Mixing Efficiency across Rayleigh-Taylor and Richtmeyer-Meshkov Fronts

Redondo, J. M.; González-Nieto, Pilar López; Cano, José L.; Garzon, G. A.

doi:10.4236/ojfd.2015.52017

Cited by 2 publications

(7 citation statements)

References 7 publications

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“…To extend the measurements to complex flows a novel pattern matching technique was developed. This technique utilises similar algorithms to those found by DigiFlow in PIV and in synthetic schlieren [10,19].…”

Section: Discussionmentioning

confidence: 99%

“…The relationship between stratification, intermittency, D(Ri) the fractal dimension of the flows and the turbulence energy spectral slope b, may be related [18][19][20]. For example the local measurements of dispersion, are related to the second order velocity moments, the skeweness and kurthosis, etc.…”

Section: Discussionmentioning

confidence: 99%

“…We have analysed the Fractal and Multi-scale instabilities leading to mixing due to RT and RM instabilities using also wavelet and Neural techniques coupled with the multi fractal measurements as described in [19,20] to aid the description of the self-similar structure within the mixing fronts. Elaboration of two-dimensional numerical simulation of evolution of the mixing region, under conditions used to drive the RT or the RM allow a parameter distribution of the incident compression wave used as boundary conditions are compared with two-dimensional numerical simulations.…”

Section: Topical Problems Of Fluid Mechanics 171 ____________________mentioning

confidence: 99%

“…This is an additional reason for rather using direct multifractal box counting methods and wavelet analysis when dealing in applications with experimental data, where many such complex interacting behaviors occur in high Reynolds number flows [16,17]. [18,19].…”

Section: Frame) We Can Thereby Define the Fractal Dimension D (I) Asmentioning

confidence: 99%

“…The models will be required to successfully simulate the key statistical elements of the experimental results. Comparison with incompressible RT and with (compressible and incompressible) Richtmyer-Meshkov instability are related with fractal generated grid flows [18][19][20]. Simulations performed at the BSC by Laizet, S. and Prof. Vassilicos with a numerical strategy to investigate fractal generated turbulence [12][13][14][15][16][17] were analysed with program ImaCalc to compare the evolution described by Redondo [18] and the variation of maximum fractal dimension and intermittency as a function of distance from the grid.…”

Section: Topical Problems Of Fluid Mechanics 171 ____________________mentioning

confidence: 99%

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Richtmyer-Meshkov and Rayleigh-Taylor Fractal Mixing

Apraiz¹,

Esteve²,

Alvarez³

et al. 2016

Topical Problems of Fluid Mechanics 2016

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Turbulence affects molecular mixing in a large variety of physical processes both in the environment, in astrophysics and in industrial situations. In some events it is interesting to enhance the transport of mass, heat, humidity and pollutants, while sometimes it is interesting to reduce mixing. Here we analyse some turbulent descriptors which reflect the mixing processes in the compressible induced instabilities that take place in shocks, such as Richtmyer-Meshkov and Rayleigh-Taylor (RM and RT). We present results related to both instabilities and discuss their spatial and temporal variability during the advance of a mixing front, and also their relationships with other scaling arguments. Two types of experiments were used in this study: Mixing generated by gravitational acceleration in low Atwood number incompressible experiments using fluids; and the full compressible shocktube experiments using interfaces between different density gases. The role of local turbulence has mostly relied on advanced visualization measurements through multifractal methods. Comparisons with numerical experiments of shock driven fronts occurring at density interfaces are also relevant. The global advance of the fronts is also measured and fractal descriptors are calculated in both Large Eddy Simulation (LES) and Kinematic Simulation KS models.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Topical Problems Of Fluid Mechanics 171 ____________________mentioning

confidence: 99%

Section: Frame) We Can Thereby Define the Fractal Dimension D (I) Asmentioning

confidence: 99%

Section: Topical Problems Of Fluid Mechanics 171 ____________________mentioning

confidence: 99%

See 3 more Smart Citations

Richtmyer-Meshkov and Rayleigh-Taylor Fractal Mixing

Apraiz¹,

Esteve²,

Alvarez³

et al. 2016

Topical Problems of Fluid Mechanics 2016

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Turbulent structure in environmental flows: effects of stratification and rotation

Matulka

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Several series of experiments in stratified and in rotating/stratified decaying flows after a grid is used to stir the two layer stable fluid brine and fresh water set up. We measure by comparing the gained potential energy with the available kinetic energy AKE, the relative efficiency of mixing. The experiments in stratified rotating flows with grid driven turbulence were both periodic (quasi stationary) and non-monotonic (decaying) forcing. This thesis compares experimental, numerical and field observations on the structure and Topology of the Stratified Rotating Flows as well as their decay, the horizontal spectra changes appreciable with slopes from 1.1 to 5, but vorticity and local circulation, and also the initial topology and forcing of the flow. A detailed study of the vorticity decay and vortex and energy structure has been performed, the new results show that neither stratified nor rotating flows exhibit pure 2D structures. The work parameterizes the role of the Richardson number and the Rossby number, both in the experiments and in the ocean visualizations is very important. The conditions of vortex decay show the effects of the internal waves in the decay turbulent conditions both for stratified and rotating flows. The parameter space (Re,Ri,Ro) has been used to interpret many previously disconnected explanations of the 2D-3D turbulent behaviour. The comparison of numerical simulations with experiments has allowed implementing new theoretical aspects of the interaction between waves and vortices finding the surprising and very interesting result that these interactions depend on the level of enstrophy. This also leads to new ways of using multifractal analysis ad intermittency in ocean environmental observations. A large collection of SAR images obtained from three European coastal areas were used for routine satellite analysis by SAR and other sensors, which seem very important to build seasonal databases of the dynamic conditions of ocean mixing. The topology of the basic flow is very important and in particular the topology of the vortices and their decay which depends on ambient factors such as wave activity, wind and currents. We find more realistic estimates of the spatial/temporal non-homogeneities (and intermittency obtained as spatial correlations of the turbulent dissipation); these values are used to parameterize the sea surface turbulence, as well as a laboratory experiments at a variety of scales. Using multi-fractal geometry as well, we can establish now a theoretical pattern for the turbulence behaviour that is reflected in the different descriptors. Vorticity evolution is smoother and different than that of scalar or tracer density. The correlation between the local Ri and the fractal dimension detected from energy or entropy is good. Using multi-fractal geometry we can also establish certain regions of higher local activity used to establish the geometry of the turbulence mixing that needs to be studied in detail when interpreting the complex balance between the direct 3D Kolmogorov type cascade and the Inverse 2D Kraichnan type cascade.

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Mixing Efficiency across Rayleigh-Taylor and Richtmeyer-Meshkov Fronts

Cited by 2 publications

References 7 publications

Richtmyer-Meshkov and Rayleigh-Taylor Fractal Mixing

Richtmyer-Meshkov and Rayleigh-Taylor Fractal Mixing

Turbulent structure in environmental flows: effects of stratification and rotation

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