543 research outputs found
Nonlinear stage of the Benjamin-Feir instability: Three-dimensional coherent structures and rogue waves
A specific, genuinely three-dimensional mechanism of rogue wave formation, in
a late stage of the modulational instability of a perturbed Stokes deep-water
wave, is recognized through numerical experiments. The simulations are based on
fully nonlinear equations describing weakly three-dimensional potential flows
of an ideal fluid with a free surface in terms of conformal variables.
Spontaneous formation of zigzag patterns for wave amplitude is observed in a
nonlinear stage of the instability. If initial wave steepness is sufficiently
high (), these coherent structures produce rogue waves. The most tall
waves appear in ``turns'' of the zigzags. For , the structures decay
typically without formation of steep waves.Comment: 11 pages, 7 figures, submitted to PR
"Breathing" rogue wave observed in numerical experiment
Numerical simulations of the recently derived fully nonlinear equations of
motion for weakly three-dimensional water waves [V.P. Ruban, Phys. Rev. E {\bf
71}, 055303(R) (2005)] with quasi-random initial conditions are reported, which
show the spontaneous formation of a single extreme wave on the deep water. This
rogue wave behaves in an oscillating manner and exists for a relatively long
time (many wave periods) without significant change of its maximal amplitude.Comment: 6 pages, 12 figure
Two-dimensional nonstationary model of the propagation of an electron beam in a vacuum
A two dimensional nonstationary model of the propagation of a relativistic electron beam injected into a vacuum is considered. Collision effects are ignored and there are no external fields. Two types of the electron current propagation are shown from the computer simulation of the Maxwell-Vlasov equations
Quasi-planar steep water waves
A new description for highly nonlinear potential water waves is suggested,
where weak 3D effects are included as small corrections to exact 2D equations
written in conformal variables. Contrary to the traditional approach, a small
parameter in this theory is not the surface slope, but it is the ratio of a
typical wave length to a large transversal scale along the second horizontal
coordinate. A first-order correction for the Hamiltonian functional is
calculated, and the corresponding equations of motion are derived for steep
water waves over an arbitrary inhomogeneous quasi-1D bottom profile.Comment: revtex4, 4 pages, no figure
Effect of rhenium on the structure and properties of the weld metal of a molybdenum alloy
The structure and properties of welds made in molybdenum alloy VM-1 as a function of rhenium concentrations in the weld metal were studied. Rhenium was introduced into the weld using rhenium wire and tape or wires of Mo-47Re and Mo-52Re alloys. The properties of the weld metal were studied by means of metallographic techniques, electron microscopy, X-ray analysis, and autoradiography. The plasticity of the weld metal sharply was found to increase with increasing concentration of rhenium up to 50%. During welding, a decarburization process was observed which was more pronounced at higher concentrations of rhenium
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