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This work investigated the effect of a porous and flexible barrier and undulating bottom on wave attenuation in a two-layer stratified fluid under the action of oblique wave incidence, using small amplitude and structural response theory. Two sets of problems with porous and flexible barriers in the absence and presence of impervious sea-wall are discussed. Two different barrier configurations, called bottom-standing and surface-piercing, were considered. The Fourier method, least-square approximation method, and mild-slope approximation method were used to tackle the physical problem. The study reveals an optimal mooring angle to prevent its deformation by surface and interfacial waves. The dissipation of interfacial waves by bottom-standing and surface-piercing barriers exhibits an inverse pattern. Comparatively longer bottoms are insensitive to the interfacial wave-induced forces on the barrier when the depth ratio changes. The contribution of inertial effects in barrier porosity is seen to be critical in protecting existing offshore structures or sea-wall. The sea-wall can be protected using bottom-standing and surface-piercing barriers in a situation of higher surface and interfacial wave energies, respectively. [ABSTRACT FROM AUTHOR]

The main purpose of the present paper is to provide practical and numerical implementations of the method of fundamental solutions for three-dimensional exterior Stokes problems with quiet far-field condition and discuss the issues therein. The solutions of the steady Stokes problems are obtained by utilizing the boundary collocation method as well as the expansion of Stokeslets, which are the fundamental solutions of the steady Stokes equations. To validate the proposed model, numerical results of a lid-driven cavity flow, uniform flow passing a sphere, and a rotating dumbbell-shaped body show good agreement with the numerical and analytical solutions available in the literature. Also, a hypothetical problem with both vorticity and velocity boundary conditions is solved and compared with the analytical solution. The proposed model is then properly exploited to obtain the flow results of uniform flow passing a pair of vertical spheres in tandem and uniform flow passing a pair of horizontal spheres in tandem. Furthermore, the accuracy of the present numerical scheme is addressed and the detail flow characteristics, such as pressure distribution, streamline contour, velocity field, and vorticity fields are sketched. DOI: 10.1061/(ASCE)0733-9399(2006)132:3(317) CE Database subject headings: Numerical models: Hydrodynamics: Particles; Boundaries; Uniform flow; Velocity.

We demonstrate that micrometer-scale spin waves can be excited in a thin film of the ferrimagnetic material yttrium iron garnet (YIG) using patterned, multi-element antennas. The magnitude of the dynamic magnetic field generated by such antennas decays exponentially along the thickness direction, and this leads to an enhanced coupling to modes having a surface-like character as opposed to a more sinusoidal bulk-like character. We have used this property to identify spin waves having a mixed bulk/surface character. [ABSTRACT FROM AUTHOR]