NONHYDROSTATIC EFFECTS IN LAYERED SHALLOW-WATER FLOWS

This paper develops a one-dimensional extension to classical layered h ydraulics that incorporates non-hydrostatic effects. General results f or a homogeneous layer in a multi-layer steady flow are applied to sin gle-and two-layer flow over a two-dimensional sill, The equation obtai ned for single-layer flows is the same as that obtained by Naghdi & Vo ngsampigoon (1986) using the direct theory of constrained fluid sheets , and compares very well with the laboratory measurements of Sivakumar an et al. (1983). The new equation derived for two-layer flows provide s excellent agreement with the laboratory measurements of Lawrence (19 93). Accurate solutions are obtained for a regime of two-layer flow wh ose behaviour cannot be explained, even qualitatively, using classical hydraulic theory.