Numerical simulation of the excitation and evolution of coherent vortices in hollow magnetized electron columns

1999 ◽  
Vol 77 (2) ◽  
pp. 105-112
Author(s):  
M Shoucri ◽  
R Marchand
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Nonlinear Evolution ◽  
Two Dimensional ◽  
Finite Element Code ◽  
Helmholtz Instability ◽  
Radial Transport ◽  
Subsequent Evolution ◽  
Azimuthal Mode ◽  
Coherent Vortices

We apply a finite-element code to study the excitation and nonlinear evolution of two-dimensional (2D) vortices in a hollow electron column using 2D guiding center equations. The perturbation (with m = 2) of the hollow column results in an instability (diocotron or Kelvin-Helmholtz instability) that evolves towards the formation of vortices (two vortices for the m = 2 perturbation). The subsequent evolution shows the nonlinear evolution of two vortices interacting to coalesce (cascading to lower azimuthal mode number), with a simultaneous radial transport toward the center of the column. PACS Nos.: 52.25.Wz, 52.65.Kj, 47.32.-y, 02.70.Dh

Numerical simulation of the excitation and evolution of high-azimuthal-mode-number coherent vortices in hollow magnetized electron columns

2001 ◽  
Vol 65 (2) ◽  
pp. 151-160 ◽  
Author(s):  
R. MARCHAND ◽  
M. SHOUCRI
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Angular Momentum ◽  
Magnetized Plasma ◽  
Mode Number ◽  
Finite Element Code ◽  
Azimuthal Mode ◽  
Nonlinear Development ◽  
Coherent Vortices ◽  
Development And Evolution

A finite-element code is used to study the excitation of a perturbation with a range of azimuthal mode numbers in hollow magnetized plasma columns, and the subsequent nonlinear development and evolution of coherent vortices interacting to coalesce, while cascading to a lower azimuthal mode number. It is shown that, even for initially higher azimuthal mode numbers, the angular momentum remains a slowly varying ideal invariant, while the system cascades to lower azimuthal mode numbers. A detailed study of the evolution is presented for initially excited m = 3, m = 4, and m = 5 azimuthal modes, which underlines the physics of the inverse cascade of angular momentum.

Numerical Simulation of Inner Support for Excavation Based on FEM Software ABAQUS

2012 ◽  
Vol 236-237 ◽  
pp. 632-635
Author(s):  
Yue Sun ◽  
Yue Nan Chen ◽  
Zhi Yun Wang
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Computational Model ◽  
Dimensional Space ◽  
General Purpose ◽  
Two Dimensional ◽  
Clay Layer ◽  
Finite Element Software ◽  
Spring Element

In two-dimensional space, an elasto-plastic finite element computational model was established to simulate inner support for excavation on the basis of the general-purpose finite element software ABAQUS. The soil was assumed to be a uniform and normally consolidated clay layer and strut was discreted by spring element. Compared with published case study, it can be concluded that FEM software AQAQUS can present one reliable simulation progress of inner support for excavation.

ON THE PROTECTION CAPABILITY OF THE FLYING PLATE AGAINST TO LONG-ROD PENETRATORS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1285-1290
Author(s):  
STANISLAV ROLC ◽  
JAROSLAV BUCHAR ◽  
ZBYNEK AKSTEIN
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Numerical Results ◽  
Finite Element Code ◽  
Plate Material ◽  
3D Finite Element ◽  
Plate Velocity ◽  
Long Rod ◽  
Protection Capability

The interaction of the flying plate with the Long-rod penetrator has been studied both experimentally and numerically using the LS DYNA 3D finite element code. The influence of the plate velocity and plate material on this interaction has been investigated in details. Numerical results show that there was a relatively large damage of the projectiles. The extent of this damage well agree with our experimental foundings. The numerical simulation of the damaged projectiles with some targets has been also performed

scholarly journals Testing the effect of water in crevasses on a physically based calving model

2012 ◽  
Vol 53 (60) ◽  
pp. 90-96 ◽  
Author(s):  
S. Cook ◽  
T. Zwinger ◽  
I.C. Rutt ◽  
S. O'Neel ◽  
T. Murray
Keyword(s):  
Finite Element ◽  
Water Depth ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Finite Element Code ◽  
Surface Mass ◽  
Starting Point ◽  
Physically Based ◽  
Calving Rate

AbstractA new implementation of a calving model, using the finite-element code Elmer, is presented and used to investigate the effects of surface water within crevasses on calving rate. For this work, we use a two-dimensional flowline model of Columbia Glacier, Alaska. Using the glacier’s 1993 geometry as a starting point, we apply a crevasse-depth calving criterion, which predicts calving at the location where surface crevasses cross the waterline. Crevasse depth is calculated using the Nye formulation. We find that calving rate in such a regime is highly dependent on the depth of water in surface crevasses, with a change of just a few metres in water depth causing the glacier to change from advancing at a rate of 3.5 kma–1 to retreating at a rate of 1.9 km a–1. These results highlight the potential for atmospheric warming and surface meltwater to trigger glacier retreat, but also the difficulty of modelling calving rates, as crevasse water depth is difficult to determine either by measurement in situ or surface mass-balance modelling.

Optimization of Bulk Hgcdte Growth in a Directional Solidification Furnace by Numerical Simulation

1995 ◽  
Vol 398 ◽  
Author(s):  
A.V. Bune ◽  
D.C. Gillies ◽  
S.L. Lehoczky
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Finite Element ◽  
Crystal Growth ◽  
Numerical Model ◽  
Directional Solidification ◽  
Growth Conditions ◽  
Finite Element Code ◽  
Interface Shape ◽  
Solidification Furnace

ABSTRACTA numerical model of heat transfer by combined conduction, radiation and convection was developed using the FIDAP finite element code for NASA's Advanced Automated Directional Solidification Furnace (AADSF). The prediction of the temperature gradient in an ampoule with HgCdTe is a necessity for the evaluation of whether or not the temperature set points for furnace heaters and the details of cartridge design ensure optimal crystal growth conditions for this material and size of crystal. A prediction of crystal/melt interface shape and the flow patterns in HgCdTe are available using a separate complementary model.

Effects of Materials on Formation of Double-Layered Liners Shaped Charges

2009 ◽  
Vol 79-82 ◽  
pp. 1277-1280
Author(s):  
Yu Zheng ◽  
Xiao Ming Wang ◽  
Wen Bin Li ◽  
Wen Jin Yao
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Numerical Simulations ◽  
Double Layer ◽  
Two Dimensional ◽  
Materials Properties ◽  
X Ray ◽  
Dimensional Finite Element ◽  
Simulation Results ◽  
Good Agreement

In order to study the effects of liner materials on the formation of Shaped Charges with Double Layer Liners (SCDLL) into tandem Explosively Formed Projectile (EFP), the formation mechanism of DLSCL was studied. Utilizing two-dimensional finite element dynamic code AUTODYN, the numerical simulations on the mechanical phenomenon of SCDLL forming into tandem EFP were carried out. X-ray pictures were obtained after Experiments on SCDLL. Comparisons between experimental results and numerical simulation results have good agreement. It can be concluded from the results that the materials properties and configurations of both liners are crucial to the formation of tandem EFP.

Experimental Analysis and Numerical Simulation of the Flow Field in Turbine Scrolls

1998 ◽  
Author(s):  
Uwe W. Menter ◽  
Thomas Klima ◽  
Heiner Pfost
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Flow Field ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Two Dimensional ◽  
3D Finite Element ◽  
Non Invasive ◽  
Flow Configurations ◽  
Selection Of

A large selection of one- and two-dimensional methods can be used to calculate the scroll geometries. This paper examines the consequences of different scroll geometry parameters under various flow configurations, including the influence of components in the scroll flow field. A combination of arrangements of the various components was investigated, (scroll/nozzle/rotor, scroll/nozzle/stator, scroll/vane support/rotor, scroll/vane support/stator), to see how the flow varied. In this particular case a frictionless scroll was designed. The turbine operates with a gas fluid. Using a non-invasive laser two-focus technique and wall pressure drillings the flow field was measured over three scroll cross sections and over its extent at φ = 186° up to φ = 211°. The theoretical analysis was performed on a computer using a commercial 3D finite element programme. Using the programme enables the theoretical flow fields of various scroll geometries to be calculated. The validity of the calculations can be assessed by comparing the theoretical calculations with the above mentioned measurements. The measurements show that by using a rotor the flow field inside the scroll remains uninfluenced by the vane support and nozzle. Measurable differences appear when the rotor is replaced by a stator, these results are confirmed by the computer program. The calculations also show that the scroll geometry has an important effect on the development of the flow field.

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