The Experts below are selected from a list of 56685 Experts worldwide ranked by ideXlab platform
Costa Antonio - One of the best experts on this subject based on the ideXlab platform.
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Testing Gas Dispersion modelling: A case study at La Soufrière volcano (Guadeloupe, Lesser Antilles)
'Elsevier BV', 2021Co-Authors: Massaro Silvia, Dioguardi Fabio, Sandri Laura, Tamburello Giancarlo, Selva Jacopo, Moune Séverine, Jessop David, Moretti Roberto, Komorowski Jean-christophe, Costa AntonioAbstract:Co-auteur étrangerInternational audienceVolcanic Gas dispersal can be a serious threat to people living near active volcanoes since it can have short- and long-term effects on human health, and severely damage crops and agricultural land. In recent decades, reliable computational models have significantly advanced, and now they may represent a valuable tool to make quantitative and testable predictions, supporting Gas dispersal forecasting and hazard assessments for public safety. Before applying a specific modelling tool into hazard quantification, its calibration and its sensitivity to initial and boundary conditions should be carefully tested against available data, in order to produce unbiased hazard quantifications. In this study, we provided a number of prototypical tests aimed to validate the modelling of Gas dispersal from a hazard perspective. The tests were carried out at La Soufrière de Guadeloupe volcano, one of the most active Gas emitters in the Lesser Antilles. La Soufrière de Guadeloupe has shown quasi-permanent deGassing of a low-temperature hydrothermal nature since its last magmatic eruption in 1530 CE, when the current dome was emplaced.We focused on the distribution of CO2 and H2S discharged fromthe threemain present-day fumarolic sources at the summit, using the measurements of continuous Gas concentrations collected in the period March–April 2017. We developed a new probabilistic implementation of the Eulerian code DISGas-2.0 for passive Gas Dispersion coupled with the mass-consistent DiagnosticWindModel, using local wind measurements and atmospheric stability information froma local meteorological station and ERA5 reanalysis data.We found that model outputswere not significantly affected by the type of wind data but rather upon the relative positions of fumaroles and measurement stations. Our results reproduced the statistical variability in daily averages of observed data over the investigated period within acceptable ranges, indicating the potential usefulness of DISGas-2.0 as a tool for reproducing the observed fumarolic deGassing and for quantifying Gas hazard at La Soufrière. The adopted testing procedure allows for anaware application of simu ation tools for quantifying the hazard, and thus we think that this kind of testing should actually be the first logical step to be taken when applying a simulator to assess (Gas) hazard in any other volcanic contexts
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Testing Gas Dispersion modelling: a case study at La Soufrière volcano (Guadeloupe, Lesser Antilles)
'Elsevier BV', 2021Co-Authors: Massaro Silvia, Dioguardi Fabio, Sandri Laura, Tamburello Giancarlo, Selva Jacopo, Moune Séverine, Moretti Roberto, Komorowski Jean-christophe, Jessop, David E., Costa AntonioAbstract:Volcanic Gas dispersal can be a serious threat to people living near active volcanoes since it can have short- and long-term effects on human health, and severely damage crops and agricultural land. In recent decades, reliable computational models have significantly advanced, and now they may represent a valuable tool to make quantitative and testable predictions, supporting Gas dispersal forecasting and hazard assessments for public safety. Before applying a specific modelling tool into hazard quantification, its calibration and its sensitivity to initial and boundary conditions should be carefully tested against available data, in order to produce unbiased hazard quantifications. In this study, we provided a number of prototypical tests aimed to validate the modelling of Gas dispersal from a hazard perspective. The tests were carried out at La Soufrière de Guadeloupe volcano, one of the most active Gas emitters in the Lesser Antilles. La Soufrière de Guadeloupe has shown quasi-permanent deGassing of a low-temperature hydrothermal nature since its last magmatic eruption in 1530 CE, when the current dome was emplaced. We focused on the distribution of CO2 and H2S discharged from the three main present-day fumarolic sources at the summit, using the measurements of continuous Gas concentrations collected in the period March–April 2017. We developed a new probabilistic implementation of the Eulerian code DISGas-2.0 for passive Gas Dispersion coupled with the mass-consistent Diagnostic Wind Model, using local wind measurements and atmospheric stability information from a local meteorological station and ERA5 reanalysis data. We found that model outputs were not significantly affected by the type of wind data but rather upon the relative positions of fumaroles and measurement stations. Our results reproduced the statistical variability in daily averages of observed data over the investigated period within acceptable ranges, indicating the potential usefulness of DISGas-2.0 as a tool for reproducing the observed fumarolic deGassing and for quantifying Gas hazard at La Soufrière. The adopted testing procedure allows for an aware application of simulation tools for quantifying the hazard, and thus we think that this kind of testing should actually be the first logical step to be taken when applying a simulator to assess (Gas) hazard in any other volcanic contexts
Yitian Fang - One of the best experts on this subject based on the ideXlab platform.
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Gas mixing in a multi stage conversion fluidized bed mfb with secondary air injection part i an experimental study
RSC Advances, 2016Co-Authors: Rong Zhang, Sufang Song, Junguo Li, Zhiyu Wang, Yitian FangAbstract:This paper investigated the distribution of secondary air after injection into a multi-stage conversion fluidized bed (MFB) cold model. Carbon dioxide (CO2) was used as the tracer and its concentration was tested. The effects of the velocity of the primary air and secondary air, the particle circulating rate, and the diameter, number and included angle with the central line of the riser of injectors on the distribution of CO2 were studied. Single- and multi-injector systems were applied, in which different designs of the secondary-air injectors were used. The radial Gas Dispersion coefficient was calculated by the dispersed plug flow model (DPFM). The concentration profile of the tracer and calculated radial Gas Dispersion coefficients indicated that lower velocity of primary air, higher velocity of secondary air and particle circulating rate, bigger size of injectors and smaller included angles of injectors helped the Gas mixing of the secondary air in the MFB. The tangential injection of secondary air would induce a gathering of Gasification agents in the region near the wall, which was undesirable for the operation of the MFB Gasifier. The variation of the penetration depth of the secondary air indicated that the penetration depth under multi-injector system was smaller than that under single-injector system when other operational parameters were uniform. Thus, according to numbers of injectors, taking the included angles between injectors and the central line of the riser into consideration, the penetration depth of the secondary air was correlated with operational parameters.
Narasimha Mangadoddy - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamic study of two phase flow of column flotation using electrical resistance tomography and pressure probe techniques
Separation and Purification Technology, 2017Co-Authors: Balraju Vadlakonda, Narasimha MangadoddyAbstract:Gas Dispersion characteristics are very important to design and selection of flotation process for the fine particle separation. Although the separation of flotation process heavily depends on hydrophobicity of given solid particles, but their rate of attachment and detachment depends on local Gas Dispersion characteristics. In this work, Gas Dispersion characteristics in a 100 mm laboratory column flotation have been investigated by exploring the flow behavior in terms of the local and mean Gas hold-up, bubble rise velocity and bubble size distribution across the column. This experimental data has been used to demonstrate the validation of the two-fluid CFD model predictions in the column flotation. The column hydrodynamics are estimated by using high speed dual planar Electrical Resistance Tomography (ERT) system and pressure transducers. In all the experiments, water is used as the liquid phase and air (bubbles) as the disperse phase. Using the ERT system, measurement of two phase distributions are examined for a wide range of design and operating conditions of the column including different spargers and frother dosage, where the flow changes from homogenous to transition bubbly flow. It is confirmed by ERT that the Gas-holdup increases with an increase in the sparger porosity, air superficial velocity, liquid height and liquid feed flow rate. To test the reliability of ERT measurements, simultaneously a set of pressure transducers is used to obtain the sectional average Gas holdup and validated. It is observed that bubble density occupancy is more at center region of the column and Gas holdup value increases with the increase of Gas superficial velocity. Dynamic Gas disengagement technique is utilized to measure bubble rise velocity and sauter mean bubble diameter. At end this ERT data has been used to validate two-fluid CFD model (modified with suitable drag and lift forces via user defined functions) predictions in the column and found a close agreement.
Donald L Ermak - One of the best experts on this subject based on the ideXlab platform.
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on the application of computational fluid dynamics codes for liquefied natural Gas Dispersion
Journal of Hazardous Materials, 2007Co-Authors: Anay Luketahanlin, Ronald P Koopman, Donald L ErmakAbstract:Computational fluid dynamics (CFD) codes are increasingly being used in the liquefied natural Gas (LNG) industry to predict natural Gas Dispersion distances. This paper addresses several issues regarding the use of CFD for LNG Dispersion such as specification of the domain, grid, boundary and initial conditions. A description of the k–ɛ model is presented, along with modifications required for atmospheric flows. Validation issues pertaining to the experimental data from the Burro, Coyote, and Falcon series of LNG Dispersion experiments are also discussed. A description of the atmosphere is provided as well as discussion on the inclusion of the Coriolis force to model very large LNG spills.
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on the application of computational fluid dynamics codes for liquefied natural Gas Dispersion
Proposed for publication in the Journal of Hazardous Materials., 2006Co-Authors: Anay Luketahanlin, Ronald P Koopman, Donald L ErmakAbstract:Computational fluid dynamics (CFD) codes are increasingly being used in the liquefied natural Gas (LNG) industry to predict natural Gas Dispersion distances. This paper addresses several issues regarding the use of CFD for LNG Dispersion such as specification of the domain, grid, boundary and initial conditions. A description of the k-{var_epsilon} model is presented, along with modifications required for atmospheric flows. Validation issues pertaining to the experimental data from the Burro, Coyote, and Falcon series of LNG Dispersion experiments are also discussed. A description of the atmosphere is provided as well as discussion on the inclusion of the Coriolis force to model very large LNG spills.
Koichi Sada - One of the best experts on this subject based on the ideXlab platform.
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Large-eddy simulation coupled to mesoscale meteorological model for Gas Dispersion in an urban district
Atmospheric Environment, 2013Co-Authors: Takenobu Michioka, Ayumu Sato, Koichi SadaAbstract:Abstract A microscale large-eddy simulation (LES) model coupled to a mesoscale LES model is implemented to estimate a ground concentration considering the meteorological influence in an actual urban district. The microscale LES model is based on a finite volume method with an unstructured grid system to resolve the flow structure in a complex geometry. The Advanced Regional Prediction System (ARPS) is used for mesoscale meteorological simulation. To evaluate the performance of the LES model, 1-h averaged concentrations are compared with those obtained by field measurements, which were conducted for tracer Gas Dispersion from a point source on the roof of a tall building in Tokyo. The concentrations obtained by the LES model without combing the mesoscale LES model are in quite good agreement with the wind-tunnel experimental data, but overestimates the 1 h averaged ground concentration in the field measurements. On the other hand, the ground concentrations using the microscale LES model coupled to the mesoscale LES are widely distributed owing to large-scale turbulent motions generated by the mesoscale LES, and the concentrations are nearly equal to the concentrations from the field measurements.
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Wind-Tunnel Experiments for Gas Dispersion in an Atmospheric Boundary Layer with Large-Scale Turbulent Motion
Boundary-Layer Meteorology, 2011Co-Authors: Takenobu Michioka, Ayumu Sato, Koichi SadaAbstract:Large-scale turbulent motions enhancing horizontal Gas spread in an atmospheric boundary layer are simulated in a wind-tunnel experiment. The large-scale turbulent motions can be generated using an active grid installed at the front of the test section in the wind tunnel, when appropriate parameters for the angular deflection and the rotation speed are chosen. The power spectra of vertical velocity fluctuations are unchanged with and without the active grid because they are strongly affected by the surface. The power spectra of both streamwise and lateral velocity fluctuations with the active grid increase in the low frequency region, and are closer to the empirical relations inferred from field observations. The large-scale turbulent motions do not affect the Reynolds shear stress, but change the balance of the processes involved. The relative contributions of ejections to sweeps are suppressed by large-scale turbulent motions, indicating that the motions behave as sweep events. The lateral Gas spread is enhanced by the lateral large-scale turbulent motions generated by the active grid. The large-scale motions, however, do not affect the vertical velocity fluctuations near the surface, resulting in their having a minimal effect on the vertical Gas spread. The peak concentration normalized using the root-mean-squared value of concentration fluctuation is remarkably constant over most regions of the plume irrespective of the operation of the active grid.
