Head losses in junction manholes for free surface flows in circular conduits

Former studies on combining flows resulted in an efficient layout of sewer junctions operated under supercritical approach flow conditions. Straight extensions allowed a reduction in the shock wave heights generated by the merging flows, so that the global discharge capacity was significantly increased. Herein, an extensive experimental campaign is presented on a physical model with the aforementioned layout, although with generalized geometrical conditions now including various conduit diameters. The effects of the main parameters governing the energy losses for combining flows were ascertained to enhance the information available from the literature. The results and their analysis provide a basis for the prediction of energy losses at junction manholes with different upstream and lateral conduit diameters and various flow conditions

Energy dissipation in sewer fall manholes

In the present literature review paper several experimental investigations on physical and numerical models of drop manholes and vortex drop shafts were considered. The examination of the experimental data led to the definition of a simple empirical equation, initially suggested for one type of drop manhole, to estimate the total head loss coefficient for both drop manholes and vortex drop shafts. The energy efficiency values, as detected by the corresponding physical and numerical tests, of all the drop structure models were also compared. The energy efficiency of vortex drop shafts is larger than in drop manholes, and it reaches easily the 90%. Drop manholes are, instead, characterized by a smaller energy efficiency, which was shown to increase as the drop height augments

Head losses in sewer junction

The functionality of sewer networks is strongly affected by the correct operation of their appurtenances; the dendritic structure of urban drainage systems implies that junction manholes represent a crucial hydraulic structure, allowing two conduits merging into one. Hydraulic features of combining flows become quite complex when supercritical flows are involved, as in the case of steep urban context, with consequent formation of shockwaves and surging phenomena. Former studies conducted by Gisonni and Hager resulted in an optimized layout of sewer junctions operated under supercritical approach flow conditions. Recently, an extensive experimental campaign was performed on a physical model with generalized geometrical conditions, including various conduit diameters. Furthermore, physical model tests have been used to implement and validate a numerical model, aiming to explore a wider range of junction angles, which were limited to 45° and 90° for the physical model. In particular, the numerical model focused on the flow condition where both approach flows are supercritical. Based on the dataset constituted from both physical and numerical model results, comprehensive equations are proposed for the prediction of energy losses at junction manholes with different upstream and lateral conduit diameters, with particular reference to supercritical combining flows

Energy head dissipation and flow pressures in vortex drop shafts

Vortex drop shafts are special manholes designed to link sewer channels at different elevations. Significant energy head dissipation occurs across these structures, mainly due to vertical shaft wall friction and turbulence in the dissipation chamber at the toe of the shaft. In the present study two aspects, sometimes neglected in the standard hydraulic design, are considered, namely the energy head dissipation efficiency and the maximum pressure force in the dissipation chamber. Different physical model results derived from the pertinent literature are analyzed. It is demonstrated that the energy head dissipation efficiency is mostly related to the flow impact and turbulence occurring in the chamber. Similarly to the drop manholes, a relation derived from a simple theoretical model is proposed for the estimation of the energy head loss coefficient. The analysis of the pressures measured on the chamber bottom allows to provide a useful equation to estimate the pressure peak in the chamber as a function of the approach flow energy head

Les jonctions avec des écoulements torrentiels

La combinaison d’écoulements représente un des phénomènes hydrauliques des plus fascinants, en particulier pour les écoulements torrentiels. L’efficacité des réseaux d’écoulement à surface libre, comme les systèmes d’évacuation des eaux en milieu urbain, dépend fortement du bon fonctionnement des regards de jonctions. Récemment, des études poussées sur modèles physiques ont permis une meilleure connaissance des caractéristiques hydrauliques principales des jonctions, fournissant ainsi de critères pour le dimensionnement de cette structure hydraulique

The Adsorptive Removal of Bengal Rose by Artichoke Leaves: Optimization by Full Factorials Design

Currently, the dye industry is increasing its production as a consequence of the growing need for their products in different manufacturing sectors, such as textiles, plastics, food, paper, etc... Thereafter, these industries generate very large volumes of effluents contaminated by these dyes, which require proper removal treatment before final discharge of the effluents into the environment. In this study, artichoke leaves were used as an economical and eco-friendly bio-adsorbent for Bengal Rose (BR) dye removal. Bio-adsorbent obtained from artichoke leaves was ground to powder size. The resulting powder was characterized by different methods, such as Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy(SEM), X-ray Diffraction (XRD), Fourier transfer infrared (FTIR), pH at point of zero charge (pHpzc), equilibrium pH, iodine number, methylene blue number, phenol number, density, Energy dispersive X-ray spectroscopy (EDX) and Thermo-gravimetric analysis (TGA). Thereafter, the bio-adsorbent was used to study its capability for removing BR dye by testing contact time, initial concentration of dye and temperature. The results show that the saturation of bio-sorbent was reached after 40 min and the removal rate of BR dye by artichoke leaves powder (ALP) was 4.07 mg/g, which corresponds to a removal efficiency of 80.1%. A design of experiences (DOE) based on a two-level full factorial design (23) was used to study the effects of different parameters, such as pH, temperature and bio-adsorbent dosage on BR dye removal efficiency. The obtained results show that the highest removal efficiency was 86.5% for the optimized values of pH (4), temperature (80 °C) and bio-adsorbent dosage (8 g/L). Furthermore, a satisfying accordance between experimental and predicted data was observed. The kinetic and isotherm studies show that the pseudo-second order model simulated adequately the obtained data and it was found that Langmuir and Temkin isotherm models are liable and suitable for evaluating the adsorption process performance. Free energy change of adsorption (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were furthermore calculated to predict the nature of the adsorption process