scholarly journals Two Dimensional MHD Simulation of Merging Plasmas in Laboratory Experiments - Focussing on its Dynamic Behaviours

1999 ◽  
Vol 75-CD (10_CD) ◽  
pp. 157-167
Author(s):  
Tomohiko WATANABE ◽  
Takaya HAYASHI ◽  
Tetsuya SATO
Keyword(s):  
Laboratory Experiments ◽  
Two Dimensional ◽  
Mhd Simulation

Quasi-two-dimensional flow on the polar β-plane: Laboratory experiments

2009 ◽  
Vol 77 (4) ◽  
pp. 502-510 ◽  
Author(s):  
S. Espa ◽  
A. Cenedese ◽  
M. Mariani ◽  
G.F. Carnevale
Keyword(s):  
Laboratory Experiments ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow

scholarly journals The magnetorotational instability prefers three dimensions

2020 ◽  
Vol 476 (2233) ◽  
pp. 20190622
Author(s):  
Jeffrey S. Oishi ◽  
Geoffrey M. Vasil ◽  
Morgan Baxter ◽  
Andrew Swan ◽  
Keaton J. Burns ◽  
...  
Keyword(s):  
Shear Rate ◽  
Angular Velocity ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Linear Instability ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Magnetorotational Instability ◽  
Dynamo Action ◽  
Wide Range

The magnetorotational instability (MRI) occurs when a weak magnetic field destabilizes a rotating, electrically conducting fluid with inwardly increasing angular velocity. The MRI is essential to astrophysical disc theory where the shear is typically Keplerian. Internal shear layers in stars may also be MRI-unstable, and they take a wide range of profiles, including near-critical. We show that the fastest growing modes of an ideal magnetofluid are three-dimensional provided the shear rate, S , is near the two-dimensional onset value, S c . For a Keplerian shear, three-dimensional modes are unstable above S  ≈ 0.10 S c , and dominate the two-dimensional modes until S  ≈ 2.05 S c . These three-dimensional modes dominate for shear profiles relevant to stars and at magnetic Prandtl numbers relevant to liquid-metal laboratory experiments. Significant numbers of rapidly growing three-dimensional modes remainy well past 2.05 S c . These finding are significant in three ways. First, weakly nonlinear theory suggests that the MRI saturates by pushing the shear rate to its critical value. This can happen for systems, such as stars and laboratory experiments, that can rearrange their angular velocity profiles. Second, the non-normal character and large transient growth of MRI modes should be important whenever three-dimensionality exists. Finally, three-dimensional growth suggests direct dynamo action driven from the linear instability.

Secondary fluid flows driven electromagnetically in a two-dimensional extended duct

2005 ◽  
Vol 461 (2058) ◽  
pp. 1659-1683 ◽  
Author(s):  
Zhi-Min Chen ◽  
W.G Price
Keyword(s):  
Steady State ◽  
Laboratory Experiments ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Two Dimensional ◽  
Slip Boundary Conditions ◽  
Slip Boundary ◽  
Wave Numbers ◽  
Motion Problem ◽  
Secondary Fluid

This study focuses on two-dimensional fluid flows in a straight duct with free-slip boundary conditions applied on the channel walls y =0 and y =2 πN with N >1. In this extended wall-bounded fluid motion problem, secondary fluid flow patterns resulting from steady-state and Hopf bifurcations are examined and shown to be dependent on the choice of longitudinal wave numbers. Some secondary steady-state flows appear at specific wave numbers, whereas at other wave numbers, both secondary steady-state and self-oscillation flows coexist. These results, derived through analytical arguments and truncation series approximation, are confirmed by simple numerical experiments supporting the findings observed from laboratory experiments.

scholarly journals Limiting stress states in granular avalanches

1998 ◽  
Vol 26 ◽  
pp. 272-276 ◽  
Author(s):  
Y.C. Tai ◽  
J.M.N.T. Gray
Keyword(s):  
Stress State ◽  
Numerical Methods ◽  
Granular Material ◽  
Laboratory Experiments ◽  
Complex Geometry ◽  
The Other ◽  
Two Dimensional ◽  
Singular Surfaces ◽  
Rapid Convergence ◽  
Stress States

The Savage-Hutter theory for granular avalanches assumes that the granular material is in either of two limiting stress states, depending on whether the motion is convergent or divergent. At transitions between convergent and divergent regions, a jump in stress occurs, which necessarily implies that there is a jump in the avalanche velocity and/or its thickness. In this paper, a regularizaron scheme is used, which smoothly switches from one stress state to the other, and avoids the generation of such singular surfaces. The resulting algorithm is more stable than previous numerical methods but shocks can still occur during rapid convergence in the run-out zone. Results are presented from two-dimensional calculations on complex geometry which illustrate that some necking features observed in laboratory experiments can be explained by the regularized Savage-Hutter model.

Numerical experiments on two-dimensional foam

1992 ◽  
Vol 241 ◽  
pp. 233-260 ◽  
Author(s):  
Thomas Herdtle ◽  
Hassan Aref
Keyword(s):  
Initial Data ◽  
Analytical Solutions ◽  
Numerical Experiments ◽  
Laboratory Experiments ◽  
Evolution Equations ◽  
Two Dimensional ◽  
Von Neumann ◽  
Cpu Time ◽  
Statistical Evolution ◽  
Physical Principles

The statistical evolution of a two-dimensional polygonal, or ‘dry’, foam during diffusion of gas between bubbles lends itself to a very simple mathematical description by combining physical principles discovered by Young. Laplace, Plateau, and von Neumann over a period of a century and a half. Following a brief review of this ‘canonical’ theory, we report results of the largest numerical simulations of this system undertaken to date. In particular, we discuss the existence and properties of a scaling regime, conjectured on the basis of laboratory experiments on larger systems than ours by Glazier and coworkers, and corroborated in computations on smaller systems by Weaire and collaborators. While we find qualitative agreement with these earlier investigations, our results differ on important, quantitative details, and we find that the evolution of the foam, and the emergence of scaling, is very sensitive to correlations in the initial data. The largest computations we have performed follow the relaxation of a system with 1024 bubbles to one with O(10), and took about 30 hours of CPU time on a Cray-YMP supercomputer. The code used has been thoroughly tested, both by comparison with a set of essentially analytic results on the rheology of a monodisperse-hexagonal foam due to Kraynik & Hansen, and by verification of certain analytical solutions to the evolution equations that we found for a family of ‘fractal foams’.

scholarly journals THE DISSIPATION OF WAVE ENERGY BY TURBULENCE

1980 ◽  
Vol 1 (17) ◽  
pp. 52
Author(s):  
Yu Kuang-ming
Keyword(s):  
General Theory ◽  
Wave Energy ◽  
Laboratory Experiments ◽  
Velocity Fields ◽  
Mixing Length ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
The Mean ◽  
Vertical Gradients ◽  
Horizontal Area

This paper first gives a brief review of the existing research works on the laws governing the dissipation of rave energy by turbulence. Starting from the general theory of turbulent motion and the writer's suggestion in regard to the mixing length of water particles in two-dimensional flow and making use of the principle of dimensional analysis and the trochidal rave theory, a formula has been derived to compute the mean dissipation per unit time and per unit horizontal area of wave energy due to turbulence. The formula takes the horizontal and vertical gradients of both the horizontal and vertical velocity fields into consideration. Coefficient in the formula has been determined through laboratory experiments.

scholarly journals STRUCTURE FORMATION IN SPECTRALLY CONDENSED TURBULENCE

2012 ◽  
Vol 19 ◽  
pp. 257-261
Author(s):  
HUA XIA ◽  
MICHAEL SHATS
Keyword(s):  
Structure Formation ◽  
Laboratory Experiments ◽  
Energy Cascade ◽  
Experimental Results ◽  
Two Dimensional ◽  
Radial Transport ◽  
Structural Formation ◽  
2D Turbulence ◽  
Inverse Energy Cascade

Two-dimensional (2D) turbulence supports the inverse energy cascade and the spectral condensate generation, which are studied in laboratory experiments. The generation of the spectral condensation via the inverse energy cascade dramatically reduces the radial transport in 2D flows. In this paper we report experimental results related to the formation of spectral condensates. The dynamics of the structural formation is reposted.

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