Numerical Simulations of the Interaction of Jets with the Intracluster Medium     

Gianluigi Bodo  Claudio Zanni  Giuseppe Murante  Paola Rossi  Silvano Massaglia  Attilio Ferrari 《Astrophysics and Space Science》2004,293(1-2):247-254

We study, by numerical simulations, the propagation of an axisymmetric supersonic jet in an isothermal King atmosphere and we analyse the evolution of the resulting X-ray properties and their dependence on the jet physical parameters. We show the existence of two distinct regimes of interaction, with strong and weak shocks. In the first case shells of enhanced X-ray emission are to be expected, whereas in the second case we expect deficit of X-ray emission coincident with the cocoon. Analysing the results of our simulations we find that the jet kinetic power is the main parameter controlling the transition between the two regimes. We also discuss, in the same scheme, the ICM heating induced by the jet propagation, considering its effects on the observed relations between the cluster X-ray luminosity and temperature and between cluster entropy and temperature.  相似文献   

On the evolutionary status of early-type galaxies in clusters at z≈ 0.2 – I. The Fundamental Plane     

Alexander Fritz  Bodo L. Ziegler  Richard G. Bower  Ian Smail  Roger L. Davies 《Monthly notices of the Royal Astronomical Society》2005,358(1):233-255

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Entrainment and Deceleration of Relativistic Jets     

Paola Rossi  Gianluigi Bodo  Silvano Massaglia  Attilio Ferrari  Andrea Mignone 《Astrophysics and Space Science》2004,293(1-2):149-155

Extragalactic radio sources are separated in two classes according to their specific luminosity: Fanaroff-Riley I and II. The origin of this dichotomy can be due either to intrinsec different properties of the AGN or to interaction of the jet with different enviroments. We assume that jets are always relativistic and supersonic close to their source, as recent observations suggest, and we explore the conditions in which the jets decelerate assuming FR I morphology. We have carried out high resolution 3D simulations for a set of parameters and in this paper we concentrate our discussion on two extreme cases.  相似文献   

A five-wave Harten–Lax–van Leer Riemann solver for relativistic magnetohydrodynamics     

A. Mignone  M. Ugliano  G. Bodo 《Monthly notices of the Royal Astronomical Society》2009,393(4):1141-1156

We present a five-wave Riemann solver for the equations of ideal relativistic magneto-hydrodynamics. Our solver can be regarded as a relativistic extension of the five-wave HLLD Riemann solver initially developed by Miyoshi & Kusano for the equations of ideal magnetohydrodynamics. The solution to the Riemann problem is approximated by a five-wave pattern, comprising two outermost fast shocks, two rotational discontinuities and a contact surface in the middle. The proposed scheme is considerably more elaborate than in the classical case since the normal velocity is no longer constant across the rotational modes. Still, proper closure to the Rankine–Hugoniot jump conditions can be attained by solving a non-linear scalar equation in the total pressure variable which, for the chosen configuration, has to be constant over the whole Riemann fan. The accuracy of the new Riemann solver is validated against one-dimensional tests and multidimensional applications. It is shown that our new solver considerably improves over the popular Harten–Lax–van Leer solver or the recently proposed HLLC schemes.  相似文献   

Exploration of Tunnel Alignment using Geophysical Methods to Increase Safety for Planning and Minimizing Risk     

Bodo Lehmann  Dirk Orlowsky  Rüdiger Misiek 《Rock Mechanics and Rock Engineering》2010,43(1):105-116

Engineering geophysics provides valuable and continuous information for the planning and execution of tunnel construction projects. For geotechnical purposes special high-resolution geophysical methods have been developed during the last decades. The importance of applying geophysical methods in addition to usually used geological and geotechnical exploration techniques is increasing. The main goal is to achieve an accurate and continuous model of the subsurface in a relative short period of operation time. The routine application of engineering geophysical methods will increase in the coming years. Due to the high acceptance of engineering geophysics at construction sites, much wider application of geophysical investigations is expected. The combination of different methods—geophysics, geology, and geotechnics as well as the so-called joint interpretation techniques—will be of essential importance. Engineering geophysics will play an important role during the three phases: geological investigation, tunnel planning, and execution of tunnel construction. If hazards are well known in advance of a tunnel project the safety of workers will essentially be increased and geological risks will be minimized by means of successful and interdisciplinary cooperation.  相似文献   

The early-type galaxy population in Abell 2218     

Bodo L. Ziegler †  Richard G. Bower  Ian Smail  Roger L. Davies  David Lee‡ 《Monthly notices of the Royal Astronomical Society》2001,325(4):1571-1590

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On Wind Forces in the Forest-Edge Region During Extreme-Gust Passages and Their Implications for Damage Patterns     

Christof Gromke  Bodo Ruck 《Boundary-Layer Meteorology》2018,166(2):269-299

We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.  相似文献   

Impact of the Atatürk Dam Lake on Agro-Meteorological Aspects of the Southeastern Anatolia Region,Turkey     

Orkan Özcan  Bodo Bookhagen  Nebiye Musaoğlu 《Journal of the Indian Society of Remote Sensing》2018,46(3):471-481

In this study, the spatial and temporal impacts of the Atatürk Dam on agro-meteorological aspects of the Southeastern Anatolia region have been investigated. Change detection and environmental impacts due to water-reserve changes in Atatürk Dam Lake have been determined and evaluated using multi-temporal Landsat satellite imageries and meteorological datasets within a period of 1984–2011. These time series have been evaluated for three time periods. Dam construction period constitutes the first part of the study. Land cover/use changes especially on agricultural fields under the Atatürk Dam Lake and its vicinity have been identified between the periods of 1984–1992. The second period comprises the 10-year period after the completion of filling up the reservoir in 1992. At this period, Landsat and meteorological time-series analyses are examined to assess the impact of the Atatürk Dam Lake on selected irrigated agricultural areas. For the last 9-year period from 2002 to 2011, the relationships between seasonal water-reserve changes and irrigated plains under changing climatic factors primarily driving vegetation activity (monthly, seasonal, and annual fluctuations of rainfall rate, air temperature, humidity) on the watershed have been investigated using a 30-year meteorological time series. The results showed that approximately 368 km² of agricultural fields have been affected because of inundation due to the Atatürk Dam Lake. However, irrigated agricultural fields have been increased by 56.3% of the total area (1552 of 2756 km²) on Harran Plain within the period of 1984–2011.  相似文献   

Landslide cost modeling for transportation infrastructures: a methodological approach     

Martin Klose  Bodo Damm  Birgit Terhorst 《Landslides》2015,12(2):321-334

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Quantifying the EEJ current with ground-based ionosonde inferred vertical E × B drifts in the morning hours over Ilorin,West Africa     

Jacob O. Adeniyi  Isaac A. Adimula  Babatunde O. Adebesin  Bodo W. Reinisch  Olusola A. Oladipo  Olayinka Olawepo  Kiyohumi Yumoto 《Acta Geophysica》2014,62(3):656-678

The relationship between the ground-based inferred vertical E × B drifts, Vz, and the magnetic equatorial electrojet current during the year of solar minima was presented. Both the diurnal and seasonal Vz variations are positively directed during the daytime and negative at nighttime. The evening time pre-reversal enhancement occurs around 19:00 LT. The fairly strong linear relationship between the electrojet current strength and Vz exhibited higher correlations during the daytime (06:00–16:00 LT). The maximum morning time proxy parameter described by E = [d (ΔH _ILR)/dt]_max in the morning hours, indicating the east-west electric field in the EEJ, corresponds reasonably well with the E × B drift and, hence, can be used as a proxy parameter for representing Vz in the morning hours. The daytime EEJ magnitude seasonal changes are connected with a change in conductivity emerging from the action of turbulence and divergence of momentum flux. These waves above the dynamo region are suggested to lead to partial counter electrojet during the equinoctial months.  相似文献