V.T.Grinchenko, G.L.Komissarova Surface waves in a system: an elastic layer on a fluid half-space |
Acoustic bulletin, Vol. 8 ¹ 4, (2005) |
| The properties of the lowest normal waves in an elastic layer on a fluid half-space are investigated. The asymptotic analysis of the dispersion equation at large wave numbers shows the existence of two different surface waves in this waveguide structure. The first normal wave, when the wavenumber (frequency) increases, forms the Stoneley wave on the contact interface between the elastic layer and fluid half-space. The second normal wave in its limit tends to Rayleigh wave on the free surface of the layer. As the frequency increases, both phase velocities tend to the velocities of the corresponding waves for half-spaces. The elastic-fluid interaction effect is strongly dependent on the mechanical properties of the fluid and elastic material. Reduction of material rigidity for elastic layer essentially effects the limiting value of that running waves phase velocities, which are independent of the radiation attenuation. In the case of the compliant material of elastic layer the limiting value of propagating wave phase velocity is that of the shear wave. For rigid material of the layer the corresponding limiting value is sound velocity in fluid. It is shown that in the case of the soft layer's material the running waves of high orders exist in the considered waveguide system, which phase velocities tend with a wavenumber to the velocity of the shear wave for layer material. The effect of dispersion on the kinematical characteristics of the normal waves and their phase velocities is illustrated for two types of elastic materials of the layers (rigid and compliant) and water as the fluid using the particular examples. |
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KEY WORDS: elastic layer, fluid half-space, normal waves, the Stoneley wave, the Rayleigh wave |
| TEXT LANGUAGE: Russian |