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If the operation of existing vortex drop shafts should be verified, then it is essential to know the hydraulic performance of these special structures under both subcritical and supercritical flow regimes. The purpose of the present research consisted of providing practical guidelines and recommendations for managing the hydraulic design and verification of subcritical and supercritical vortex drop shafts. The examination of various experimental results from physical model investigations allowed to show that the inlet channel and the spiral inlet behaved differently depending on the energy approach flow content. The main dissimilarity lay, however, in the functioning of the vertical shaft and the dissipation chamber. The rotation of the falling flow along the vertical shaft was more evident for approaching supercritical flows. Severe flow conditions in terms of water depths and bottom pressures could be observed in the dissipation chamber under a supercritical flow regime. The design of this special component must be carried with prudence compared with the subcritical flow regime because failure events as the chamber submergence and the crash of the bottom surface just under the shaft outlet may occur for approaching supercritical flows.

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.

In the last years green roofs are being used as a control measure for urban stormwater management as they retain, detain and slowly release rainwater. Green roofs present many economic, social and environmental benefits. After a general overview of the main features of green roofs, the paper focuses on the main outcomes highlighted by selected literature studies on the hydraulic performance of green roofs. The hydraulic efficiency has been specifically assessed through the definition of two parameters of great interest to design the tailwater drainage system: the peak reduction and the volume reduction indexes.

The hydraulic efficiency of the Helley-Smith sampler is well documented when aligned with the flow field. Sediment sampler’s misalignment with respect to the flow and riverbed can introduce additional uncertainty into the measured bedload transport. The objective of this paper is to use field data collected on the Danube River to identify potential errors in bedload transport measurement resulting from misalignment of the Helley-Smith sampler with the local flow field. The results show that compass and pitch/roll data can be used to determine the relative orientation of the sampler with respect to the mean flow velocity vector and to identify potential outliers in the measured dataset. According to the results, outliers can be identified based on the following criteria for sampler misalignment: deviation from mean flow >25° and pitch/roll angle >10°.

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.