E. Orsi

Experimental study of velocity fields in rectangular shallow reservoirs

Velocity fields in rectangular shallow reservoirs with different length-to-width and expansion ratios were investigated in an experimental study, to evaluate the effect of geometry on the flow field. A wide range of combinations of these two non-dimensional geometric parameters were tested at constant hydraulic conditions. Ultrasound velocity profilers were used to measure the horizontal velocity components across the entire reservoir surface, allowing for the visualization of streamlines and of the instantaneous and average velocities. Five different types of flow patterns were identified, depending on the values of the length-to-width ratio and expansion ratio of the reservoir. Asymmetrical flow patterns were found to develop for certain combinations of these geometric parameters despite the perfect reservoir symmetry. A critical comparison of these new experimental results with those of other works is provided.

Coupling between flow and sediment deposition in rectangular shallow reservoirs

Flow velocity and sedimentation patterns were investigated experimentally and numerically in shallow rectangular reservoirs with different asymmetric locations of the inlet and outlet channels. Velocity fields were measured in the entire reservoir, both for clear water flow and with suspended sediments. Thickness of sediment deposits was mapped in the whole reservoir by means of a laser light method. In one of the studied geometric configurations, injection of suspended sediments led to a complete change in the observed flow field. Experimental results were compared with numerical simulations performed with the depth-averaged flow model WOLF 2D, using a depth-averaged k–ϵ turbulence model. The simulations lead to accurate predictions of the velocity profiles and the change in flow pattern as a result of sediment deposits was successfully reproduced.

Pressure Fluctuation on Structures: Experimental Data Analysis,

Pressure fluctuations have been recorded on the upstream face of a sill with the presence of a hydraulic jump. Pressures have been investigated through 12 different flow configurations and in 9 vertical points on the central axis of the sill. The maximum-recorded value depends both on the sampling frequency and on the experiment duration: that leads to the question of which pressure value has to be considered to design the structures. Different models of structures have been adopted. A comparison with natural frequencies of such structures is carried out, after performing a scale transformation of both pressures and frequencies using the Froude similitude, according to different authors. Natural frequencies of the simpler structures have been computed, while they have been taken from literature for complex structures. Then a spectral analysis has been carried out on the recorded data. Results show that in general there is little difference between the design carried out with the average-recorded and the spectra-analysis pressure values. Pressure fluctuations might produce a stronger excitation when the natural frequency of the structure is abnormally low. Instead, there are no problems when the structure is a baffle or a sill. An experimental formula is also suggested in order to assess design forces on this kind of structure.

Aerobic transformations of organic matters in sewer wastewater, a case study of Milan, Italy

Abstract Today, we know that not only the sewers carry urban wastewater, but also act as chemical and biological reactors, in which both organic and inorganic substances undergo significant transformations. This article describes a study on the western part of the sewer system of the city of Milan. The hydraulic model of the sewer system was coupled with the chemical and dynamic biological model to assess the extent of the degradation of organic matter in the network. The hydraulic and biological models were calibrated with real data obtained at the entrance of the wastewater treatment plant (WWTP) ‘Milan South’ and assuming standard values of daily per capita loads of COD and BOD5.

Study on industrial macropollutants discharges in Milan sewer system

Purpose – The purpose of this paper is to study the transformation of some macropollutants including hydrocarbons, surfactants and metals in Milan west sewer basin. The study is part of a wider research (named SWARMNET and proposed by Politecnico di Milano and Metropolitana Milanese S.p.A and has been classified as fundable by the Ministry of Education, University and Research of Italy), aiming at installing a monitoring system for measurement of accidental discharge of pollutants from industrial activities and real-time protection of the wastewater treatment plant (WWTP) by avoiding dangerous discharges entering the sewers. Good effluent and waste sludge quality allow safe agricultural reuse of both streams. Other objectives include food safety, lower treatment costs and reduction of pollution of soil, surface and groundwater. Design/methodology/approach – The west basin of Milan sewer network, discharging to San Rocco WWTP was considered. Among 700 industries, 16 have been selected for their specific ch...

Instabilities in a Flow-Control Valve

This paper is about some instabilities that have been observed during the testing procedure of a flow-control valve. It was observed that the complete closure of the valve was very often reached after a transient state with oscillating behaviour of its mobile element whose displacement was recorded by means of proximity sensors, facing on opposite sides the moving body of the valve. The outputs have been collected by two signal conditioning devices and sent to a dual channel spectrum analyser. Measurements have also been performed through a servo-accelerometer which has been fixed to the pipe. The influence of the pipe length on the behaviour of the system was studied. The oscillations recorded by the proximity sensors are fairly well reproduced by a series of square waves, with a number of low amplitude, strongly damped, higher frequency contents. During a single test the frequency of the oscillations is not a constant but increases in its central part. The phenomenon cannot be related to one of the natural frequencies of the piping system, that are much higher. The observed frequency depends on the length of the adduction pipe.

Performance Indicators For Water Supply Networks: A Real Case Study

After a brief summary of few possibilities for evaluating a water supply network, the decision for Performance Indicator (PI) is made, giving reasons. Two series of PIS are presented, applied to an existing network and the results are criticised. One of these series is selected for evaluating the rehabilitation works which have to be done on the network to solve problems that have been already noticed. The carried out solutions have been discussed, finding a good agreement between the PI results and the real world ones. Anyhow, further research is required in order to keep into account economic implications for the engineering solutions.