Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593795
Title: An application of the method of characteristics to tidal computations in estuaries
Author: Webster, John A.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1968
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Abstract:
The nonlinear hyperbolic partial differential equations applicable to long wave propagation in two spatial dimensions are derived, under the assumptions of hydrostatic pressure distribution and quadratic bed friction. The relevance of linearised versions of these equations to various tidal configurations is discussed. Linearisation, and the assumption of harmonic wave motion, reduces the hyperbolic system to elliptic form, so that steady-state solutions become available. Conventional harmonic methods are unsatisfactory in shallow estuaries, where the unsteady tidal conditions must be computed by an initial value method. The potential existence of discontinuities in the solution domain of the hyperbolic long wave equations is demonstrated, and the associated characteristic surfaces, which separate disturbed and undisturbed regions within this domain, are delineated. An explicit numerical technique, based on finite difference approximations to the differential relationships which hold on these characteristic surfaces, is proposed. The modifications necessary at the estuary boundaries are described. The stability and consistency criteria associated with the proposed method are established. Violation of the consistency conditions causes a computer program based on estuary schematisation by an orthogonal curvilinear grid to fail in a complex bidirectional situation. However, comparisons with the harmonic solutions in various unidirectional test cases show good agreement, and shallow-water effects appear to be correctly reproduced. A program based on a rectangular network is found to satisfy the consistency conditions. The computational efficiency achieved is comparable to that available with direct finite difference techniques. Finally, the inclusion in the proposed numerical scheme of additional estuarial parameters is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.593795  DOI: Not available
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