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European Physical Journal. E, Soft Matter

Michele Buzzicotti, Patricio Clark Di Leoni, Luca Biferale
Rotating turbulence is an example of a three-dimensional system in which an inverse cascade of energy, from the small to the large scales, can be formed. While usually understood as a byproduct of the typical bidimensionalization of rotating flows, the role of the three-dimensional modes is not completely comprehended yet. In order to shed light on this issue, we performed direct numerical simulations of rotating turbulence where the 2D modes falling in the plane perpendicular to rotation are removed from the dynamical evolution...
November 12, 2018: European Physical Journal. E, Soft Matter
Miljan Dašić, Igor Stanković, Konstantinos Gkagkas
We present a molecular dynamics study of the effects of confinement on the lubrication and flow properties of ionic liquids. We use a coarse-grained salt model description of ionic liquid as a lubricant confined between finite solid plates and subjected to two dynamic regimes: shear and cyclic loading. The impact of confinement on the ion arrangement and mechanical response of the system has been studied in detail and compared to static and bulk properties. The results have revealed that the wall slip has a profound influence on the force built-up as a response to mechanical deformation and that at the same time in the dynamic regime interaction with the walls represents a principal driving force governing the behaviour of ionic liquid in the gap...
November 2, 2018: European Physical Journal. E, Soft Matter
Isabella Petrelli, Pasquale Digregorio, Leticia F Cugliandolo, Giuseppe Gonnella, Antonio Suma
With the help of molecular dynamics simulations we study an ensemble of active dumbbells in purely repulsive interaction. We derive the phase diagram in the density-activity plane and we characterise the various phases with liquid, hexatic and solid character. The analysis of the structural and dynamical properties, such as enstrophy, mean-square displacement, polarisation, and correlation functions, shows the continuous character of liquid and hexatic phases in the coexisting region when the activity is increased starting from the passive limit...
October 25, 2018: European Physical Journal. E, Soft Matter
M C Cetinkaya, S Ustunel, H Ozbek, S Yildiz, J Thoen
We present new high-resolution experimental data for the temperature behavior of optical birefringence for a series of mixture of the liquid crystals octyloxycyanobiphenyl (8OCB) and nonyloxycyanobiphenyl (9OCB) by using a rotating analyzer technique. The birefringence data have been used to probe the temperature dependence of the nematic order parameter [Formula: see text]. We have then arrived at values for possible entropy discontinuities at the nematic-smectic A transition temperature [Formula: see text] from the detailed inspection of [Formula: see text] data in the immediate vicinity of [Formula: see text]...
October 25, 2018: European Physical Journal. E, Soft Matter
Aziz Fennouri, Joana Ramiandrisoa, Laurent Bacri, Jérôme Mathé, Régis Daniel
Seeking new tools for the analysis of glycosaminoglycans, we have compared the translocation of anionic oligosaccharides from hyaluronic acid using aerolysin and [Formula: see text]-hemolysin nanopores. We show that pores of similar channel length and diameter lead to distinct translocation behavior of the same macromolecules, due to different structural properties of the nanopores. When passing from the vestibule side of the nanopores, short hyaluronic acid oligosaccharides could be detected during their translocation across an aerolysin nanopore but not across an [Formula: see text]-hemolysin nanopore...
October 23, 2018: European Physical Journal. E, Soft Matter
Anja Gemeinhardt, Miriam Martinsons, Michael Schmiedeberg
We explore the growth of colloidal quasicrystals with dodecagonal symmetry in two dimensions by employing Brownian dynamics simulations. On the one hand, we study the growth behavior of structures obtained in a system of particles that interact according to an isotropic pair potential with two typical length scales. On the other hand, we consider patchy colloids that possess only one typical interaction length scale but prefer given binding angles. In case of the isotropic particles, we show that an imbalance in the competition between the two distances might lead to defects with wrong nearest-neighbor distances in the resulting structure...
October 22, 2018: European Physical Journal. E, Soft Matter
Ruben A Verschoof, Xiaojue Zhu, Dennis Bakhuis, Sander G Huisman, Roberto Verzicco, Chao Sun, Detlef Lohse
In this study, we combine experiments and direct numerical simulations to investigate the effects of the height of transverse ribs at the walls on both global and local flow properties in turbulent Taylor-Couette flow. We create rib roughness by attaching up to 6 axial obstacles to the surfaces of the cylinders over an extensive range of rib heights, up to blockages of 25% of the gap width. In the asymptotic ultimate regime, where the transport is independent of viscosity, we emperically find that the prefactor of the [Formula: see text] scaling (corresponding to the drag coefficient [Formula: see text] being constant) scales with the number of ribs [Formula: see text] and by the rib height [Formula: see text]...
October 22, 2018: European Physical Journal. E, Soft Matter
Jyotsana Lal
The results on Winsor phases, droplet and bicontinous microemulsions phases with polymer-grafted lipids studied by Small Angle Neutron Scattering (SANS) are reported below, together with the contrast variation techniques used to characterize the average curvature in the system. We have clearly shown that polymer-grafted lipids change the interaction between microemulsion droplets --it need not be just repulsive but could also be attractive. They induce structural changes or bring about complete phase changes as observed visually in the Winsor phases when added in sufficient amounts...
October 18, 2018: European Physical Journal. E, Soft Matter
Meng Xu, Haihu Liu
Immiscible two-phase flow in porous media is commonly encountered in industrial processes and environmental issues, such as enhanced oil recovery and the migration of fluids in an unsaturated zone. To deepen the current understanding of its underlying mechanism, this work focuses on the factors that influence the relative permeability and specific interfacial length of a two-phase flow in porous media, i.e., fluid saturation, viscosity ratio and contact angle. The lattice Boltzmann color-gradient model is adopted for pore-scale investigations, and the main findings are obtained as follows...
October 18, 2018: European Physical Journal. E, Soft Matter
Zhen-Ting Wang, Chun-Lai Zhang, Song-Bo Cen
Wind velocity and saltating grain count rate in the natural unsteady aeolian sediment transport are synchronously measured on the gently inclined windward slope of one horn of a large barchan. The obtained time series of these two variables are analyzed, by using the improved complete ensemble empirical mode decomposition and wavelet coherence, to investigate the wind-saltation interactions at different timescales. It is found that the wind-saltation trend relation obeys the traditional low-order polynomial expressions, and saltation mode is roughly proportional to its corresponding wind mode if they are strongly correlated...
October 12, 2018: European Physical Journal. E, Soft Matter
Tatyana Lyubimova, Valentina Shevtsova, Fabrizio Croccolo
No abstract text is available yet for this article.
October 12, 2018: European Physical Journal. E, Soft Matter
Maria Ekiel-Jeżewska, Robert Boniecki, Marek Bukowicki, Marta Gruca
In this short review, we visualize the fluid velocity generated by a point force close to a plane free surface or a plane rigid wall. We present separately contributions from all the multipoles which form the corresponding classical systems of images. Such graphical images might be useful in the theoretical and numerical modeling of the dynamics of micro-objects moving close to an interface.
October 12, 2018: European Physical Journal. E, Soft Matter
Lyndon Koens, Hang Zhang, Martin Moeller, Ahmed Mourran, Eric Lauga
Many microorganisms and artificial microswimmers use helical appendages in order to generate locomotion. Though often rotated so as to produce thrust, some species of bacteria such Spiroplasma, Rhodobacter sphaeroides and Spirochetes induce movement by deforming a helical-shaped body. Recently, artificial devices have been created which also generate motion by deforming their helical body in a non-reciprocal way (A. Mourran et al. Adv. Mater. 29, 1604825, 2017). Inspired by these systems, we investigate the transport of a deforming helix within a viscous fluid...
October 11, 2018: European Physical Journal. E, Soft Matter
R Kree, A Zippelius
We discuss the flow field and propulsion velocity of active droplets, which are driven by body forces residing on a rigid gel. The latter is modelled as a porous medium which gives rise to permeation forces. In the simplest model, the Brinkman equation, the porous medium is characterised by a single lengthscale [Formula: see text] --the square root of the permeability. We compute the flow fields inside and outside of the droplet as well as the energy dissipation as a function of [Formula: see text]. We furthermore show that there are optimal gel fractions, giving rise to maximal linear and rotational velocities...
October 11, 2018: European Physical Journal. E, Soft Matter
Saroj Kumar Nandi, N S Gov
The dynamics within active fluids, driven by internal activity of the self-propelled particles, is a subject of intense study in non-equilibrium physics. These systems have been explored using simulations, where the motion of a passive tracer particle is followed. Similar studies have been carried out for a soft glassy material that is driven by shearing its boundaries. In both types of systems the non-equilibrium motion have been quantified by defining a set of "effective temperatures", using both the tracer particle kinetic energy and the fluctuation-dissipation relation...
October 11, 2018: European Physical Journal. E, Soft Matter
A Gupta, H J H Clercx, F Toschi
Anisotropic particles are present in many natural and industrial flows. Here we perform direct numerical simulation (DNS) of turbulent pipe flows with dispersed finite-size prolate spheroids simulated by means of the lattice Boltzmann method (LBM). We consider three different particle shapes: spheroidal (aspect ratio 2 and 3) and spherical. These three simulations are complemented with a reference simulation of a single-phase flow. For the sake of comparison, all simulations, laden or unladen have the same energy input...
October 3, 2018: European Physical Journal. E, Soft Matter
Himani Garg, Enrico Calzavarini, Gilmar Mompean, Stefano Berti
The aggregation properties of heavy inertial particles in the elastic turbulence regime of an Oldroyd-B fluid with periodic Kolmogorov mean flow are investigated by means of extensive numerical simulations in two dimensions. Both the small- and large-scale features of the resulting inhomogeneous particle distribution are examined, focusing on their connection with the properties of the advecting viscoelastic flow. We find that particles preferentially accumulate on thin highly elastic propagating structures and that this effect is the largest for intermediate values of particle inertia...
October 2, 2018: European Physical Journal. E, Soft Matter
Kyryło A Simonov
Extreme deformations of the DNA double helix attracted a lot of attention during the past decades. Particularly, the determination of the persistence length of DNA with extreme local disruptions, or kinks, has become a crucial problem in the studies of many important biological processes. In this paper we review an approach to calculate the persistence length of the double helix by taking into account the formation of kinks of arbitrary configuration. The reviewed approach improves the Kratky-Porod model to determine the type and nature of kinks that occur in the double helix, by measuring a reduction of the persistence length of the kinkable DNA...
September 28, 2018: European Physical Journal. E, Soft Matter
Guilherme V Bossa, Daniel L Z Caetano, Sidney J de Carvalho, Klemen Bohinc, Sylvio May
Mean-field electrostatics is used to calculate the differential capacitance of an electric double layer formed at a planar electrode in a symmetric 1:1 electrolyte. Assuming the electrolyte is also ion-size symmetric, we derive analytic expressions for the differential capacitance valid up to fourth order in the surface charge density or surface potential. Our mean-field model accounts exclusively for electrostatic interactions but includes an arbitrary non-ideality in the mixing entropy of the mobile ions...
September 27, 2018: European Physical Journal. E, Soft Matter
S M Ghazi, R Aliabadi
We examined the accuracy of the free volume approximation (FVA) to calculate the isotropic-nematic (IN) transition properties of thermotropic and lyotropic rods between two parallel hard walls. This approximation has been proposed to ease the calculation of the confined systems. It approximates the free energy of the confined particles with a bulk free energy. It predicts a special point for these two types of liquid crystals where the first-order IN transition changes to the second one by decreasing either the temperature, the density or the pore width...
September 26, 2018: European Physical Journal. E, Soft Matter
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