scholarly journals Order out of chaos: Shifting paradigm of convective turbulence

2021 ◽  
Author(s):  
Sergej Zilitinkevich ◽  
Evgeny Kadantsev ◽  
Irina Repina ◽  
Evgeny Mortikov ◽  
Andrey Glazunov
Keyword(s):  
Large Scale ◽  
Vertical Mixing ◽  
Fluid Flows ◽  
Stratified Turbulence ◽  
Conventional Theory ◽  
New Paradigm ◽  
Chaotic Motions ◽  
Low Viscosity ◽  
Self Organized ◽  
Almost All

AbstractTurbulence is ever produced in the low-viscosity/large-scale fluid flows by the velocity shears and, in unstable stratification, by buoyancy forces. It is commonly believed that both mechanisms produce the same type of chaotic motions, namely, the eddies breaking down into smaller ones and producing direct cascade of turbulent kinetic energy and other properties from large to small scales towards viscous dissipation. The conventional theory based on this vision yields a plausible picture of vertical mixing and remains in use since the middle of the 20th century in spite of increasing evidence of the fallacy of almost all other predictions. This paper reveals that in fact buoyancy produces chaotic vertical plumes, merging into larger ones and producing an inverse cascade towards their conversion into the self-organized regular motions. Herein, the velocity shears produce usual eddies spreading in all directions and making the direct cascade. This new paradigm is demonstrated and proved empirically; so, the paper launches a comprehensive revision of the theory of unstably stratified turbulence and its numerous geophysical or astrophysical applications.

scholarly journals Exploiting self-organized criticality in strongly stratified turbulence

2021 ◽  
Vol 933 ◽  
Author(s):  
Gregory P. Chini ◽  
Guillaume Michel ◽  
Keith Julien ◽  
Cesar B. Rocha ◽  
Colm-cille P. Caulfield
Keyword(s):  
Large Scale ◽  
Ad Hoc ◽  
Three Dimensional ◽  
Boussinesq Equations ◽  
Marginal Stability ◽  
Small Scale ◽  
Stratified Turbulence ◽  
Self Organized ◽  
Reduced Equations ◽  
Self Organized Criticality

A multiscale reduced description of turbulent free shear flows in the presence of strong stabilizing density stratification is derived via asymptotic analysis of the Boussinesq equations in the simultaneous limits of small Froude and large Reynolds numbers. The analysis explicitly recognizes the occurrence of dynamics on disparate spatiotemporal scales, yielding simplified partial differential equations governing the coupled evolution of slow large-scale hydrostatic flows and fast small-scale isotropic instabilities and internal waves. The dynamics captured by the coupled reduced equations is illustrated in the context of two-dimensional strongly stratified Kolmogorov flow. A noteworthy feature of the reduced model is that the fluctuations are constrained to satisfy quasilinear (QL) dynamics about the comparably slowly varying large-scale fields. Crucially, this QL reduction is not invoked as an ad hoc closure approximation, but rather is derived in a physically relevant and mathematically consistent distinguished limit. Further analysis of the resulting slow–fast QL system shows how the amplitude of the fast stratified-shear instabilities is slaved to the slowly evolving mean fields to ensure the marginal stability of the latter. Physically, this marginal stability condition appears to be compatible with recent evidence of self-organized criticality in both observations and simulations of stratified turbulence. Algorithmically, the slaving of the fluctuation fields enables numerical simulations to be time-evolved strictly on the slow time scale of the hydrostatic flow. The reduced equations thus provide a solid mathematical foundation for future studies of three-dimensional strongly stratified turbulence in extreme parameter regimes of geophysical relevance and suggest avenues for new sub-grid-scale parametrizations.

Increase in chaotic motions of atoms in a large-scale self-organized motion

1996 ◽  
Vol 54 (2) ◽  
pp. 1504-1509 ◽  
Author(s):  
Tadashi Watanabe ◽  
Hideo Kaburaki
Keyword(s):  
Large Scale ◽  
Chaotic Motions ◽  
Self Organized

The sugar and alcohol industry in the biofuels and cogeneration era: a paradigm change (part II)

2014 ◽  
pp. 97-104 ◽  
Author(s):  
Electo Eduardo Silv Lora ◽  
Mateus Henrique Rocha ◽  
José Carlos Escobar Palacio ◽  
Osvaldo José Venturini ◽  
Maria Luiza Grillo Renó ◽  
...  
Keyword(s):  
Large Scale ◽  
New Technologies ◽  
Process Integration ◽  
Animal Feed ◽  
Raw Materials ◽  
Biofuel Production ◽  
New Paradigm ◽  
Alcohol Industry ◽  
Feed Production ◽  
Steam Parameters

The aim of this paper is to discuss the major technological changes related to the implementation of large-scale cogeneration and biofuel production in the sugar and alcohol industry. The reduction of the process steam consumption, implementation of new alternatives in driving mills, the widespread practice of high steam parameters use in cogeneration facilities, the insertion of new technologies for biofuels production (hydrolysis and gasification), the energy conversion of sugarcane trash and vinasse, animal feed production, process integration and implementation of the biorefinery concept are considered. Another new paradigm consists in the wide spreading of sustainability studies of products and processes using the Life Cycle Assessment (LCA) and the implementation of sustainability indexes. Every approach to this issue has as an objective to increase the economic efficiency and the possibilities of the sugarcane as a main source of two basic raw materials: fibres and sugar. The paper briefly presents the concepts, indicators, state-of-the-art and perspectives of each of the referred issues.

Thin structure of heterogeneous and multiphase fluid flows

2012 ◽  
Vol 9 (1) ◽  
pp. 175-180
Author(s):  
Yu.D. Chashechkin
Keyword(s):  
Large Scale ◽  
Fundamental System ◽  
Fluid Flows ◽  
Regular Solutions ◽  
Flow Models ◽  
Group Methods ◽  
Wide Range ◽  
Thin Structure ◽  
Multiphase Fluid ◽  
Complete Solutions

According to the results of visualization of streams, the existence of structures in a wide range of scales is noted: from galactic to micron. The use of a fundamental system of equations is substantiated based on the results of comparing symmetries of various flow models with the usage of theoretical group methods. Complete solutions of the system are found by the methods of the singular perturbations theory with a condition of compatibility, which determines the characteristic equation. A comparison of complete solutions with experimental data shows that regular solutions characterize large-scale components of the flow, a rich family of singular solutions describes formation of the thin media structure. Examples of calculations and observations of stratified, rotating and multiphase media are given. The requirements for the technique of an adequate experiment are discussed.

Modeling Extinction

2003 ◽  
Author(s):  
M. E. J. Newman ◽  
R. G. Palmer
Keyword(s):  
Evolutionary Biology ◽  
Large Scale ◽  
Competitive Exclusion ◽  
Applied Mathematics ◽  
Santa Fe ◽  
New Approach ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Extinction Events ◽  
Mass Extinction Events

Developed after a meeting at the Santa Fe Institute on extinction modeling, this book comments critically on the various modeling approaches. In the last decade or so, scientists have started to examine a new approach to the patterns of evolution and extinction in the fossil record. This approach may be called "statistical paleontology," since it looks at large-scale patterns in the record and attempts to understand and model their average statistical features, rather than their detailed structure. Examples of the patterns these studies examine are the distribution of the sizes of mass extinction events over time, the distribution of species lifetimes, or the apparent increase in the number of species alive over the last half a billion years. In attempting to model these patterns, researchers have drawn on ideas not only from paleontology, but from evolutionary biology, ecology, physics, and applied mathematics, including fitness landscapes, competitive exclusion, interaction matrices, and self-organized criticality. A self-contained review of work in this field.

scholarly journals New Targeted Therapies and Immunotherapies for Locally Advanced Periocular Malignant Tumours: Towards a New ‘Eye-Sparing’ Paradigm?

Cancers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2822
Author(s):  
Arnaud Martel ◽  
Sandra Lassalle ◽  
Alexandra Picard-Gauci ◽  
Lauris Gastaud ◽  
Henri Montaudie ◽  
...  
Keyword(s):  
Targeted Therapies ◽  
Paradigm Shift ◽  
Adjuvant Radiotherapy ◽  
Locally Advanced ◽  
Second Step ◽  
Malignant Tumours ◽  
New Paradigm ◽  
Eye Pain ◽  
Almost All ◽  
Orbital Lesions

The management of periocular skin malignant tumours is challenging. Surgery remains the mainstay of treatment for localised eyelid cancers. For more locally advanced cancers, especially those invading the orbit, orbital exenteration has long been considered the gold standard; however, it is a highly disfiguring and traumatic surgery. The last two decades have been marked by the emergence of a new paradigm shift towards the use of ‘eye-sparing’ strategies. In the early 2000s, the first step consisted of performing wide conservative eyelid and orbital excisions. Multiple flaps and grafts were needed, as well as adjuvant radiotherapy in selected cases. Although being incredibly attractive, several limitations such as the inability to treat the more posteriorly located orbital lesions, as well as unbearable diplopia, eye pain and even secondary eye loss were identified. Therefore, surgeons should distinguish ‘eye-sparing’ from ‘sight-sparing’ strategies. The second step emerged over the last decade and was based on the development of targeted therapies and immunotherapies. Their advantages include their potential ability to treat almost all tumours, regardless of their locations, without performing complex surgeries. However, several limitations have been reported, including their side effects, the appearance of primary or secondary resistances, their price and the lack of consensus on treatment regimen and exact duration. The aim of this article was to review the evolution of the management of locally advanced periocular malignant tumours over the last three decades and highlight the new paradigm shift towards the use of ‘eye-sparing’ strategies.

RESEARCH OF EXTERNAL MASS TRANSFER PROCESSES FOR ADSORPTION FROM SOLUTIONS IN A APPARATUS WITH STIRRING

2021 ◽  
pp. 11-20
Author(s):  
V. Solovej ◽  
K. Gorbunov ◽  
V. Vereshchak ◽  
O. Gorbunova
Keyword(s):  
Mass Transfer ◽  
Energy Spectrum ◽  
Energy Dissipation ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Wave Number ◽  
Wave Form ◽  
Local Isotropy ◽  
Stirred Vessel ◽  
Almost All

A study has been mode of transport-controlled mass transfer-controlled to particles suspended in a stirred vessel. The motion of particle in a fluid was examined and a method of predicting relative velocities in terms of Kolmogoroff’s theory of local isotropic turbulence for mass transfer was outlined. To provide a more concrete visualization of complex wave form of turbulence, the concepts of eddies, of eddy velocity, scale (or wave number) and energy spectrum, have proved convenient. Large scale motions of scale contain almost all of the energy and they are directly responsible for energy diffusion throughout the stirring vessel by kinetic and pressure energies. However, almost no energy is dissipated by the large-scale energy-containing eddies. A scale of motion less than is responsible for convective energy transfer to even smaller eddy sires. At still smaller eddy scales, close to a characteristic microscale, both viscous energy dissipation and convection are the rule. The last range of eddies has been termed the universal equilibrium range. It has been further divided into a low eddy size region, the viscous dissipation subrange, and a larger eddy size region, the inertial convection subrange. Measurements of energy spectrum in mixing vessel are shown that there is a range, where the so called -(5/3) power law is effective. Accordingly, the theory of local isotropy of Kolmogoroff can be applied because existence of the internal subrange. As the integrated value of local energy dissipation rate agrees with the power per unit mass of liquid from the impeller, almost all energy from the impeller is viscous dissipated in eddies of microscale. The correlation for mass transfer to particles suspended in a stirred vessel is recommended. The results of experimental study are approximately 12 % above the predicted values.

Why Do People Stay Poor?

2021 ◽  
Author(s):  
Clare Balboni ◽  
Oriana Bandiera ◽  
Robin Burgess ◽  
Maitreesh Ghatak ◽  
Anton Heil
Keyword(s):  
Occupational Choice ◽  
Large Scale ◽  
Choice Model ◽  
Effective Means ◽  
Threshold Level ◽  
Poverty Traps ◽  
Asset Transfer ◽  
Small Livestock ◽  
Program Costs ◽  
Almost All

Abstract There are two broad views as to why people stay poor. One emphasizes differences in fundamentals, such as ability, talent, or motivation. The other, the poverty traps view, emphasizes differences in opportunities which stem from access to wealth. To test between these two views, we exploit a large-scale, randomized asset transfer and an 11-year panel of 6,000 households who begin in extreme poverty. The setting is rural Bangladesh and the assets are cows. The data supports the poverty traps view—we identify a threshold level of initial assets above which households accumulate assets, take on better occupations (from casual labor in agriculture or domestic services to running small livestock businesses), and grow out of poverty. The reverse happens for those below the threshold. Structural estimation of an occupational choice model reveals that almost all beneficiaries are misallocated in the work they do at baseline and that the gains arising from eliminating misallocation would far exceed the program costs. Our findings imply that large transfers which create better jobs for the poor are an effective means of getting people out of poverty traps and reducing global poverty.

Opuntia ficus-indica (prickly pear).

2021 ◽  
Author(s):  
Nick Pasiecznik
Keyword(s):  
Vitamin C ◽  
Large Scale ◽  
Time Lag ◽  
Prickly Pear ◽  
Invasive Weeds ◽  
Historical Records ◽  
Opuntia Ficus Indica ◽  
Actual Risk ◽  
Invasive Spread ◽  
Almost All

Abstract O. ficus-indica is highly valued as a fruit-producing cactus, also yielding 'leaves' that are used as a vegetable and browsed by livestock. It has been introduced widely from its native Mexico to almost all countries where the climate is suitable. The fruit is very rich in vitamin C and is exploited commercially in many areas. Many countries, especially in Asia, have recently established large-scale commercial plantations. However, O. ficus-indica, like several other species of Opuntia, have been known to spread and become invasive weeds. Historical records, however, appear to indicate a time-lag of about 100 years between introduction and the beginnings of invasive spread thus the actual risk may be low.

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