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We studied theoretically and experimentally the transformation, attenuation, and setup due to shoaling and breaking of internal waves in a two-layer fluid system on a uniform slope. An image processing technique was used to illustrate 2D instantaneous displacements of density interface. These results were compared with the calculated values by using the method of characteristics, the simple shoaling model with energy dissipation, and the momentum balance equation based on a radiation stress concept. | Mechanics of Internal Waves Propagating over a Varying Bottom Slope Motohiko Umeyama3 Abstract We studied theoretically and experimentally the transformation attenuation and setup due to shoaling and breaking of internal waves in a two-layer fluid system on a uniform slope. An image processing technique was used to illustrate 2D instantaneous displacements of density interface. These results were compared with the calculated values by using the method of characteristics the simple shoaling model with energy dissipation and the momentum balance equation based on a radiation stress concept. We also measured the upper and lower velocity fields for progressive internal waves by using Particle Image Velocimetry PIV . Keywords Internal waves Slopes Setup Radiation stress Image processing technique PIV 1. Introduction The mechanism of internal waves in a two-layer system comprising homogeneous fluids of slightly different densities has been studied in the Coastal and Ocean Engineering Laboratory at Tokyo Metropolitan University. In the research of Umeyama 2002 an image processing technique was first used to illustrate the temporal variations of the density interface in a wave tank. Umeyama and Shintani 2004 installed a Plexiglas plate in the same wave tank to observe the runup and breaking of internal waves over it. The profile of internal waves and the mixture of upper and lower layer waters were obtained using more advanced imaging technique. Later Umeyama and Shintani 2006 extended the aspects of internal wave mechanics into the transformation attenuation setup and undertow during shoaling and breaking events. Experiments were performed over a gentle slope and the observed data were used to confirm theoretical solutions by the method of characteristics the energy dissipation model with the radiation stress and the momentum balance equation. Recently Umeyama 2008 studied transformation processes and nonlinear properties of internal waves over a uniform slope in a two .