1,720,966 research outputs found
Flow regimes on stepped spillways
No full textThe recent improvements of the construction techniques and the particular attention to the environment have renewed the interest in stepped spillways. New experimental investigations have been carried out at the Technical University of Bari, extending the available data on the hydraulic behaviour. The classification of flow regimes has been re-analysed, taking into account the mathematical relationships derived from the technical literature. The study confirms the difficulties in understanding the problem and points out the need for standard experimental procedures, for refining the hydraulic comprehension of the problem
Probabilistic evaluation of flow duration curves in semi-arid basins
No full textThe flow duration curve (FDC) is a relationship between any given discharge value and the percentage of time that this discharge is exceeded, or, in other words, the relationship between magnitude and frequency of streamflow discharges. In this work, according to a probabilistic approach to the FDCs, the percentage of time is considered as a fraction of the year and the FDC is derived linking each discharge to the expected value of the fraction of the year during which such discharge is exceeded. In particular, a method for the evaluation of the FDC with a fixed return period T (T-year FDC) is proposed. The FDC is considered as a function bounded above and below. The upper and lower bounds are assumed equal to the corresponding T-year fractiles of, respectively, the annual maximum and minimum probability distribution of the mean daily discharge. The FDC is then modeled as a logarithmic transformed discharge following a Pearson Type 1 distribution (Beta function). In the case of intermittent flow regimes, which characterize the study cases presented (Puglia, Southern Italy), such approach had to be used in order to produce a satisfactory agreement between abserved and modeled FDCs. The methodology proposed seems promising in the framework of the regional evaluation of the T-year FDCs and when dealing with ungauged river catchments
Air Inlet valve as a protection device against water hammer
No full textThis paper reports the results of a theoretical and experimental investigation to prove the effectiveness of an air inlet valve as a protection device against water hammer in delivery mains of pumping stations where, upon sudden stopping of pumps, cavitation conditions may occur close to the station. Theoretical research has proved that the valve, though simple and of very low cost, can considerably reduce pressure rise resulting from unsteady flow and the first experimental results fully confirm the forecasts of the theoretical model
Dissipation efficiency of stepped spillways
No full textThis study on hydraulic structures used for dissipating energy downstream from dams offers interesting suggestions for applied research aiming to improve hydraulic efficiency and constrain construction costs without neglecting environmental aspects.
Extensive experimental tests have been carried out in the laboratory of Dipartimento di Ingegneria delle Acque at Bari Polytechnic. Three different geometric configurations were analysed, each characterised by a constant step number and step height, but with different chute slopes. The experimental study focused on two aspects of physical interpretation of the phenomenon: the first concerned with the definition of the flow conditions, as defined by the device geometry and the flow dynamics, and the second with the evaluation of the rate of energy dissipation. The results seem to confirm the notorious difficulties in understanding the problem, even if the experimental data show the same trend as those obtained by other researchers
Preventive Approach to Reduce Risk Caused by Failure of a Rainwater Drainage System: The Case Study of Corato (Southern Italy)
No full textThe presence of ancient underground urban drainage system in cities entails serious risks to public safety. Often, the presence of these hydraulic structures is forgotten and their projects missing in public offices. In this work the critical issues of the old urban drainage system of Corato, a city in the south of Italy, are described. In particular, through a targeted identification, acquisition and spatialization of key variables, and subsequent processing in a GIS software, a method for risk assessment has been provided. The choice of key variables was carried out through visual inspections and acquisition of “historical criti-calities” of the urban drainage system. Finally, this paper presents a methodology, calibrated on the old city of Corato, to evaluate the risk caused by the presence of this hydraulic infrastructure, in order to help technicians to define the correct order of operations to be carried out
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