Clustering and Turbophoresis in a Shear Flow without Walls

We investigate the spatial distribution of inertial particles suspended in the bulk of a turbulent inhomogeneous flow. By means of direct numerical simulations of particle trajectories transported by the turbulent Kolmogorov flow, we study large and small scale mechanisms inducing inhomogeneities in the distribution of heavy particles. We discuss turbophoresis both for large and weak inertia, providing heuristic arguments for the functional form of the particle density profile. In particular, we argue and numerically confirm that the turbophoretic effect is maximal for particles of intermediate inertia. Our results indicate that small-scale fractal clustering and turbophoresis peak in different ranges in the particles' Stokes number and the separation of the two peaks increases with the flow's Reynolds number.Comment: 13 pages, 5 figure

Instability of a dusty Kolmogorov flow

Suspended particles can significantly alter the fluid properties and, in particular, can modify the transition from laminar to turbulent flow. We investigate the effect of heavy particle suspensions on the linear stability of the Kolmogorov flow by means of a multiple scale expansion of the Eulerian model originally proposed by Saffman (1962). We find that, while at small Stokes numbers particles always destabilize the flow (as already predicted by Saffman in the limit of very thin particles), at sufficiently large Stokes numbers the effect is non-monotonic in the particle mass fraction and particles can both stabilize and destabilize the flow. Numerical analysis is used to validate the analytical predictions. We find that in a region of the parameter space the multiple-scale expansion overestimates the stability of the flow and that this is a consequence of the breakdown of the scale separation assumptions.Comment: 12 pages, 3 figure

Survey archaeology and regional analysis. A conceptual model on the selection of past dynamics during the Holocene in Wadi Abiod, Aures, Eastern Algeria

This paper inserted within a geoarchaeological study, provides a model for the investigation and the support of past dynamics of a mountainous landscape in the Aures region (Algeria) during the Holocene. It introduces the first analysis based on the detailed mapping of morphological features of the study area in relation with a typomorphology theoretical model that was confronted with data from archaeological research. Our results suggest that the choice of the prehistorical movement processes has been driven by the outcrop of some deposits and the presence of specific landforms, such as high and low-relief areas. This approach was applied to a sector with controversial archaeological evidences (the valley of Wadi Abiod), where geological and morphological analyses support archaeological research in the reconstruction of the ancient pathways during the Holocene. This integrated approach can help archaeologists to understand and then discover ancient courses crossing complex in impervious landscapes such as the intramountain Lands

a smartphone application for supporting the data collection and analysis of the cultural heritage damaged during natural disasters

The adverse impacts of natural disasters on lives and livelihoods, as well as regional and local economies, are increasingly evident, and losses to both tangible and intangible cultural heritage due to these disasters pay an important role in the total amount. In fact, damages to sites, structures and artifacts of cultural and historical value, as well as impacts to cultural tourism and the financial resources, produce a strong competitive disadvantage on local communities. Emergency decision making, based on awareness of the suffered damages, can play a crucial role in the attempts of improving resilience of the strategic elements; however, this process typically requires a fast overview on large territories. In this work, we propose a novel framework for obtaining an agile solution to quickly collect and analyze picture galleries and information provided by both internal staff and citizens through commercially available mobile devices. This solution virtually generates a network of information sources during emergency time (e.g., a seismic sequence), and allows to produce a situation map in GIS environment, hence supporting the health status analysis of cultural heritage over time. This paper presents the prototype system composed of: (1) a smartphone application for the acquisition of new information and the examination of existing one; (2) a web-service for exchanging data with databases; and (3) a local service that makes use of a proper piece of software for obtaining a 3D reconstruction from new picture galleries. The proposed system results in a scalable, exportable and modular tool useful during the emergency and for preserving memories of local communities

Enhancing students' skills in technical writing and LSP translation through tele-collaboration projects: teaching students in seven nations to manage complexity in multilateral international collaboration

International audiencePartnerships involving language projects have been common, but most have paired just two nations at a time (Jarvenpaa & Leidner, 1999; Flammia, 2005, 2012; Herrington, 2005, 2008; Humbley et al., 2005; Stärke-Meyerring & Andrews, 2006; Mousten et al., 2010). That changed in 2010, when universities in five nations, long involved in the Trans-Atlantic Project (TAP) began a far more complex international learning-by-doing project (Maylath et al., 2013). By 2012, universities in two more nations were added. In forming their students into cross-cultural virtual teams (CCVTs), instructors asked, how can students best learn experientially to manage complex international/interlingual technical documentation projects? During multilateral collaborations, two projects took place simultaneously: a translation-editing project and a writing-usability testing- translation project. The undertakings’ complexity was central in the students’ learning, thereby preparing students for the international, multilingual, multicultural environments in which students can be expected to operate after they graduate. Further, the projects succeeded in increasing trans-cultural and language awareness among students with little in extra funding

Operational volcanic ash monitoring during Etna volcanic crises

Operational systems able to monitor volcanic ash in real time and provide both critical eruption parameters and useful warnings to emergency responders and government agencies should be implemented in most volcanic observatories worldwide. Over the past ten years, more than fifty lava fountains occurred at Mt. Etna (Italy) that produced eruption columns more than 10 km a.s.l. and generated large tephra fallout around the volcano flanks. For civil protection purposes, there was the need to improve the already existing monitoring systems daily run at the Istituto Nazionale di Geofisica and Vulcanologia, mainly based on eruption scenarios (weak and strong plume scenarios). We present a new upgraded system that has multiple objectives: i) to have a fast system able to best identify the type of eruptive scenario; ii) to forecast the tephra deposit in near real time, i.e. within a few hours from the eruptive event; iii) to determine the area impacted by clasts larger than 5 cm that could severely injure hikers, guides, and volcanologists and damage infrastructures in proximity of Etna summit craters. This new system is based on the real-time estimate of column height from the analysis of images taken by SEVIRI satellite and by new calibrated cameras and using meteorological parameters obtained by local models.PublishedVienna , Austria6V. Pericolosità vulcanica e contributi alla stima del rischi

Near-Real-Time Tephra Fallout Assessment at Mt. Etna, Italy

During explosive eruptions, emergency responders and government agencies need to make fast decisions that should be based on an accurate forecast of tephra dispersal and assessment of the expected impact. Here, we propose a new operational tephra fallout monitoring and forecasting system based on quantitative volcanological observations and modelling. The new system runs at the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE) and is able to provide a reliable hazard assessment to the National Department of Civil Protection (DPC) during explosive eruptions. The new operational system combines data from low-cost calibrated visible cameras and satellite images to estimate the variation of column height with time and model volcanic plume and fallout in near-real-time(NRT). The new system has three main objectives: (i) to determine column height in NRT using multiple sensors (calibrated cameras and satellite images); (ii) to compute isomass and isopleth maps of tephra deposits in NRT; (iii) to help the DPC to best select the eruption scenarios run daily by INGV-OE every three hours. A particular novel feature of the new system is the computation of an isopleth map, which helps to identify the region of sedimentation of large clasts (≥5 cm) that could cause injuries to tourists, hikers, guides, and scientists, as well as damage buildings in the proximity of the summit craters. The proposed system could be easily adapted to other volcano observatories worldwide.Publishedid 29876V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa

Airborne LiDAR and Hyperspectral Data to Support the Seismic Vulnerability of Urban Environments

The seismic vulnerability analysis of urban environments is an operational issue that concerns the comprehensive knowledge of both building structural features and soils geophysical parameters, especially when considering areas that are prone to hydrogeological and seismic disasters. The protection of such environments, together with the population growth and the urbanization processes, requires a multi-disciplinary approach aiming at providing both an effective assessment of urban resources and synthetic parameters for managing post crisis events, restoration activities and search & rescue operations. Within such a framework, airborne Light Detection and Ranging (LiDAR) and Hyperspectral sensors have demonstrated to be powerful remote sensing instruments, whose jointly use allow providing meaningful parameters to describe both the topographic settings of urbanized areas and the buildings properties, in terms of geometrical, spectral and structural features. Based on this rationale, in this study, the operational benefits obtained by combining airborne LiDAR and Hyperspectral measurements are provided to support the seismic vulnerability assessment of urban seismic areas. The digital elevation model as well as the building height and the shape of the observed area are gathered by using airborne LiDAR measurements. Spectral and structural information of urban buildings are provided through the supervised classification of IMSpectorV10E VNIR (wavelength range between 400 and 1000nm subdivided into 503 bands) measurements acquired by the IPERGEO sensor. The objective is to combine the different products provided by LiDAR and Hyperspectral image processing analysis within a Geographic Information System (GIS) platform, to evaluate the intrinsic properties of buildings (e.g. perimeter, covered area, height and type of roofs) together with the topographic features of the surrounding area (e.g. the surface height and slope) for providing synthetic parameters and thematic maps useful for seismic assessment and mitigation purposes, such as: (i) the identification of steep slope areas, (ii) the analysis of building roof typology for supporting the evaluation of structural load conditions, (iii) the detection of critical structures (e.g. asbestos buildings), (iv) the identification of primary roads (in terms of escape or access routes) for supporting search and rescue operations, (v) the analysis of main road conditions after building collapses. Meaningful experimental results, gathered for the historical center of Cosenza city (Italy), allow demonstrating the benefits of the proposed approach for both seismic assessment and mitigation purposes. The present work is supported and funded by Ministero dell'Universita, dell'Istruzione e della Ricerca (MIUR) under the project PON01-02710 "MASSIMO" - "Monitoraggio in Area Sismica di SIstemi MOnumentali"

A new way to reduce the impact from tephra fallout during Etna explosive eruptions

The frequent number of explosive events at Mt. Etna, in Italy, over the last ten years, has made necessary the improvement of volcanic ash monitoring and forecasting system at the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE). Tephra fallout produced during Etna lava fountains largely impact the population living on the volcano flanks. In addition, during one of the most powerful paroxysms, large clasts fell in proximal areas injured tourists and hikers. To reduce risk, the Italian Department Civil Protection (DPC) asked and funded INGV-OE to do a research project finalized to three specific objectives. First, identify the plume scenario (i.e. weak plume scenario (WPS) and strong plume scenarios (SPS)) based on 1-D plume model. Second, forecast characteristics of tephra deposition using near real time observations. Third, identify the region possibly impacted by large clasts (>5 cm). Two algorithms were developed to measure the column height. One from the calibrated images of two visible cameras installed on the S and W flanks of the volcano, respectively; and the other one from satellite data using a procedure based on the computation of the volcanic plume-top brightness temperature at 10.8 mm. The analysis of lava fountains that occurred between 2011 and 2015 provided the opportunity to differentiate between weak, transitional and strong plumes. The uncertainty associated with eruption source parameters, while maintaining a fixed plume height, was also assessed. In the near future the implementation of these products into the INGV-OE - monitoring room will guarantee a better and timely information to civil protection authorities charged of risk prevention at different levels of responsibility.PublishedNapoli6V. Pericolosità vulcanica e contributi alla stima del rischi