Rotational superradiant scattering in a vortex flow

Torres, Theo and Patrick, Sam and Coutant, Antonin and Richartz, Mauricio and Tedford, Edmund W. and Weinfurtner, Silke (2017) Rotational superradiant scattering in a vortex flow. Nature Physics . ISSN 1745-2481

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Abstract

When an incident wave scatters off of an obstacle, it is partially reflected and partially transmitted. In theory, if the obstacle is rotating, waves can be amplified in the process, extracting energy from the scatterer. Here we describe in detail the first laboratory detection of this phenomenon, known as superradiance 1, 2, 3, 4. We observed that waves propagating on the surface of water can be amplified after being scattered by a draining vortex. The maximum amplification measured was 14% ± 8%, obtained for 3.70 Hz waves, in a 6.25-cm-deep fluid, consistent with the superradiant scattering caused by rapid rotation. We expect our experimental findings to be relevant to black-hole physics, since shallow water waves scattering on a draining fluid constitute an analogue of a black hole 5, 6, 7, 8, 9, 10, as well as to hydrodynamics, due to the close relation to over-reflection instabilities 11, 12, 13.

Item Type: Article
Keywords: Fluid dynamics, High-energy astrophysics
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Mathematical Sciences
Identification Number: 10.1038/nphys4151
Depositing User: Eprints, Support
Date Deposited: 29 Jun 2017 10:31
Last Modified: 30 Jun 2017 00:13
URI: http://eprints.nottingham.ac.uk/id/eprint/43862

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