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  • 1
    Publication Date: 2018
    Description: This paper proposes a methodological approach to the re-use of reservoir sediments for coastal nourishment. The proposed approach represents a point of convergence between water and sediment management, coastal protection from erosion and the re-use of sediments dredged from reservoirs. In particular, this study indicates a general protocol of actions and a reference legislative scenario for the use of sediment from reservoirs for beach nourishment as an alternative to sediment from sea caves or land caves. Quantitative characterization of reservoir sediments and their qualitative characterization are the fundamental steps to define the compatibility between reservoir sediment and beach sand. The study was applied to a real case of Southern Italy known as the Guardialfiera Reservoir.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 2
    Publication Date: 2014-03-11
    Description: ABSTRACT A large-time analytical solution is proposed for the spatial variance and coefficient of variation of the depth-averaged concentration due to instantaneous, cross-sectionally uniform solute sources in pseudo-rectangular open channel flows. The mathematical approach is based on the use of the Green functions and on the Fourier decomposition of the depth-averaged velocities, coupled with the method of the images. The variance spatial trend is characterized by a minimum at the center of the mass and two mobile, decaying symmetrical peaks which, at very large times, are located at the inflexion points of the average Gaussian distribution. The coefficient of variation, which provides an estimate of the expected percentage deviation of the depth-averaged point concentrations about the section-average, exhibits a minimum at the center which decays like t -1 and only depends on the river diffusive time-scale. The defect of cross-sectional mixing quickly increases with the distance from the center, and almost linearly at large times. Accurate numerical Lagrangian simulations were performed to validate the analytical results in pre-asymptotic and asymptotic conditions, referring to a particularly representative sample case for which cross-sectional depth and velocity measurements were known from a field survey. In addition, in order to discuss the practical usefulness of computing large-time concentration spatial moments in river flows, and resorting to directly measured input data, the order of magnitude of section-averaged concentrations and corresponding coefficients of variation was estimated in field conditions and for hypothetical contamination scenarios, considering a unit normalized mass impulsively injected across the transverse section of 81 U.S. rivers.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2012-08-16
    Description: This paper shows how an exact analytical solution for the transient-state spatial moments of the cross-sectional average tracer concentration in large open channel flows can be derived from the depth-averaged advection-diffusion equation resorting to the method of Green's functions, without any simplifying assumption about the regularity of the actual concentration field, the smallness of the fluctuations, or the large space-time scale of variation of the average concentration gradient (justifying the a priori localization of the problem), which were the basis of the classic Taylor dispersion theory. The results reveal that in agreement with the findings by Aris (1956) and later by others for flows within a conduit, there are an initial centroid displacement and a variance deficit dependent on the specific position and dimension of the initial injection. The second central moment asymptotically tends to the linearly increasing function predictable on the basis of Taylor's classic theory, and the skewness, which is constantly zero for the cross-sectionally uniform injection, in the case of nonuniform initial distributions tends to slowly vanish after having reached a maximum. Thus, the persistent asymmetry exhibited by the field concentration data, as well as the retardations and the accelerations in the peak trajectory, can be justified without making any a priori assumption about the physical mechanism underlying their appearance, like transient storage phenomena, just by rigorously solving the governing equation for the cross-sectional average concentration in the presence of nonuniform, asymmetrically located solute injections.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Publication Date: 2017-10-01
    Description: Water, Vol. 9, Pages 751: An Analytical Model of Fickian and Non-Fickian Dispersion in Evolving-Scale Log-Conductivity Distributions Water doi: 10.3390/w9100751 Authors: Marilena Pannone The characteristics of solute transport within log-conductivity fields represented by power-law semi-variograms are investigated by an analytical Lagrangian approach that accounts for the automatic frequency cut-off induced by the initial contaminant plume size. The transport process anomaly is critically controlled by the magnitude of the Péclet number. Interestingly enough, unlike the case of fast-decaying correlation functions (i.e., exponential or Gaussian), the presence of intensive transverse diffusion acts as an antagonist mechanism in the process of Fickian regime achievement. On the other hand, for markedly advective conditions and finite initial plume size, even the ergodic longitudinal dispersion coefficient turns out to be asymptotically constant, and the corresponding expected concentration distribution can therefore be obtained by conventional mathematical methods.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 5
    Publication Date: 2018-04-14
    Description: Water, Vol. 10, Pages 478: Longitudinal Dispersion in Straight Open Channels: Anomalous Breakthrough Curves and First-Order Analytical Solution for the Depth-Averaged Concentration Water doi: 10.3390/w10040478 Authors: Marilena Pannone Domenica Mirauda Annamaria De Vincenzo Bruno Molino A first-order analytical solution is proposed for the actual depth-averaged concentration of tracers in shallow river flows in the presence of large Peclet numbers (defined as the ratio of section-averaged velocity times channel width to turbulent diffusion coefficient). The solution shows how complete transverse mixing is never achieved due to the typical shape of the velocity and diffusion coefficient profile, which alternatively tend—depending on the downstream location of the cross-section—to concentrate the mass at the centre or at the boundaries of the cross-section itself. The first-order analytical solution proves to be consistent with the results of Lagrangian numerical simulations based on real-field input data, which show how the solute mass breakthrough curves always exhibit anomalous behaviour and a considerable and persistent delay when compared with those that are analytically obtained by assuming a truly one-dimensional process.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 6
    Publication Date: 2018-03-26
    Description: Water, Vol. 10, Pages 378: Simplified Entropic Model for the Evaluation of Suspended Load Concentration Water doi: 10.3390/w10040378 Authors: Domenica Mirauda Annamaria De Vincenzo Marilena Pannone Suspended sediment concentration is a key aspect in the forecasting of river evolution dynamics, as well as in water quality assessment, evaluation of reservoir impacts, and management of water resources. The estimation of suspended load often relies on empirical models, of which efficiency is limited by their analytic structure or by the need for calibration parameters. The present work deals with a simplified fully-analytical formulation of the so-called entropic model in order to reproduce the vertical distribution of sediment concentration. The simplification consists in the leading order expansion of the generalized spatial coordinate of the entropic velocity profile that, strictly speaking, applies to the near-bed region, but that provides acceptable results also near the free surface. The proposed closed-form solution, which highlights the interplay among channel morphology, stream power, secondary flows, and suspended transport features, allows reducing the needed number of field measurements and, therefore, the time of field activities. Its accuracy and robustness were successfully tested based on the comparison with laboratory data reported in literature.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 7
    Publication Date: 2013-11-11
    Description: Present work is aimed at the derivation of a simply usable equation for the total flow resistance associated with river bedforms, by a unifying approach allowing for bypassing some of the limiting restrictions usually adopted in similar types of studies. Specifically, we focused on the effect induced by the out-of-phase free surface undulations appearing in presence of sand dunes. The proposed expression, obtained by combining the balance of momentum referred to the control volume whose longitudinal dimension coincides with the dune wavelength and the energy balance integrated between its extreme sections, was tested by comparison with some laboratory experimental measurements available in the literature and referred to steady flow past fixed, variably rough bedforms. In terms of shear stress or friction factor, the proposed theory provides estimates in good agreement with the real data, especially if evaluated against the performances provided by other classical similar approaches. Moreover, when analyzed in terms of hydrodynamic dispersive properties as a function of the skin roughness on the basis of a previously derived analytical solution, the dune-covered beds seem to behave like meandering channels, responsible for a globally enhanced fluid particles longitudinal spreading, with a relatively reduced effect in the presence of less pronounced riverbed modelling.
    Print ISSN: 1110-757X
    Electronic ISSN: 1687-0042
    Topics: Mathematics
    Published by Hindawi
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  • 8
    Publication Date: 2018-01-18
    Description: Entropy, Vol. 20, Pages 69: An Entropic Model for the Assessment of Streamwise Velocity Dip in Wide Open Channels Entropy doi: 10.3390/e20010069 Authors: Domenica Mirauda Marilena Pannone Annamaria De Vincenzo The three-dimensional structure of river flow and the presence of secondary currents, mainly near walls, often cause the maximum cross-sectional velocity to occur below the free surface, which is known as the “dip” phenomenon. The present study proposes a theoretical model derived from the entropy theory to predict the velocity dip position along with the corresponding velocity value. Field data, collected at three ungauged sections located along the Alzette river in the Grand Duchy of Luxembourg and at three gauged sections located along three large rivers in Basilicata (southern Italy), were used to test its validity. The results show that the model is in good agreement with the experimental measurements and, when compared with other models documented in the literature, yields the least percentage error.
    Electronic ISSN: 1099-4300
    Topics: Chemistry and Pharmacology , Physics
    Published by MDPI Publishing
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  • 9
    Publication Date: 2014-12-23
    Print ISSN: 1436-3240
    Electronic ISSN: 1436-3259
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Published by Springer
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  • 10
    Publication Date: 2004-09-01
    Print ISSN: 0169-3913
    Electronic ISSN: 1573-1634
    Topics: Geosciences , Technology
    Published by Springer
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