Date of Award

Spring 1980

Project Type

Dissertation

Program or Major

Theoretical and Applied Mechanics

Degree Name

Doctor of Philosophy

Abstract

The surface slope induced pressure gradient, mean current velocity profile, and bottom stress are investigated both theoretically and experimentally for a tidal channel in a well-mixed estuary. The theory focuses on the use of eddy viscosity models. Surface slope estimates based on tide predictions, current velocity profile measurements, and stress estimates from near bottom turbulence measurements are used to investigate the dynamic balance in the tidal channel, and to evaluate the eddy viscosity models. The principal terms in the dynamic balance were found to be the surface slope induced pressure gradient and the bottom stress. The magnitude of the near bottom stress measured in Little Bay ranged from 5 to 40 dynes/cm('2) for near bottom current velocities of 10 to 60 cm/s. Three functional forms for the depth variation of the eddy viscosity coefficient (constant, linear, and parabolic) were evaluated. Eddy viscosity model predictions using the parabolic eddy viscosity coefficient compared most favorably with field data. Two lower boundary conditions are investigated; the usual no-slip condition, and a near bottom stress condition. The current velocity solution of the eddy viscosity model, using the latter boundary condition, is a linear function of bottom stress and surface slope. Thus, instead of specifying surface slope and the stress boundary condition to predict current velocity, the equations are rearranged to predict surface slope and bottom stress for a least squares fit to current velocity profile data. This procedure, called the Extended Profile Method, can be used to predict bottom stress and surface slope to first order accuracy.

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