In this paper, the dynamics of pressure peaks in a single viscoelastic pipe with a leak (leaky pi... more In this paper, the dynamics of pressure peaks in a single viscoelastic pipe with a leak (leaky pipe) is examined by means of laboratory and numerical experiments. Experimental tests are the necessary premise to a reliable calibration of a 1-D numerical model which allows to investigate in detail a wide range of both geometrical and flow conditions by taking into account not only the leak but also energy dissipation due to viscoelasticity and unsteady friction. In the analysis, the decay of the maximum values of the pressure is assumed as a representative characteristic of the dynamics of the examined transients in the long term. The numerical campaign has pointed out the characteristic quantities affecting the investigated phenomenon as well as the structure of the pressure decay law.
Delineation of Wellhead Protection Areas in the Umbria Region. 1. A simplified Procedure
Procedia Environmental Sciences, 2015
ABSTRACT In the Umbria region a large number of small groundwater resources is exploited to suppl... more ABSTRACT In the Umbria region a large number of small groundwater resources is exploited to supply drinkable water to customers. More than 400 of the wells and springs managed by Umbra Acque S.p.A., one of the three Umbrian managers, draw less than 10 l/s and about 240 of them supply less than 1 l/s. The national and the regional regulations do not differentiate in the protection area delineation guidelines between large and small resources, although different degree of knowledge about the aquifer and economical budget for the operation can be expected. For these reasons, here we propose a procedure for delineating the wellhead protection areas, based on simplified models and techniques, particularly suited for the Umbria region.
The effect of demand uncertainty in water distribution systems (WDS) is a key problem, especially... more The effect of demand uncertainty in water distribution systems (WDS) is a key problem, especially for water company assets. The presence or absence of demands, their number, size, and locations significantly affect the functioning of a pipe system and its response to a transient. The validity and the effectiveness of the Lagrangian model is firstly investigated by means of a comparison with a Method of Characteristics model in frictionless systems. Demands locations are stochastically varied to assess the impact of the uncertainty of the geometry of the network on transient propagation. A normal distribution has been used to model the uncertainty of demand location.
Variable speed pumps (VSPs) are widely used in water distribution systems (WDSs). They can increa... more Variable speed pumps (VSPs) are widely used in water distribution systems (WDSs). They can increase the efficiency of the system and reduce the energy consumptions, when the functioning conditions move away from those used for the design. Affinity laws allow to model the characteristic curve of VSPs, in terms of dimensionless flow, head and power. Efficiency of the VSPs can also be predicted, although the effects of the variation in the rotation speed can be questioned. In this paper, the experimental data acquired by TeaAcque at the Mantova Casale pumping station are interpreted by means of the dimensionless equations derived by the affinity laws. The measured "wire to water" efficiency of the system is compared to the theoretical one.
Pump speed, input power, pressure and discharge data are analyzed for evaluating functioning cond... more Pump speed, input power, pressure and discharge data are analyzed for evaluating functioning conditions of Casale pumping station in Mantova, Italy, managed by TeaAcque. A model based on the affinity laws is used to simulate the behavior of the installed variable speed pumps. Quadratic and cubic polynomial curves are used to fit the pump data given by the affinity laws. Such curves allow predicting the efficiency when the functioning conditions change. The relationship between the rotation speed and the efficiency is also derived.
This paper is an extension of a previous paper , in which a transient test procedure is discussed... more This paper is an extension of a previous paper , in which a transient test procedure is discussed on the basis of field tests executed in the steel water distribution system (WDS) of Novara in the northwestern part of Milan, Italy, managed by Metropolitana Milanese S.p.A. In this paper, tests are repeated by modifying test conditions and improving the successive analysis. In particular, since the pump switching off is slow and unmodifiable, some of the main connections reached by the pressure waves before the end of the maneuver have been closed during the test. In such a way, the interference between the maneuver and the system has been reduced. The wavelet transform (WT) is used to evaluate the pressure wave speed of the supply pipe. In order to estimate the other pressure wave speeds, an optimization procedure is carried out. First of all, a skeletonization of the network is operated and then a Lagrangian model (LM) and a Genetic Algorithm (GA) are coupled considering such a skeletonized system. By minimizing the difference between numerical and experimental pressure signals, the optimal values of the pressure wave speeds are obtained. Finally the procedure is checked by comparing the experimental pressure signal and the one obtained by LM considering the optimal values of the pressure wave speeds and the actual network.
Due to the experimental evidence, in the last decades the leak law, i.e. the relationship between... more Due to the experimental evidence, in the last decades the leak law, i.e. the relationship between the system functioning conditions and the leakage, has been seriously questioned. Some corrections have been introduced in the classical orifice equation to take into account all the relevant parameters it depends on (e.g. leak shape, pipe material and thickness, ...). Even if a perfect law is derived for a single leak in a pipe still an open issue remains, that is the use of the same leak law for a whole network or district. In terms of practical applications, the link from a single leak outflow to a system leakage is relevant since it allows the transfer of the results from laboratory experiments to real systems -from the local scale of a single leak to the global scale of a district with several different leaks. In this paper the effect of the spatial variation of the leak law parameters at the local scale on leak law determination at a global scale are considered. Conclusions on the possible comparison between the laws at the two scales are given.
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Papers by C. Capponi