Experimental study of internal gravity waves over a slope
Cacchione, David A.
MetadataShow full item record
LocationNew England continental margin
A series of laboratory experiments were conducted in a glass wave tank to investigate the propagation of internal gravity waves up a sloping bottom in a fluid with constant Brunt-Vaisala frequency. Measurements of the wave motion in the fluid interior were primarily taken with electrical conductivity probes; measurements in the boundary layer were made with dye streaks and neutrally buoyant particles. The results indicate that, outside of the breaking zone, the amplitude and horizontal wave number of the high-frequency waves increase lineariy with decreasing depth; this is shown to agree with existing linear, inviscid solutions. A zone of breaking or runup is induced by these high-frequency waves well upslope. Shadowgraph observations show that, if the wave characteristics are coincident, or nearly so, with the bottom slope, the upslope propagation of the low-frequency waves causes a line of regularly spaced vortices to form along the slope. Subsequent mixing in the vortex cells creates thin horizontal laminae that are more homogeneous than the adjacent layers. These laminae slowly penetrate the fluid interior, creating a step-like vertical density structure. Available linear theoretical solutions for the velocity in the viscous boundary layer, determined to be valid for certain experimental conditions, are used to develop a criterion for incipient motion of bottom sediment induced by shoaling internal waves. The maximum sediment sizes that can be placed into motion, according to this criterion, are larger than certain mean sediment sizes on the continental margin off New England. This suggests that internal waves might induce initial sediment movement. Speculation about the geological effects of breaking and vortex instabilities is also given. These processes, not definitely measured in the field as yet, might also be conducive to sediment movement.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1970
Showing items related by title, author, creator and subject.
Waldbauer, Jacob R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)Biological activity has shaped the surface of the earth in numerous ways, but life’s most pervasive and persistent global impact has been the secular oxidation of the surface environment. Through primary production – the ...
Temporal variability and vertical structure in larval abundance : the potential roles of biological and physical processes Garland, Elizabeth D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-02)Recruitment variability in benthic invertebrate populations results from variability in planktonic larval supply and from processes occurring during and after larval settlement onto the seafloor. The focus of this thesis ...
Physiological and behavioral diagnostics of nitrogen limitation for the toxic dinoflagellate Alexandrium fundyense Poulton, Nicole J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-09)One challenge in phytoplankton ecology is to measure species-specific physiological responses to changes in environmental conditions. Of particular importance in this regard are harmful algal bloom (RAB) species such as ...