| Abstract: | This paper investigates a wavefilter which could effectively eliminate re-reflected waves generated in a wave flume over a certain range of wave periods. The wavefilter is not required to change its thickness for different incoming wave periods and is, therefore, termed here a permanent wavefilter. The structure comprises of a set of multilayer porous media. Their related properties such as porosities, friction factors and thickness are sought with the hope of developing a structure which could serve the desired purpose.A theoretical study has been performed. It was found that a multilayer porous media could eliminate re-reflected waves without resorting to adjusting the medium property whenever wave period changes, only if the thickness of the media has to exceed a certain amount.Generally speaking, a thicker multilayer porous media is needed for longer-period waves, while a thinner one is suitable for shorter-period waves. The wavefilter considered here could serve both eliminating re-reflected waves and also providing a desired median wave height if all of those related factors of the media have been properly selected and if the generated waves are restricted to not too wide a range of wave periods. However, it is unlikely that a wavefilter with fixed thickness can remain effective over too wide a range of wave period. |
