The two-dimensional problems of scattering and radiation of small-amplitude
water waves by thin vertical porous plates in finite water depth are consi
dered using the linear water wave theory. Applying the method of eigenfunct
ion expansion, these boundary value problems are converted to certain dual
series relations. Solutions to these relations are then obtained by a suita
ble application of the least squares method. For the scattering problem, fo
ur different basic configurations of the barriers are investigated, namely,
(I) a surface-piercing barrier, (II) a bottom-standing barrier, (III) a to
tally submerged barrier, and (IV) a barrier with a gap. The performance of
these types of barriers as a breakwater are examined by studying the variat
ion of their reflection and transmission coefficients, hydrodynamic forces
and moments for different values of the porous effect parameter defined by
Chwang [J. Fluid Mech. 132, 395-406 (1983)], or the Chwang parameter. For t
he radiation problem, three types of wavemakers, which resemble types (I),
(II), and (III) of the above-mentioned configuration, are analyzed. The dep
endence of the amplitude to stroke ratio on other parameters is also invest
igated to study the features of these wavemakers. (C) 2000 American Institu
te of Physics. [S1070- 6631(00)00201-4].