Search results for "Plume"

Turbulences of the supersonic gas flow during cold spraying and their negative effects: A DNS CFD analysis coupled with experimental observation and …

2020

Abstract This paper investigates the phenomenological flow during cold spraying through DNS CFD analysis and experimental observations. The transient DNS computation shows that the gas flow begins to be instable inside the nozzle and generates self-sustained intermittent swirls across the nozzle exit due the shearing behavior of the flow. There is alternate swirling within the separated sheared layers on top and then on bottom of the jet, at sporadic time intervals. The swirls are not strictly periodic in nature, but they recur with an irregular frequency. The temperature field exhibits analogous variation and the thermal turbulence produces a heating confinement within the end zone of the …

Contrail formation in the tropopause region caused by emissions from an Ariane 5 rocket

2016

Rockets directly inject water vapor and aerosol into the atmosphere, which promotes the formation of ice clouds in ice supersaturated layers of the atmosphere. Enhanced mesospheric cloud occurrence has frequently been detected near 80 km altitude a few days after rocket launches. Here, we present unique evidence for cirrus formation in the tropopause region caused by ice nucleation in the exhaust plume from an Ariane 5-ECA rocket. Meteorological reanalysis data from the European Centre for Medium-Range Weather Forecasts show significant ice supersaturation at the 100 hPa level in the American tropical tropopause region on 26 November 2011. Near 17 km altitudes temperatures are below the Sch…

Stratospheric Aerosols After Pinatubo: Results from the 1991/2 Airborne Arctic Stratospheric Expedition (AASE II)

1996

The Airborne Arctic Stratospheric Expedition II involved measurements of key quantities concerning the chemistry and physics of the stratospheric ozone loss from the NASA operated DC-8 and ER-2 platforms. The series of AASE II flights was conducted between August 22, 1991, until March 26, 1992, from Moffett Field (California), Fairbanks (Alaska), and Bangor (Maine). The timing and location of the AASE II flights permitted to obtain a large data basis pertaining to the effects of the Mt. Pinatubo volcanic plume spreading in the northern hemispheric stratosphere. This contribution presents results obtained from the ER-2 in-situ measurements up to altitudes of ≈ 20 km in the polar stratosphere…

Mantle Plumes

2001

A magmatic failed rift beneath the Gongola arm of the upper Benue trough, Nigeria?

2001

Abstract A magnetic anomaly map of the Gongola arm of the upper Benue trough was compiled from existing half-degree sheets of the upper Benue trough. The map is dominated by an elongated NE–SW magnetic low anomaly that stretches over a 100 km distance and has an average width of about 20 km. A combination of Werner deconvolution and forward modeling techniques on selected profiles across the major NE–SW anomaly lead to the conclusion that the anomaly may be caused by predominantly mafic rocks at depths of between 6 and 10 km, well below the base of the sediments, which are generally not more than 4.5 km thick. The presence of large and continuous bodies of mafic rocks indicated by these res…

Geodynamic Setting of the Tertiary Hocheifel Volcanism (Germany), Part I: 40Ar/39Ar geochronology

2007

The Eifel volcanism is part of the Cenozoic Central European Volcanic Province and is located close to the Rhine Graben which has been formed by rifting and subsidence since the Eocene. Whereas the Quaternary volcanism of the Eifel appears to be genetically related to mantle plume activity, the cause of the Tertiary volcanism of the Hocheifel volcanic field is less clear. Here, we present geochronological evidence for the geotectonic setting of the Tertiary Eifel volcanism based on 40Ar/39Ar dating of 27 samples from 25 volcanic occurrences. Included are samples from the northern Upper Rhine Graben in order to evaluate a possible relationship between Hocheifel volcanism and Rhine Graben tap…

Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves

2016

AbstractVolcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencie…

Lithosphere Structure, Heat Flow, Gravity, and Other Geoparameters in Central Europe

1991

To clarify structure and evolution of Central European lithosphere, an approach is taken which combines several methods: multivariate statistical data analysis and modelling of data sets, as geology, crustal structure, seismic travel times, heat flow, gravity, geoid heights, topography, vertical motions and unloading affects.

The use of tree-rings and foliage as an archive of volcanogenic cation deposition.

2007

Tree cores (Pinus nigra ssp. laricio) and leaves (Castanea sativa) from the flanks of Mount Etna, Sicily were analysed by ICP-MS to investigate whether volcanogenic cations within plant material provide an archive of a volcano's temporal and spatial depositional influence. There is significant compositional variability both within and between trees, but no systematic dendrochemical correlation with periods of effusive, explosive or increased degassing activity. Dendrochemistry does not provide a record of persistent but fluctuating volcanic activity. Foliar levels of bioaccumulated cations correspond to modelled plume transport patterns, and map short-term volcanic fumigation. Around the fl…

Classifying Major Explosions and Paroxysms at Stromboli Volcano (Italy) from Space

2021

Stromboli volcano has a persistent activity that is almost exclusively explosive. Predominated by low intensity events, this activity is occasionally interspersed with more powerful episodes, known as major explosions and paroxysms, which represent the main hazards for the inhabitants of the island. Here, we propose a machine learning approach to distinguish between paroxysms and major explosions by using satellite-derived measurements. We investigated the high energy explosive events occurring in the period January 2018–April 2021. Three distinguishing features are taken into account, namely (i) the temporal variations of surface temperature over the summit area, (ii) the magnitude of the …