CONFRONTO TRA UN MODELLO DINAMICO ED UNO STAZIONARIO NELLA VALUTAZIONE DELLE PERDITE REALI ED APPARENTI DI UNA RETE DI DISTRIBUZIONE

Nel presente articolo è stato applicato un modello dinamico di simulazione idraulica delle reti di distribuzione per la valutazione delle perdite idriche reali ed apparenti. Sono stati sviluppati uno modello di domanda al nodo che simula i serbatoi privati ed un modulo per la stima delle perdite apparenti. Le perdite reali sono state modellate attraverso una relazione generale che esprime la portata effluente dalla perdita come una funzione della pressione. I risultati ottenuti sono stati confrontati con le stime modellistiche basate su di un approccio stazionario.

A model of the filling process of an intermittent distribution network

In many countries, private tanks are acquired by users to reduce their vulnerability to intermittent supply. The presence of these local reservoirs modifies the user demand pattern and usually increases user water demand at the beginning of the service period depending on the tank filling process. This practice is thus responsible for the inequality that occurs among users: those located in advantaged positions of the network are able to obtain water resources soon after the service period begins, while disadvantaged users have to wait much longer, after the network is full. This dynamic process requires the development of ad hoc models in order to obtain reliable results. This paper discus…

Uno studio numerico del moto turbolento in un canale con parete scabra

A coupled Finite Volume–Smoothed Particle Hydrodynamics method for incompressible flows

Abstract An hybrid approach is proposed which allows to combine Finite Volume Method (FVM) and Smoothed Particle Hydrodynamics (SPH). The method is based on the partitioning of the computational domain into a portion discretized with a structured grid of hexahedral elements (the FVM-domain ) and a portion filled with Lagrangian particles (the SPH-domain ), separated by an interface made of triangular elements. A smooth transition between the solutions in the FVM and SPH regions is guaranteed by the introduction of a layer of grid cells in the SPH-domain and of a band of virtual particles in the FVM one (both neighboring the interface), on which the hydrodynamic variables are obtained throug…

Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: Advances Toward a Universal Roughness Correlation

The downward shift of the mean velocity profile in the logarithmic region, known as roughness function, $$\Delta U^+$$ , is the major macroscopic effect of roughness in wall bounded flows. This speed decrease, which is strictly linked to the friction Reynolds number and the geometrical properties which define the roughness pattern such as roughness height, density, shape parameters, has been deeply investigated in the past decades. Among the geometrical parameters, the effective slope (ES) seems to be suitable to estimate the roughness function at fixed friction Reynolds number, Re $$_{\tau }$$ . In the present work, the effects of several geometrical parameters on the roughness function, i…

Effetti della formazione dello strato Limite Interno in atmosfera sulle circolazioni indotte dal vento in corpi idrici naturali

Effect of the junction angle on turbulent flow at a hydraulic confluence

Despite the existing knowledge concerning the hydrodynamic processes at river junctions, there is still a lack of information regarding the particular case of low width and discharge ratios, which are the typical conditions of mountain river confluences. Aiming at filling this gap, laboratory and numerical experiments were conducted, comparing the results with literature findings. Ten different confluences from 45 ∘ to 90 ∘ were simulated to study the effects of the junction angle on the flow structure, using a numerical code that solves the 3D Reynolds Averaged Navier-Stokes (RANS) equations with the k- ϵ turbulence closure model. The results showed that the higher the junction angle, the …

A multi-domain approach for smoothed particle hydrodynamics simulations of highly complex flows

Abstract An efficient and accurate method is proposed to solve the incompressible flow momentum and continuity equations in computational domains partitioned into subdomains in the framework of the smoothed particle hydrodynamics method. The procedure does not require any overlap of the subdomains, which would result in the increase of the computational effort. Perfectly matching solutions are obtained at the surfaces separating neighboring blocks. The block interfaces can be both planar and curved surfaces allowing to easily decompose even geometrically complex domains. The smoothing length of the kernel function is maintained constant in each subdomain, while changing between blocks where…

The effect of geometrical parameters on the discharge capacity of meandering compound channels

A number of methods and formulae has been proposed in the literature to estimate the discharge capacity of compound channels. When the main channel has a meandering pattern, a reduction in the conveyance capacity for a given stage is observed, which is due to the energy dissipations caused by the development of strong secondary currents and to the decrease of the main channel bed slope with respect to the valley bed slope. The discharges in meandering compound channels are usually assessed applying, with some adjustments, the same methods used in the straight compound channels. Specifically, the sinuosity of the main channel is frequently introduced to account for its meandering pattern, al…

Analysis of the Impact of the intermittent distribution by modelling the network filling processes.

Balance equation of generalised sub-grid scale (SGS) turbulent kinetic energy in a new tensorial dynamic mixed SGS model

A new dynamic model is proposed in which the eddy viscosity is defined as a symmetric second rank tensor, proportional to the product of a turbulent length scale with an ellipsoid of turbulent velocity scales. The employed definition of the eddy viscosity allows to remove the local balance assumption of the SGS turbulent kinetic energy formulated in all the dynamic Smagorinsky-type SGS models. Furthermore, because of the tensorial structure of the eddy viscosity the alignment assumption between the principal axes of the SGS turbulent stress tensor and the resolved strain-rate tensor is equally removed, an assumption which is employed in the scalar eddy viscosity SGS models. The proposed mod…

Fluid-structure interaction approach with smoothed particle hydrodynamics and particle-spring systems

This paper presents a novel three-dimensional fluid-structure interaction (FSI) approach, where the meshless smoothed particle hydrodynamics (SPH) method is used to simulate the motion of incompressible fluid flows, whilst structures are represented by a simplified approach based on particle-spring systems. The proposed FSI technique allows to use independent spatial-temporal resolutions for the fluid and structural computational domains. The particle-spring elastic constants are calibrated and relationships with the mechanical material properties, Young's modulus and Poisson's ratio, are determined. Fluid and structure computational domains are separated by interfaces made of triangular el…

L'esperienza maturata in Sicilia nel campo della dissalazione

Energy Recovery in Water Distribution Networks. Implementation of Pumps as Turbine in a Dynamic Numerical Model

In complex networks characterized by the presence of private tanks, water managers usually apply intermittent distribution, thus reducing the water volumes supplied to the users, or use Pressure Reduction Valves (PRV) for controlling pressure in the network. The application of Pump As Turbines (PATs) appears as an alternative and sustainable solution to either control network pressure as well as to produce energy. In the present paper, the hydrodynamic model, already presented by De Marchis et al. (2011) was further developed introducing the dynamic analysis of PATs. The model was applied to a district of Palermo network (Italy) characterized by intermittent distribution and by inequities a…

The effect of the slope of irregularly distributed roughness elements on turbulent wall-bounded flows

Wall roughness produces a downward shift of the mean streamwise velocity profile in the log region, known as the roughness function. The dependence of the roughness function on the height and arrangement of roughness elements has been confirmed in several studies where regular rough walls were analysed; less attention has been paid to non-regular rough walls. Here, a numerical analysis of turbulent flows over irregularly shaped rough walls is performed, clearly identifying the importance of a parameter, called the effective slope (ES) of the wall corrugations, in characterizing the geometry of non-smooth irregular walls. The effective slope proves to be one of the fundamental geometric para…

Three-dimensional numerical analysis of turbulent wind-induced flows in the Lake Balaton (Hungary)

A dynamic subgrid-scale tensorial eddy viscosity model

In the Navier-Stokes equations the removal of the turbulent fluctuating velocities with a frequency above a certain fixed threshold, employed in the Large Eddy Simulation (LES), causes the appearance of a turbulent stress tensor that requires a number of closure assumptions. In this paper insufficiencies are demonstrated for those closure models which are based on a scalar eddy viscosity coefficient. A new model, based on a tensorial eddy viscosity, is therefore proposed; it employs the Germano identity [1] and allows dynamical evaluation of the single required input coefficient. The tensorial expression for the eddy viscosity is deduced by removing the widely used scalar assumption of the …

Un modello per il riempimento delle reti di distribuzione idrica in presenza di turnazione del servizio

Interpreting and modelling field data for wastewater dispersion into sea through dimensional analysis

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– $${\varepsilon}$$ turbulence model for the Reynolds stresses. The numerical analysis allows to identify the relative contribution of the forces affecting the hydrodynamic circulation …

ESTENSIONE DELLA TECNICA DI ‘IMMERSED-BOUNDARY’ A GRIGLIE DI CALCOLO IN COORDINATE CURVILINEE

Le tecnologie utilizzate negli impianti di dissalazione

Effects of irregular two-dimensional and three-dimensional surface roughness in turbulent channel flows

Abstract Wall-resolved Large Eddy Simulation of fully developed turbulent channel flows over two different rough surfaces is performed to investigate on the effects of irregular 2D and 3D roughness on the turbulence. The two geometries are obtained through the superimposition of sinusoidal functions having random amplitudes and different wave lengths. In the 2D configuration the irregular shape in the longitudinal direction is replicated in the transverse one, while in the 3D case the sinusoidal functions are generated both in streamwise and spanwise directions. Both channel walls are roughened in such a way as to obtain surfaces with statistically equivalent roughness height, but different…

Un modello di simulazione dei fenomenici riempimento di reti di distribuizione idrica

UN MODELLO NUMERICO NON STAZIONARIO PER LO STUDIO DEI FENOMENI TRANSITORI DURANTE IL RIEMPIMENTO DELLE RETI DI DISTRIBUZIONE IDRICA: ANALISI DELLA RESISTENZA IN MOTO NON UNIFORME

Particle-Laden Turbulent Channel Flow with Wall-Roughness

Turbulent flows transporting a dispersed-phase are found in many environmental applications and engineering devices. Particle-laden flows are characterized by several peculiar phenomenologies such as preferential particle concentration and turbulence modulation of the carrier-phase due to the presence of the inertial particles [1].

Acqua dolce dal mare – L’esperienza di un trentennio di dissalazione in Sicilia

Simulazione numerica tridimensionale dei campi di moto indotti dal vento

3D Numerical Simulationof Curved Open Channel Flows

Idraulica Volume Secondo

Acqua dolce dal mare. L’esperienza di un trentennio di dissalazione in Sicilia

Wind- and tide-induce currents in the Stagnone Lagoon (Sicily)

Embedding Monitoring Systems for Cured-In-Place Pipes

This paper proposes a non-intrusive electrical measurement system for monitoring some relevant parameters in pipeline systems. Temperature and flow-rate are monitored, using MEMS sensors. The flow-rate is evaluated by measuring pipe vibration, with a 3 axis accelerometer, induced by turbulence when fluid flows within the tube. The sensors are embedded, during the curing process of the cured-in-place pipes, in the pipes wall making the system suitable to be installed in renewed or new pipeline. The first experimental results show that it may be possible to obtain, at low-cost, a fully monitored distribution network.

Sensitivity of wind-induced shallow lake circulation patterns on changes in lakeshore land use

Numerical simulation of internal boundary-layer development and comparison with atmospheric data

A finite-volume numerical model is employed to investigate the adaptation of the atmospheric boundary layer to a change in the underlying surface roughness, such as that existing in the transition from land to the free surface of a water body. Numerical results are validated by comparison with neutral stratification atmospheric data and compared with the internal boundary-layer (IBL) heights computed using a number of existing empirical formulae. The numerical analysis allows an extension of the fetch range in which the existing formulae, calibrated only by comparison with short fetch data, may be applied. An argument is offered that the spatial variability of the water surface roughness sh…

Analysis of the impact of intermittent distribution by modelling the network-filling process

In many countries, users acquire private tanks to reduce their vulnerability to water scarcity. In such conditions, water managers often apply intermittent distribution in order to reduce the water volumes supplied to the users. This practice modifies the hydraulic behaviour of the network and determines competition among users that need to collect enough water resource for their uses. Intermittent distribution is thus responsible for the inequality that can occur among users: those located in advantaged positions of the network are able to obtain water resources soon after the service period begins, while others have to wait much longer, after the network is full. This paper analyses the i…

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

AbstractDeposition and resuspension mechanisms in particle-laden turbulent flows are dominated by the coherent structures arising in the wall region. These turbulent structures, which control the turbulent regeneration cycles, are affected by the roughness of the wall. The particle-laden turbulent flow in a channel bounded by irregular two-dimensional rough surfaces is analysed. The behaviour of dilute dispersions of heavy particles is analysed using direct numerical simulations (DNS) to calculate the three-dimensional turbulent flow and Lagrangian tracking to describe the turbophoretic effect associated with two-phase turbulent flows in a complex wall-bounded domain. Turbophoresis is inves…

Il progetto Mentori per la Didattica dell’Università degli Studi di Palermo: l’estensione del numero dei partecipanti, la figura del Mentore Senior e le esperienze di innovazione didattica

L’esperienza del Progetto Mentore (PM) nasce nel 2013 dalla percezione, da parte di diversi docenti dell’Ateneo di Palermo, che l’Accademia italiana stesse abbandonando a sé stessa la funzione didattica, confidando di fatto nelle capacità di ognuno di organizzarsi, aggiornarsi e valutarsi (Felisatti, Scialdone, Cannarozzo, & Pennisi, 2019; Caradonna, Morale, Pace, Scargiali, Scialdone, & Auteri, 2020). Tale impressione era tra le altre cose basata sul fatto che nessuno dei sistemi di valutazione dei docenti universitari (il processo di abilitazione scientifica nazionale, ma anche la stessa valutazione della qualità dei corsi di studio) mettesse enfasi sulla necessità da parte del do…

Experimental and Numerical Study on the Flow Field and Friction Factor in a Pressurized Corrugated Pipe

An experimental campaign including measurement of pressure drops and velocity profiles was conducted on the pressurized flow in a commercial corrugated pipe. The results show that the empirical graphs suggested by Morris in the fifties may produce inaccurate assessments of the friction factor, in particular, for low Reynolds numbers. The experimental data was then reproduced by means of a numerical model with the large eddy simulation (LES) technique. The friction factor behavior for low and relatively high Reynolds numbers was thus investigated. The numerical simulations were in good agreement with the experimental results, showing the LES suitability to predict the effect of the pipe wall…

INFLUENZA DELLA PENDENZA MEDIA DELLE CORRUGAZIONI DI UNA PARETE SCABRA SUL CAMPO DI MOTO TURBOLENTO

Solid sediment transport in turbulent channel flow over irregular rough boundaries

Abstract The presence of a loading of dispersed particles in a turbulent flow affects the dynamics of the carrier flow field which, in turn, drives grains movement. The focus of the paper is on the analysis of the coupling effects between near-bed turbulence structures and the dynamics of dispersed suspended solid particles in wall-bounded turbulent multiphase flows. We consider turbulent horizontal channel flows bounded by rough boundaries. The friction Reynolds number of the unladen flow is R e τ = 180 and the dispersed phase spans one order of magnitude of particle diameter. To analyze sedimentation and suspended phase transport, we adopt concepts and modeling ideas derived from the Eule…

Analisi dei fenomeni di riempimento di reti di distribuzione idrica con il metodo delle caratteristiche.

I sistemi di distribuzione della risorsa idrica possono essere classificati, in funzione del tipo di erogazione, in due principali categorie: erogazione “alla domanda” ed erogazione “turnata”. Sebbene il metodo di erogazione alla domanda garantisca la migliore e più efficiente gestione della rete idrica, gli enti gestori si trovano spesso costretti ad adottare sistemi di erogazione di tipo turnato. Tale tipo di distribuzione, caratterizzata da transitori di riempimento e vuotamento della rete, presenta diverse criticità principalmente connesse alla sperequazione tra gli utenti nell’accesso alla risorsa idrica e all’insorgere di sovrapressioni e depressioni durante i transitori. Nella memori…

Field and numerical study of river confluence flow structures

River hydrodynamics Turbulent open channel flow and transport phenomena

A distributed-memory MPI parallelization scheme for multi-domain incompressible SPH

A parallel scheme for a multi-domain truly incompressible smoothed particle hydrodynamics (SPH) approach is presented. The proposed method is developed for distributed-memory architectures through the Message Passing Interface (MPI) paradigm as communication between partitions. The proposal aims to overcome one of the main drawbacks of the SPH method, which is the high computational cost with respect to mesh-based methods, by coupling a multi-resolution approach with parallel computing techniques. The multi-domain approach aims to employ different resolutions by subdividing the computational domain into non-overlapping blocks separated by block interfaces. The particles belonging to differe…

The impacts of the ALE and hydrostatic-pressure approaches on the energy budget of unsteady free-surface flows

Abstract This paper focuses on the energy budget in the calculation of unsteady free-surface flows on moving grids with and without using the ‘arbitrary Lagrangian–Eulerian’ (ALE) formulation or hydrostatic-pressure assumption. The numerical tool is an in-house general-purpose solver for the unsteady, incompressible and homogeneous Navier–Stokes equations in a Cartesian domain. An explicit fractional-step method and co-located finite-volume method are used for the second-order accurate integrations in time and space. The test cases are nonlinear and linear irrotational standing waves, which allow to characterise the impacts of an ALE or Eulerian formulation with moving grids by comparison w…

PANORMUS-SPH. A new Smoothed Particle Hydrodynamics solver for incompressible flows

Abstract A new Smoothed Particle Hydrodynamics (SPH) solver is presented, fully integrated within the PANORMUS package [7] , originally developed as a Finite Volume Method (FVM) solver. The proposed model employs the fully Incompressible SPH approach, where a Fractional Step Method is used to make the numerical solution march in time. The main novelty of the proposed model is the use of a general and highly flexible procedure to account for different boundary conditions, based on the discretization of the boundary surfaces with a set of triangles and the introduction of mirror particles with suitable hydrodynamic properties. Both laminar and turbulent flows can be solved (the latter using t…

Three dimensional numerical simulation of wind driven flows in closed channels and basins

In the paper, a fully 3D finite-volume numerical model is developed and employed for the prediction of wind-induced flows in a regular channel and in a square basin with a complex bathymetry. Numerical results are compared with laboratory experiments.Numerical tests are then performed to investigate whether simplifying assumptions about the pressure distribution and the turbulente stresses representation can be employed in the simulation of wind-driven flows. The hydrostatic pressure assumption, resulting in the use of “quasi-3D” models, proved to be reasonably acceptable in order to obtain the vertical profile of the streamwise velocity component away from the boundaries. The quasi-3D mode…

Numerical simulation of a wawe generator: A case of study

The aim of present work is the numerical simulation of a linear generator, capable of directly converting the kinetic energy, available by the wave, into electrical energy, through the device linear motion (up and down). In this paper, we intend to propose a numerical simulation approach to immersed devices by applying the Immersed Boundary Method. The Theory of linear wave is used to study and reproduce sea conditions and the computational domain is created based on observations available for the site in which it is envisaged the positioning of the device.

AN IMPROVED IMMERSED BOUNDARY METHOD FOR COMPLEX GEOMETRY ENVIRONMENTAL FLOWS

Modelling analysis of distribution network filling process during intermittent supply

The paper presents the modeling results of the filling process of a water distribution network subjected to intermittent supply. The local tanks built by users for reducing their vulnerability to intermittent supply increase user water demand at the beginning of the service period and the time required for completely fill the network. Such a delicate process is responsible of the inequalities taking part among users. Users located in advantaged positions can receive water resources soon after the beginning of the service period while disadvantaged users have to wait until the network is full. Such an highly dynamic process requires ad-hoc models to be developed in order to obtain reliable r…

ANALYSIS OF THE EFFECT OF SINUOSITY IN THE DISCHARGE CAPACITY OF MEANDERING COMPOUND CHANNELS

3D Numerical Simulation of Curved Open Channel Flows

Large eddy simulations on the effect of the irregular roughness shape on turbulent channel flows

Abstract Large Eddy Simulations (LES) are carried out to investigate on the mean flow in turbulent channel flows over irregular rough surfaces. Here the attention is focused to selectively investigate on the effect induced by crests or cavities of the roughness. The irregular shape is generated through the super-imposition of sinusoidal functions having random amplitude and four different wave-lengths. The irregular roughness profile is reproduced along the spanwise direction in order to obtain a 2D rough shape. The analysis of the mean velocity profiles shows that roughness crests induce higher effect in the outer-region whereas roughness cavities cause the highest effects in the inner-reg…

Wind profile restructuring due to the roughness reduction in land-water transition

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

The analysis of water distribution networks has to take into account the variability of users' water demand and the variability of network boundary conditions. In complex systems, e.g. those characterized by the presence of local private tanks and intermittent distribution, this variability suggests the use of dynamic models that are able to evaluate the rapid variability of pressures and flows in the network. The dynamic behavior of the network also affects the performance of valves that are used for controlling the network. Pressure reduction valves (PRVs) are used for controlling pressure and reducing leakages. Highly variable demands can produce significant fluctuation of the PRV set po…

Investigation of the hemodynamic flow conditions and blood-induced stresses inside an abdominal aortic aneurysm by means of a SPH numerical model.

The estimation of blood flow-induced loads occurring on the artery wall is affected by uncertainties hidden in the complex interaction of the pulsatile flow, the mechanical parameters of the artery, and the external support conditions. To circumvent these difficulties, a specific tool is developed by combining the aorta displacements measured by an electrocardiogram-gated-computed tomography angiography, with the blood velocity field computed by a smoothed particle hydrodynamics (SPH) numerical model. In the present work, the SPH model has been specifically adapted to the solution of the 3D Navier-Stokes equations inside a domain with boundaries of prescribed motion. Images of the abdominal…

CFD simulations of spacer-filled channels for pressure retarded osmosis applications

Different spacer features and operating conditions were investigated in order to identify a good compromise between concentration polarization and pumping power reductions.

Inflow/outflow pressure boundary conditions for smoothed particle hydrodynamics simulations of incompressible flows

Abstract Open Boundary treatment is a well-known issue in the Smoothed Particle Hydrodynamics (SPH) method, mainly when the truly Incompressible (ISPH) approach is employed. In the paper a novel method is proposed to set pressure boundary conditions in the computational domain inlets and outlets, without requiring the velocity profile assignment. The new technique allows to treat in the same way inflow and outflow sections, effectively dealing with the release of new particles at inlets and the deactivation of the ones leaving the domain through the outlets. Several 3D numerical tests, both in the laminar and turbulent regimes, are carried out to validate the proposed numerical scheme consi…

MODELLAZIONE DELLA QUALITÀ DELLE ACQUE NEI RICETTORI IN TEMPO DI PIOGGIA

Controllo dell’inquinamento delle acque meteoriche e qualità dei corpi idrici ricettori: l’esperienza del bacino Nord di Palermo

The impact of terrain roughness and water level changes on windinduced shallow lake circulation patterns.

Un modello di simulazione dei fenomeni di riempimento di reti di distribuzione idrica

Numerical observations of turbulence structure modification in channel flow over 2D and 3D rough walls

Abstract The effects of wall roughness on turbulence structure modifications were explored by numerical experiments, carried out using Large Eddy Simulation techniques. The wall geometry was made using an archetypal artificial method, thus to achieve irregular two- and three-dimensional shapes. The proposed roughness shapes are highly irregular and are characterised by high and small peaks, thus it can be considered a practical realistic roughness. Their effects are analysed comparing the turbulence quantities over smooth, 2D and 3D rough walls of fully developed channel flow at relatively low friction Reynolds number Re τ = 395 . Both transitional and fully rough regimes have been investig…

L'implementazione dell'approccio ALE per la simulazione dei campi di moto a superficie libera

Turbulence structures over irregular rough surfaces

Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysed through wall-resolving large eddy simulation (LES). Both walls of the channel are roughened through the superimposition of sinusoidal functions having random amplitude and four different wavelengths. The downward shift of the velocity profile in the log region due to the roughness, known as roughness function, is well captured in the simulations. The spanwise and wall-normal turbulence intensities are found to increase with the roughness height, while the streamwise component decreases. The analysis of the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation, confirmed by the vort…

Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: The Role of Geometrical Parameters

Almost all bounded flows, in nature and industry, are bounded by rough boundaries. Important efforts have been made, in fact, to analyse the physics of the fluids over such geometries. Basically, rough walls strongly influence the total energy dissipation, with important consequences in the form of higher costs especially in industrial applications.

Three-dimensional numerical simulations on wind- and tide-induced currents: The case of Augusta Harbour (Italy)

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 usi…

Detecting the chaotic nature of advection in complex river flows

In order to detect signatures of chaotic advection in river surface motion, surface buoys equipped with GPS were deployed in a field experiment in River Danube, Hungary. The buoys were released in the vicinity of groynes where complex mixing processes occur. A detailed analysis of the trajectories was carried out, focusing on the time evolution of the distance between buoy pairs. The analysis included the determination and comparison of local Lyapunov exponents and prediction times of finite-time hyperbolic behaviour, which is related to strong mixing. Despite of the small number of applied buoys we found evidence on Lagrangian chaos in the wake of a groyne field. In order to supplement the…

Analisi dell’effetto di una scabrezza irregolare sulle strutture turbolente

Controllo dell'inquinamento delle acque meteoriche e qualità dei corpi idrici ricettori

Modelling of E. colidistribution 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 p…

Numerical Simulations of the Hydrodynamics of the Abdominal Aorta Aneurysm (AAA) Using a Smoothed Particle Hydrodynamics Code with Deformable Wall Preliminary Results

We present some preliminary results of the numerical simulations of the hydrodynamic characteristics of an abdominal aorta aneurysm (AAA) patient specific test case. Images of the AAA lumen have been acquired in 10 discrete time-steps through a stabilized cardiac cycle by electrocardiogram-gated computer tomography angiography, and are used to approximate the in vivo, time dependent kinematic fields of the (internal) arterial wall. The flow field is simulated by a Smoothed Particle SPH numerical model, where the kinematics of the boundary of the computational domain (the internal aortic vessel) is the one computed by the above procedure. The outputs of the SPH model, i.e., pressure and flow…

Modelling of thrombus formation using smoothed particle hydrodynamics method

In this paper a novel model, based on the smoothed particle hydrodynamics (SPH) method, is proposed to simulate thrombus formation. This describes the main phases of the coagulative cascade through the balance of four biochemical species and three type of platelets. SPH particles can switch from fluid to solid phase when specific biochemical and physical conditions are satisfied. The interaction between blood and the forming blood clot is easily handled by an innovative monolithic FSI approach. Fluid-solid coupling is modelled by introducing elastic binds between solid particles, without requiring detention and management of the interface between the two media. The proposed model is able to…

Interaction between turbulent structures and particles in roughened channel

Abstract The distribution of inertial particles in turbulent flows is highly non-uniform and is driven by the local dynamics of the turbulent structures of the underlying carrier flow field. In the specific context of dilute particle-laden wall-bounded flows, deposition and resuspension mechanisms are dominated by the interaction between inertial particles and coherent turbulent structures characteristic of the wall region. The macroscopic behavior of these two-phase systems is influenced by particle inertia, which plays a role at the microscale of a single dispersed element. These turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the wall rough…

Large-Eddy Simulation in LSPIV techniques: the study of surface turbolence

<p>In recent years, technological advances have been observed in environmental monitoring field, leading to a rapid spread of innovative technologies overcoming many historical challenges. In river monitoring field the use of image-based techniques provides non-intrusive measurements ensuring the best safety conditions for operators. The most used optical methods are the Large-Scale Particle Image Velocimetry (LSPIV) and the Large-Scale Particle Tracking Velocimetry (LSPTV).</p><p>In LSPIV and LSPTV techniques a floating tracer is introduced on the water surface and its motion is recorded by commercial devices (e.g. digital cameras). Resulting video…

Gli aspetti economici e gestionali della dissalazione

Large scale circulations in shallow lakes

I processi disponibili per la dissalazione di acque marine e salmastre

Idraulica

Simulazione numerica tridimensionale del campi de moto indotti dal vento

Nell’articolo viene proposto un modello numerico tridimensionale al volume finiti, che viene utilizzato per la simulazione di campi di moto indotti dal mento in corpi idrici con batimetria complessa. I risultati numerici sono confrontati con misure sperimentali. Al fine di verificare gli effetti sul calcolo del campi idrodinamici di alcume ipotesi simplificative, relative alla distribuzione verticale della pressione e degli sforzi di Reynolds, sono stati quindi condotti alcuni test numerici, dai quali si è evidenziato che l’ipotesi di distribuzione idrostatica delle pressioni, cui si fa ricorso nelle approssinazioni di tipo “quasi-3D”, può essere utilizzata per il carcolo del profili vertic…

Estimation of the Roughness Function in Turbulent Flows Using the Slope of the Roughness

In the last decades, important efforts have been made to better understand the effects of surface roughness on the mean flow. These studies have been performed investigating turbulent channel flows, turbulent boundary layers or pipe flows. The most evident effect of the roughness is the increase of the overall resistance, corresponding to a decrease of the mean streamwise velocity profile in the logarithmic region. This reduction is known as roughness function \(\varDelta U^+\) (the symbol \(^+\) represents quantities made non dimensional using the friction velocity \(u_{\tau }\), or the viscous length scale \(\nu /u_{\tau }\)).

A BASIC DECISION SUPPORT SYSTEM FOR IMPROVING SERVICE LEVEL IN INTERMITTENT WATER DISTRIBUTION SYSTEMS

Interpreting and modelling field data for wastewater dispersion into sea trough dimensional analysis

This paper deals with the mathematical and experimental characterization of a coastal urban wastewater discharge in the South Tyrrhenian Sea, namely the Golfo di Palermo, western Sicily (Italy). The stretch of water lying before the central part of the capital town receives the wastewater originating from about 200 000 inhabitants. The sewage is currently still discharged on-shore without any prior treatment by a free-surface outfall called “Porta Felice”. The Municipality is currently implementing a plan to connect the sewerage system of these areas to the main wastewater treatment plant; at the moment, however, no mitigation measure has been applied yet and the quality of the Gulf is stil…

An improved immersed boundary method for curvilinear grids

Abstract In the present paper we propose an extension of the direct-forcing immersed boundary technique, recently developed and employed by Verzicco and co-authors [Fadlun EA, Verzicco R, Orlandi P, Mohd-Yusof J. Combined immersed-boundary finite-difference methods for three-dimensional complex flow simulations. J Comput Phys 2000;161:35–60; Verzicco R, Fatica M, Iaccarino G, Moin P, Khalighi B. Large eddy simulation of a road vehicle with drag-reduction devices. AIAA J 2002;40(12):2447–55; Cristallo A, Verzicco R. Combined immersed boundary/large-eddy-simulations of incompressible three-dimensional complex flows. Flow Turbul Combust 2006;77(1–4):3–26.] and successively improved by Balaras …

Analisi dell'effetto di scabrezze irregolari 2D e 3D sui campi di moto turbolenti.

CONTROLLO DELL’INQUINAMENTO DELLE ACQUE METEORICHE E QUALITÀ DEI CORPI IDRICI RICETTORI: L’ESPERIENZA DEL BACINO NORD DI PALERMO

Large eddy simulation of inertial particles dispersion in a turbulent gas-particle channel flow bounded by rough walls

The purpose of this paper is to understand the capability and consistency of large eddy simulation (LES) in Eulerian–Lagrangian studies aimed at predicting inertial particle dispersion in turbulent wall-bounded flows, in the absence of ad hoc closure models in the Lagrangian equations of particle motion. The degree of improvement granted by LES models is object of debate, in terms of both accurate prediction of particle accumulation and local particle segregation; therefore, we assessed the accuracy in the prediction of the particle velocity statistics by comparison against direct numerical simulation (DNS) of a finer computational mesh, under both one-way and two-way coupling regimes. We p…