共查询到20条相似文献，搜索用时 31 毫秒
1.
HUANG Suiliang 《国际泥沙研究》1998,(2)
ＶＡＲＩＡＴＩＯＮＳＯＦＷＡＴＥＲＳＵＲＦＡＣＥＧＲＡＤＩＥＮＴＡＮＤＶＥＬＯＣＩＴＹＤＩＳＴＲＩＢＵＴＩＯＮＣＡＵＳＥＤＢＹＷＡＴＥＲＪＥＴＳＨＵＡＮＧＳｕｉｌｉａｎｇ１ＡＢＳＴＲＡＣＴＵｓｉｎｇｆｌｕｍｅｅｘｐｅｒｉｍｅｎｔｓ,ｔｈｉｓｐａｐｅｒ... 相似文献
2.
Short-lived plasma jets of various scales, from giant X-ray jets more than 300 Mm in extent to numerous small jets with sizes
typical of macrospicules, are the phenomena observed in the solar corona in extreme ultraviolet and X-ray emission. Small
jets are particularly prominent in polar coronal holes. They are close neighbors of tiny bright loops and coincide in time
with their sudden brightening and increase in size. The geometric shape of the jets and their location suggest that they arise
near singular null points of the coronal magnetic field. These points appear in coronal holes due to the emergence of small
bipolar or unipolar magnetic structures within large-scale unipolar cells. Polar jets show a distinct vertical plasma motion
in a coronal hole that introduces significant momentum and mass into the solar wind flow. Investigating the dynamics of polar
jets can elucidate certain details in the problem of fast solar wind acceleration. 相似文献
3.
CHAO JiPing & LIU Fei National Marine Environmental Forecasting Center Beijing China The First Institute of Oceanography SOA Qingdao China Key Laboratory Regional Climate-Environment for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(1):153-160
Based on the developed Anderson and Moore's theory about cross-equatorial inertial jets and a nonlinear equivalence shallow water model, new universal functions are determined by the characters of the vortical large-scale air flow (atmosphere) or ocean current (ocean) related to the jet, then the potential vorticity and energy conservation equations along the streamline in the cross-equatorial in-ertial jets can be obtained. Because the governing equations are nonlinear, some limited multiple equi-libria of cross-equatorial inertial jets may exist. According to the character of large-scale air flow or ocean current outside the jets, the existent criterion for multiple eqnilibria in cross-equatorial inertial jets is discussed, and two examples for multiple equilibia of nonlinear governing equations are given. 相似文献
4.
Andrew Orr Edward Hanna Julian C.R. Hunt John Cappelen Konrad Steffen AG Stephens 《Pure and Applied Geophysics》2005,162(10):1747-1778
The main characteristic features of stable atmospheric flows over a large mountain plateau are summarised and then compared with mesoscale and synoptic scale numerical simulation, meteorological analysis, satellite imagery, and surface observations for the cases of flows over Southern Greenland for four wind directions. The detailed features are identified using the concepts and scaling of stably stratified flow over large mountains with variations in surface roughness, elevation, and heating. For westerly and easterly winds detached jets form at the southern tip, where coastal jets converge, which propagate large distances across the ocean. Near coasts katabatic winds can combine with barrier jets and wake flows generated by synoptic winds. Note how the approach flow rises/falls over southern Greenland for easterly/westerly winds, leading in both cases to more cloud on the western side. Some conclusions are drawn about the large-scale influences of these flows; detached jets in the atmosphere; air-sea interaction; formation of low pressure systems. For accurate simulations of these flows, mesoscale models are necessary with resolutions of order of 20 km or less. 相似文献
5.
We show a mechanism whereby the jets result during the development of β-plumes (i.e., low-frequency Rossby waves that establish gyre circulations) in a model of ocean-basin circulation. The energy originates in baroclinic meanders of circulation at the eastern boundary of the ocean. Eddies are intimately related and occur as a result of the instability of this process. This mechanism does not rely on the existence of the small-scale turbulence to establish zonal flows. Zonal jets can then be amplified by eddies arranged in certain order in the flow. The underlying dynamics include the propagation of linear and nonlinear basin scale Rossby waves. The related barotropic theory for these waves is developed here. We demonstrate the radiative development of jets and β-plumes in a laboratory experiment using a rotating fluid with a paraboloidal free surface. The dynamical fields are measured by the laboratory analog of the satellite altimetry. 相似文献
6.
Nocturnal basin low-level jets: an integrated study 总被引：1，自引：0，他引：1
Joan Cuxart 《Acta Geophysica》2008,56(1):100-113
Low-level jets (LLJs) are a very common feature in the nocturnal stably stratified boundary layer. Many factors can intervene
in their generation, linked basically to effects of baroclinity. A special kind of low-level jets is composed by the nocturnal
katabatic and basin flows, generated over terrain slopes. A study of observed LLJs in the Duero Basin is shown here, combining
observational data and modelling experiments. Normalized in respect to the maximum wind height, the dynamic characteristics
of the jets are similar: a two-layer system, with a stably stratified layer below the jet maximum and a near neutral layer
above, with a very stable layer separating them at the level of the wind maximum. There is vertical mixing above and below
the jet, and the connection between these layers takes place occasionally in a very turbulent manner. 相似文献
7.
L. P. Babich A. Yu. Kudryavtsev M. L. Kudryavtseva I. M. Kutsyk 《Geomagnetism and Aeronomy》2008,48(3):378-391
Gigantic upward atmospheric discharges have been numerically simulated. The space-time distributions of the self-consistent electric field strength and charged particle densities have been obtained. The brightness, color, and evolution in the space and time of fluorescence above a thundercloud, which agree with the data of field observations of such high-altitude optical phenomena as blue jets and red sprites, have been calculated. It has been indicated that large duration of blue jets results from the emission of a decaying ion plasma of the air. The yields of hard gamma rays and neutrons, generated by upward discharges, have been calculated. 相似文献
8.
Daniele Andronico Antonio Cristaldi Paola Del Carlo Jacopo Taddeucci 《Journal of Volcanology and Geothermal Research》2009,180(2-4):110
The 2002–03 flank eruption of Etna was characterized by two months of explosive activity that produced copious ash fallout, constituting a major source of hazard and damage over all eastern Sicily. Most of the tephra were erupted from vents at 2750 and 2800 m elevation on the S flank of the volcano, where different eruptive styles alternated. The dominant style of explosive activity consisted of discrete to pulsing magma jets mounted by wide ash plumes, which we refer to as ash-rich jets and plumes. Similarly, ash-rich explosive activity was also briefly observed during the 2001 flank eruption of Etna, but is otherwise fairly uncommon in the recent history of Etna. Here, we describe the features of the 2002–03 explosive activity and compare it with the 2001 eruption in order to characterize ash-rich jets and plumes and their transition with other eruptive styles, including Strombolian and ash explosions, mainly through chemical, componentry and morphology investigations of erupted ash. Past models explain the transition between different styles of basaltic explosive activity only in terms of flow conditions of gas and liquid. Our findings suggest that the abundant presence of a solid phase (microlites) may also control vent degassing and consequent magma fragmentation and eruptive style. In fact, in contrast with the Strombolian or Hawaiian microlite-poor, fluidal, sideromelane clasts, ash-rich jets and plumes produce crystal-rich tachylite clasts with evidence of brittle fragmentation, suggesting that high groundmass crystallinity of the very top part of the magma column may reduce bubble movement while increasing fragmentation efficiency. 相似文献
9.
N. I. Izhovkina 《Geomagnetism and Aeronomy》2010,50(3):362-368
Electric fields in the near-Earth space was studied in the experiments with artificial plasma clouds and jets in the ionosphere
and magnetosphere. The development of a nonmonotonous plasma density stratification of an artificial plasma formation, with
the scale of strata across the geomagnetic field reaching several meters and tens of meters, was observed. It has been indicated
that the electrodynamics of plasma clouds and jets, decomposing into strata, depends on the excitation and decay of fast oscillations
of the electronic plasma component against a background of slow oscillations of the ionic component at frequencies of magnetized
plasma electrostatic oscillations (electrostatic Bernstein modes of the plasma electronic and ionic components and ion acoustic
oscillations). 相似文献
10.
Thomas J Maccarone and Elmar Koerding discuss the phenomenon of astrophysical jets, from their discovery to the latest theories about their origins. 相似文献
11.
The aim of this study is to investigate tide–surge interaction in narrow channels with complex and relatively shallow topography. A high-resolution depth-integrated tidal and storm surge model has been implemented for the Tjeldsund channel which is an important sailing lane in northern Norway. A horizontal grid resolution down to 50 m is applied in order to represent the complex bottom topography and the formation of jets and small-scale eddies. Two typically storm surge events in December 2004 have been examined in detail. The tide–surge interaction is found to influence the generation of higher harmonics and the formation of eddies in the current field. In some cases, the magnitude of storm surge currents may reach the same magnitude as the tidal currents enhancing the formation of jets and eddies. 相似文献
12.
REVIEW ON LOCAL SCOUR DUE TO JETS 总被引：1，自引：0，他引：1
ArindamSARKAR SubhasishDEY 《国际泥沙研究》2004,19(3):210-238
The safety of an apron of the energy dissipator is threatened by the large-scale scour in the downstream of the apron due to the erosive action of a horizontal jet issuing from a sluice opening. Also, large-scale deposition of the scoured sediments due to an impinging jet in a plunging pool type energy dissipator affects the passage of flow adversely in the downstream channels. Owing to the significant practical importance, the problem of local scour due to jets has been studied by many investigators, In this paper, a comprehensive review of the up-to-date investigations on local scour due to horizontal and impinging jets is presented including all possible aspects, such as scouring process, parameters affecting scour, time variation of scour velocity distribution on the apron and within the scour hole, development of boundary layer thickness, bed shear stress, scour estimation formulas and protection works. 相似文献
13.
Geomagnetism and Aeronomy - The goal of the work is to identify and study the dynamics of solar hot jets. Collimated, ray-like structures with temperatures above the transition-zone temperature are... 相似文献
14.
This paper investigates the behavior of katabatic flow induced by an idealized, thermally inhomogeneous surface; a strip of
surface cooling that has a finite width in the along-slope direction and is infinitely long in the cross-slope direction.
Numerical simulations using the Boussinesq equations of motion and the thermodynamic energy equation are performed for various
slope angles and strip lengths. The underlying dynamical processes in the katabatic jet and the near environment are explored
by considering the along-slope momentum balance after a steady state has been achieved.
The inhomogeneous nature of the surface forcing also induces a response in the environment that extends very far away from
the sloped surface. Nearly horizontal jets close to the vertical heights of both sides of the cold strip are observed in the
environment. A horizontal vorticity analysis is performed on these horizontal jets to ascertain their dynamical structure. 相似文献
15.
Evolution of droplets in subsea oil and gas blowouts: Development and validation of the numerical model VDROP-J 总被引：1，自引：0，他引：1
Lin Zhao Michel C. Boufadel Scott A. Socolofsky Eric Adams Thomas King Kenneth Lee 《Marine pollution bulletin》2014
The droplet size distribution of dispersed phase (oil and/or gas) in submerged buoyant jets was addressed in this work using a numerical model, VDROP-J. A brief literature review on jets and plumes allows the development of average equations for the change of jet velocity, dilution, and mixing energy as function of distance from the orifice. The model VDROP-J was then calibrated to jets emanating from orifices ranging in diameter, D, from 0.5 mm to 0.12 m, and in cross-section average jet velocity at the orifice ranging from 1.5 m/s to 27 m/s. The d50/D obtained from the model (where d50 is the volume median diameter of droplets) correlated very well with data, with an R2 = 0.99. Finally, the VDROP-J model was used to predict the droplet size distribution from Deepwater Horizon blowouts. The droplet size distribution from the blowout is of great importance to the fate and transport of the spilled oil in marine environment. 相似文献
16.
Several field studies in bays and estuaries have revealed pronounced subsurface maxima in the vertical profiles of the current amplitude of the principal tidal harmonic, or of its vertical shear, over the water column. To gain fundamental understanding about these phenomena, a semi-analytical model is designed and analysed, with focus on the sensitivity of the vertical structure of the tidal current amplitude to formulations of the vertical shape of the eddy viscosity. The new analytical solutions for the tidal current amplitude are used to explore their dependence on the degree of surface mixing, the vertical shape of eddy viscosity in the upper part of the water column and the density stratification. Sources of surface mixing are wind and whitecapping. Results show three types of current amplitude profiles of tidal harmonics, characterised by monotonically decreasing shear towards the surface, “surface jumps” (vertical shear of tidal current amplitude has a subsurface maximum) and “subsurface jets” (maximum tidal current amplitude below the surface), respectively. The “surface jumps” and “subsurface jets” both occur for low turbulence near the surface, whilst additionally the surface jumps only occur if the eddy viscosity in the upper part of the water column decreases faster than linearly to the surface. Furthermore, “surface jumps” take place for low density stratification, while and “subsurface jets” occur for high density stratification. The physics causing the presence of surface jumps and subsurface jets is also discussed. 相似文献
17.
18.
This paper deals with the summit eruptions of 2015–2016, as well as with the 2016 subterminal eruption of Klyuchevskoi. We estimate the dimensions of the depression that was produced by a landfall in the southeastern trough of the volcano. We estimated the volume and area of landfall deposits. The observed volumes of landfalls during the terminal eruptions of 1944?1945, 1985, and 2016 can vary within 0.006?0.140 km3. The theoretical volumes can reach 4?8 km3. We discuss the leading factors that cause landfalls on Klyuchevskoi. These include irreversible creep at depth, the influence of cracks and fissuring in the volcanic cone, as well as the constant intrusive activity of the volcano. Geodetic measurements revealed that the rates of sliding for several individual patches on the slopes varied between 6.7 cm/yr and 19.4 cm/yr. Video and photographic observations were used to estimate the thermal power of stable steam–gas and ash jets, volume of pyroclastics, and the volume of the erupted lava. The thermal power of the steam–gas jets for 2015 was approximately 122 × 106 kW, that of the gas–ash jets was 5.9 × 106 kW. The volume of discharged pyroclastic material was V = 0.00007 km3 for 2015 and V = 0.0003 km3 for 2016. 相似文献
19.
《Journal of Volcanology and Geothermal Research》2006,149(1-2):62-84
The Ferrar large igneous province of Antarctica contains significant mafic volcaniclastic deposits, some of which are interpreted to fill large vent complexes. Such a complex was re-examined at Coombs Hills to map individual steep-sided cross-cutting bodies in detail, and we found several contrasting types, two of which are interpreted to have filled subterranean passageways forcefully opened from below into existing, non-consolidated debris. These transient conduits were opened because of the propagation of debris jets – upward-moving streams of volcaniclastic debris, steam, magmatic gases +/− liquid water droplets – following explosive magma–aquifer interaction. Some debris jets probably remained wholly subterranean, whereas others made it to the surface, but the studied outcrops do not allow us to differentiate between these cases. The pipes filled with country rock-rich lapilli-tuff or tuff-breccia are interpreted to have formed following phreatomagmatic explosions occurring near the walls or floor of the vent complex, causing fragmentation of both magma and abundant country rock material. In contrast, some of the cross-cutting zones filled with basalt-rich tuff-breccia or lapilli-tuff could have been generated following explosions taking place within pre-existing basalt-bearing debris, well away from the complex walls or floor. We infer that once focused jets were formed, they did not incorporate significant amounts of existing debris while travelling through them; instead, incorporation of fragments from the granular host took place near explosion sites. Other basalt-rich tuff-breccia zones, accompanied by domains of in situ peperite and coherent basalt pods, are inferred to have originated by less violent processes. 相似文献
20.
An experimental investigation was made of the upstream influence in front of two‐dimensional obstacles when they were towed in a linearly stratified fluid. The experiments were performed in a plexiglas channel 30.5 feet long, 2 feet high and 14 inches wide filled with a linearly stratified salt solution. Velocity measurements and flow visualization were obtained by neutrally buoyant liquid droplets and dye lines. Density measurements were made by a salinity probe. The existence of unattenuated upstream influence in front of an obstacle was quantitatively documented for the first time. It occurred in the form of multiple unattenuated horizontal jets when there was a separated open wake behind the obstacle. These jets were identified to be the super‐position of “columnar disturbance modes”. The total number of columnar modes was determined solely by the Froude number of the flow and was equal to the number of lee‐wave modes excited. The drag due to upstream columnar modes was estimated and found to be lower than the drag due to the lee wave modes: 相似文献