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Trapping modes in the theory of surface waves

Published online by Cambridge University Press:  24 October 2008

F. Ursell
Affiliation:
Department of MathematicsThe UniversityManchester

Abstract

It is shown that a mass of fluid bounded by fixed surfaces and by a free surface of infinite extent may be capable of vibrating under gravity in a mode (called a trapping mode) containing finite total energy. Trapping modes appear to be peculiar to the theory of surface waves; it is known that there are no trapping modes in the theory of sound. Two trapping modes are constructed: (1) a mode on a sloping beach in a semi-infinite canal of finite width, (2) a mode near a submerged circular cylinder in an infinite canal of finite width. The existence of trapping modes shows that in general a radiation condition for the waves at infinity is insufficient for uniqueness.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1951

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References

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