Computer analysis of a high-speed film of the plane turbulent mixing layer

1982 ◽  
Vol 119 ◽  
pp. 323-345 ◽  
Author(s):  
Miguel A. Hernan ◽  
Javier Jimenez
Keyword(s):  
Turbulent Mixing ◽  
High Speed ◽  
Digital Image Analysis ◽  
Mixing Layer ◽  
Quantitative Information ◽  
Large Structure ◽  
Turbulent Mixing Layer ◽  
High Speed Film ◽  
History Of ◽  
Cine Film

To evaluate the usefulness of digital image analysis in extracting quantitative information from flow pictures we have studied a 16 mm ciné film of a turbulent mixing layer. A sequence of 373 frames is digitized and analysed to isolate and measure the concentration eddies that constitute the large structure and to follow their individual evolution in time. As a result, statistics are given on the life history of the eddies, the structure of the amalgamation process and the amount of entrainment, as measured by area change, due to amalgamation as compared to the total. It is found that most of the entrainment occurs during the normal life of eddies and not during pairing. Mixing intermittency is computed from the observed shape of the eddies and seen to compare well with previous measurements. The significance of these results in modelling the mixing layer is discussed briefly and some comments are given on the general usefulness of the techniques presented.

scholarly journals On density effects and large structure in turbulent mixing layers

1974 ◽  
Vol 64 (4) ◽  
pp. 775-816 ◽  
Author(s):  
Garry L. Brown ◽  
Anatol Roshko
Keyword(s):  
Turbulent Mixing ◽  
High Speed ◽  
Density Ratio ◽  
Mixing Layer ◽  
Density Fluctuations ◽  
Large Structure ◽  
Density Effects ◽  
Large Structures ◽  
Different Gases ◽  
Compressibility Effects

Plane turbulent mixing between two streams of different gases (especially nitrogen and helium) was studied in a novel apparatus. Spark shadow pictures showed that, for all ratios of densities in the two streams, the mixing layer is dominated by large coherent structures. High-speed movies showed that these convect at nearly constant speed, and increase their size and spacing discontinuously by amalgamation with neighbouring ones. The pictures and measurements of density fluctuations suggest that turbulent mixing and entrainment is a process of entanglement on the scale of the large structures; some statistical properties of the latter are used to obtain an estimate of entrainment rates. Large changes of the density ratio across the mixing layer were found to have a relatively small effect on the spreading angle; it is concluded that the strong effects, which are observed when one stream is supersonic, are due to compressibility effects, not density effects, as has been generally supposed.

Wavelet analysis of shearless turbulent mixing layer

2021 ◽  
Vol 33 (2) ◽  
pp. 025109
Author(s):  
T. Matsushima ◽  
K. Nagata ◽  
T. Watanabe
Keyword(s):  
Wavelet Analysis ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Turbulent Mixing Layer

scholarly journals Mixing and chemical reactions in a turbulent liquid mixing layer

1986 ◽  
Vol 170 ◽  
pp. 83-112 ◽  
Author(s):  
M. M. Koochesfahani ◽  
P. E. Dimotakis
Keyword(s):  
Reynolds Number ◽  
Gas Phase ◽  
Turbulent Mixing ◽  
High Speed ◽  
High Reynolds Number ◽  
Schmidt Number ◽  
Mixing Layer ◽  
Entrainment Ratio ◽  
High Reynolds ◽  
Mixed Fluid

An experimental investigation of entrainment and mixing in reacting and non-reacting turbulent mixing layers at large Schmidt number is presented. In non-reacting cases, a passive scalar is used to measure the probability density function (p.d.f.) of the composition field. Chemically reacting experiments employ a diffusion-limited acid–base reaction to directly measure the extent of molecular mixing. The measurements make use of laser-induced fluorescence diagnostics and high-speed, real-time digital image-acquisition techniques.Our results show that the vortical structures in the mixing layer initially roll-up with a large excess of fluid from the high-speed stream entrapped in the cores. During the mixing transition, not only does the amount of mixed fluid increase, but its composition also changes. It is found that the range of compositions of the mixed fluid, above the mixing transition and also throughout the transition region, is essentially uniform across the entire transverse extent of the layer. Our measurements indicate that the probability of finding unmixed fluid in the centre of the layer, above the mixing transition, can be as high as 0.45. In addition, the mean concentration of mixed fluid across the layer is found to be approximately constant at a value corresponding to the entrainment ratio. Comparisons with gas-phase data show that the normalized amount of chemical product formed in the liquid layer, at high Reynolds number, is 50% less than the corresponding quantity measured in the gas-phase case. We therefore conclude that Schmidt number plays a role in turbulent mixing of high-Reynolds-number flows.

Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity

2010 ◽  
Vol 51 (1) ◽  
pp. 51-63 ◽  
Author(s):  
Shiyao Bian ◽  
James F. Driscoll ◽  
Brian R. Elbing ◽  
Steven L. Ceccio
Keyword(s):  
Flow Field ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Field Measurements ◽  
Rectangular Cavity ◽  
Time Resolved ◽  
Turbulent Mixing Layer
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