Surface flow profiles for dry and wet granular materials by Particle Tracking Velocimetry; the effect of wall roughness

Two-dimensional Particle Tracking Velocimetry (PTV) is a promising technique to study the behaviour of granular flows. The aim is to experimentally determine the free surface width and position of the shear band from the velocity profile to validate simulations in a split-bottom shear cell geometry. The position and velocities of scattered tracer particles are tracked as they move with the bulk flow by analyzing images. We then use a new technique to extract the continuum velocity field, applying coarse-graining with the postprocessing toolbox MercuryCG on the discrete experimental PTV data. For intermediate filling heights, the dependence of the shear (or angular) velocity on the radial coordinate at the free surface is well fitted by an error function. From the error function, we get the width and the centre position of the shear band. We investigate the dependence of these shear band properties on filling height and rotation frequencies of the shear cell for dry glass beads for rough and smooth wall surfaces. For rough surfaces, the data agrees with the existing experimental results and theoretical scaling predictions. For smooth surfaces, particle-wall slippage is significant and the data deviates from the predictions. We further study the effect of cohesion on the shear band properties by using small amount of silicon oil and glycerol as interstitial liquids with the glass beads. While silicon oil does not lead to big changes, glycerol changes the shear band properties considerably. The shear band gets wider and is situated further inward with increasing liquid saturation, due to the correspondingly increasing trend of particles to stick together

Discrete element modelling of granular column collapse tests with industrial applications

Describing the behaviour of granular materials is a challenging issue for the industry. Our work concerns packaging industries where packing equipment is designed to handle a wide range of powders and bulk solids with varying physical and mechanical properties. While packaging, a variety of material conveying techniques are used ranging from air fluidisation to discharge of material through a hopper. Thereby even a small improvement in their efficiency can lead to significant benefits, both financial and environmental. Flowability of powders and bulk solids is often experimentally investigated using granular column collapse, as this test provides deep insights into the kinematics of granular flow both at particle and bulk levels [1]. Here, we consider a quasi-two-dimensional set-up with a reservoir containing the granular pile which is instantaneously released onto a channel where run-out takes place. Instead of experiments, we use discrete particle simulations allowing us to quantitatively link bulk-level observations to particle-level properties of the materials, besides enabling inverse analysis leading to indirect measures of micro-scale parameters. We present a simulation strategy aimed at controlling several particle parameters influencing the run-out: - Polydispersity in size, using different particle size distributions; and also in shape, comparing the use of spherical and non-spherical particles, namely cylinders and ellipsoids. - Mechanical properties of the contacts, comprising normal stiffness and dissipation, as well as sliding, rolling and torsion coefficients. Specifically, hygroscopic behaviour of bulk materials is inspected modifying the contact law parameters. Additionally at the bulk level, air fluidisation of the columns before release is studied through the initial packing state by changing the volume fraction of the piles. Numerical simulations are implemented with the open-source code MercuryDPMPostprint (published version

Discrete element modelling of granular column collapse tests with industrial applications

The effect of particle size distribution on dry granular flows of spherical particles has been numerically investigated. A quasi-two-dimensional granular column collapse set-up has been modelled using the Discrete Element Method (DEM). Systems formed by monodisperse particles of radius R = 0.01 m and polydisperse particles of the same average radius and coefficient of uniformity Cu = 1.9 have been studied for initial granular columns aspect ratios of 1.1 and 2.2. The results using monodisperse and narrow particle size distributions show similar evolution of the run-out profiles, the final run-out distance being reached in less than one second in every configuration. Averaged velocity fields have been obtained, from which peak values of longitudinal and vertical components of velocity have been found

Mercury DPM: fast, flexible particle simulations in complex geometries part II: applications

MercuryDPM is a particle-simulation software developed open-source by a global network of researchers. It was designed ​ab initio to simulate realistic geometries and materials, thus it contains several unique features not found in any other particle simulation software. These features have been discussed in a companion paper published in the DEM7 conference proceedings; here we present several challenging setups implemented in MercuryDPM ​ . Via these setups, we demonstrate the unique capability of the code to simulate and analyse highly complex geotechnical and industrial applications.These tups implemented include complex geometries such as (i) a screw conveyor, (ii) steady-state inflow conditions for chute flows, (iii) a confined conveyor belt to simulate a steady-state breaking wave, and(iii)aquasi-2D cylindrical slice to efficiently study shear flows.​MercuryDPM is also parallel, which we showcase via a multi-million particle simulations of a rotating drum. We further demonstrate how to simulate complex particle interactions, including: (i)deformable, charged clay particles; and (ii) liquid bridges and liquid migration in wet particulates, (iii) non-spherical particles implemented via superquadrics. Finally, we show how to analyse and complex systems using the unique micro-macro mapping (coarse-graining) tool MercuryCG

Controlling transmembrane protein concentration and orientation in supported lipid bilayers

The trans-membrane protein – proteorhodopsin (pR) has been incorporated into supported lipid bilayers (SLB). In-plane electric fields have been used to manipulate the orientation and concentration of these proteins, within the SLB, through electrophoresis leading to a 25-fold increase concentration of pR

Comparative return of imports into the state of Negri Sembilan during the years, 1916 and 1915.

Supplement to the F.M.S Government Gazette, May 11th, 1917. It also contains 'Comparative return of exports into the state of Negri Sembilan during the years, 1916 and 1915'

Perturbation of the yeast mitochondrial lipidome and associated membrane proteins following heterologous expression of Artemia-ANT

Heterologous expression is a landmark technique for studying a protein itself or its effect on the expression host, in which membrane-embedded proteins are a common choice. Yet, the impact of inserting a foreign protein to the lipid environment of host membranes, has never been addressed. Here we demonstrated that heterologous expression of the Artemia franciscana adenine nucleotide translocase (ANT) in yeasts altered lipidomic composition of their inner mitochondrial membranes. Along with this, activities of complex II, IV and ATP synthase, all membrane-embedded components, were significantly decreased while their expression levels remained unaffected. Although the results represent an individual case of expressing a crustacean protein in yeast inner mitochondrial membranes, it cannot be excluded that host lipidome alterations is a more widespread epiphenomenon, potentially biasing heterologous expression experiments. Finally, our results raise the possibility that not only lipids modulate protein function, but also membrane-embedded proteins modulate lipid composition, thus revealing a reciprocal mode of regulation for these two biomolecular entities