Laboratory Experiments of Wave Attenuation by Mud
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Date
2014-09-26
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Johns Hopkins University
Abstract
Muddy deposits make up a large region of the world's coastal lands such as the Gulf of Mexico, the Louisiana coastline, and the Persian Gulf. These regions serve as valuable resources for the world's population for commerce, leisure activities, and sustainability. Human activities depend on the comprehensive understanding of the natural occurrences that take place in these coastal zones. The interaction between waves and the muddy sea bottom has profound effects on these human activities because the damping of waves in these regions creates turbidity, which can disrupt the natural habitat for marine and coastal life.
The purpose of this study is to better understand the mechanisms of water wave damping over mud as a function of water depth, wave height and period. In a series of laboratory experiments, the damping rate was determined for different wave parameters in intermediate and shallow water for a kaolinite mud bed. The results show that the damping rate is highly dependent on the rate of work performed by the waves on the bottom.
Damping in deep water was also observed in laboratory experiments. Water waves propagating over a mud bottom in deep water are not affected by the bottom. However, two superimposed short waves can create a wave group that generates an associated long bound wave that will extend the wave pressure to the bottom and dissipate energy. In a series of laboratory experiments of various wave group parameters, the damping rate was measured with a variety of methods.
A theory for the nonlinear interaction of two short waves propagating with arbitrary angles in deep water was developed extending the work of Longuet-Higgins (1950). The theoretical expression of the water surface elevation of waves, the bottom pressure, the velocities were developed. A further series of laboratory experiments on mud behavior showed the damping rate of waves to be a function of the wave characteristics and the amplitude of the bottom response.
These findings will improve the theoretical understanding of wave damping mechanisms in shallow, intermediate and deep water. This in turn should enable authorities and planners to shape more effective long-term environmental policies for coastal regions to protect both land and marine life.
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Keywords
Wave groups, Mud, Prony method