Identification of large scale structures in a turbulent jet using optical techniques

1998 ◽  
Author(s):  
Ivonne Nelson ◽  
C. Truman
Keyword(s):  
Large Scale ◽  
Turbulent Jet ◽  
Optical Techniques ◽  
Large Scale Structures ◽  
Scale Structures

The evolution and nature of large‐scale structures in the turbulent jet

1992 ◽  
Vol 4 (4) ◽  
pp. 803-811 ◽  
Author(s):  
M. Yoda ◽  
L. Hesselink ◽  
M. G. Mungal
Keyword(s):  
Large Scale ◽  
Turbulent Jet ◽  
Large Scale Structures ◽  
Scale Structures

Observations of dispersion of entrained fluid in the self-preserving region of a turbulent jet

1987 ◽  
Vol 183 ◽  
pp. 163-173 ◽  
Author(s):  
D. Joseph Shlien
Keyword(s):  
Large Scale ◽  
Peak Velocity ◽  
Turbulent Jet ◽  
Axial Distance ◽  
Large Scale Structures ◽  
Jet Nozzle ◽  
The Mean ◽  
Scale Structures ◽  
Processing Techniques ◽  
Mean Concentration

Ambient fluid of a submerged water jet was continuously tagged with fluorescent dye at a point outside the turbulent region (at 33 jet nozzle diameters from the jet exit). This made it possible to follow the tagged entrained fluid to 73 jet diameters downstream of the exit, a distance unattainable by other methods. The dispersion of the tagged fluid in a plane containing the jet axis and the tagging source was observed and recorded using photography and simple digital image-processing techniques. Most of the entrainment activity appeared to be the result of engulfment by the large-scale structures over an axial distance of ± 1.7B from the source where B is the half-peak velocity radius. The entrained fluid crossed the jet centreline within a downstream distance of Δx = 1.5B.Downstream of the entrainment region, the spread rate of the tagged entrained fluid was close to that of the turbulent jet fluid. However, the peak mean concentration of the tagged entrained fluid was located near the r/x = 0.1 line closest to the tagging source and shifted very slowly towards the jet centreline. A self-preserving distribution of the mean concentration appears to have been approached after a distance of 6B downstream from the tagging source but further verification is needed owing to experimental uncertainties.A small fraction of the tagged entrained fluid was found on the side of the jet remote from the tagging source. On rare occurrences, tagged entrained fluid was observed at the interface most remote from the source.

scholarly journals Large-scale structures of scalar and velocity in a turbulent jet flow

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jesse Reijtenbagh ◽  
Jerry Westerweel ◽  
Willem Van de Water
Keyword(s):  
Velocity Field ◽  
Finite Time ◽  
Large Scale ◽  
Concentration Field ◽  
Turbulent Jet ◽  
Moving Frame ◽  
Mean Flow ◽  
Turbulent Structures ◽  
Large Scale Structures ◽  
Scale Structures

We study the relation between large-scale structures in the concentration field with those in the velocity field in a dye-seeded turbulent jet. The scalar concentration in a plane is measured using laser-induced fluorescence. Uniform concentration zones of an advected scalar are identified using cluster analysis. We simultaneously measure the two-dimensional velocity field using particle image velocimetry. The structures in the velocity field are characterized by finite-time Lyapunov exponents. The measurement of the scalarand velocity fields moves with the mean flow. In this moving frame, turbulent structures remain in focus long enough to observe well-defined ridges of the finite-time Lyapunov field. This field gauges the rate of point separation along Lagrangian trajectories; it was measured both for future and past times since the instant of observation. The edges of uniform concentration zones are correlated with the ridges of the past-time Lyapunov field, but not with those of the future-time Lyapunov field.

scholarly journals Large-scale structures of scalar and velocity in a turbulent jet flow

2021 ◽  
Vol 6 (8) ◽  
Author(s):  
Jesse Reijtenbagh ◽  
Jerry Westerweel ◽  
Willem van de Water
Keyword(s):  
Large Scale ◽  
Jet Flow ◽  
Turbulent Jet ◽  
Large Scale Structures ◽  
Turbulent Jet Flow ◽  
Scale Structures

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

scholarly journals The organization and control of an evolving interdependent population

2015 ◽  
Vol 12 (108) ◽  
pp. 20150044 ◽  
Author(s):  
Dervis C. Vural ◽  
Alexander Isakov ◽  
L. Mahadevan
Keyword(s):  
Evolutionary Game Theory ◽  
Large Scale ◽  
Social Evolution ◽  
Evolutionary Game ◽  
Large Scale Structures ◽  
External Perturbations ◽  
Emergence Of Cooperation ◽  
Scale Structures ◽  
And Control ◽  
Evolutionarily Stable

Starting with Darwin, biologists have asked how populations evolve from a low fitness state that is evolutionarily stable to a high fitness state that is not. Specifically of interest is the emergence of cooperation and multicellularity where the fitness of individuals often appears in conflict with that of the population. Theories of social evolution and evolutionary game theory have produced a number of fruitful results employing two-state two-body frameworks. In this study, we depart from this tradition and instead consider a multi-player, multi-state evolutionary game, in which the fitness of an agent is determined by its relationship to an arbitrary number of other agents. We show that populations organize themselves in one of four distinct phases of interdependence depending on one parameter, selection strength. Some of these phases involve the formation of specialized large-scale structures. We then describe how the evolution of independence can be manipulated through various external perturbations.

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