Analysis of large-scale fluctuation structures in the scrape-off layer of the Wendelstein 7-AS stellarator

2001 ◽  
Vol 8 (12) ◽  
pp. 5171-5180 ◽  
Author(s):  
O. Grulke ◽  
T. Klinger ◽  
M. Endler ◽  
A. Piel ◽  
Keyword(s):  
Large Scale ◽  
Scale Fluctuation ◽  
Large Scale Fluctuation

scholarly journals On Landau’s prediction for large-scale fluctuation of turbulence energy dissipation

2006 ◽  
Vol 18 (1) ◽  
pp. 015103 ◽  
Author(s):  
Hideaki Mouri ◽  
Masanori Takaoka ◽  
Akihiro Hori ◽  
Yoshihide Kawashima
Keyword(s):  
Energy Dissipation ◽  
Large Scale ◽  
Turbulence Energy ◽  
Turbulence Energy Dissipation ◽  
Scale Fluctuation ◽  
Large Scale Fluctuation

Two-point Correlation Function and Power Spectrum at Very Large Scales

2005 ◽  
Vol 201 ◽  
pp. 449-450
Author(s):  
Z.-G. Deng ◽  
X.-Y. Xia
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Correlation Functions ◽  
Large Scale ◽  
Wave Number ◽  
Scale Fluctuation ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Redshift Survey ◽  
Large Scale Fluctuation

Subsamples of galaxies with different morphological types have been sorted out from Stromlo-APM redshift survey. Two-point correlation function for each subsample has been calculated. The two-point correlation functions for all subsamples show very large scale fluctuation. We show that the two-point correlation function with fluctuation could be fitted by a modified power spectrum with power excess at wave number comparable to the scale of the fluctuation.

scholarly journals Study of the X-Ray Background Spectrum and Its Large-Scale Fluctuation with ASCA

2002 ◽  
Vol 54 (3) ◽  
pp. 327-352 ◽  
Author(s):  
Akihiro Kushino ◽  
Yoshitaka Ishisaki ◽  
Umeyo Morita ◽  
Noriko Y. Yamasaki ◽  
Manabu Ishida ◽  
...  
Keyword(s):  
Large Scale ◽  
Background Spectrum ◽  
X Ray ◽  
Scale Fluctuation ◽  
X Ray Background ◽  
Large Scale Fluctuation

A numerical study of the transition of jet diffusion flames

1990 ◽  
Vol 431 (1882) ◽  
pp. 301-314 ◽  
Keyword(s):  
Reynolds Number ◽  
Diffusion Coefficient ◽  
Large Scale ◽  
Numerical Study ◽  
Small Scale ◽  
Surface Model ◽  
Flame Surface ◽  
Transition Mechanism ◽  
Air Stream ◽  
Scale Fluctuation

A numerical study on the transition from laminar to turbulent of two-dimensional fuel jet flames developed in a co-flowing air stream was made by adopting the flame surface model of infinite chemical reaction rate and unit Lewis number. The time dependent compressible Navier–Stokes equation was solved numerically with the equation for coupling function by using a finite difference method. The temperature-dependence of viscosity and diffusion coefficient were taken into account so as to study effects of increases of these coefficients on the transition. The numerical calculation was done for the case when methane is injected into a co-flowing air stream with variable injection Reynolds number up to 2500. When the Reynolds number was smaller than 1000 the flame, as well as the flow, remained laminar in the calculated domain. As the Reynolds number was increased above this value, a transition point appeared along the flame, downstream of which the flame and flow began to fluctuate. Two kinds of fluctuations were observed, a small scale fluctuation near the jet axis and a large scale fluctuation outside the flame surface, both of the same origin, due to the Kelvin–Helmholtz instability. The radial distributions of density and transport coefficients were found to play dominant roles in this instability, and hence in the transition mechanism. The decreased density in the flame accelerated the instability, while the increase in viscosity had a stabilizing effect. However, the most important effect was the increase in diffusion coefficient. The increase shifted the flame surface, where the large density decrease occurs, outside the shear layer of the jet and produced a thick viscous layer surrounding the jet which effectively suppressed the instability.

scholarly journals Increased fluctuation in a butterfly metapopulation leads to diploid males and decline of a hyperparasitoid

2018 ◽  
Vol 285 (1885) ◽  
pp. 20180372
Author(s):  
Abhilash Nair ◽  
Etsuko Nonaka ◽  
Saskya van Nouhuys
Keyword(s):  
Large Scale ◽  
Balancing Selection ◽  
Host Population ◽  
Diploid Male ◽  
Fragmented Landscape ◽  
Genetic Rescue ◽  
Effective Population ◽  
Diploid Males ◽  
Population Extinction ◽  
Scale Fluctuation

Climate change can increase spatial synchrony of population dynamics, leading to large-scale fluctuation that destabilizes communities. High trophic level species such as parasitoids are disproportionally affected because they depend on unstable resources. Most parasitoid wasps have complementary sex determination, producing sterile males when inbred, which can theoretically lead to population extinction via the diploid male vortex (DMV). We examined this process empirically using a hyperparasitoid population inhabiting a spatially structured host population in a large fragmented landscape. Over four years of high host butterfly metapopulation fluctuation, diploid male production by the wasp increased, and effective population size declined precipitously. Our multitrophic spatially structured model shows that host population fluctuation can cause local extinctions of the hyperparasitoid because of the DMV. However, regionally it persists because spatial structure allows for efficient local genetic rescue via balancing selection for rare alleles carried by immigrants. This is, to our knowledge, the first empirically based study of the possibility of the DMV in a natural host–parasitoid system.

scholarly journals Synthesis of Small and Large Scale Dynamos

2002 ◽  
Vol 12 ◽  
pp. 739-741
Author(s):  
Kandaswamy Subramanian
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Magnetic Reynolds Number ◽  
Mhd Equations ◽  
Magnetic Helicity ◽  
Small Scale ◽  
Quantum Mechanical ◽  
Closure Model ◽  
Scale Fluctuation ◽  
Small Scale Fluctuation

AbstractUsing a closure model for the evolution of magnetic correlations, we uncover an interesting plausible saturated state of the small-scale fluctuation dynamo (SSD) and a novel anology between quantum mechanical tunnelling and the generation of large-scale fields. Large scale fields develop via the α-effect, but as magnetic helicity can only change on a resistive timescale, the time it takes to organize the field into large scales increases with magnetic Reynolds number. This is very similar to the results which obtain from simulations using the full MHD equations.

Long-Term and Short-Term Fluctuations in the Catches of Coastal Pelagic Fisheries Around Japan

1973 ◽  
Vol 30 (12) ◽  
pp. 2361-2367 ◽  
Author(s):  
F. Nagasaki
Keyword(s):  
Large Scale ◽  
Kuroshio Current ◽  
Individual Species ◽  
Short Term ◽  
Intermediate Period ◽  
Pelagic Fishes ◽  
Consistent Trend ◽  
Scale Fluctuation ◽  
The Kuroshio

Although the total landings of coastal pelagic fishes around Japan have been fairly stable for 10 years, the catch of individual species has shown violent fluctuations. The catch of Hokkaido herring and the sardine is decreasing and shows no signs of recovery. The catch of saury has also decreased sharply since 1960, but that of mackerel has increased substantially. There are big yearly fluctuations in the landings of squid, horse-mackerel, and anchovy, but no consistent trend either way has been shown. Apparently the great variations in stock abundance relate to the hydrographic complex in the waters around Japan. As most of the important coastal pelagic fishes spawn and spend their early life in the area of the continental shelf of the southern half of the Japanese islands, the location and the strength of the Kuroshio current play an important role in the ever-changing environmental conditions. Although the causes of these fluctuations are largely unknown, they can be classified as long, intermediate and short-term. The large-scale fluctuation over a long term, as in the case of the Hokkaido herring and the sardine, may possibly be due to evacuation of the main spawning grounds. The intermediate period of fluctuation is caused by the degree of survival of the young. A variety of causes must be responsible for the short-term fluctuation, including survival, for which there is no consistent trend, and the effect of the Kuroshio current on the distribution of the young fish.

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