Effect of undulating bottom on wave interaction with a floating flexible plate coupled with a flexible porous barrier

Abstract

In the present study, under the assumption of small amplitude water wave theory and structural response, effect of bed undulation on the wave interaction with a combination of flexible porous barrier and a flexible floating plate, is studied. The flexible porous barrier is modelled using the porous wave maker-theory while the elastic floating plate is modelled using thin plate theory. The physical problem is handled for solution using eigenfunction expansion method by matching pressure and velocity at interface boundaries while finite difference method is used to deal with modified mild-slope equation. In the present study, two types of plate configurations are namely (a) finite plate and (b) semi-infinite plate. To understand the role of undulating seabed, wave and structural parameters, in attenuating wave force and plate deflection, numerical results are computed and compared with available literature. It is found that full wave reflection occurs for certain critical angle and wave force acting on the barrier vanishes for the same critical angle for the semi-infinite plate case while the wave reflection tends to attain maximum value at critical angle for the finite case and these maximum value increases with the increase of plate length. It is observed that less wave reflection occurs for sloping bed profile compare to rest of the bed profile. The study reveals that positioning a barrier between plate and undulated region, helps in the reduction of plate deflection significantly. As special case, wave interaction problem with a finite floating elastic plate is studied experimentally and the experimental result has shown good agreement with the numerical result. The findings of the present study are likely to be of immense help in the design of various types of marine structures for protecting very large floating structures (VLFS). The present theory can be extended to handle large class of acoustic wave interaction problems with flexible porous structures.