Modular Limit for Flumes of Rectangular Compound Sections


Abstract: A series of laboratory experiments were carried out in a flow measurement flume of rectangular compound cross section to investigate the effect of the throat width and step height on the values of modular limit and the drowned flow reduction factor. Nine different models made of Plexiglas were tested in a horizontal flume for large range of discharges. The calculated modular limits were related to relevant parameters. Modular limit values as high as 95\% were obtained. Small margins in the available head difference can cause extremely high submergence ratio, which makes the precise discharge calculation impossible. For practical purposes, modular limit value can be computed for a known throat length and measured head, h_1 from related figures.

Keywords: Open channel, Submerged flow, Modular limit, Flumes, Compound cross section

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