Intake shape and boundary-related considerations in the operation and design of storm-sewer drop structures

This paper presents the results of an experimental investigation into the hydraulic efficiency of a vertically oriented water intake. Under low submergence conditions, the operation of such an intake is affected significantly by the formation of surface vortices, which result in significant flow reduction and the downstream entrainment of air and swirl. The experimental work considered the fact that vortex formation is governed by the geometrical characteristics of the intake, including the diameter, local shape, submergence, surrounding boundary, etc, and the velocity distribution in the approaching flow. Therefore, an experimental study was conducted to investigate the influence that the local shape and the proximity to nearby boundaries have on the hydraulic performance of a vertical water intake. The results of this experimental investigation will hopefully lead to a better understanding of the phenomena governing the flow in such structures and to the elaboration of improved engineering design guidelines. Key words: drop structures, experimental program, drop shafts, intakes, inlets, vortex flow. Cet article presente les resultats d'une etude experimentale de l'efficacite hydraulique d'une prise d'eau verticale. Dans des conditions de faible submersion, le fonctionnement d'une telle prise est grandement affecte par la formation de vortex de surface, ce qui reduit considerablement le debit et entraine de l'air et des tourbillons en aval. Le travail experimental considerait que la formation de vortex etait regie par les caracteristiques geometriques de la prise, dont le diametre, la forme, la submersion, les limites environnantes, etc. ainsi que la repartition des vitesses dans l'eau qui approche de la prise. Ainsi, une etude experimentale a ete realisee afin d'examiner l'influence respective de la forme locale et de la proximite aux limites environnantes sur le rendement hydraulique de la prise d'eau verticale. Les resultats de cette etude experimentale meneront probablement a une meilleure comprehension des phenomenes regissant l'ecoulement dans de telles structures ainsi qu'a une elaboration de meilleures lignes directrices pour la conception technique. Mots-cles: chutes, programme experimental, puits verticaux, prises, entrees, ecoulement tourbillonnaire. [Traduit par la Redaction]
Introduction Vertically oriented water-intake structures, such as 'shaft' or 'morning glory' spillways and storm-sewer 'drop' structures, transport water abruptly from a higher to a lower elevation in the water transmission [...]