15 research outputs found
Horizon effects for surface waves in wave channels and circular jumps
Surface waves in classical fluids experience a rich array of black/white hole
horizon effects. The dispersion relation depends on the characteristics of the
fluid (in our case, water and silicon oil) as well as on the fluid depth and
the wavelength regime. In some cases, it can be tuned to obtain a relativistic
regime plus high-frequency dispersive effects. We discuss two types of ongoing
analogue white-hole experiments: deep water waves propagating against a
counter-current in a wave channel and shallow waves on a circular hydraulic
jump.Comment: 4 pages, 2 figs. To appear in: Proceedings of the Spanish Relativity
Meeting (ERE2010
Horizon effects with surface waves on moving water
Surface waves on a stationary flow of water are considered, in a linear model
that includes the surface tension of the fluid. The resulting gravity-capillary
waves experience a rich array of horizon effects when propagating against the
flow. In some cases three horizons (points where the group velocity of the wave
reverses) exist for waves with a single laboratory frequency. Some of these
effects are familiar in fluid mechanics under the name of wave blocking, but
other aspects, in particular waves with negative co-moving frequency and the
Hawking effect, were overlooked until surface waves were investigated as
examples of analogue gravity [Sch\"utzhold R and Unruh W G 2002 Phys. Rev. D 66
044019]. A comprehensive presentation of the various horizon effects for
gravity-capillary waves is given, with emphasis on the deep water/short
wavelength case kh>>1 where many analytical results can be derived. A
similarity of the state space of the waves to that of a thermodynamic system is
pointed out.Comment: 30 pages, 15 figures. Minor change
Observation of negative-frequency waves in a water tank: A classical analogue to the Hawking effect?
The conversion of positive-frequency waves into negative-frequency waves at
the event horizon is the mechanism at the heart of the Hawking radiation of
black holes. In black-hole analogues, horizons are formed for waves propagating
in a medium against the current when and where the flow exceeds the wave
velocity. We report on the first direct observation of negative-frequency waves
converted from positive-frequency waves in a moving medium. The measured degree
of mode conversion is significantly higher than expected from theory
Negative energy waves in a shear flow with a linear profile
International audienc
Wave blocking phenomenon of surface waves on a shear flow with aconstant vorticity
International audienc
The transformation behaviour of “alucones”, deposited by molecular layer deposition, in nanoporous Al2O3 layers
International audienc