On the three-dimensional structure of the inertial wave field in a rectangular basin with one sloping boundary

Inertial waves propagate obliquely through a rotating fluid with an angle with respect to the rotation axis that is determined by the ratio of wave frequency and rotation frequency. This constraint leads to wave focusing or defocusing upon reflection at a sloping wall. In an enclosed basin repeated reflection may lead to standing waves or wave attractors: limit cycles to which all energy converges. In a two-dimensional setting (including the rotation-axis), wave patterns can be predicted mathematically; in three dimensions this is not generally possible, but ray-tracing indicated that attractors can still be found due to refractive trapping in the along-channel direction. Two wave attractors and a standing wave were investigated experimentally in a rectangular basin with a sloping wall, using particle image velocimetry. Wave attractors and a standing wave were indeed observed, with inhomogeneous energy and phase distribution in the along-channel direction, different for the different attractors and the standing wave. This behaviour can be partly understood using ray-tracing. Scale estimates revealed that the width of the attractor is limited by nonlinear advection.