An Experimental Investigation of Strong Turbulence in a Sheared Magnetoplasma Column

1974 ◽  
Vol 52 (18) ◽  
pp. 1739-1749
Author(s):  
J. E. Robinson ◽  
L. M. Lidsky
Keyword(s):  
Experimental Investigation ◽  
Large Amplitude ◽  
Temporal Evolution ◽  
Broad Band ◽  
Particle Interaction ◽  
Turbulence Theory ◽  
Larmor Radius ◽  
Band Spectrum ◽  
Strong Turbulence ◽  
Amplitude Mode

An experimental investigation of low frequency (ω < Ω1) strong turbulence in a transversely sheared magnetoplasma column is reported. A single large amplitude mode and a broad band spectrum are observed in the radial region of sheared azimuthal velocity. The large amplitude mode, previously identified as Kelvin–Helmholtz turbulence, is studied with respect to coherence, amplitude saturation, and temporal evolution. General agreement is found with Dupree's strong turbulence theory. However, both coherent and incoherent trapping appear to be important for amplitude saturation and coherence. Spatial spreading of the mode is also observed during temporal evolution indicating a more complex wave particle interaction than is currently assumed in nonlinear theory. Using correlation techniques, the broad band spectrum is found to consist of azimuthally propagating clumps of 'ballistic modes' which produce an [Formula: see text] spectrum. The clumps have a scale size of the order of a Larmor radius, propagate with the average rotation velocity, appear to be amplitude limited by trapping, and diffuse spatially as they decay. This observation of clumps represents the first experimental identification of 'ballistic modes' in a magnetoplasma column.

scholarly journals Understanding (coupled) large amplitude motions: the interplay of microwave spectroscopy, spectral modeling, and quantum chemistry

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ha Vinh Lam Nguyen ◽  
Isabelle Kleiner
Keyword(s):  
Fourier Transform ◽  
Quantum Chemistry ◽  
Large Amplitude ◽  
Environmental Chemistry ◽  
Broad Band ◽  
Microwave Spectroscopy ◽  
Rotational Spectrum ◽  
Spectral Modeling ◽  
Rotational Spectra ◽  
Large Amplitude Motions

AbstractA large variety of molecules contain large amplitude motions (LAMs), inter alia internal rotation and inversion tunneling, resulting in tunneling splittings in their rotational spectrum. We will present the modern strategy to study LAMs using a combination of molecular jet Fourier transform microwave spectroscopy, spectral modeling, and quantum chemical calculations to characterize such systems by the analysis of their rotational spectra. This interplay is particularly successful in decoding complex spectra revealing LAMs and providing reference data for fundamental physics, astrochemistry, atmospheric/environmental chemistry and analytics, or fundamental researches in physical chemistry. Addressing experimental key aspects, a brief presentation on the two most popular types of state-of-the-art Fourier transform microwave spectrometer technology, i.e., pulsed supersonic jet expansion–based spectrometers employing narrow-band pulse or broad-band chirp excitation, will be given first. Secondly, the use of quantum chemistry as a supporting tool for rotational spectroscopy will be discussed with emphasis on conformational analysis. Several computer codes for fitting rotational spectra exhibiting fine structure arising from LAMs are discussed with their advantages and drawbacks. Furthermore, a number of examples will provide an overview on the wealth of information that can be drawn from the rotational spectra, leading to new insights into the molecular structure and dynamics. The focus will be on the interpretation of potential barriers and how LAMs can act as sensors within molecules to help us understand the molecular behavior in the laboratory and nature.

Iterative approach to strong turbulence theory

1980 ◽  
Vol 23 (7) ◽  
pp. 1301 ◽  
Author(s):  
Georg Knorr ◽  
Michael Mond
Keyword(s):  
Turbulence Theory ◽  
Iterative Approach ◽  
Strong Turbulence

Aerodynamics of a two-dimensional bluff body with the cross-section of a train

2020 ◽  
Vol 23 (12) ◽  
pp. 2679-2693 ◽  
Author(s):  
Huan Li ◽  
Xuhui He ◽  
Hanfeng Wang ◽  
Si Peng ◽  
Shuwei Zhou ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Large Amplitude ◽  
High Speed ◽  
Bluff Body ◽  
Mean Amplitude ◽  
Two Dimensional ◽  
Aerodynamic Forces ◽  
Moderate Reynolds Number ◽  
Amplitude Mode

Experiments on the aerodynamics of a two-dimensional bluff body simplified from a China high-speed train in crosswinds were carried out in a wind tunnel. Effects of wind angle of attack α varying in [−20°, 20°] were investigated at a moderate Reynolds number Re = 9.35 × 104 (based on the height of the model). Four typical behaviors of aerodynamics were identified. These behaviors are attributed to the flow structure around the upper and lower halves of the model changing from full to intermittent reattachment, and to full separation with a variation in α. An alternate transition phenomenon, characterized by an alteration between large- and small-amplitude aerodynamic fluctuations, was detected. The frequency of this alteration is about 1/10 of the predominant vortex shedding. In the intervals of the large-amplitude behavior, aerodynamic forces fluctuate periodically with a strong span-wise coherence, which are caused by the anti-symmetric vortex shedding along the stream-wise direction. On the contrary, the aerodynamic forces fluctuating at small amplitudes correspond to a weak span-wise coherence, which are ascribed to the symmetric vortex shedding from the upper and lower halves of the model. Generally, the mean amplitude of the large-amplitude mode is 3 times larger than that of the small one. Finally, the effects of Reynolds number were examined within Re = [9.35 × 104, 2.49 × 105]. Strong Reynolds number dependence was observed on the model with two rounded upper corners.

scholarly journals The broad-band spectrum of Cygnus X-1 measured by INTEGRAL

2006 ◽  
Vol 446 (2) ◽  
pp. 591-602 ◽  
Author(s):  
M. Cadolle Bel ◽  
P. Sizun ◽  
A. Goldwurm ◽  
J. Rodriguez ◽  
P. Laurent ◽  
...  
Keyword(s):  
Broad Band ◽  
Band Spectrum

scholarly journals Experimental investigation on large amplitude standing wave induced in closed tubes with varying cross section

2004 ◽  
Vol 25 (2) ◽  
pp. 153-158
Author(s):  
Md. Anwar Hossain ◽  
Masaaki Kawahashi ◽  
Tomoyoshi Nagakita ◽  
Hiroyuki Hirahara
Keyword(s):  
Experimental Investigation ◽  
Standing Wave ◽  
Cross Section ◽  
Large Amplitude ◽  
Wave Induced

scholarly journals An Experimental Investigation of Low Power, Long Duration Rotamak Discharges

1987 ◽  
Vol 40 (2) ◽  
pp. 157 ◽  
Author(s):  
IR Jones ◽  
MDE Turley ◽  
JE Wedding ◽  
G Durance ◽  
GR Hogg ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Low Power ◽  
Large Amplitude ◽  
Toroidal Field ◽  
Forced Oscillations ◽  
Hydrogen Plasmas ◽  
Compact Torus ◽  
Long Duration

A rotamak device is described in which compact torus plasmas are generated using relatively low RF input powers (~ a few kW). Compact torus configurations are generated in both argon and hydrogen plasmas and are sustained for ~ 9 ms. These configurations appear to be grossly stable and show no tendency to disrupt even when subjected to large amplitude forced oscillations. A configuration incorporating a toroidal field is also investigated.

Convergence of strong turbulence theory

1973 ◽  
Vol 16 (9) ◽  
pp. 1505 ◽  
Author(s):  
J. J. Thomson
Keyword(s):  
Turbulence Theory ◽  
Strong Turbulence

scholarly journals Nonlinear Mirror and Weibel modes: peculiarities of quasi-linear dynamics

2010 ◽  
Vol 28 (12) ◽  
pp. 2161-2167 ◽  
Author(s):  
O. A. Pokhotelov ◽  
R. Z. Sagdeev ◽  
M. A. Balikhin ◽  
V. N. Fedun ◽  
G. I. Dudnikova
Keyword(s):  
Distribution Function ◽  
Mode Coupling ◽  
Nonlinear Evolution ◽  
Particle Interaction ◽  
Velocity Distribution Function ◽  
Larmor Radius ◽  
Initial Stage ◽  
Plasma State ◽  
Bgk Modes ◽  
Mirror Mode

Abstract. A theory for nonlinear evolution of the mirror modes near the instability threshold is developed. It is shown that during initial stage the major instability saturation is provided by the flattening of the velocity distribution function in the vicinity of small parallel ion velocities. The relaxation scenario in this case is accompanied by rapid attenuation of resonant particle interaction which is replaced by a weaker adiabatic interaction with mirror modes. The saturated plasma state can be considered as a magnetic counterpart to electrostatic BGK modes. After quasi-linear saturation a further nonlinear scenario is controlled by the mode coupling effects and nonlinear variation of the ion Larmor radius. Our analytical model is verified by relevant numerical simulations. Test particle and PIC simulations indeed show that it is a modification of distribution function at small parallel velocities that results in fading away of free energy driving the mirror mode. The similarity with resonant Weibel instability is discussed.

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