Turbulent diffusion in two-dimensional, strongly magnetized plasmas

1985 ◽  
Vol 34 (1) ◽  
pp. 77-94 ◽  
Author(s):  
H. L. Pécseli ◽  
T. Mikkelsen
Keyword(s):  
Turbulent Transport ◽  
Low Frequency ◽  
Two Dimensions ◽  
Magnetized Plasma ◽  
Two Dimensional ◽  
Drift Wave Turbulence ◽  
Field Fluctuations ◽  
The Mean ◽  
Wavenumber Spectrum ◽  
Convective Cells

Particle diffusion is investigated in a strictly two-dimensional collisionless guiding-centre model for a strongly magnetized plasma. An analytical expression is presented for the entire time variation of the mean square test-particle displacement in the limit of low-frequency, strongly turbulent, electric field fluctuations. The analysis relies on an explicit integral expression for the Lagrangian autocorrelation function in terms of the Eulerian wavenumber spectrum and a time-varying weight function. Bohm diffusion is discussed by means of a simple model spectrum. The analysis applies for turbulent transport associated with electrostatic convective cells, magnetostatic cells and drift wave turbulence with the assumption of local homogeneity and isotropy in two dimensions.

NUMERICAL INVESTIGATION OF UNSTEADY COMBUSTOR TURBINE INTERACTION FOR FLEXIBLE POWER GENERATION

2021 ◽  
pp. 1-22
Author(s):  
Federico Lo Presti ◽  
Marwick Sembritzky ◽  
Benjamin Winhart ◽  
Pascal Post ◽  
Francesca di Mare ◽  
...  
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Two Dimensional ◽  
Periodic Load ◽  
Migration Patterns ◽  
Solution Approach ◽  
Periodic Disturbances ◽  
Turbine Inlet ◽  
The Mean ◽  
Industrial Gas Turbine

Abstract In the present study low-frequency disturbances introduced by a periodic load variation have been simulated and superimposed to the inhomogeneous, unsteady flow entering a 3-stage, high-pressure industrial gas turbine fed by a can-type combustion chamber comprising 6 silo-burners. The effects of the unsteadiness realized at the combustor exit have been investigated by means of Detached Eddy Simulations, whereby a density-based solution approach with detailed thermodynamics has been employed. The periodic disturbances at the turbine inlet have been obtained by means of an artificially generated, unsteady field, resulting from a two-dimensional snapshot of the flow field at the combustor exit. Also, a combustor failure has been mimicked by reducing (respectively increasing) the mean temperature in some of the turbine inlet regions corresponding to the outlet of two burners. The propagation and amplitude changes of temperature fluctuations have been analyzed in the frequency domain. Tracking of the temperature fluctuations' maxima at the lowest frequencies revealed characteristic migration patterns indicating that the corresponding fluctuations persist with a non-negligible amplitude up to the last rows. A distinct footprint could also be observed at the same locations when a combustor failure was simulated, showing that, in principle, the early detection of combustor failures is indeed possible.

The turbulent transport of suspended sediment in open channels

1954 ◽  
Vol 224 (1158) ◽  
pp. 322-335 ◽  
Keyword(s):  
Velocity Gradient ◽  
Turbulent Transport ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Two Dimensional ◽  
Linear Variation ◽  
Similar Material ◽  
Two Dimensional Flow ◽  
The Mean ◽  
Gradient Condition

Fine sediment is carried in suspension by turbulent flow under steady conditions, provided that similar material is present on the bed. An equation is deduced for the variation with depth of the sediment concentration for two-dimensional flow. It is found necessary to take account of the volume occupied by the sediment, this being particularly important near the bed. The result agrees with recent observations by Vanoni (1946). A velocity distribution obtained by Kármán, using a linear variation of shear with depth, is generalized by omitting the infinite velocity gradient condition at the bed and is found to be in good agree­ment with Vanoni’s measurements. A slight difference is found between the mean sediment velocity in the direction of flow and that of the water.

scholarly journals 6,6′-[(1E,1′E)-Oxybis(4,1-phenylene)bis(azanylylidene)bis(methanylylidene)]bis(2-methylphenol): supramolecular assemblies in two dimensions mediated by weak C—H...N, C—H...O and C—H...π interactions

2018 ◽  
Vol 74 (5) ◽  
pp. 687-690 ◽  
Author(s):  
Md. Azharul Arafath ◽  
Huey Chong Kwong ◽  
Farook Adam ◽  
Mohd. R. Razali
Keyword(s):  
Schiff Base ◽  
Two Dimensions ◽  
Dihedral Angles ◽  
Two Dimensional ◽  
Π Interactions ◽  
Compound C ◽  
Dimensional Network ◽  
Phenyl Rings ◽  
The Mean ◽  
Centrosymmetric Dimers

The title compound, C28H24N2O3, is a flexible Schiff base, having a dihedral angle of 59.53 (5)° between the mean planes of two phenyl rings bounded in the centre by a single O atom. The dihedral angles between the mean planes of the phenyl rings bonded to the central O atom and the mean planes of the terminal methylphenol rings are 31.47 (6) and 36.03 (5)°, respectively. The sp 2-hybridized character of the azanylylidene groups is confirmed by their bond lengths and bond angles. In the crystal, molecules are linked into centrosymmetric dimers by weak C—H...N interactions and connected into dimeric chains through weak C—H...O interactions. These chains are interconnected into a two-dimensional network parallel to (1\overline{2}1) via weak C—H...π interactions.

Nonlinear plasma waves with steady-state d.c. current

1994 ◽  
Vol 52 (3) ◽  
pp. 373-390 ◽  
Author(s):  
S. Rauf ◽  
J. A. Tataronis
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Low Frequency ◽  
Travelling Wave ◽  
Magnetized Plasma ◽  
Two Dimensional ◽  
Antenna Structure ◽  
Background Magnetic Field ◽  
The Waves ◽  
Dimensional Wave

Using a low-frequency, low-β model of a magnetized plasma, several nonlinear waves are studied. All the waves share the property that they have a self- consistent time-averaged current in the steady state. The first wave is a one- dimensional solitary wave that propagates obliquely to a static magnetic field. The wave magnetic field has a kink structure, which results in the production of the time-averaged current. A two-dimensional wave that propagates parallel to the background magnetic field is also discussed. This is a forced wave, requiring an antenna structure to support it in the steady state. The characteristics of the two-dimensional wave are dependent upon the wave speed, which in turn is determined by the speed of the travelling wave on the external antenna.

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

Urbanicity, City Delegations, and Two-Dimensional Liberalism

2018 ◽  
Author(s):  
Thomas K. Ogorzalek
Keyword(s):  
National Level ◽  
Two Dimensions ◽  
Political Order ◽  
Two Dimensional ◽  
Local Institutions ◽  
Horizontal Integration ◽  
National Politics ◽  
United Front ◽  
Strategies For Success

This theoretical chapter develops the argument that the conditions of cities—large, densely populated, heterogeneous communities—generate distinctive governance demands supporting (1) market interventions and (2) group pluralism. Together, these positions constitute the two dimensions of progressive liberalism. Because of the nature of federalism, such policies are often best pursued at higher levels of government, which means that cities must present a united front in support of city-friendly politics. Such unity is far from assured on the national level, however, because of deep divisions between and within cities that undermine cohesive representation. Strategies for success are enhanced by local institutions of horizontal integration developed to address the governance demands of urbanicity, the effects of which are felt both locally and nationally in the development of cohesive city delegations and a unified urban political order capable of contending with other interests and geographical constituencies in national politics.

Despeckling of Sar Images Using Shrinkage of Two-Dimensional Discrete Orthonormal S-Transform

2020 ◽  
pp. 2150023
Author(s):  
Priya R. Kamath ◽  
Kedarnath Senapati ◽  
P. Jidesh
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Relevant Information ◽  
Detection Algorithm ◽  
Two Dimensional ◽  
Sar Images ◽  
S Transform ◽  
Processing Step ◽  
Frequency Components ◽  
Shock Filter

Speckles are inherent to SAR. They hide and undermine several relevant information contained in the SAR images. In this paper, a despeckling algorithm using the shrinkage of two-dimensional discrete orthonormal S-transform (2D-DOST) coefficients in the transform domain along with shock filter is proposed. Also, an attempt has been made as a post-processing step to preserve the edges and other details while removing the speckle. The proposed strategy involves decomposing the SAR image into low and high-frequency components and processing them separately. A shock filter is used to smooth out the small variations in low-frequency components, and the high-frequency components are treated with a shrinkage of 2D-DOST coefficients. The edges, for enhancement, are detected using a ratio-based edge detection algorithm. The proposed method is tested, verified, and compared with some well-known models on C-band and X-band SAR images. A detailed experimental analysis is illustrated.

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