Large-scale optics: ocean waves

Even Mehlum

doi:10.1117/12.22253

1 July 1990 Large-scale optics: ocean waves

Even Mehlum

Proceedings Volume 1319, Optics in Complex Systems; (1990) https://doi.org/10.1117/12.22253
Event: 15th International Optics in Complex Systems, 1990, Garmisch, Germany

Abstract

Since 1970 The Center for Industrial Research and Norwave in Oslo have been heavily engaged in research in wave physics. This work includes projects in Computer holography Seismic holography and Holographic lenses for acoustical cameras. The largest of the " wave projects" however is devoted to the extraction of useful energy from ocean waves. This work has been concentrated around the development of two new pieces of hardware. The first is a holographic lens for focusing ocean waves. The second is a horn-shaped chute for collection of water wave energy. In both cases the pieces of hardware are small compared to the wavelength. This fact invalidates many of the approximations that are in routine use in design and evaluation in optical work. The lecture will concentrate on a visual presentation on how these pieces work in practise. I will also try to point out where the techniques may be of utility for other wave phenomena. ARE WATER WAVES WAVES? The question posed in the heading is not stupid since as we shall see the flow is governed by Laplace''s equation which is an elliptic rather than a hyperbolic differential equation. We start out with a presentation of the governing equations for an inviscid irrotational and incompressible liquid with a free surface (the ocean). The flow inside the water is described by means of a velocity potential 4(x while the surface elevation given by i(x t). The depth is h(x atz 1. 2 + (V4) +g 0 at z 2. V2c0 3. ah4 aha4 atz 4. Physical quantities are derived from the potential via the following equations: v 5. 1 2 P Po+ (V4) +gz)p -h 6. 2 / SPIE Vol. 1319 Optics in Complex Systems (1990)

Citation Download Citation

Even Mehlum "Large-scale optics: ocean waves", Proc. SPIE 1319, Optics in Complex Systems, (1 July 1990); https://doi.org/10.1117/12.22253

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