About the specification of erosion flux for soft stratified cohesive sediments |
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| Authors: | Georges Chapalain Y Peter Sheng and André T Temperville |
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| Institution: | (1) Laboratoire d'Ecologie Numérique, Université des Sciences et Technologies de Lille, U.R.A. 1363, Bâtiment SN3, 59655 Villeneuve d'Ascq, France;(2) Coastal and Oceanographic Engineering Department, University of Florida, 336, Weil Hall, 32611 Gainesville, Florida;(3) Laboratoire de Ecoulements Géophysiques et Industriels, Institut de Mécanique de Grenoble, BP 53X, 38041 Grenoble, France |
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| Abstract: | The present paper deals with the specification of bed erosion flux that accounts for the effects of sediment-induced stratification in the water column. Owing to difficulties in measuring the bed shear stress  b and the erosive shear strength s, we suggest a series of methods that combine laboratory and numerical experiments. A simplified turbulent transport model that includes these effects helps to quantify b and s. Focusing on soft stratified beds, the present study considers erosion rate formulas of the form  =f exp {Tb-Ts ] } where is a model constant (=1 for Gularte's (1978) formula and =1/2 for Parchure's (1984) formula). First, the bed erosive strength profile s(Z) is adjusted by  forcing the turbulent transport model with measured erosion rates. Second, three procedures are suggested to determine the erosion rate formula coefficients f and : a global procedure and two different layer-by-layer procedures. Each procedure is applied to an erosion experiment conducted in a rotating annular flume by Villaret and Paulic (1986). The use of the layer-by-layer procedure based on a least squares fitting technique provides a closer fit than the global procedure. The present study points out the complementarity of experimental and numerical approaches and also suggests possible improvements in laboratory test procedures. |
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| Keywords: | mud erosion rate formula suspended sediment stratification effects numerical model finite-difference method laboratory experiment |
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