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Title: Some non-linear and frictional effects in tidal currents and gravity waves
Author: Johns, Bryan
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 1963
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Previous investigations into wave induced mass transport have been restricted to two spatial dimensions, and, in view of the assumption of high frequency oscillations, the rotation of the earth neglected. Following a brief discussion of existing two-dimensional theories, fundamental ideas of wave induced mass transport are developed for a three-dimensional region. The analysis is separately considered for high and low frequency oscillations, between which are found significant differences. These concepts are then employed to determine the mass transport beneath doubly modulated gravity waves (high frequency oscillations) and tidal oscillations (low frequency oscillations). The predictions furnish a possible explanation of the occurrence of off-shore sand bars and the movement of bottom sediment in shallow ocean regions. A further consideration included is an assessment of the ability of edge waves on sloping continental shelves to transport loose coastal material, and for high frequency oscillations a seaward movement is deduced. The subsequent section of the work considers the formulation of a two-dimensional model for mass transport in turbulent conditions, and with varying distributions of eddy viscosity, the resulting transports are calculated. The final chapter, although not directly concerned with mass transport phenomena, is regarded as being relevant to the thesis. It is devoted to a generalisation of the boundary layer technique as a means of introducing bottom friction into gravity wave models. The method is found to predict an attenuation with time consistent with the well known approach via the Navier-Stokes equations, and seems well suited as a tool to be further exploited. -
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available