排序方式： 共有16条查询结果，搜索用时 15 毫秒
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Alexei Kritsuk Tomasz Plewa Ewald Müller 《Monthly notices of the Royal Astronomical Society》2001,326(1):11-22
We use hydrodynamic simulations with adaptive grid refinement to study the dependence of hot gas flows in X-ray luminous giant elliptical galaxies on the efficiency of heat supply to the gas. We consider a number of potential heating mechanisms including Type Ia supernovae and sporadic nuclear activity of a central supermassive black hole. As a starting point for this research we use an equilibrium hydrostatic recycling model. We show that a compact cooling inflow develops, if the heating is slightly insufficient to counterbalance radiative cooling of the hot gas in the central few kiloparsecs. An excessive heating in the centre, instead, drives a convectively unstable outflow. We model the onset of the instability and a quasi-steady convective regime in the core of the galaxy in two dimensions assuming axial symmetry.
Provided the power of net energy supply in the core is not too high, the convection remains subsonic. The convective pattern is dominated by buoyancy driven large-scale mushroom-like structures. Unlike in the case of a cooling inflow, the X-ray surface brightness of an (on average) isentropic convective core does not display a sharp maximum at the centre. A hybrid model, which combines a subsonic peripheral cooling inflow with an inner convective core, appears to be stable. We also discuss observational implications of these results. 相似文献
Provided the power of net energy supply in the core is not too high, the convection remains subsonic. The convective pattern is dominated by buoyancy driven large-scale mushroom-like structures. Unlike in the case of a cooling inflow, the X-ray surface brightness of an (on average) isentropic convective core does not display a sharp maximum at the centre. A hybrid model, which combines a subsonic peripheral cooling inflow with an inner convective core, appears to be stable. We also discuss observational implications of these results. 相似文献
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Greg Weirs Vikram Dwarkadas Tomek Plewa Chris Tomkins Mark Marr-Lyon 《Astrophysics and Space Science》2005,298(1-2):341-346
As a component of the Flash Center’s validation program, we compare FLASH simulation results with experimental results from
Los Alamos National Laboratory. The flow of interest involves the lateral interaction between a planar M
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= 1.2 shock wave with a cylinder of gaseous sulfur hexafluoride (SF6) in air, and in particular the development of primary and secondary instabilities after the passage of the shock. While the
overall evolution of the flow is comparable in the simulations and experiments, small-scale features are difficult to match.
We focus on the sensitivity of numerical results to simulation parameters. 相似文献
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Crustal profiles of active continental collisional belt: Czechoslovak deep seismic reflection profiling in the West Carpathians 总被引：1，自引：0，他引：1
&#;estmr Tomek Libu&#;e Dvo&#;áková Ivan Ibrmajer Rudolf Jirícek Tomás Koráb 《Geophysical Journal International》1987,89(1):383-388
Summary. Czechoslovak deep seismic reflection profiles across the West Carpathians, the first in the Alpine-Himalayan belt, and surface geological data, suggest that the passive margin of the Eurasian plate was obliquely overriden by the upper Carpatho-Pannonian plate during the end of the Krosno sea subduction some 17-14 Ma ago. The following period was dominated by slight oblique continental collision (transpression and transtension) of the West Carpathian-East Alpine continental material escaping from the East Alpine collision zone and Eurasian Brunovistulic passive margin. Crustal shortening in the North was accommodated by significant northerly dipping backthrusting and crustal thickening. Backthrusting is clearly observable on deep seismic lines 2T and 3T. Different subsidence features are present on the deep seismic line 3T. There are active pull-apart graben in the Vienna basin, mid-Miocene (16–10 Ma) low-angle normal faulting in the Danube basin, and there is a normal simple shear zone offsetting the Moho boundary beneath the Danube basin. 相似文献
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Špičák A. Horálek J. Boušková A. Tomek Č. Vaněk J. 《Studia Geophysica et Geodaetica》1999,43(1):87-106
We are proposing a hypothesis that earthquake swarms in the West Bohemia/Vogtland seismoactive region are generated by magmatic activity currently transported to the upper crustal layers. We assume that the injection of magma and/or related fluids and gases causes hydraulic fracturing which is manifested as an earthquake swarm at the surface. Our statements are supported by three spheres of evidence coming from the western part of the Bohemian Massif: characteristic manifestations of recent geodynamic activity, the information from the neighbouring KTB deep drilling project and from the 9HR seismic reflection profile, and the detailed analysis of local seismological data. (1) Recent manifestations of geodynamic activity include Quaternary volcanism, rich CO
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emissions, anomalies of mantle-derived
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He, mineral springs, moffets, etc. (2) The fluid injection experiment in the neighbouring KTB deep borehole at a depth of 9 km induced hundreds of micro-earthquakes. This indicates that the Earth's crust is near frictional failure in the western part of the Bohemian Massif and an addition of a small amount of energy to the tectonic stress is enough to induce an earthquake. Some pronounced reflections in the closely passing 9HR seismic reflection profile are interpreted as being caused by recent magmatic sills in the crust. (3) The local broadband seismological network WEBNET provides high quality data that enable precise localization of seismic events. The events of the January 1997 earthquake swarm are confined to an extremely narrow volume at depths of about 9 km. Their seismograms display pronounced reflections of P- and S-waves in the upper crust. The analysis of the process of faulting has disclosed a considerable variability of the source mechanism during the swarm.
We conclude that the mechanism of intraplate earthquake swarms generated by magma intrusions is similar to that of induced seismicity. As the recent tectonic processes and manifestations of geodynamic activity are similar in European areas with repeated earthquake swarm occurrence (Bohemian Massif, French Massif Central, Rhine Graben), we assume that magma intrusions and related fluid and gas release at depths of about 10 km are the universal cause of intraplate earthquake swarm generation 相似文献
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M. de Val-Borro R. G. Edgar P. Artymowicz P. Ciecielag P. Cresswell G. D'Angelo E. J. Delgado-Donate G. Dirksen S. Fromang A. Gawryszczak H. Klahr W. Kley W. Lyra F. Masset G. Mellema R. P. Nelson S.-J. Paardekooper A. Peplinski A. Pierens T. Plewa K. Rice C. Schäfer R. Speith 《Monthly notices of the Royal Astronomical Society》2006,370(2):529-558
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C. C. Kuranz R. P. Drake T. L. Donajowski K. K. Dannenberg M. Grosskopf D. J. Kremer C. Krauland D. C. Marion H. F. Robey B. A. Remington J. F. Hansen B. E. Blue J. Knauer T. Plewa N. Hearn 《Astrophysics and Space Science》2007,307(1-3):115-119
We present data from recent high-energy-density laboratory experiments designed to explore the Rayleigh–Taylor instability
under conditions relevant to supernovae. The Omega laser is used to create a blast wave structure that is similar to that
of the explosion phase of a core-collapse supernova. An unstable interface is shocked and then decelerated by the planar blast
wave, producing Rayleigh–Taylor growth. Recent experiments were performed using dual, side-on, x-ray radiography to observe
a 3D “egg crate” mode and an imposed, longer-wavelength, sinusoidal mode as a seed perturbation. This paper explores the method
of data analysis and accurately estimating the position of important features in the data. 相似文献
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M. J. Grosskopf R. P. Drake C. C. Kuranz A. R. Miles J. F. Hansen T. Plewa N. Hearn D. Arnett J. C. Wheeler 《Astrophysics and Space Science》2009,322(1-4):57-63
The National Ignition Facility (NIF) will soon provide experiments with far more than ten times the energy than has been previously available on laser facilities. In the context of supernova-relevant hydrodynamics, this will enable experiments in which hydrodynamic instabilities develop from multiple, coupled interfaces in a diverging explosion. This paper discusses the design of such blast-wave-driven explosions in which the relative masses of the layers are scaled to those within the star. It reports scaling simulations with CALE to model the global dynamics of such an experiment. CALE is a hybrid, Arbitrary Lagrangian-Eulerian code. The simulations probed the instability growth and multi-interface interactions in mass-scaled systems using different materials. The simulations assist in the target design process and in developing an experiment that can be diagnosed. 相似文献