scholarly journals Vortex clustering, polarisation and circulation intermittency in classical and quantum turbulence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Juan Ignacio Polanco ◽  
Nicolás P. Müller ◽  
Giorgio Krstulovic
Keyword(s):  
Turbulent Flows ◽  
Quantum Turbulence ◽  
Spatial Arrangement ◽  
Coarse Grained ◽  
Quantum Case ◽  
Discrete Vortex ◽  
Turbulence Intermittency ◽  
Kolmogorov Turbulence ◽  
Velocity Circulation ◽  
Spatio Temporal

AbstractThe understanding of turbulent flows is one of the biggest current challenges in physics, as no first-principles theory exists to explain their observed spatio-temporal intermittency. Turbulent flows may be regarded as an intricate collection of mutually-interacting vortices. This picture becomes accurate in quantum turbulence, which is built on tangles of discrete vortex filaments. Here, we study the statistics of velocity circulation in quantum and classical turbulence. We show that, in quantum flows, Kolmogorov turbulence emerges from the correlation of vortex orientations, while deviations—associated with intermittency—originate from their non-trivial spatial arrangement. We then link the spatial distribution of vortices in quantum turbulence to the coarse-grained energy dissipation in classical turbulence, enabling the application of existent models of classical turbulence intermittency to the quantum case. Our results provide a connection between the intermittency of quantum and classical turbulence and initiate a promising path to a better understanding of the latter.

scholarly journals Direct numerical simulation of intermittent turbulence under stably stratified conditions

2015 ◽  
Vol 2 (1) ◽  
pp. 179-241 ◽  
Author(s):  
P. He ◽  
S. Basu
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Open Channel ◽  
Temporal Evolution ◽  
Intermittent Turbulence ◽  
Bursting Events ◽  
Spatio Temporal ◽  
Channel Region ◽  
Laminar And Turbulent Flows

Abstract. In this paper, we simulate intermittent turbulence (also known as bursting events) in stably stratified open-channel flows using direct numerical simulation. Clear signatures of this intriguing phenomenon are observed for a range of stabilities. However, the spatio-temporal characteristics of intermittency are found to be strongly stability-dependent. In general, the bursting events are much more frequent near the bottom wall than in the upper-channel region. A steady coexistence of laminar and turbulent flows is detected at various horizontal planes in very stable cases. This spatially intermittent pattern is found to propagate downstream and strongly correlate with the temporal evolution of intermittency. Last, a long standing hypothesis by Blackadar, i.e., the strong connection between local stability and intermittent turbulence, is corroborated by this modeling study.

Study on Laminar Turbulent Transition in Square Arrayed Rod Bundles

2021 ◽  
Author(s):  
Carolina S. B. Dutra ◽  
Elia Merzari
Keyword(s):  
Turbulent Flows ◽  
Flow Behavior ◽  
Spectral Element ◽  
Linear Instability ◽  
Rod Bundles ◽  
Rod Bundle ◽  
Turbulent Transition ◽  
Spatio Temporal ◽  
The Stability ◽  
Laminar Turbulent Transition

Abstract The study of coolant flow behavior in rod bundles is of relevance to the design of nuclear reactors. Although laminar and turbulent flows have been researched extensively, there are still gaps in understanding the process of laminar-turbulent transition. Such a process may involve the formation of a gap vortex street as the consequence of a related linear instability. In the present work, a parametric study was performed to analyze the spatially developing turbulence in a simplified geometry setting. The geometry includes two square arrayed rod bundle subchannels with periodic boundary conditions in the cross-section. The pitch-to-diameter ratios range from 1.05 to 1.20, and the length of the domain was selected to be 100 diameters. No-slip condition at the wall, and inlet-outlet configuration were employed. Then, to investigate the stability of the flow, the Reynolds number was varied from 250 to 3000. The simulations were carried out using the spectral-element code Nek5000, with a Direct Numerical Simulation (DNS) approach. Data were analyzed to examine this Spatio-temporal developing instability. In particular, we evaluate the location of onset and spatial growth of the instability.

scholarly journals Reaction–diffusion basis of retroviral infectivity

2016 ◽  
Vol 374 (2080) ◽  
pp. 20160148 ◽  
Author(s):  
S. Kashif Sadiq
Keyword(s):  
Chemical Reactions ◽  
Membrane Surface ◽  
Reaction Diffusion ◽  
Coarse Graining ◽  
Coarse Grained ◽  
Multiscale Approach ◽  
The Matrix ◽  
Membrane Bound ◽  
Spatio Temporal ◽  
Dynamics Simulations

Retrovirus particle (virion) infectivity requires diffusion and clustering of multiple transmembrane envelope proteins (Env 3 ) on the virion exterior, yet is triggered by protease-dependent degradation of a partially occluding, membrane-bound Gag polyprotein lattice on the virion interior. The physical mechanism underlying such coupling is unclear and only indirectly accessible via experiment. Modelling stands to provide insight but the required spatio-temporal range far exceeds current accessibility by all-atom or even coarse-grained molecular dynamics simulations. Nor do such approaches account for chemical reactions, while conversely, reaction kinetics approaches handle neither diffusion nor clustering. Here, a recently developed multiscale approach is considered that applies an ultra-coarse-graining scheme to treat entire proteins at near-single particle resolution, but which also couples chemical reactions with diffusion and interactions. A model is developed of Env 3 molecules embedded in a truncated Gag lattice composed of membrane-bound matrix proteins linked to capsid subunits, with freely diffusing protease molecules. Simulations suggest that in the presence of Gag but in the absence of lateral lattice-forming interactions, Env 3 diffuses comparably to Gag-absent Env 3 . Initial immobility of Env 3 is conferred through lateral caging by matrix trimers vertically coupled to the underlying hexameric capsid layer. Gag cleavage by protease vertically decouples the matrix and capsid layers, induces both matrix and Env 3 diffusion, and permits Env 3 clustering. Spreading across the entire membrane surface reduces crowding, in turn, enhancing the effect and promoting infectivity. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

Origin of glacial ridges (OIS 6) in the Kaskaskia Sublobe, southwestern Illinois, USA

2012 ◽  
Vol 78 (2) ◽  
pp. 341-352 ◽  
Author(s):  
Nathan D. Webb ◽  
David A. Grimley ◽  
Andrew C. Phillips ◽  
Bruce W. Fouke
Keyword(s):  
Debris Flows ◽  
Spatial Arrangement ◽  
Coarse Grained ◽  
Ice Flow ◽  
Glacial Ice ◽  
Distinctive Features ◽  
Fine Grained ◽  
The North ◽  
Till Fabric ◽  
Glacial Landforms

AbstractThe origin of Illinois Episode (OIS 6) glacial ridges (formerly: ‘Ridged Drift’) in the Kaskaskia Basin of southwestern Illinois is controversial despite a century of research. Two studied ridges, containing mostly fluvial sand (OSL ages: ~ 150 ± 19 ka), with associated debris flows and high-angle reverse faults, are interpreted as ice-walled channels. A third studied ridge, containing mostly fine-grained till, is arcuate and morainal. The spatial arrangement of various ridge types can be explained by a glacial sublobe in the Kaskaskia Basin, with mainly fine-grained ridges along the sublobe margins and coarse-grained glaciofluvial ridges in a paleodrainage network within the sublobe interior. Illinois Episode till fabric and striation data demonstrate southwesterly ice flow that may diverge near the sublobe terminus. The sublobe likely formed as glacial ice thinned and receded from its maximum extent. The Kaskaskia Basin contains some of the best-preserved Illinois Episode constructional glacial landforms in the North American midcontinent. Such distinctive features probably result from ice flow and sedimentation into this former lowland, in addition to minimal postglacial erosion. Other similar OIS 6 glacial landforms may exist in association with previously unrecognized sublobes in the midcontinent, where paleo-lowlands might also have focused glacial sedimentation.

scholarly journals Design Metrics in Quantum Turbulence Simulations: How Physics Influences Software Architecture

2004 ◽  
Vol 12 (3) ◽  
pp. 185-196 ◽  
Author(s):  
Damian W.I. Rouson ◽  
Yi Xiong
Keyword(s):  
Data Structures ◽  
Quantum Turbulence ◽  
Object Oriented Programming ◽  
Coarse Grained ◽  
Local Data ◽  
Design Metrics ◽  
Dynamically Reconfigurable ◽  
Fine Grained ◽  
Scientific Simulations ◽  
Global Operations

The information hiding philosophy of object-oriented programming encourages localizing data structures within objects rather than sharing data globally across different classes of objects. This emphasis on local data leads naturally to fine-grained data abstractions, particularly in scientific simulations involving large collections of small, discrete physical or mathematical objects. This paper focuses on a subset of such simulations where dynamically reconfigurable links bind the objects together. It is demonstrated that fine-grained data structures reduce the complexity of local operations on the data at the potential expense of increased global operation complexity. Two metrics are used to describe data structures: granularity is the number of instantiations required to cover the data space, whereas extent is the continuously traversable length of the data along a given direction. These definitions are applied to two abstractions for simulating the turbulent motion of quantum vortices in superfluid liquid helium. Several local and global operations on a fine-grained linked list are compared with those on a coarse-grained array. It is demonstrated that fine-grained data structures recover the simplicity of more coarse-grained structures if maximal extent is maintained as the granularity increases.

scholarly journals Spatio-Temporal Interurban Regularities in the Global South

2021 ◽  
Author(s):  
Bartosz Prokop ◽  
John Friesen
Keyword(s):  
Urban Areas ◽  
Temporal Evolution ◽  
Pair Correlation ◽  
Deep Understanding ◽  
Spatial Arrangement ◽  
Global South ◽  
Urban Systems ◽  
Urban Structures ◽  
Impervious Area ◽  
Spatio Temporal

The reality of people’s lives has shifted from rural to urban areas, where an ever-increasing proportion of the world’s population lives. Providing infrastructure to serve these areas, especially in the Global South, is a key task of sustainable development. A deep understanding of the spatial arrangement and scales of these urban structures and their temporal evolution can help to develop innovative solutions to issues of energy, water, or transportation infrastructures. For this purpose, in this work we study the temporal evolution of urban built-up structures (Global Artificial Impervious Area) and population distributions (Global Human Settlement Population) in four regions of the Global South (Argentina, India, Egypt, and Nigeria). We qualitatively analyze regularity through the pair correlation function and subsequently identify typical scales within the different interurban systems. In doing so, we identify that especially the large settlement objects arrange themselves in a regular way and thus typical scales exist in urban systems. Thus, settlement objects are usually located about 20 to 40 km apart from each other. This information can be used to develop sustainable infrastructure concepts, for example for passenger transport between settlements.

scholarly journals Why a Large-Scale Mode Can Be Essential for Understanding Intracellular Actin Waves

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1533 ◽  
Author(s):  
Carsten Beta ◽  
Nir S. Gov ◽  
Arik Yochelis
Keyword(s):  
Large Scale ◽  
Mass Conservation ◽  
Coarse Grained ◽  
Cellular Functions ◽  
Multi Scale ◽  
Spatio Temporal ◽  
Actin Waves ◽  
Inhibitor Type ◽  
Activator Inhibitor Type

During the last decade, intracellular actin waves have attracted much attention due to their essential role in various cellular functions, ranging from motility to cytokinesis. Experimental methods have advanced significantly and can capture the dynamics of actin waves over a large range of spatio-temporal scales. However, the corresponding coarse-grained theory mostly avoids the full complexity of this multi-scale phenomenon. In this perspective, we focus on a minimal continuum model of activator–inhibitor type and highlight the qualitative role of mass conservation, which is typically overlooked. Specifically, our interest is to connect between the mathematical mechanisms of pattern formation in the presence of a large-scale mode, due to mass conservation, and distinct behaviors of actin waves.

Introduction To Renormalization Group Modeling Of Turbulence

1996 ◽  
Author(s):  
Steven A. Orszag ◽  
I. Staroselsky,
Keyword(s):  
Renormalization Group ◽  
Turbulent Flows ◽  
Equations Of Motion ◽  
Turbulence Models ◽  
Coarse Grained ◽  
Small Scale ◽  
Flow Problems ◽  
Group Modeling ◽  
Systematic Derivation ◽  
Incompressible Turbulence

The renormalization group (RNG) and related e-expansion methods are a powerful technique that allow the systematic derivation of coarse-grained equations of motion for turbulent flows and, in particular, the derivation of sophisticated turbulence models based on the fundamental underlying physics. The RNG method provides a convenient calculus for the analysis of complex physical effects in complex flows. The details of the RNG method applied to fluid mechanics differ in some crucial respects from how renormalization group techniques are applied to field theories in other branches of physics. At the present time, the RNG methods for fluid dynamics are by no means rigorously justified, so their utility must be based on the quality and quantity of results to which they lead. In this paper we discuss the basis for the RNG method and then illustrate its application to a variety of turbulent flow problems, emphasizing those points where further analysis is needed. The application of a field-theoretic method like the RNG technique to turbulence is based on the fundamental assumption of universality of small scales in turbulent flows. Such universal behavior was first suggested over 50 years ago in the seminal work of A. N. Kolmogorov who argued that the small-scale spectrum of incompressible turbulence is universal and characterized by two numbers, the rate of energy dissipation ε per unit mass and the kinematic viscosity v.

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