Mechanisms of Fluid-Mud Interactions Under Waves

Book excerpt: Long-term goals: The goals of this project are to investigate the mechanisms for wave dissipation in the presence of bottom mud. There are a variety of possible mechanism for the decay of wave energy as waves propagate over muds; however, they have not all been validated in the field nor quantified in terms of their relative importance and damping rates in the field or the laboratory. Further new mechanisms may be found. Implementation of these mechanisms into numerical models will provide the ability to infer from the sea surface the nature of the bottom material. Objectives: We are measuring wave damping due to mud off the coast of Louisiana, quantifying the dynamics of the bottom mechanisms responsible for the dissipation of wave energy. We are examining different mechanisms for the damping of wave energy by bottom mud in the laboratory and through the use of theoretical and numerical models. These damping mechanisms include the direct forcing of the mud by the wave-induced bottom pressure and velocities; indirect forcing through nonlinear surface wave effects (including wave groups); resonant forcing of interfacial waves at the water/mud interface; damping and shear instabilities in the lutocline; and large scale broadband mechanisms that involve a complex sea state and a combination of the above mechanisms.