@article {42615, title = {Friction of a slider on a granular layer: non-monotonic thickness dependence and effect of boundary conditions}, journal = {Physical Review E}, volume = {73}, year = {2006}, month = {JAN}, pages = {010301}, type = {Article}, abstract = {

We investigate the effective friction encountered by a mass sliding on a granular layer as a function of bed thickness and boundary roughness conditions. The observed friction has minima for a small number of layers before it increases and saturates to a value that depends on the roughness of the sliding surface. We use an index-matched interstitial liquid to probe the internal motion of the grains with fluorescence imaging in a regime where the liquid has no significant effect on the measured friction. The shear profiles obtained as a function of depth show a decrease in slip near the sliding surface as the layer thickness is increased. We propose that the friction depends on the degree of grain confinement relative to the sliding surfaces.

}, doi = {10.1103/PhysRevE.73.010301}, author = {Siavoshi, Saloome and Orpe, Ashish V. and Kudrollim, Arshad} } @article {42614, title = {Lubrication effects on the flow of wet granular materials}, journal = {Physical Review E}, volume = {76}, year = {2007}, month = {APR}, pages = {Article No. 031302}, type = {Article}, abstract = {

We investigate the dynamics of a partially saturated grain-liquid mixture with a rotating drum apparatus. The drum is partially filled with the mixture and then rotated about its horizontal axis. We focus on the continuous avalanching regime and measure the impact of the volume fraction and viscosity of the liquid on the dynamic surface angle. The inclination angle of the surface is observed to increase sharply to a peak and then decrease as a function of liquid volume fraction. The height of the peak is observed to increase with rotation rate. For higher liquid volume fractions, the inclination angle of the surface can decrease with viscosity before increasing. The viscosity where the minimum occurs decreases with the rotation rate of the drum. Limited measurements of the flow depth were made, and these were observed to show only fractional changes with volume fraction and rotation speeds. We show that the qualitative features of our observations can be understood by analyzing the effect of lubrication forces on the time scale over which particles come in contact.

}, doi = {10.1103/PhysRevE.76.031302}, author = {Xu, Qing and Orpe, Ashish V. and Kudrolli, Arshad} } @article {42612, title = {Rheology of surface granular flows}, journal = {Journal of Fluid Mechanics}, volume = {571}, year = {2007}, month = {JAN}, pages = {1-32}, type = {Article}, abstract = {

Surface granular flow, comprising granular material flowing on the surface of a heap of the same material, occurs in several industrial and natural systems. The rheology of such a flow was investigated by means of measurements of velocity and number-density profiles in a quasi-two-dimensional rotating cylinder, half-filled with a model granular material {\textendash} monosize spherical stainless-steel particles. The measurements were made at the centre of the cylinder, where the flow is fully developed, using streakline photography and image analysis. The stress profile was computed from the number-density profile using a force balance which takes into account wall friction. Mean-velocity and root-mean-square (r.m.s.)-velocity profiles are reported for different particle sizes and cylinder rotation speeds. The profiles for the mean velocity superimpose when distance is scaled by the particle diameter d and velocity by a characteristic shear rate and the particle diameter, where βm is the maximum dynamic angle of repose and βs is the static angle of repose. The maximum dynamic angle of repose is found to vary with the local flow rate. The scaling is also found to work for the r.m.s. velocity profiles. The mean velocity is found to decay exponentially with depth in the bed, with decay length λ = 1.1d. The r.m.s. velocity shows similar behaviour but with λ = 1.7d. The r.m.s. velocity profile shows two regimes: near the free surface the r.m.s. velocity is nearly constant and below a transition point it decays linearly with depth. The shear rate, obtained by numerical differentiation of the velocity profile, is not constant anywhere in the layer and has a maximum which occurs at the same depth as the transition in the r.m.s. velocity profile. Above the transition point the velocity distributions are Gaussian and below the transition point the velocity distributions gradually approach a Poisson distribution. The shear stress increases roughly linearly with depth. The variation in the apparent viscosity η with r.m.s. velocity u shows a relatively sharp transition at the shear-rate maximum, and in the region below this point the apparent viscosity η \~{} u-1.5. The measurements indicate that the flow comprises two layers: an upper low-viscosity layer with a nearly constant r.m.s. velocity and a lower layer of increasing viscosity with a decreasing r.m.s. velocity. The thickness of the upper layer depends on the local flow rate and is independent of particle diameter while the reverse is found to hold for the lower-layer thickness. The experimental data is compared with the predictions of three models for granular flow.

}, doi = {10.1017/S002211200600320X}, author = {Orpe, Ashish V. and Khakhar, Devang V.} } @article {42611, title = {Velocity correlations in dense granular flows observed with internal imaging}, journal = {Physical Review Letters}, volume = {98}, year = {2007}, month = {JUN}, pages = {238001}, type = {Article}, abstract = {

We show that the velocity correlations in uniform dense granular flows inside a silo are similar to the hydrodynamic response of an elastic hard-sphere liquid. The measurements are made using a fluorescent refractive-index-matched interstitial fluid in a regime where the flow is dominated by grains in enduring contact and fluctuations scale with the distance traveled, independent of flow rate. The velocity autocorrelation function of the grains in the bulk shows a negative correlation at short time and slow oscillatory decay to zero similar to simple liquids. Weak spatial velocity correlations are observed over several grain diameters. The mean square displacements show an inflection point indicative of caging dynamics. The observed correlations are qualitatively different at the boundaries.

}, doi = {10.1103/PhysRevLett.98.238001}, author = {Orpe, Ashish V. and Kudrolli, Arshad} } @article {42610, title = {Erosion of a granular bed driven by laminar fluid flow}, journal = {Journal of Fluid Mechanics}, volume = {605}, year = {2008}, month = {JUN}, pages = {47-58}, type = {Article}, abstract = {

Motivated by examples of erosive incision of channels in sand, we investigate the motion of individual grains in a granular bed driven by a laminar fluid to give us new insights into the relationship between hydrodynamic stress and surface granular flow. A closed cell of rectangular cross-section is partially filled with glass beads and a constant fluid flux Q flows through the cell. The refractive indices of the fluid and the glass beads are matched and the cell is illuminated with a laser sheet, allowing us to image individual beads. The bed erodes to a rest height hr which depends on Q. The Shields threshold criterion assumes that the non-dimensional ratio θ of the viscous stress on the bed to the hydrostatic pressure difference across a grain is sufficient to predict the granular flux. Furthermore, the Shields criterion states that the granular flux is non-zero only for θ \> θc. We find that the Shields criterion describes the observed relationship hr ∝ Q1/2 when the bed height is offset by approximately half a grain diameter. Introducing this offset in the estimation of θ yields a collapse of the measured Einstein number q* to a power-law function of θ - θc with exponent 1.75 {\textpm} 0.25. The dynamics of the bed height relaxation are described well by the power-law relationship between the granular flux and the bed stress.

}, doi = {10.1017/S0022112008001389}, author = {Lobkovsky Alexander E. and Orpe, Ashish V. and Molloy, Ryan and Kudrolli, Arshad and Rothman, D. H.} } @article { ISI:000263598900010, title = {Fast decay of the velocity autocorrelation function in dense shear flow of inelastic hard spheres}, journal = {EPL}, volume = {84}, number = {6}, year = {2008}, month = {DEC}, pages = {64003}, publisher = {EDP SCIENCES S A}, type = {Article}, address = {17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE}, abstract = {

We find in complementary experiments and event-driven simulations of sheared inelastic hard spheres that the velocity autocorrelation function psi(t) decays much faster than t(-3/2) obtained for a fluid of elastic spheres at equilibrium. Particle displacements are measured in experiments inside a gravity-driven flow sheared by a rough wall. The average packing fraction obtained in the experiments is 0.59, and the packing fraction in the simulations is varied between 0.5 and 0.59. The motion is observed to be diffusive over long times except in experiments where there is layering of particles parallel to boundaries, and diffusion is inhibited between layers. Regardless, a rapid decay of psi(t) is observed, indicating that this is a feature of the sheared dissipative fluid, and is independent of the details of the relative particle arrangements. An important implication of our study is that the non-analytic contribution to the shear stress may not be present in a sheared inelastic fluid, leading to a wider range of applicability of kinetic theory approaches to dense granular matter. Copyright (C) EPLA, 2008

}, issn = {0295-5075}, doi = {10.1209/0295-5075/84/64003}, author = {Orpe, Ashish V. and Kumaran, V. and Reddy, K. Anki and Kudrolli, Arshad} } @article { ISI:000270383400068, title = {Physical test of a particle simulation model in a sheared granular system}, journal = {Physical Review E}, volume = {80}, number = {3}, year = {2009}, month = {SEP}, pages = {031305}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {

We report a detailed comparison of a slow gravity-driven sheared granular flow with a discrete-element simulation performed in the same geometry. In the experiments, grains flow inside a silo with a rectangular cross section and are sheared by a rough boundary on one side and smooth boundaries on the other sides. Individual grain position and motion are measured using a particle index-matching imaging technique where a fluorescent dye is added to the interstitial liquid which has the same refractive index as the glass beads. The simulations use a Cundall-Strack contact model between the grains using contact parameters that have been used in many other previous studies and ignore the hydrodynamic effects of the interstitial liquid. Computations are performed to understand the effect of particle coefficient of friction, elasticity, contact model, and polydispersity on mean flow properties. We then perform a detailed comparison of the particle fluctuation properties as measured by the displacement probability distribution function and the mean square displacement. All in all, our study suggests a high level of quantitative agreement between the simulations and experiments.

}, issn = {1539-3755}, doi = {10.1103/PhysRevE.80.031305}, author = {Rycroft, Chris H. and Orpe, Ashish V. and Kudrolli, Arshad} } @conference { ISI:000280550300020, title = {Shear induced diffusion in dense granular flows}, booktitle = {IUTAM-ISIMM Symposium on Mathematical Modeling and Physical Instances of Granular Flows}, series = {AIP Conference Proceedings}, volume = {1227}, year = {2010}, note = {IUTAM-ISIMM Symposium on Mathematical Modeling and Physical Instances of Granular Flows, Reggio Calabria, ITALY, SEP 14-18, 2009}, month = {JUN}, pages = {221-229}, publisher = {IUTAM; ISIMM; Italian Inst Higher Math; US Natl Sci Fdn; Reg Council Reggio Calabria; Prov Reggio Calabria; Mediterranean Univ Reggio Calabria}, organization = {IUTAM; ISIMM; Italian Inst Higher Math; US Natl Sci Fdn; Reg Council Reggio Calabria; Prov Reggio Calabria; Mediterranean Univ Reggio Calabria}, address = {2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USA}, abstract = {

The dynamics of dense granular flows subjected to gravity induced shear are investigated experimentally using the refractive index matching technique. The system consists of grains flowing inside a bin with a rectangular cross-section and sheared by a rough boundary on one side and smooth boundaries on the remaining sides. The particles flow within a viscous interstitial liquid having the same refractive index as particles and are imaged in the bulk using laser fluorescence. The particle positions are identified very accurately and tracked over long durations to obtain the mean and fluctuating properties. The shear is observed to be non-linear and localized in a region of 3 to 4 particles near the boundary. The boundary imposes a packing order, and the grains are observed to flow in layers, parallel to the shearing boundary, which get progressively more disordered with distance from the walls. We have also carried out soft particle simulations in a equivalent system incorporating the Cundall-Strack contact model between the particles and ignoring the hydrodynamic effects of the interstitial liquid to understand the effect of particle friction coefficient, elasticity, contact model and polydispersity on the mean and fluctuating flow properties. We find the mean velocity and the number density of the particles as a function of flow cross-section and the particle fluctuation properties observed in the experiments and the simulations to in very good agreement after appropriate scaling.

}, keywords = {DEM, Diffusion, granular, index matching, LAMMPS, laser fluorescence}, isbn = {978-0-7354-0772-5}, issn = {0094-243X}, doi = {10.1063/1.3435393}, author = {Orpe, Ashish V. and Rycroft, Chris H. and Kudrolli, Arshad A.}, editor = {Goddard, J. D. and Jenkins, J. T. and Giovine, P.} } @article { ISI:000305276600039, title = {Flow-induced channelization in a porous medium}, journal = {EPL}, volume = {98}, number = {5}, year = {2012}, month = {JUN}, pages = {58003}, publisher = {EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY}, address = {6 RUE DES FRERES LUMIERE, MULHOUSE, 68200, FRANCE}, abstract = {

Flow through a saturated, granular, porous medium can lead to internal erosion, preferential flow enhancement, and the formation of channels within the bulk of the medium. We examine this phenomenon using a combination of experimental observations, continuum theory and numerical simulations in a minimal setting. Our experiments are carried out by forcing water through a Hele-Shaw cell packed with bidisperse grains. When the local flow-induced stress exceeds a critical threshold, the smaller grains are dislodged and transported. This changes the porosity of the medium, thence, the local hydraulic conductivity, and leads to the development of erosional channels. Erosion is ultimately arrested due to the drop in the mean pressure gradient, while most of the flow occurs through the channels. We describe this using a minimal multiphase description of erosion where the volume fraction of the fluid, mobile, and immobile, grains change in space and time. Numerical solutions of the resulting initial boundary value problem yield results for the dynamics and morphology that are in qualitative agreement with our experiments. In addition to providing a basis for channelization in porous media, our study highlights how heterogeneity in porous media may arise from flow as a function of the erosion threshold. Copyright (C) EPLA, 2012

}, issn = {0295-5075}, doi = {10.1209/0295-5075/98/58003}, author = {Mahadevan, A. and Orpe, Ashish V. and Kudrolli, A. and Mahadevan, L.} } @article { ISI:000346833500005, title = {Flow of granular matter in a silo with multiple exit orifices: jamming to mixing}, journal = {Physical Review E}, volume = {90}, number = {6}, year = {2014}, month = {DEC}, pages = {062206}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {

We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flowing regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.

}, issn = {1539-3755}, doi = {10.1103/PhysRevE.90.062206}, author = {Kamath, Sandesh and Kunte, Amit and Doshi, Pankaj and Orpe, Ashish V.} } @article { ISI:000348532300001, title = {Spontaneous jamming and unjamming in a hopper with multiple exit orifices}, journal = {Physical Review E}, volume = {90}, number = {2}, year = {2014}, month = {AUG}, pages = {020201}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {

We show that the flow of granular material inside a two-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For hoppers with small orifice widths, intermittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e., avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the interorifice distance. The unjamming is driven primarily by fluctuations alone when the interorifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow to unjam.

}, issn = {1539-3755}, doi = {10.1103/PhysRevE.90.020201}, author = {Kunte, Amit and Doshi, Pankaj and Orpe, Ashish V.} } @article { ISI:000379040200026, title = {Fingering instability of a suspension film spreading on a spinning disk}, journal = {Physics of Fluids}, volume = {28}, number = {6}, year = {2016}, month = {JUN}, pages = {063303}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {

The spreading of a thin film of suspension on a spinning disk and the accompanying contact line instability is studied through flow visualization experiments. The critical radius for the onset of instability shows an increase with increase in the particle fraction (phi(p)) before decreasing slightly at the highest value of phi(p) studied, while the instability wavelength (lambda) exhibits a non-monotonic dependence. The value of lambda is close to that for a partially wetting liquid at lower phi(p), it decreases with increasing phi(p) to a minimum before increasing again at largest phi(p). The non-monotonic trends observed for lambda are discussed in light of the linear stability analysis of thin film equations derived for suspensions by Cook et al. [{\textquoteright}{\textquoteright}Linear stability of particle-laden thin films,{\textquoteright}{\textquoteright} Eur. Phys. J.: Spec. Top. 166, 77 (2009)] and Balmforth et al. [{\textquoteright}{\textquoteright}Surface tension driven fingering of a viscoplastic film,{\textquoteright}{\textquoteright} J. Non Newtonian Fluid Mech. 142, 143 (2007)]. Published by AIP Publishing.

}, issn = {1070-6631}, doi = {10.1063/1.4953174}, author = {Kulkarni, Mayuresh and Sahoo, Subhadarshinee and Doshi, Pankaj and Orpe, Ashish V.} } @article {42606, title = {Passive microrheology in the effective time domain: analysing time dependent colloidal dispersions}, journal = {Soft Matter}, volume = {12}, year = {2016}, month = {AUG}, pages = {8167-8176}, abstract = {

We studied the aging dynamics of an aqueous suspension of LAPONITE (R), a model time dependent soft glassy material, using a passive microrheology technique. This system is known to undergo physical aging during which its microstructure evolves progressively to explore lower free energy states. Optical microscopy is used to monitor the motion of micron-sized tracer probes embedded in a sample kept between two glass plates. The mean square displacements (MSD) obtained from the motion of the tracer particles show a systematic change from a purely diffusive behavior at short aging times to a subdiffusive behavior as the material ages. Interestingly, the MSDs at all the aging times as well as different LAPONITE (R) concentrations superpose remarkably to show a time-aging time master curve when the system is transformed from the real time domain to the effective time domain, which is obtained by rescaling the material clock to account for the age dependent relaxation time. The transformation of the master curve from the effective time domain to the real time domain leads to the prediction of the MSD in real time over a span of 5 decades when the measured data at individual aging times are only over 2 decades. Since the MSD obtained from microrheology is proportional to the creep compliance of a material, by using the Boltzmann superposition principle along with the convolution relation in the effective time domain, we predict the stress relaxation behavior of the system in real time. This work shows that the effective time approach applied to microrheology facilitates the prediction of long time creep and relaxation dynamics of a time dependent soft material by carrying out short time experiments at different aging times.

}, doi = {10.1039/c6sm00829a}, author = {Vyas, Bhavna M. and Orpe, Ashish V. and Kaushal, Manish and Joshi, Yogesh M.} } @article {44231, title = {Spreading dynamics of superposed liquid drops on a spinning disk}, journal = {Physics of Fluids}, volume = {30}, year = {2018}, month = {JAN}, pages = {012110}, type = {Article}, abstract = {

We have experimentally studied simultaneous spreading of superposed drops of two Newtonian liquids on top of a horizontal spinning disk using the flow visualization technique. An inner drop of high surface tension liquid is placed centrally on the disk followed by a drop of outer liquid (lower surface tension) placed exactly above that. The disk is then rotated at a desired speed for a range of volume ratios of two liquids. Such an arrangement of two superposed liquid drops does not affect the spreading behavior of the outer liquid but influences that of the inner liquid significantly. The drop spreads to a larger extent and breaks into more fingers (Nf) as compared to the case where the same liquid is spreading in the absence of outer liquid. The experimentally observed number of fingers is compared with the prediction using available theory for single liquid. It is found that the theory over-predicts the value of Nf for the inner liquid while it is covered by an outer liquid. We provide a theoretical justification for this observation using linear stability analysis. Our analysis demonstrates that for small but finite surface tension ratio of the two liquids, the presence of the outer interface reduces the value of the most unstable wave number which is equivalent to the decrease in the number of fingers observed experimentally. Finally, sustained rotation of the disk leads to the formation of droplets at the tip of the fingers traveling outwards. Published by AIP Publishing.

}, issn = {1070-6631}, doi = {10.1063/1.5002601}, author = {Sahoo, Subhadarshinee and Orpe, Ashish V. and Doshi, Pankaj} } @article {46067, title = {Friction-mediated flow and jamming in a two-dimensional silo with two exit orifices}, journal = {Physical Review E}, volume = {100}, year = {2019}, month = {JUL }, pages = {012901}, type = {Article}, abstract = {

We show that the interparticle friction coefficient significantly influences the flow and jamming behavior of granular materials exiting through the orifice of a two-dimensional silo in the presence of another orifice located in its vicinity. The fluctuations emanating from a continuous flow through a larger orifice results in an intermittent flow through the smaller orifice consisting of sequential jamming and flowing events. The mean time duration of jammed and flow events, respectively, increase and decrease monotonically with increasing interparticle friction coefficient. The frequency of unjamming instances (n(u)), however, shows a nonmonotonic behavior comprising an increase followed by a decrease with increasing friction coefficient. The decrease on either side of the maximum, then, represents a system moving progressively towards a permanently jammed or a permanently flowing state. The overall behavior shows a systematic dependence on the interorifice distance, which determines the strength of the fluctuations reaching the smaller orifice leading to unjamming instances. The probability distributions of jamming and flowing times are nearly similar for different combinations of friction coefficients and interorifice distances studied and, respectively, exhibit exponential and power-law tails.

}, issn = {2470-0045}, doi = {10.1103/PhysRevE.100.012901}, author = {Orpe, Ashish V. and Doshi, Pankaj} } @article {46918, title = {Microstructure and yielding of capillary force induced gel}, journal = {Rheologica Acta}, volume = {59}, year = {2020}, month = {MAY}, pages = {291-306}, type = {Article}, abstract = {

We have investigated the rheology and structure of a gel formed from a mixture of non-Brownian particles and two immiscible liquids. The suspension of particles in a liquid undergoes gelation upon the addition of a small content of second, wetting liquid which forms liquid bridges between particles leading to a sample spanning network. The rheology of this gel primarily exhibits a yield stress at low shear rates followed by a linear variation of shear stress at high shear rates. The apparent yield stress extracted from the flow curves increases rapidly with volume fraction of the second liquid before saturation, while it exhibits a monotonic increase with increasing particle concentration. Rescaling of the yield stress curves using suitable shift factors results in an empirical expression for the yield stress showing squared dependence on liquid fraction and a rapid increase with particle fraction above a certain value, both combined in a highly non-linear manner. The microstructural variations with changing secondary liquid content and particle fractions are captured using three-dimensional X-ray tomography technique. The microstructure is observed to show increased local compactness with increased liquid content and increased spatial homogeneity with increased particle fractions. The images from X-ray tomography are analysed to obtain the distributions of particle-particle bonds (coordination number) in the system which serve to explain the observed yield stress behaviour in a qualitative manner.

}, keywords = {Capillary force, Flow curve, gel, Microstructure, Rheology, Yield stress}, issn = {0035-4511}, doi = {10.1007/s00397-020-01189-6, Early Access Date = MAR 2020}, author = {Huprikar, Sameer and Usgaonkar, Saurabh and Lele, Ashish K. and Orpe, Ashish V.} } @article {47459, title = {Slip behavior during pressure driven flow of Laponite suspension}, journal = {Physics of Fluids}, volume = {33}, year = {2021}, month = {MAY}, type = {Article}, abstract = {

We investigate pressure driven pipe flow of Laponite suspension, as a model thixotropic fluid. The tendency of the suspension to age is controlled by addition of sodium chloride salt to vary the ionic strength. We use a syringe pump to prescribe the flow and observe that a steady state flow is obtained. Unusually, the steady state pressure drop required to maintain a constant flow rate decreases with an increase in the flow rate, in qualitative contrast to the expectation for Poiseuille flow. We demonstrate that experimental results obtained by varying the flow rate, salt concentration, and flow geometry (pipe diameter and length) can be collapsed onto a single universal curve that can be rationalized by invoking slip of the suspension at the tube walls. The Laponite suspension exhibits plug-like flow, yielding at the tube walls. Our results suggest that the slip length varies linearly with the flow rate and inversely with the tube diameter.

}, doi = {10.1063/5.0051044}, author = {Kamdi, Prophesar M. and Orpe, Ashish V. and Kumaraswamy, Guruswamy} } @article {49078, title = {Flow and clogging behavior of a mixture of particles in a silo}, journal = {Physics of Fluids }, volume = {36}, year = {2024}, month = {MAY}, type = {Article}, abstract = {

We investigated the clogging behavior observed during the flow of aspherical particles from a silo in the presence of spherical particles of different sizes and proportions using flow visualization experiments and discrete element method simulations. The size of the avalanche, essentially the tendency of clogging, exhibits non-monotonic dependence on the spherical particle volume fraction. For small enough content of spherical particles, the clogging tendency intensifies, whereas it reduces rapidly for high enough spherical particle fractions, with a minimum in between. The non-monotonic behavior is observed to persist over for different spherical particle sizes. The overall behavior is shown to arise due to competing effects between the localized total particle fraction influencing avalanche strength and mean size of the particles exiting the silo, influencing the probability of arch formation.

}, issn = {1070-6631}, doi = {10.1063/5.0205141}, author = {Bhure, Sukhada C. and Doshi, Pankaj and Orpe, Ashish V.} }