1,721,359 research outputs found
Parametri di controllo per la gestione delle reti di distribuzione idrica: una proposta metodologica
No full textImpact of aperture variability on flow and transport properties of a single fracture
No full textA study of flow and transport in a variable aperture fracture is presented within a stochastic approach. The log-aperture is modeled as a stationary and correlated random space function, and a Monte Carlo procedure is adopted to assess the influence of aperture variability on hydraulic and transport parameters. The fracture hydraulic aperture and longitudinal dispersivity are derived as functions of log-aperture variance and correlation scale, and the numerical results are compared to an existing analytical first-order theory, valid for an infinite fracture
Disponibilità idrica dell'acquifero freatico costiero della Regione Emilia-Romagna e analisi dei fattori di rischio
No full textDrainage of viscous gravity currents from the edge of a porous or fractured domain with variable properties
No full textTecniche di riduzione dei modelli ed analisi di sensitività globale per la calibrazione di modelli di trasporto in mezzi porosi
No full textGROUND HEAT TRANSFER FROM A DRAINAGE TRENCH
No full textThe energy performance of a shallow ground heat exchanger constituted by a drainage trench is studied. The 12 x 2 £ 0.5 m trench is dug in shallow soil and filled with gravel; two vertical tubes at the opposite ends of the trench act as inlet and outlet of the working fluid, which flows into the closed loop of a system for heating/cooling of a residential building. Groundwater flow and heat transfer in the porous domain surrounding the trench are analyzed via a 3D numerical model, performing a 3-year simulation. The thermal impact of the exchanger is analyzed considering different boundary conditions (first/second kind), given as daily time series at the ground surface. The trench shows a good specific energy production and a significant capacity of smoothing thermal waves, and can be considered a convenient alternative in shallow applications
Monitoring Soil Water Content via Wireless Underground Communication Networks: the Impact of Uncertainty in Soil Textural Parameters
No full textPrediction of effective Forchheimer coefficient for one- and two-dimensional flows in heterogeneous geologic media
No full textNon-linear flow in porous media, governed by the Forchheimer equation, interacts with domain heterogeneity when geologic media are involved. In Forchheimer’s law, the pressure gradient is equal to the sum of a linear term in the flow rate (akin to Darcy’s law) and a quadratic term proportional to the second power of the flow rate; the latter coefficient of proportionality is the Forchheimer coefficient. As most experimental values of the Forchheimer coefficient have been derived at the laboratory scale, it is necessary to investigate its upscaling at the field scale in heterogeneous aquifers. Consider a uniform pressure gradient flow in a spatially heterogeneous, perfectly layered permeability random field with a given probability density distribution. The local Forchheimer coefficient β is related to the local permeability k value via an empirical inverse power-law correlation reading β=a/k^c, having an experimental basis and widely adopted in the literature, where a is a constant and c an exponent in the range 0-2. Under the ergodic hypothesis, the effective permeability and Forchheimer coefficient can be derived in two limit cases under one-dimensional flow: (i) a serial arrangement, with flow crossing layers having different permeability, and (ii) a parallel arrangement, with parallel flows within layers of different permeability. Results obtained for the effective permeability recover the lower and upper bounds valid for 1-D Darcy flow in heterogeneous media, i.e., harmonic and arithmetic mean of the permeability distribution for the series and parallel arrangement, respectively. The expressions obtained for the effective Forchheimer coefficient generalize previous formulations derived for a discrete parameter variation. In particular, an expression for the effective Forchheimer coefficient is derived in closed form for the serial arrangement, while numerical values are derived for the parallel arrangement. The impact of spatial variability is assessed adopting a lognormal permeability distribution. The effective Forchheimer coefficient βeff increases with the permeability coefficient of variation for both arrangements; for the serial case, it also increases with the exponent c; the opposite is true for the parallel arrangement. One-dimensional results obtained for serial and parallel arrangements provide lower and upper bounds for evaluating the effective Forchheimer coefficient in 2-D flows. Results for 2-D isotropic media are derived heuristically via geometric averaging of the 1-D expressions
Field monitoring of a HGHE Flat Panel
No full textIn this paper we describe an experimental setting devised to investigate the behaviour of a novel type of horizontal ground heat exchanger (HGHE), consisting of a flat panel positioned horizontally and edgeways at shallow depth. At the experimental site, two flat panel HGHE are coupled with an hydraulic closed loop in which warm/cool water is circulated to simulate cooling/heating mode. Seveny-seven digital thermal sensors are installed along eleven different lines to monitor the soil temperature distribution during a dynamic test. A 15-days measurement campaign was performed during the spring of 2011, allowing to reconstruct temperature profiles within the soil and estimate an energetic performance of 60-140 W/m. These results were validated by comparing the temperature profiles with an approximate analytical solution, and performing an energy balance. The latter yielded values of heat exchanged at the soil surface in the order of 7 W/m2, comparing favorably with literature results
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