9 research outputs found
Ge-diode detector combined with crystal-diffraction spectrometer permits high-resolution gamma ray spectroscopy
Crystal-diffraction spectrometer, combined with a lithium-drifted Ge-diode detector, performs high-resolution gamma ray spectroscopy on the complicated neutron-capture gamma ray spectra. The system is most useful in the 1-3 MeV energy range and improves the signal to background ratio
Turbulence and passive scalar transport in a free-slip surface
We consider the two-dimensional (2D) flow in a flat free-slip surface that
bounds a three-dimensional (3D) volume in which the flow is turbulent. The
equations of motion for the two-dimensional flow in the surface are neither
compressible nor incompressible but strongly influenced by the 3D flow
underneath the surface. The velocity correlation functions in the 2D surface
and in the 3D volume scale with the same exponents. In the viscous subrange the
amplitudes are the same, but in the inertial subrange the 2D one is reduced to
2/3 of the 3D amplitude. The surface flow is more strongly intermittent than
the 3D volume flow. Geometric scaling theory is used to derive a relation
between the scaling of the velocity field and the density fluctuations of a
passive scalar advected on the surface.Comment: 11 pages, 10 Postscript figure
Turbulence in a free surface
We report an experimental and numerical study of turbulent fluid motion in a
free surface. The flow is realized experimentally on the surface of a tank
filled with water stirred by a vertically oscillating grid positioned well
below the surface. Particles floating on the surface are used to visualize the
flow. The effect of surface waves appears to be negligible. The flow is
unconventional in that it is confined to two dimensions but does not have
squared vorticity as a conservation law, that it is not divergence free and
that it inherits scaling features of the mean square velocity differences
S_2(R) and the vorticity fluctuations Omega(R) from the bulk 3-d turbulence.Comment: 4 pages, 4 Postscript figure