scholarly journals Shear-induced diffusion: the role of granular clusters

2021 ◽  
Vol 249 ◽  
pp. 03035
Author(s):  
Matthew Macaulay ◽  
Pierre Rognon

This paper is concerned with the physical mechanisms controlling shear-induced diffusion in dense granular flows. The starting point is that of the granular random walk occurring in diluted granular flows, which underpins Bagnold’s scaling relating the coefficient of self-diffusion to the grain size and shear rate. By means of DEM simulations of plane shear flows, we measure some deviations from this scaling in dense granular flows with and without contact adhesion. We propose to relate these deviations to the development of correlated motion of grains in these flows, which impacts the magnitude of grain velocity fluctuations and their time persistence.

2018 ◽  
Vol 858 ◽  
Author(s):  
Matthew Macaulay ◽  
Pierre Rognon

We investigate the effect of intergranular cohesive forces on the properties of self-diffusion in dense granular flows. The study is based on a series of simulated plane shear flows at different inertial and cohesion numbers, in which transverse diffusivities are measured. Results evidence an increase in diffusivity by up to two orders of magnitude when introducing cohesion. This strong effect is analysed using the Green–Kubo framework, expressing the diffusivity in terms of instantaneous grain velocity fluctuations and their time correlation. This analysis shows that cohesion, by forming enduring clusters in the flow, enhances the velocity fluctuations and their time persistence, which both contribute to enhancing grain mixing and self-diffusion.


Soft Matter ◽  
2021 ◽  
Author(s):  
Riccardo Artoni ◽  
Michele Larcher ◽  
James T. Jenkins ◽  
Patrick Richard

The self-diffusivity tensor in homogeneously sheared dense granular flows is anisotropic. We show how its components depend on solid fraction, restitution coefficient, shear rate, and granular temperature.


Author(s):  
Olivier Pouliquen ◽  
Yoel Forterre

A non-local theory is proposed to model dense granular flows. The idea is to describe the rearrangements occurring when a granular material is sheared as a self-activated process. A rearrangement at one position is triggered by the stress fluctuations induced by rearrangements elsewhere in the material. Within this framework, the constitutive law, which gives the relation between the shear rate and the stress distribution, is written as an integral over the entire flow. Taking into account the finite time of local rearrangements, the model is applicable from the quasi-static regime up to the inertial regime. We have checked the prediction of the model in two different configurations, namely granular flows down inclined planes and plane shear under gravity, and we show that many of the experimental observations are predicted within the self-activated model.


2014 ◽  
Vol 764 ◽  
pp. 171-192 ◽  
Author(s):  
Pierre G. Rognon ◽  
Thomas Miller ◽  
Bloen Metzger ◽  
Itai Einav

AbstractWe explore how the rheology of dense granular flows is affected by the presence of sidewalls. The study is based on discrete element method simulations of plane-shear flows between two rough walls, prescribing both the normal stress and the shear rate. Results confirm previous observations for different systems: large layers near the walls develop where the local viscosity is not constant, but decreases when approaching the walls. The size of these layers can reach several dozen grain diameters, and is found to increase when the flow decelerates, as a power law of the inertial number. Two non-local models are found to adequately explain such features, namely the kinetic elasto-plastic fluidity (KEP) model and the eddy viscosity model (EV). The analysis of the internal kinematics further shows that the vorticity and its associated length scale may be a key component of these non-local behaviours.


2020 ◽  
Vol 10 (3) ◽  
pp. 186-193
Author(s):  
REN YANYAN ◽  

The friendship between nations lies in the mutual affinity of the people, and the people’s affinity lies in the communion of hearts. The cultural and humanities cooperation between China and Russia has a long history. In recent years, under the role of the“Belt and Road” initiative, the SCO, and the Sino-Russian Humanities Cooperation Committee, Sino-Russian culture and humanities cooperation has continued to deepen. Entering a new era, taking the opportunity to promote Sino-Russian relations into a “new era China-Russia comprehensive strategic cooperative partnership”, the development of human relations between the two countries has entered a new historical starting point, while also facing a series of problems and challenges. This article is based on the current status of Sino-Russian human relations in the new era, interprets the characteristics of Sino-Russian human relations in the new era, analyzes the problems and challenges of Sino-Russian human relations in the new era, and tries to propose solutions and solutions with a view to further developing Sino-Russian cultural and humanities relations in the new era. It is a useful reference, and provides a reference for future related research, and ultimately helps the Sino-Russian cultural and humanities relations in the new era to be stable and far-reaching.


2015 ◽  
Vol 5 (3) ◽  
pp. 44-62
Author(s):  
Laura Gómez Urquijo

The objective of this article is to contribute to the discussion on the validity of new instruments to enhance cohesion in the European Union (EU). First, we question to which extent cohesion policy is submitted to the new economic governance. Second, we discuss this subordination affects the fulfillment of cohesion aims. This question is especially relevant due to the increase of inequalities in the current economic crisis and the great diversity among State Members (including social protection systems and expenses). Thus, our starting point is the new economic governance framework and its impact on the fulfillment of cohesion objectives. Statistical data are considered with this aim. Next, we will assess the role of European Structural and Investment Funds to eventually compensate public expense cuts, as well as its subordination to the macroeconomic government. This aspect will be contrasted through the study of Country Specific Recommendations given by the European Semester. Spanish El objetivo de este artículo es contribuir a la discusión sobre la validez de los nuevos instrumentos para fomentar la cohesión en la Unión Europea. Nos preguntamos en qué modo queda sometida la política de cohesión a la nueva gobernanza económica y cómo afecta a la efectividad para cubrir susfines. Esta cuestión es particularmente relevante ante el incremento de las desigualdades suscitado en la crisis económica actual. Por ello, nuestro punto de partida es el nuevo marco de gobernanza económica y su impacto en el cumplimiento de los objetivos de cohesión, considerando para ello datos estadísticos. A continuación, valoraremos, el papel de los Fondos Estructurales y de Inversión Europeos como posibles compensadores de la reducción del gasto público así como su subordinación al gobierno macroeconómico. Esta cuestión será contrastada también a través del examen de las Recomendaciones Específicas por país dadas por el Semestre Europeo. French Le but de cet article est de contribuer à la discussion sur la validité de nouveaux instruments pour promouvoir la cohésion dans l'UE. Nous avons considéré, d'une part, en quoi la politique de cohésion est soumise à la nouvelle gouvernance économique et, d'autre part, la façon dont elle utilise l'efficacité pour répondre à ses fins.Cette question est particulièrement pertinente étant donnée l'augmentation de l'inégalité soulevée par la crise économique actuelle, dans un contexte de grande diversité d'États membres, notamment en ce qui concerne les systèmes de protection sociale et les dépenses publiques. Par conséquent, notre point de départ s'inscrit dans le nouveau cadre de gouvernance économique et son impact sur la mise en œuvre des objectifs de cohésion, à partir de la prise en compte de données statistiques. Pour ce faire, nous évaluons le rôle des Fonds Structurels Européens, leur capacité de compenser la réduction des dépenses publiques et leur subordination au gouvernement macroéconomique. Ce e question sera également abordée par l'examen des recommandations spécifiques par pays fournies par le Semestre Européen.


2021 ◽  
Vol 11 (14) ◽  
pp. 6301
Author(s):  
Giulia Grisolia ◽  
Mariarosa Astori ◽  
Antonio Ponzetto ◽  
Antonio Vercesi ◽  
Umberto Lucia

Recently, a non-equilibrium thermodynamic approach has been developed in order to model the fundamental role of the membrane electric potential in the cell behaviour. A related new viewpoint is introduced, with a design of a photobiomodulation treatment in order to restore part of the visual field. Here, a first step in experimental evidence of the validity of the thermodynamic approach is developed. This result represents the starting point for future experimental improvements for light stimulation in order to improve the quality of life of the patients. The future possible therapy will be in addition to the pharmacological treatments.


AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chunmiao Jiang ◽  
Gongbo Lv ◽  
Jinxin Ge ◽  
Bin He ◽  
Zhe Zhang ◽  
...  

AbstractGATA transcription factors (TFs) are involved in the regulation of growth processes and various environmental stresses. Although GATA TFs involved in abiotic stress in plants and some fungi have been analyzed, information regarding GATA TFs in Aspergillusoryzae is extremely poor. In this study, we identified and functionally characterized seven GATA proteins from A.oryzae 3.042 genome, including a novel AoSnf5 GATA TF with 20-residue between the Cys-X2-Cys motifs which was found in Aspergillus GATA TFs for the first time. Phylogenetic analysis indicated that these seven A. oryzae GATA TFs could be classified into six subgroups. Analysis of conserved motifs demonstrated that Aspergillus GATA TFs with similar motif compositions clustered in one subgroup, suggesting that they might possess similar genetic functions, further confirming the accuracy of the phylogenetic relationship. Furthermore, the expression patterns of seven A.oryzae GATA TFs under temperature and salt stresses indicated that A. oryzae GATA TFs were mainly responsive to high temperature and high salt stress. The protein–protein interaction network of A.oryzae GATA TFs revealed certain potentially interacting proteins. The comprehensive analysis of A. oryzae GATA TFs will be beneficial for understanding their biological function and evolutionary features and provide an important starting point to further understand the role of GATA TFs in the regulation of distinct environmental conditions in A.oryzae.


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