ... | physics |
9,591 | Long time correlations in Lagrangian dynamics: a key to intermittency in turbulence | physics.flu-dyn | New aspects of turbulence are uncovered if one considers flow motion from the
perspective of a fluid particle (known as the Lagrangian approach) rather than
in terms of a velocity field (the Eulerian viewpoint). Using a new experimental
technique, based on the scattering of ultrasounds, we have obtained a direct
measur... | physics |
9,592 | The Approach of Turbulence to the Locally Homogeneous Asymptote as Studied using Exact Structure-Function Equations | physics.flu-dyn | Equations that follow from the Navier-Stokes equation and incompressibility
but with no other approximations are called "exact" here. Exact equations
relating 2nd and 3rd-order structure functions are obtained, as is an exact
incompressibility condition on the 2nd-order velocity structure function.
Ensemble, temporal, ... | physics |
9,593 | Large time behavior for vortex evolution in the half-plane | physics.flu-dyn | In this article we study the long-time behavior of incompressible ideal flow
in a half plane from the point of view of vortex scattering. Our main result is
that certain asymptotic states for half-plane vortex dynamics decompose
naturally into a nonlinear superposition of soliton-like states. Our approach
is to combine... | physics |
9,594 | Lagrangian Probability Distributions of Turbulent Flows | physics.flu-dyn | We outline a statistical theory of turbulence based on the Lagrangian
formulation of fluid motion. We derive a hierarchy of evolution equations for
Lagrangian N-point probability distributions as well as a functional equation
for a suitably defined probability functional which is the analog of Hopf's
functional equatio... | physics |
9,595 | An alternative interpretation for the Holm "alpha model" | physics.flu-dyn | By re-interpreting a recent successful closure procedure in terms of local
spatial averaging and the neglect of fluctuations about that average, it is
shown how the results of that closure scheme (the ''alpha model'') may be more
simply derived. | physics |
9,596 | The Hydraulic Jump In Two Dimensions | physics.flu-dyn | The first quantitative calculation of the hydraulic jump was carried out only
a few years ago by Bohr et al. Since it is the only calculation of the jump, we
have analysed it from a slightly different point of view.Our results are
similar to those of Bohr et.al. | physics |
9,597 | Mechanism of finite-amplitude double-component convection due to different boundary conditions | physics.flu-dyn | A new mechanism of double-component convection is discovered. It emerges in a
horizontal layer of Boussinesq fluid as a stable stratification due to flux
boundary conditions is added to an unstable gradient specified by fixed
boundary values. A large enough perturbation substantially decreases the stable
flux gradient ... | physics |
9,598 | Vortex Ring Reconnections | physics.flu-dyn | We investigate numerically the Navier-Stokes dynamics of reconnecting vortex
rings at small $Re$ number. We find that reconnections are dissipative due to
the smoothing of vorticity gradients at reconnection kinks and to the formation
of secondary structures of stretched anti-parallel vorticity which transfer
kinetic e... | physics |
9,599 | Exact Second-Order Structure-Function Relationships | physics.flu-dyn | Equations that follow from the Navier-Stokes equation and incompressibility
but with no other approximations are "exact.". Exact equations relating second-
and third-order structure functions are studied, as is an exact
incompressibility condition on the second-order velocity structure function.
Opportunities for inves... | physics |
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