1,720,977 research outputs found
Lagrangian micromixing models for concentration fluctuations. An overview
Full text linkThis study presents a brief overview of the main features, theoretical formulations and validation tests of some Lagrangian micromixing models, currently used for estimations of the ensemble mean and the turbulent fluctuations of concentration. Their application fields regards several pollutant dispersion phenomena such as: accidents (power or production plants, terroristic attacks, hydrocarbons storage and transport, extraordinary emissions), odours (power plants and energy production from waste resourcescompost, dumps, incinerators, biogas storage and smokes-, high enthalpy geothermic plants-sulfide hydrogen-, animal farms), micro-scale dispersion from continuous or spot emissions (traffic pollutants, power and production plants, dispersion in aquatic environments...), industrial processes (combustion, pollutant treatment,...), strong non-linear relationship between concentration and damage (inflammable substances, explosions,..), reactions depending on instantaneous concentrations. © 2012 Science Publication
SPH Modelling of Dam-break Floods, with Damage Assessment to Electrical Substations
No full textThe Smoothed Particle Hydrodynamics code SPHERA (RSE SpA) is validated on a laboratory urban dam-break flood. Comparisons with a porous Shallow Water Equations - Finite Volume Method 2D model are also reported. SPHERA provides a performance comparable with the state-of-the-art code, with results closer to the measured values during the most risky flood stage. Some improvements of SPHERA predictions are achieved by a direct modelling of the mobile gate triggering the flood. SPHERA is also empowered with a substation-flooding damage model, which distinguishes the functional damage due to the substation out of service from the material damage to the substation components. SPHERA is finally applied to a full-scale catastrophic 3D dam-break flood, which interacts with a lower hydroelectric reservoir, covers four residential areas and two electrical substations, whose related damage is assessed. SPHERA is distributed on a GitHub public repository, included the input files of this study
WCSPH with limiting viscosity for modelling landslide hazard at the slopes of artificial reservoir
Full text linkUrban scale air quality assessment with a harmonized multi-scale model
No full textThe performances of an open-source multi-scale air quality model are discussed in this work. The model CAMx-LPiG is implemented to assess air quality in urban areas, with a special focus on road traffic emissions. We aim for developing a flexible and adaptable modelling tool, able to capture from intra-urban up to basin scale processes of both primary and secondary pollutants. Such tool could become a standard to monitor air quality and assess the effects of mobility policies in urban areas
A closed-form solution for the deposition of atmospheric particulate matter on electrical insulators
No full textThe present study provides a simplified closed-form solution for the deposition flux of atmospheric Particulate Matter on electrical insulators. Due to the lack of experimental data on deposition over this type of solid bodies, the mathematical model is closed by means of a 4D regression procedure on obstacle-scale numerical data. This dataset is obtained with the Lagrangian Stochastic Model SPRAY-WEB (Università del Piemonte Orientale et al., 2021). The code was already validated on Particulate Matter dispersion and deposition on solid obstacles (Amicarelli et al. in Environ Fluid Mech 21(2): 433–463, 2021) and is here applied to a XP-70 porcelain-disk electrical insulator. A published tutorial is associated with this numerical dataset (SPRAY-WEB, 2021). The verification metrics on the performance of the closed-form solution show that the errors lie below the guideline thresholds for air-quality numerical simulations (Chang and Hanna in Meteorol Atmos Phys 87:167–196, 2004) and are limited by a Maximum Gross Error of ca.24% for an external verification. Although they cannot be used to close any mathematical model or to represent any specific event, the long-term averaged deposition fluxes of Zhang et al. (IEEE Trans Dielectr Electr Insulat 21(4):1901–1909, 2014. 10.1109/TDEI.2014.004343) are associated with the same insulator used for this study. With respect to the full-scale experiment mentioned above, the present solution provides an overestimation of 13%. The closed-form solution can be used for instantaneous preliminary estimates or be integrated within air-quality numerical codes for fast assessments of contamination maps for electrical insulators. Such applications aim to quantify the insulator functional damage (i.e., flashovers, short-circuits). The closed-form solution can be also generalized any time new data are available
Lagrangian micromixing modelling of reactive scalar statistics. Scalar mixing layer in decaying grid turbulence
No full textA Lagrangian micro-mixing numerical model estimates the concentration statistics of reactive pollutants (NO, O3 and NO2) of a scalar mixing layer in decaying grid turbulence. A stochastic macro-mixing scheme computes the fluid particle trajectories, which describe the turbulent flow (Lagrangian turbulence), whereas the micro-mixing scheme interaction by the exchange with the conditional mean (IECM), implementing a new formulation for the mixing time, represents the dissipation of concentration turbulent fluctuations due to molecular diffusion. The non-homogeneous reaction-dominated limit (NHRDL) of the conserved scalar theory simulates chemical reactions. The numerical model integrates these three schemes and is validated by comparison with experimental and direct numerical simulation (DNS) data, whereas inter-comparisons with other numerical models are also reported. The study focuses on the reliability of Lagrangian stochastic modelsin representing micro-scale pollutant dispersion (air quality) and the importance of representing chemical reactions depending on instantaneous concentrations rather than their means
SPHERA v.9.0.0: A Computational Fluid Dynamics research code, based on the Smoothed Particle Hydrodynamics mesh-less method
Full text linkSPHERA v.9.0.0 (RSE SpA) is a FOSS CFD-SPH research code validated on the following application fields: floods with transport of solid bodies and bed-load transport; fast landslides and their interactions with water reservoirs; sediment removal from water bodies; fuel sloshing tanks; hydrodynamic lubrication for energy efficiency actions in the industrial sector. SPHERA is featured by several numerical schemes dealing with: transport of solid bodies in fluid flows; treatment of fixed and mobile solid boundaries; dense granular flows and an erosion criterion. The source and executable codes, the input files and the free numerical chain of SPHERA v.9.0.0 are presented. Some reference validations and applications are also provided. SPHERA is developed and distributed on a GitHub public repository. Program summary: Program title: SPHERA v.9.0.0 Licensing provisions: GNU General Public License 3 (GPL) Programming language: Fortran 95 Supplementary material: software documentation/guide, 34 tutorials Journal Reference of previous version: Amicarelli A., R. Albano, D. Mirauda, G. Agate, A. Sole, R. Guandalini; 2015; A Smoothed Particle Hydrodynamics model for 3D solid body transport in free surface flows; Computers & Fluids, 116:205–228. DOI 10.1016/j.compfluid.2015.04.018 Does the new version supersede the previous version?: Yes Reasons for the new version: scheme for dense granular flows (i.e. bed-load transport, fast landslides); reference Journal publication: Amicarelli A., B. Kocak, S. Sibilla, J. Grabe; 2017; A 3D Smoothed Particle Hydrodynamics model for erosional dam-break floods; International Journal of Computational Fluid Dynamics, 31(10):413-434; DOI 10.1080/10618562.2017.1422731 Nature of problem (approx. 50–250 words): SPHERA v.9.0.0 has been applied to free-surface and multi-phase flows involving the following application fields: floods (with transport of solid bodies, bed-load transport and a domain spatial coverage up to some hundreds of squared kilometres), fast landslides and wave motion, sediment removal from water reservoirs, fuel sloshing tanks, hydrodynamic lubrication. Solution method (approx. 50–250 words): SPHERA v.9.0.0 is a research FOSS (“Free/Libre and Open-Source Software”) code based on the SPH (“Smoothed Particle Hydrodynamics”) technique, a mesh-less Computational Fluid Dynamics numerical method for free surface and multi-phase flows. The five numerical schemes featuring SPHERA v.9.0.0 deal with: dense granular flows; transport of solid bodies in free surface flows; boundary treatment for both mobile and fixed frontiers; 2D erosion criterion. Additional comments including Restrictions and Unusual features (approx. 50–250 words): SPHERA v.9.0.0 is a 3D research FOSS (“Free/Libre and Open-Source Software”) code (developed under the subversion control system Git) with peculiar features for: floods (with transport of solid bodies, bed-load transport and a domain spatial coverage up to some hundreds of squared kilometres), fast landslides and wave motion, sediment removal from water reservoirs, fuel sloshing tanks, hydrodynamic lubrication. The whole numerical chain of SPHERA is made of FOSS, freeware and Open Data numerical tools. References: SPHERA (RSE SpA), https://github.com/AndreaAmicarelliRSE/SPHERA, last access on 28May2019 Amicarelli A., G. Agate, R. Guandalini; 2013; A 3D Fully Lagrangian Smoothed Particle Hydrodynamics model with both volume and surface discrete elements; International Journal for Numerical Methods in Engineering, 95: 419–450, DOI: 10.1002/nme.4514 Amicarelli A., R. Albano, D. Mirauda, G. Agate, A. Sole, R. Guandalini; 2015; A Smoothed Particle Hydrodynamics model for 3D solid body transport in free surface flows; Computers & Fluids, 116:205–228. DOI 10.1016/j.compfluid.2015.04.018 Amicarelli A., B. Kocak, S. Sibilla, J. Grabe; 2017; A 3D Smoothed Particle Hydrodynamics model for erosional dam-break floods; International Journal of Computational Fluid Dynamics, 31(10):413-434; DOI 10.1080/10618562.2017.1422731 Manenti S., S. Sibilla, M. Gallati, G. Agate, R. Guandalini; 2012; SPH Simulation of Sediment Flushing Induced by a Rapid Water Flow; Journal of Hydraulic Engineering ASCE 138(3): 227–311. Di Monaco A., S. Manenti, M. Gallati, S. Sibilla, G. Agate, R. Guandalini; 2011; SPH modelling of solid boundaries through a semi-analytic approach. Engineering Applications of Computational Fluid Mechanics, 5(1):1-15
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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