Search

Severe rain events can subject our existing drainage systems to capacity. While the conveyance capacity of sewers can be increased by temporarily tolerating a full pipe flow condition, the complex dynamics of water-air mixture occurring in vertical dropshafts can largely restrict the overall conveyance capacity of drainage systems. In this study, the hydraulic performance of plunging flow dropshafts is investigated experimentally with respect to their conveyance capacity. The model dropshaft consisted of an upstream horizontal inflow pipe, a vertical circular shaft, and an outflow pipe discharging to the atmosphere. Five setups were built with [D.sub.s]/[D.sub.i] from 1.0 to 3.0 for the range of drop heights H/[D.sub.s] = 3.0 to 21.0, where [D.sub.i] is the inlet pipe diameter, [D.sub.s] the shaft diameter, and H the drop height. A wide range of discharges up to Q* = 25 was tested, where Q* = Q/[(g[D.sup.5.sub.i]).sup.(1/2)]. Flow patterns recognized within the shaft (free flow, surface roller, plug flow, slug flow, and full pipe flow) help to assess the two stages of choking: the incipient and fully choked state. Criteria to predict choking occurrences were developed experimentally. The flow is considered to reach its conveyance capacity when an incipient choking state is visible. For a typical dropshaft with [D.sub.s]/[D.sub.i] = 2, Q* was found to be approximately 5. Key words: discharge capacity, hydraulics, hydraulic structures, plunging flow dropshaft. Des precipitations severes peuvent pousser les systemes d'evacuation des eaux actuels a completement remplir les systemes. Bien que la capacite d'evacuation des egouts puisse etre accrue en tolerant temporairement une condition d'ecoulement a plein tuyau, la dynamique complexe du melange air-eau survenant dans les puits verticaux peut grandement restreindre la capacite globale de transport des systemes d'evacuation des eaux. La presente etude examine la capacite de transport hydraulique des puits plongeants. Le puits modele comportait un tuyau horizontal d'arrivee en amont, un puits circulaire vertical et un tuyau de sortie se dechargeant a l'air libre. Cinq installations ont ete construites en utilisant des rapports [D.sub.s]/[D.sub.i] de 1,0 a 3,0 pour une plage de hauteurs de chute H/[D.sub.s] = 3,0 a 21,0, ou [D.sub.i] est le diametre interne du tuyau, [D.sub.s] est le diametre du puits et H la hauteur de chute. Une grande plage de decharges, jusqu'a Q* = 25 a ete testee, ou Q* = Q/[(g[D.sup.5.sub.i]).sup.(1/2)]. Des patrons d'ecoulement reconnus dans le puits (ecoulement libre, rouleau de surface, ecoulement en piston, ecoulement sublaminaire et ecoulement a plein tuyau) aident a evaluer les deux niveaux de blocage: l'etat initial et l'etat pleinement bloque. Les criteres pour predire les frequences de blocage ont ete developpes au moyen d'experiences. L'ecoulement est presume avoir atteint sa capacite de transport lorsqu'un etat de blocage initial est visible. Pour un puits vertical typique ou [D.sub.s]/[D.sub.i] = 2, le Q* etait d'environ 5. [Traduit par la Redaction] Mots-cles: capacite d'elimination, hydraulique, structures hydrauliques, puits vertical plongeant., Introduction The hydraulic performance of a vertical plunging dropshaft has not yet been investigated in relation to its conveyance capacity. The conveyance capacity of a dropshaft is defined as the [...]

This paper reports on a laboratory investigation into the performance of a novel stacked drop manhole design where two identical rectangular manholes are stacked one beside the other but at different heights so that there is a drop in elevation from one to the other. The focus of the study was to estimate the energy dissipation that occurs in such stacked manholes during diverse inflow conditions. Flow regimes inside the structure were identified and the effectiveness of the design was assessed under variable inflow conditions. Total energy dissipation in the stacked manhole was found to range from about 50% to 90%, and the contribution of each manhole chamber to the overall energy dissipation was assessed. A relationship between water depths in the manhole chambers and the corresponding outflow conditions was established. In addition, an analysis of the flow patterns and flow regimes highlighted the relevant parameters involved in the mechanisms of energy dissipation. Key words: urban hydraulics, drop manhole, energy dissipation. Cet article aborde une etude en laboratoire sur le rendement d'une nouvelle conception de regards avec chute empiles ou deux regards rectangulaires identiques sont empiles avec une difference d'elevation. Cette etude porte principalement sur l'estimation de la dissipation d'energie dans un tel regard empile pour diverses conditions de debit entrant. Les regimes d'ecoulement dans la structure ont ete identifies et l'efficacite de la conception a ete abordee sous des conditions variables de debit entrant. La dissipation d'energie totale dans le regard empile se trouvait entre 50% et 90% et la contribution de chaque chambre du regard a ete evaluee par rapport a la dissipation d'energie globale. Une relation entre les profondeurs d'eau dans les chambres des regards et les conditions de sortie est determinee. De plus, une analyse des schemas hydrauliques et des regimes d'ecoulement a fait ressortir les parametres applicables aux mecanismes de dissipation de l'energie. Mots-cles : hydraulique urbaine, regard avec chute, dissipation d'energie. [Traduit par la Redaction], 1. Introduction Outfalls discharging into rivers should ensure that their erosive capacity is not detrimental to the receiving river or creek system. Windermere Subdivision is a recently constructed urban development [...]

The physicochemical aging for parts of Sheet Molding Compound should be considered for their lifetime management and reusability. This material has a complex morphology and contains porosity due to the process and to shrinkage compensation. This SMC study has two complementary approaches. One describes the morphological consequences of water uptake, showing the decrease in the total amount and the fractal dimension of micro-voids by scanning electron microscopy and image processing. The other shows, by mechanical spectrometry, the effect of water on physical or chemical bonds. In both cases, the 'low profile agent' in SMC plays an important role. The molecular mobility was taken as a sensor parameter for the structural changes at the molecular scale, highlighting and quantifying the first steps of the aging. The loss factor level increases, and the activation energies are modified, even for the first aging days. The analysis shows recovery for the material near the relaxation peak of the low profile agent, since the curve recovers its initial shape., INTRODUCTION Composites based on unsaturated polyesters (UP) have been gaining increasing utilization in the automotive industry, because of their good characteristics (economy, versatility, aspect and mechanics). Especially, SMC is used [...]