896 research outputs found
Rotating Liquid Drops: Plateaus Experiment Revisited
The dynamics of liquid drops rotating in another liquid were studied experimentally with an oil drop suspended in a neutral buoyancy tank. New stable shapes not predicted by the theory were observed
Analytic expression for Taylor-Couette stability boundary
We analyze the mechanism that determines the boundary of stability in
Taylor-Couette flow. By simple physical argument we derive an analytic
expression to approximate the stability line for all radius ratios and all
speed ratios, for co- and counterrotating cylinders. The expression includes
viscosity and so generalizes Rayleigh's criterion. We achieve agreement with
linear stability theory and with experiments in the whole parameter space.
Explicit formulae are given for limiting cases.Comment: 6 pages (LaTeX with REVTEX) including 4 figures (Postscript) Revised,
discussion of two additional references. See also
http://staff-www.uni-marburg.de/~esse
Transient growth in Taylor-Couette flow
Transient growth due to non-normality is investigated for the Taylor-Couette
problem with counter-rotating cylinders as a function of aspect ratio eta and
Reynolds number Re. For all Re < 500, transient growth is enhanced by
curvature, i.e. is greater for eta < 1 than for eta = 1, the plane Couette
limit. For fixed Re < 130 it is found that the greatest transient growth is
achieved for eta between the Taylor-Couette linear stability boundary, if it
exists, and one, while for Re > 130 the greatest transient growth is achieved
for eta on the linear stability boundary. Transient growth is shown to be
approximately 20% higher near the linear stability boundary at Re = 310, eta =
0.986 than at Re = 310, eta = 1, near the threshold observed for transition in
plane Couette flow. The energy in the optimal inputs is primarily meridional;
that in the optimal outputs is primarily azimuthal. Pseudospectra are
calculated for two contrasting cases. For large curvature, eta = 0.5, the
pseudospectra adhere more closely to the spectrum than in a narrow gap case,
eta = 0.99
Competition between Traveling Fluid Waves of Left and Right Spiral Vortices and Their Different Amplitude Combinations
Stability, bifurcation properties, and the spatiotemporal behavior of
different nonlinear combination structures of spiral vortices in the counter
rotating Taylor-Couette system are investigated by full numerical simulations
and by coupled amplitude equation approximations. Stable cross-spiral
structures with continuously varying content of left and right spiral modes are
found. They provide a stability transferring connection between the initially
stable, axially counter propagating wave states of pure spirals and the axially
standing waves of so-called ribbons that become stable slightly further away
from onset of vortex flow.Comment: 4 pages, 5 figure
The CNGS Neutrino Beam
The CERN to Gran Sasso Neutrino beam (CNGS) was commissioned at CERN in early
August 2006 and was first sent at low intensity to Gran Sasso on August 17,
2006. The Borexino, LVD and OPERA experiments continued the commissioning of
their detectors and started taking data with practically no dead time. The CNGS
collected several hundred events with clean time distributions.Comment: 11 pages, 14 EPS figures. Lecture given at the 2nd Latin American
School on Cosmic Rays and Astrophysics, Puebla, Mexico, 30th August - 8th
September 200
New type of magneto-rotational instability in cylindrical Taylor-Couette flow
We study the stability of cylindrical Taylor-Couette flow in the presence of
combined axial and azimuthal magnetic fields, and show that adding an azimuthal
field profoundly alters the previous results for purely axial fields. For small
magnetic Prandtl numbers Pm, the critical Reynolds number Re_c for the onset of
the magneto-rotational instability becomes independent of Pm, whereas for
purely axial fields it scales as Pm^{-1}. For typical liquid metals, Re_c is
then reduced by several orders of magnitude, enough that this new design should
succeed in realizing this instability in the laboratory
Determining Neutrino Mass Hierarchy by Precision Measurements in Electron and Muon Neutrino Disappearance Experiments
Recently a new method for determining the neutrino mass hierarchy by
comparing the effective values of the atmospheric \Delta m^2 measured in the
electron neutrino disappearance channel, \Delta m^2(ee), with the one measured
in the muon neutrino disappearance channel, \Delta m^2(\mu \mu), was proposed.
If \Delta m^2(ee) is larger (smaller) than \Delta m^2(\mu \mu) the hierarchy is
of the normal (inverted) type. We re-examine this proposition in the light of
two very high precision measurements: \Delta m^2(\mu \mu) that may be
accomplished by the phase II of the Tokai-to-Kamioka (T2K) experiment, for
example, and \Delta m^2(ee) that can be envisaged using the novel Mossbauer
enhanced resonant \bar\nu_e absorption technique. Under optimistic assumptions
for the systematic uncertainties of both measurements, we estimate the
parameter region of (\theta_13, \delta) in which the mass hierarchy can be
determined. If \theta_13 is relatively large, sin^2 2\theta_13 \gsim 0.05, and
both of \Delta m^2(ee) and \Delta m^2(\mu \mu) can be measured with the
precision of \sim 0.5 % it is possible to determine the neutrino mass hierarchy
at > 95% CL for 0.3 \pi \lsim \delta \lsim 1.7 \pi for the current best fit
values of all the other oscillation parameters.Comment: 12 pages, 6 postscript figure
Performance of Hamamatsu 64-anode photomultipliers for use with wavelength--shifting optical fibres
Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used
with wavelength--shifting optical fibres to read out scintillator strips in the
MINOS near detector. We report on measurements of the gain, efficiency,
linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met
MINOS requirements.Comment: 15 pages, 12 figures. Accepted by Nucl. Inst. Meth.
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