Mauro De Marchis

Three-dimensional numerical simulations on wind- and tide-induced currents

The hydrodynamic circulation in the coastal area of the Augusta Bay (Italy), located in the eastern part of Sicily, is analysed. Due to the heavy contamination generated by the several chemical and petrochemical industries active in the zone, the harbour was declared a Contaminated Site of National Interest. To mitigate the risks connected with the industrial activities located near the harbour, it is important to analyse the hydrodynamic circulation in the coastal area. To perform such analysis, a parallel 3D numerical model is used to solve the Reynolds-averaged momentum and mass balance, employing the k-e turbulence model for the Reynolds stresses. The numerical model is parallelized using the programing technology - Message Passing Interface (MPI) and applying the domain decomposition procedure.The Augusta Bay circulation is mainly due to the relative contribution of the wind force acting over the free surface and the tidal motion through the mouths. Due to the geometric complexity of the domain and the presence of several piers along the coast, a curvilinear boundary-fitted computational grid was used, where cells corresponding to land areas or to wharfs were excluded from the computation. Comparisons between numerical results and field measurements were performed. Three different simulations were performed to selectively isolate the effect of each force, wind and tide, acting in the considered domain. The current in the basin was successfully estimated on the basis of the numerical results, demonstrating the specific role of wind and tidal oscillation in the hydrodynamic circulation inside the harbour. We model the hydrodynamic flow field induced by wind and tide.We examine the water volume exchange between open sea and lagoon.The importance of three dimensional numerical model is investigated.We validate the numerical model in complex environmental domain.We applied an Open source MPI parallel numerical models.

Modelling of E. coli distribution in coastal areas subjected to combined sewer overflows

Rivers, lakes and the sea were the natural receivers of raw urban waste and storm waters for a long time but the low sustainability of such practice, the increase of population and a renewed environmental sensibility increased researcher interest in the analysis and mitigation of the impact of urban waters on receiving water bodies (RWB). In Europe, the integrated modelling of drainage systems and RWB has been promoted as a promising approach for implementing the Water Framework Directive. A particular interest is given to the fate of pathogens and especially of Escherichia coli, in all the cases in which an interaction between population and the RWB is foreseen. The present paper aims to propose an integrated water quality model involving the analysis of several sewer systems (SS) discharging their polluting overflows on the coast in a sensitive marine environment. From a modelling point of view, the proposed application integrated one-dimensional drainage system models with a complex three-dimensional model analysing the propagation in space and time of E. coli in the coastal marine area. The integrated approach was tested in a real case study (the Acicastello bay in Italy) where data were available both for SS model and for RWB propagation model calibration. The analysis shows a good agreement between the model and monitored data. The integrated model was demonstrated to be a valuable tool for investigating the pollutant propagation and to highlight the most impacted areas.

Wind- and tide-induced currents in the Stagnone lagoon (Sicily)

The hydrodynamic circulation is analyzed in the coastal lagoon of Stagnone di Marsala, a natural reserve located in the north-western part of Sicily, using both experimental measurements and numerical simulations. Field measurements of velocities and water levels, carried out using an ultrasound sensor (3D), are used to validate the numerical model. A 3D finite-volume model is used to solve the Reynolds-averaged momentum and mass balance differential equations on a curvilinear structured grid, employing the k–

Concept of a New Pluviometer for Metering Rainfall Erosivity

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Effects of roughness on particle dynamics in turbulent channel flows: a DNS analysis

turbulence model for the Reynolds stresses. The numerical analysis allows to identify the relative contribution of the forces affecting the hydrodynamic circulation inside the lagoon. In the simulations only wind and tide forces are considered, neglecting the effects of water density changes. Two different conditions are considered. In the first both the wind stress over the free-surface and the tidal motion are imposed. In the second the wind action is neglected, to separately analyze the tide-induced circulation. The comparison between the two test cases highlights the fundamental role of the wind on the hydrodynamics of the Stagnone lagoon, producing a strong vertical recirculation pattern that is not observed when the flow is driven by tides only.

Pump as turbine implementation in a dynamic numerical model: cost analysis for energy recovery in water distribution network

The distribution of inertial particles in turbulent flows is highly nonuniform and is governed by the local dynamics of the turbulent structures of the underlying carrier flow field. In wall-bounded flows, wall roughness strongly affects the turbulent flow field, nevertheless its effects on the particle transport in two-phase turbulent flows has been still poorly investigated. The issue is discussed here by addressing direct numerical simulations of a dilute dispersion of heavy particles in a turbulent channel flow, bounded by irregular two-dimensional rough surfaces, in the one-way coupling regime.

Energy Saving in Water Distribution Network through Pump as Turbine Generators: Economic and Environmental Analysis

Rainfall is the main driver of several natural phenomena having a large impact on human activities. Its monitoring is then very important for natural disaster prevention and for the preservation of the environment. One important phenomenon is related to soil displacement due to rainfall impact. The intensity of physical soil degradation, detachment and transport of soil particles by raindrop splash and interrill erosion is largely controlled by rainfall characteristics. There is still a lot of debate as to whichparameter expresses the best rainfall erosivity. Due to the limited data ondrop-size distribution of natural rainfall and the time consuming nature of methods to obtain these data, rain erosivity parameters are commonly obtained from empirical relationships based on rainfall intensity. This paper describes an a new pluviometer able to measure several raindrop variables and assess rainfall kinetic energy at the impact with the ground. It enables one to measure drop size and drop velocity in real time and thus any parameter linked to rainfall erosivity. The pluviometer is based on the combination of optical and electrical sensors and it is based on cheap technologies in order to allow the easy distribution of several monitoring station on the analyzed area. A description of the device and of its sensor is presented in the present paper.

Implementation of pressure reduction valves in a dynamic water distribution numerical model to control the inequality in water supply

LESs are carried out in turbulent channel flows to investigate on the effects of realistic wall roughness on turbulence structures. To this aim irregular 2D and 3D roughness geometries were reproduced superimposing sinusoidal functions. The two configurations, having the same mean roughness height, give rise to different values of the roughness function in the log region. Thus, not only the mean statistical quantities of the roughness affect turbulence but also the element shape plays a fundamental role. The spatial inhomogeneities of the height of the roughness peaks and cavity regions locally destroy the coherent pattern of the flow and strongly modify the elongated turbulence structures typical characteristic of flat surfaces.