DETERMINATION OF THE INTERFACIAL EDDY DIFFUSION COEFFICIENT OF A HIGHLY STRATIFIED ESTUARY

Yu-Hwa Wang

Abstract


Estuaries may be sequentially classified into highly stratified, moderately mixed and vertically homogeneous. An important difference between moderately stratified or vertically homogeneous estuaries, and highly stratified estuaries (salt wedges) is that, in the former, tidal currents are sufficient to cause turbulent mixing of fresh water and sea water over the full depth of the estuary. In the latter, a distinct interface or interfacial layer exists which separates the two nearly homogeneous layers. The vertical advectlon of salt in this two-layer flow is the dominant process in maintaining the salt balance. This paper presents an analytical model describing this process. Experiments have been conducted in the laboratory to compare with the developed theory. A large number of publications concerning estuarine dynamics are available for moderately mixed and vertically homogeneous estuaries. Relatively little information, however, is available for highly stratified estuaries. In an earlier work Keulegan (1949) defined the critical velocity of the upper layer at which the entrainment of the salt water layer starts. A summary of Keulegan's work may be found in Chappter 11 of the book, "Estuary and Coastline Hydrodynamics" edited by Ippen (1966). Recently Partheniades et. al. (1975) reviewed Schijf-Schonfeld's analytical work and Keulegan's experimental data with regard to the length, shape and shear stresses of a saline wedge. Wang (1975) compared his laboratory measurements of interfacial stresses with Lock's Theory.

Keywords


interfacial eddy; diffusion coefficient; estuary; stratified estuary

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