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In this paper we propose a mesoscale model for polar fluids and numerically investigate its validity by considering well known benchmark cases: the steady and unsteady Poiseuille and the low Reynolds lid-driven cavity flow. Analytical and numerical results are compared with our numerical results and a very good agreement is found. Then we consider not yet investigated high Reynolds lid-driven cavity flow cases, obtaining consistent and interesting results, which encourage to apply the proposed model to more complex cases. [ABSTRACT FROM AUTHOR]

The solution of fluid dynamics problems has recently witnessed a remarkable increase in the formulation of Boltzmann-based approaches, mainly triggered by the numerous advantages stemming from the concrete possibility of employing a low number of allowed velocities, which is the basis of the Lattice-Boltzmann (LB) methods. The field of Shallow Water (SW) modeling also took advantage of these techniques, but there are still open problems related to the practical impossibility to simulate transcritical flows while retaining the intrinsic simplicity of the LB approaches. This problem is even more crucial if one considers that transcritical flows always develop whenever a transition over dry bed occurs. Since such vertically integrated models are currently the mostly employed ones for simulating technically interesting flows, and since these flows often require the flooding of an initially dry bed, the application of LB methods seems to be facing its limits. The Gas Kinetic Method (GKM) overcomes this issue, integrating the Boltzmann equations in continuous velocity space. In this work, we formulate and extensively test a GKM-based model for solving the SW equations, which is able to manage the propagation over uneven dry bed. The benchmarking, carried out against analytical, experimental and previously proposed numerical reference solutions, shows promising results of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract: Numerous Deep-Seated Gravitational Slope Deformations (DSGSDs) occur throughout Italy, that originate from particular tectono-stratigraphic settings, relief, seismicity, deglaciation, as well as from intense and deep processes of chemico-physical weathering of crystalline–metamorphic rocks. These DSGSDs are particularly widespread in the Calabrian mountains. This study is focused on the Mt. Granieri–Salincriti slope, on the Ionian side of the Serre Massif, where granites and granodiorites (Stilo Unit, Palaeozoic) are in contact with metamorphites through a thermal–metamorphic aureole. This setting generates deep geochemical processes, inducing intense chemical weathering. These processes are mainly due to the interaction between groundwater and the sulphides that are contained in the local pegmatitic–hydrothermal intrusions, especially along the thermal–metamorphic contact belt. The Mt. Granieri–Salincriti slope has an important DSGSD, which is associated with many active and/or quiescent landslides. Among these landslides, the Salincriti rock avalanche-debris flow (about 2 M m3) represents the paroxysmal and terminal stage of the deep creep deformations of Mt. Granieri, typifying a geological setting that is common in the Calabrian Arc. This multi-disciplinary study assessed the weathering susceptibility of the local crystalline–metamorphic rocks, especially those lying along thermal–metamorphic contact belts, by characterising the weathering horizons and the spatial distribution of weathering in the rock mass. The study was also aimed at identifying the relations between weathering, above all deep geochemical processes, effects on rocks and slope morphodynamics. The methodology was based on detailed geological data, geological–engineering surveys, geomorphology and surface hydrogeology analyses, as well as physico-mechanical laboratory tests. These investigations, supported by a monitoring program, led to the development of an engineering–geological model of the slope. Geological character (attributed to a thermal–metamorphic contact belt), geomorphological evidence and geomechanical elements elucidated the interactions between deep geochemical processes and weak belts in the investigated rocks, as well as the critical role that these interactions play in the evolution of deep-seated creep deformations and associated shallow landslides. [Copyright &y& Elsevier]

The Lattice Boltzmann Method (LBM) is a mesoscopic method founded on the kinetic theoryof Boltzmann and has been proven to describe successfully flows of hydraulic interest such asturbulent, multicomponent and multiphase flows. The main advantage of the LBM, comparedto more traditional methods of the Computational Fluid Dynamics, are: the simplicity of theset of explicit algebraic equations forming the computational algorithm, the ease ofdescription of complex boundaries and the proneness of the LBM to provide unprecedentedparallel scalability on a large number of architectures. Thus, the computational resourcesavailable nowadays make the employment of 3D models feasible to study large-scaleproblems as well. In this work, a fully 3D LBM model is developed and applied to the simulation of freesurface impulsive flows. The evolution of the free surface is here tracked by means of a 3Dinterface tracking model and coupled to the traditional LBM algorithm. Dam-breakevents are simulated and LBM numerical results are compared to both analytical andexperimental reference results. The latter are relative to symmetrical dam-break,asymmetrical dam-break, dam-break over a triangular obstacle, dam-break with anisolated building and the laboratory model of the Toce river test case. The accuracy ofthe model is assessed by comparing depth and velocity values, when available,at some gauge locations. The study shows that the LBM provides a remarkablyaccurate description of the phenomena. The results are very promising for futureapplications of this kind of models for the study of realistic hydraulic problems. [ABSTRACT FROM AUTHOR]

• Polydisperse shallow granular flow equations are obtained. • The Discrete Boltzmann Equation model equivalent to the polydisperse shallow granular flow equations is presented and proposed as solution method. • Several 1 D and 2 D flows, concerned with the propagation of discontinuities in three-phase shallow granular flows are investigated. A polydisperse shallow mixture consisting of N p solid phases (N p ≥ 1) and one fluid phase (the ambient fluid) is a reliable model for several industrial and environmental flows, as e.g. landslides, avalanches, debris flows and fluidized beds. The description and prediction of these flows is of primary importance, mainly with respect to the mitigation and protection from natural hazards. This paper is aimed at deriving the polydisperse shallow granular flow equations by depth-averaging mass and momentum equations of the mixture and at formulating an equivalent Discrete Boltzmann Equation (hereinafter DBE) model as solution method. The reason is the simplicity and the versatility of the DBE, which consists of a set of purely advective, linear, first order partial differential equations, whose numerical integration does not need sophisticated methods. Both 1 D and 2 D benchmarks, concerning with the propagation of discontinuities in three-phase shallow granular flows, are obtained by applying the finite differences Lax-Friedrichs (hereinafter LF) method to the polydisperse shallow granular flow equations. The overall agreement is good, showing that the DBE and the LF numerical results are equivalent. [ABSTRACT FROM AUTHOR]

In this paper a Discrete Boltzmann Equation model (hereinafter DBE) is proposed as solution method of the two-phase shallow granular flow equations, a complex nonlinear partial differential system, resulting from the depth-averaging procedure of mass and momentum equations of granular flows. The latter, as e.g. a debris flow, are flows of mixtures of solid particles dispersed in an ambient fluid. The reason to use a DBE, instead of a more conventional numerical model (e.g. based on Riemann solvers), is that the DBE is a set of linear advection equations, which replaces the original complex nonlinear partial differential system, while preserving the features of its solutions. The interphase drag function, an essential characteristic of any two-phase model, is accounted for easily in the DBE by adding a physically based term. In order to show the validity of the proposed approach, the following relevant benchmark tests have been considered: the 1D simple Riemann problem, the dam break problem with the wet–dry transition of the liquid phase, the dry bed generation and the perturbation of a state at rest in 2D. Results are satisfactory and show how the DBE is able to reproduce the dynamics of the two-phase shallow granular flow. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the findings from a study on gravity-induced slope deformations along the northern slope of Mt. Nuria (Rieti-Italy). The slope extends from the village of Pendenza to the San Vittorino plain and hosts the Peschiera River springs, i.e. the most important springs of the Central Apennines (average discharge: about 18 m3/s). Detailed geological-geomorphological and geomechanical surveys, supported by a site stress-strain monitoring system and laboratory tests, led us to define the main evolutionary features of the studied phenomena. Based on the collected data, a “geological-evolutionary model” was developed with a view to identifying a spatio-temporal correlation between relief forms, jointing of the rock mass and its stress conditions. The geological-evolutionary model was expected to improve numerical simulations and to test our assumptions. The numerical model also allowed us to simulate changes in the stress-strain conditions of the rock mass and correlate them with jointing, seepage, as well as with site-detected and site-monitored forms and deformations. In particular, significant relations between seepage, tensile stresses within the rock mass, karst solution and collapse of cavities were identified. [Copyright &y& Elsevier]

COVID-19 pandemic in Italy displayed a spatial distribution that made the tracking of its time course quite difficult. The most relevant anomaly was the marked spatial heterogeneity of COVID-19 diffusion. Lombardia region accounted for around 60% of fatal cases (while hosting 15% of Italian population). Moreover, 86% of fatalities concentrated in four Northern Italy regions. The 'explosive' outbreak of COVID-19 in Lombardia at the very beginning of pandemic fatally biased the R-like statistics routinely used to control the disease dynamics. To (at least partially) overcome this bias, we propose a new index RI = dH/dI (daily derivative ratio of H and I, given H = Healed and I = Infected), corresponding to the ratio between healed and infected patients relative daily changes. The proposed index is less flawed than R by the uncertainty related to the estimated number of infected persons and allows to follow (and possibly forecast) epidemic dynamics in a largely model-independent way. To analyze the dynamics of the epidemic, starting from the beginning of the virus spreading—when data are insufficient to make an estimate by adopting SIR model—a "sigmoidal family with delay" logistic model was introduced. That approach allowed in estimating the epidemic peak using the few data gathered even before mid-March. Based on this analysis, the peak was correctly predicted to occur by end of April. Analytical methodology of the dynamics of the epidemic we are proposing herein aims to forecast the time and intensity of the epidemic peak (forward prediction), while allowing identifying the (more likely) beginning of the epidemic (backward prediction). In addition, we established a relationship between hospitalization in intensive care units (ICU) versus deaths daily rates by avoiding the necessity to rely on precise estimates of the infected fraction of the population The joint evolution of the above parameters over time allows for a trustworthy and unbiased estimation of the dynamics of the epidemic, allowing us to clearly detect the qualitatively different character of the 'so-called' second wave with respect to the previous epidemic peak. [ABSTRACT FROM AUTHOR]

Nowadays the Lattice Boltzmann Method (LBM), thanks to its mesoscale approach, is a powerful tool when dealing with upscaling problems in Fluid Dynamics. In this study a numerical investigation on the flow through fractured porous media has been performed, based on a three dimensional LBM model developed at the Engineering Department of the Roma Tre University. Two different kinds of porous matrices, consisting of deterministic and random arrays of spheres, have been considered. The formers have been arranged both as a primitive and body centred cubic system. The latters are characterized both by monodisperse and by polydisperse diameters. In order to calculate the permeability of every considered porous medium, the Darcy's experiment has been simulated. Then a channel has been considered in every porous matrix, giving raise to different fractured porous media. The Darcy's experiment has been repeated with the fractured porous media and the LBM has been used as a numerical lab to verify the ranges of validity of upscaled models based on the analytical solution of flow in equivalent porous media. It has been found that numerical and analytical results are in good agreement when a fractured deterministic porous medium is considered. In this case the order of magnitude of the relative error, defined as the absolute value of the percentage difference between the numerical and analytical velocity on the axis of the channel, is equal to few percents. Moreover, the error decreases with the permeability: the greater the permeability, the smaller the error. LBM numerical results obtained considering random fractured porous media are characterised by a relative error larger than that corresponding to numerical results obtained considering deterministic fractured porous media, being equal permeability and hydrodynamic conditions. Future work is addressed to the understanding of how the parameters characterizing the random fractured porous media affect the results obtained by applying the LBM model and the difference with the reference results. [ABSTRACT FROM AUTHOR]

Regional and teleseismic earthquakes can induce displacements along joints in a landslideinvolved rocky slope in Central Italy. The rarity of these effects is due to specific physical properties of the seismic signals associated with: (i) the energy content, (ii) the distribution of relative energy and peak of ground acceleration related to the ground motion components and (iii) the spectral amplitude distribution in the frequency domain; these properties allow the triggering earthquakes to be distinguished from the others. The observed effects are relevant when compared to the direction of the landslide movement and the dimensions of the involved rock mass volume. The landslide movement is less constrained in the direction parallel to the dip of the slope and the landslide dimensions are associated with characteristic periods that control the landslide deformational response in relation to the spectral content of the ground motion. The earthquake-induced displacements are significant because they have the same order of magnitude as the average annual cumulative displacement based on a decade of strain measurements within the slope. [ABSTRACT FROM AUTHOR]

Abstract: Over the last decades, time-of-failure semi-empirical prediction functions have been developed and applied to different landslides with mixed results. In this study, a field experiment was carried out to calibrate these functions with the simultaneous consideration of small-size landslides and landslides that occur on slopes modified by human activities. Four years of continuous monitoring using an integrated platform consisting of both traditional sensors (i.e., inclinometers, piezometers, load cells, topographic measurement) and innovative remote-sensing equipment (i.e., Terrestrial SAR Interferometer) resulted in the collection of a notably large amount of data. Several landslides affecting different slopes (i.e., cut slopes, cut slopes covered by spritz-beton and slopes stabilised by anchored bulkheads) were observed as part of the experiment, thus facilitating the inference of detailed information for the pre-failure behaviour. Nine landslides were back-analysed, thus allowing for calibration of the failure prediction functions for different types of slopes. From these observations, it was found that events occurring on slopes modified by human interventions could be effectively predicted using the Voight function if suitable parameters are used. As a general remark, the landslides that originate from cut slopes in natural terrain behave similar to large landslides reported in the literature (similar values of A and α) while landslides that originate from cut slopes covered by spritz beton and slopes stabilised by anchored bulkheads show α values that are significantly lower and A values that are significantly higher than those of landslides on natural terrains. [Copyright &y& Elsevier]

Abstract: The incision of a natural or an artificial slope in a clay deposit initiates a morphological evolution and determines variations of the internal state of stress in the deposit. This evolution can be analyzed considering the variations over time of the lateral stress at rest coefficient K0. This paper is focused on the evolution of the K0 in overconsolidated clay deposits submitted to the incision of natural slopes. The proposed idea is that, under specific morphological and evolutionary conditions, a value of K0 <1 could be considered reliable even for medium–high OC clay deposits. This idea is here discussed with the support of in-situ and laboratory data from: i) pressuremeter tests performed in overconsolidated clay deposits in Central Italy and ii) a scaled physical modeling experiment reproducing a normally consolidated clay deposit. This study suggests that when dealing with clay deposits subjected to a simultaneous vertical and horizontal unloading due to slope incision, the K0 coefficient should be considered a parameter variable as a function of the different stress–strain evolutions experienced by each portion of the deposit. The portions involved in the slope incision had different evolutions and are represented by different K0 values. As a consequence, diverse amounts of decrease distinguish the evolution of the K0 for natural rather than artificial slopes. [Copyright &y& Elsevier]

Abstract: On 30 January 2009, a rock slide involving approximately 0.23Mm3 of highly jointed gneiss from the local Ercinic substratum was recorded in southern Italy. The landslide occurred after exceptional autumnal rainfalls and involved a quarry whose activity has been documented over the past 10years by aerial images. An engineering-geology model of the slope involved in the landslide was developed based on the geomechanical classification of the outcropping rock masses, the ISRM (2007) indexes Ib (the block size index) and Jv (the volumetric joint count), and the observed geological setting of the slope. An equivalent continuum approach was adopted to attribute strength and stiffness parameter values to the different classes of jointed rock masses. A simplified evolutionary model of the slope was developed, starting from 300ka (i.e., from the erosional phase following the deposition of the 300-m-a.s.l. marine terrace deposits overlaying the gneiss substratum) to 30 January 2009. The model took into account the main depositional phases as indicated by the Pleistocene marine terrace deposits and the documented stages of quarry activity. Time-dependent stress–strain numerical modelling was performed by the FDM software FLAC 6.0. A visco-plastic Burger model was used to back-analyse the landslide event and to define the values of the rheological parameters for the jointed gneiss. The results, which were strongly constrained by the geomorphological evidences and by the displacement field observed before and after the landslide, demonstrated a combination of i) time-dependent gravitational slope deformation and ii) anthropogenic release due to quarry activity, which induced a progressive failure process and an increase in the jointing within the gneissic rock mass located behind the cut-wall of the quarry. Failure was ultimately triggered by intense rainfalls that occurred in the 3months before the landslide. The stress–strain numerical modelling demonstrated the reliability of visco-plastic rheology for simulating the rock mass creep in this case history: viscosity values in the range of 1019–1023 Pa·s were derived. [Copyright &y& Elsevier]

This paper presents the results of a study on a deep-seated gravitational slope deformation affecting the eastern slope of the Mt. Rocchetta ridge (central Apennines, Italy). Fieldwork identified the ongoing deformational process and assisted in defining its mechanisms, evolution and controlling factors. An equivalent continuum approach was adopted to characterize the rock mass with some modification for the temporal and spatial scale of the process. A visco-elastic-plastic rheological model was adopted for the numerical analysis, which also took into account the groundwater flow feeding the Capo Volturno spring. The results of the numerical analysis are consistent with the observed geomorphic evidence and suggest a morpho-evolutionary model of the ridge characterized by an initial phase of rock mass creep followed by a rock mass spreading process, mainly controlled by the viscous behaviour but with a significant contribution from groundwater for the smaller scale instabilities. [ABSTRACT FROM AUTHOR]