Low-frequency wave propagation in an elastic plate floating on a two-layered fluid

• Wave propagation in an elastic plate loaded with two-layered fluid of a finite depth is considered.
• Asymptotic analysis of the dispersion relation is done and several regimes of wave motion are identified.
• The thin layer approximation is derived.
• It is shown that the static pre-stress of a plate results in generation of waves with zero group velocity and triggers veering phenomenon.

For some technical applications related to the ice–sea interaction, it is necessary to predict waveguide properties of elastic plates floating on a relatively thin layer of water, which has a non-uniform density distribution across its depth. The issue of particular concern is propagation of low-frequency waves in such a coupled waveguide. In the present paper, a stratified fluid is modelled as two homogeneous, inviscid and incompressible layers with slightly different densities. The lighter layer of fresh water lies on top of the heavier layer of salty water. The former one produces fluid loading at the pre-stressed plate, whereas the latter one is bounded by the sea bottom. The classical asymptotic methods are employed to identify significant regimes of wave motion in such a three-component waveguide. Dispersion diagrams obtained from approximate dispersion relations are compared with their exact counterparts. The phenomena of veering and generation of waves with zero group velocity induced by pre-stress are identified and quantified.