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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME D: Maritime and Coastal Research and Engineering : Effects of bottom-height changes on maximal exchange-flow estimates in channels with quadraticshape...
Effects of bottom-height changes on maximal exchange-flow estimates in channels with quadraticshape cross sections
Author : Janek Laanearu, Peter A. Davies, Tiit Koppel
This study is motivated by the difficulties in applying internal hydraulics theory to density-driven exchange flows in the river estuary conditions. River estuary has usually complex morphodynamic character in bottom shape and application of hydraulic model for density-driven exchange is not straightforward due to unique bottom geometry and roughness elements. The geometrical problem arising from natural channels is that the cross-sectional perimeters do not, in general, have analytical relationships between width and depth changes. In this study the internal regimes of two-layer flow are presented for non-rectangular channels with sill and without surface-width changes and constant shape. The internal regimes of exchange flow over sills in rectangular channel are employed for comparison. Hydraulic regimes are quantified in terms of a shape parameter ξ representing the ratio of the crosssectional area of the chosen channel section to that of the bank full area. The internal flow solutions are parameterized by densimetric Froude numbers of two-layer flow, formulated in terms of this parameter ξ (Laanearu and Davies, 2007). For density-driven exchange over sills, two or three control points G2 = 1 solutions can be found. One control is located at the sill section and other controls at the exit section in the side of dense-water pool. The solution with three control points is presented for the net flow case in the non-rectangular channel. The exchange flow problem without net flow is solved by the equations describing the flow at the two control points at the sill and channel exit. The internal-energy function and internal flux equation for the quadratic channel are used to present parameterized solutions in the internal Froude numbers space. In particular, two features of a maximal exchange flows in the quadratic channels are determined; 1) the dependence of interface position and transport on sill height changes and 2) locations of controls in the Froude-number plane.
File Size : 6,186 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME D: Maritime and Coastal Research and Engineering
Date Published : 01/07/2007
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