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Artykuły w czasopismach na temat „Immersed Granular flows”

Autor: Grafiati

Data publikacji: 6 września 2023

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1

Amarsid, L., J. Y. Delenne, P. Mutabaruka, Y. Monerie, F. Perales i F. Radjai. "Scaling behavior of immersed granular flows". EPJ Web of Conferences 140 (2017): 09044. http://dx.doi.org/10.1051/epjconf/201714009044.

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Polanía, Oscar, Nicolás Estrada, Mathieu Renouf, Emilien Azéma i Miguel Cabrera. "Granular column collapse: The role of particle size polydispersity on the velocity and runout". E3S Web of Conferences 415 (2023): 02017. http://dx.doi.org/10.1051/e3sconf/202341502017.

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Geophysical mass flows involve particles of different sizes, a property termed polydispersity. The granular column collapse is a simplified experiment for studying transitional granular flows. Our research focuses on the role that polydispersity has on the velocity and runout distance of dry and immersed granular columns, undergoing a numerical and experimental study. Our results highlight that polydispersity does not have a strong effect on the collapse of dry columns. On the contrary, the collapse sequence of immerse granular columns strongly depend on the polydispersity level.

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3

Constant, Matthieu, Frédéric Dubois, Jonathan Lambrechts i Vincent Legat. "An hybrid multiscale model for immersed granular flows". EPJ Web of Conferences 140 (2017): 09021. http://dx.doi.org/10.1051/epjconf/201714009021.

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4

Jandaghian, Mojtaba, Abdelkader Krimi i Ahmad Shakibaeinia. "Enhanced weakly-compressible MPS method for immersed granular flows". Advances in Water Resources 152 (czerwiec 2021): 103908. http://dx.doi.org/10.1016/j.advwatres.2021.103908.

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5

DOPPLER, DELPHINE, PHILIPPE GONDRET, THOMAS LOISELEUX, SAM MEYER i MARC RABAUD. "Relaxation dynamics of water-immersed granular avalanches". Journal of Fluid Mechanics 577 (19.04.2007): 161–81. http://dx.doi.org/10.1017/s0022112007004697.

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We study water-immersed granular avalanches in a long rectangular cell of small thickness. By video means, both the angle of the granular pile and the velocity profiles of the grains across the depth are recorded as a function of time. These measurements give access to the instantaneous granular flux. By inclining the pile at initial angles larger than the maximum angle of stability, avalanches are triggered and last for a long time, up to several hours for small grains, during which both the slope angle and the granular flux relax slowly. We show that the relaxation is quasi-steady so that there is no inertia: the relaxation at a given time is controlled only by the slope angle at that time. This allows us to adapt a frictional model developed recently for dry or water-immersed grains flowing in stationary conditions. This model succeeds well in reproducing our unsteady avalanche flows, namely the flowing layer thickness, the granular flux and the temporal relaxation of the slope. When a water counter-flow is applied along the pile, the granular avalanches are slowed down and behave as if granular friction were increased by an amount proportional to the water flow. All these findings are also reproduced well with the same friction model by taking into account the additional fluid force.

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6

Yang, G. C., L. Jing, C. Y. Kwok i Y. D. Sobral. "A comprehensive parametric study of LBM-DEM for immersed granular flows". Computers and Geotechnics 114 (październik 2019): 103100. http://dx.doi.org/10.1016/j.compgeo.2019.103100.

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7

PAILHA, MICKAËL, i OLIVIER POULIQUEN. "A two-phase flow description of the initiation of underwater granular avalanches". Journal of Fluid Mechanics 633 (25.08.2009): 115–35. http://dx.doi.org/10.1017/s0022112009007460.

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A theoretical model based on a depth-averaged version of two-phase flow equations is developed to describe the initiation of underwater granular avalanches. The rheology of the granular phase is based on a shear-rate-dependent critical state theory, which combines a critical state theory proposed by Roux & Radjai (1998), and a rheological model recently proposed for immersed granular flows. Using those phenomenological constitutive equations, the model is able to describe both the dilatancy effects experienced by the granular skeleton during the initial deformations and the rheology of wet granular media when the flow is fully developed. Numerical solutions of the two-phase flow model are computed in the case of a uniform layer of granular material fully immersed in a liquid and suddenly inclined from horizontal. The predictions are quantitatively compared with experiments by Pailha, Nicolas & Pouliquen (2008), who have studied the role of the initial volume fraction on the dynamics of underwater granular avalanches. Once the rheology is calibrated using steady-state regimes, the model correctly predicts the complex transient dynamics observed in the experiments and the crucial role of the initial volume fraction. Quantitative predictions are obtained for the triggering time of the avalanche, for the acceleration of the layer and for the pore pressure.

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8

Hare, Jenna, i Alex E. Hay. "Remote acoustic measurement of the velocity within water-immersed gravity-driven granular flows". Journal of the Acoustical Society of America 148, nr 4 (październik 2020): 2484. http://dx.doi.org/10.1121/1.5146883.

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9

Constant, Matthieu, Frédéric Dubois, Jonathan Lambrechts i Vincent Legat. "Implementation of an unresolved stabilised FEM–DEM model to solve immersed granular flows". Computational Particle Mechanics 6, nr 2 (29.09.2018): 213–26. http://dx.doi.org/10.1007/s40571-018-0209-4.

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10

DBOUK, Talib. "A suspension balance direct-forcing immersed boundary model for wet granular flows over obstacles". Journal of Non-Newtonian Fluid Mechanics 230 (kwiecień 2016): 68–79. http://dx.doi.org/10.1016/j.jnnfm.2016.01.003.

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11

Szymanek, Ewa, Artur Tyliszczak i Maciej Marek. "Numerical analysis of heat and mass transfer through beds of spherical and non-spherical elements". Journal of Physics: Conference Series 2367, nr 1 (1.11.2022): 012012. http://dx.doi.org/10.1088/1742-6596/2367/1/012012.

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Abstract Many issues related to mass and heat transfer through beds of granular materials are still not fully understood. In this work, non-isothermal turbulent flow is analysed within granular layers of spherical and non-spherical elements. We apply a volume penalization (VP) approach formulated in the framework of an immersed boundary technique (IB) on Cartesian computational meshes. It allows modelling flows around solid objects with almost arbitrarily complex shapes and in any form of contact. The validation of the solution accuracy is performed against ANSYS Fluent simulations using body-fitted meshes and experimental literature data. It shows the capability of the IB-VP approach for the simulations of flows in complex geometries. The main research focuses on the comparison of the influence of various types of particles and their temperature on vorticity, turbulence level and pressure drop inside and behind the granular bed. In particular, we analyse how the shape of the solid particles affects the efficiency of heat transfer in different flow conditions. The obtained results reveal the occurrence of very complex flow structures (recirculation and stagnation regions) inside beds. Comparison of results also point out preferred configurations of the beds.

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12

Cui, Kahlil F. E., Gordon G. D. Zhou, Lu Jing, Xiaoqing Chen i Dongri Song. "Generalized friction and dilatancy laws for immersed granular flows consisting of large and small particles". Physics of Fluids 32, nr 11 (1.11.2020): 113312. http://dx.doi.org/10.1063/5.0024762.

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13

Carvalho, J. R. F. G., J. M. P. Q. Delgado i M. A. Alves. "Diffusion cloud around and downstream of active sphere immersed in granular bed through which fluid flows". Chemical Engineering Science 62, nr 10 (maj 2007): 2813–20. http://dx.doi.org/10.1016/j.ces.2007.02.009.

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14

Sarno, Luca, Yongqi Wang, Yih-Chin Tai, Maria Nicolina Papa i Paolo Villani. "Chute flows of dry granular media: Numerical simulations by a well-posed multilayer model and comparisons with experiments". E3S Web of Conferences 415 (2023): 02018. http://dx.doi.org/10.1051/e3sconf/202341502018.

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Debris flows and avalanches are dangerous natural phenomena, characterized by the gravity-driven motion of granular media immersed in a fluid. For an appropriate hazard assessment or disaster mitigation by scenario investigation, it is crucial to capture the underlying dynamics of the granular solid phase. For this purpose, a multilayer depth-averaged approach represents a promising and computationally efficient tool over fully three-dimensional models. Here we use a mathematically well-posed multilayer model, which implements the µ(I)-rheology and a dilatancy law depending on the inertial number, I, and compare the numerical results of the model with laboratory experiments of steady uniform chute flows over an erodible bed. The well-posedness of the model for any value of I, which is essential to get convergent numerical solutions, is achieved by considering an approximation of the in-plane stress gradients, directly emerging from the µ(I)-rheology. The predicted velocity profiles show a very good agreement with the experimental ones, measured by particle image velocimetry (PIV). The volume fraction profiles by the multilayer model are also in good qualitative agreement with those measured by using the stochastic-optical method (SOM), while they tend to overestimate the volume fraction measurements in the more dilute upper region, closer to the free surface.

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15

Hanes, Daniel M., i Douglas L. Inman. "Observations of rapidly flowing granular-fluid materials". Journal of Fluid Mechanics 150 (styczeń 1985): 357–80. http://dx.doi.org/10.1017/s0022112085000167.

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The rapid shearing of a mixture of cohesionless glass spheres and air or water was studied in an annular, parallel-plate shear cell designed after Savage (1978). Two types of flow were observed. In the first type of flow the entire mass of the granular material was mobilized. At high shear rates the shear and normal stresses were found to be quadratically dependent upon the mean shear rate (at constant volume concentration), in general agreement with the observations of Bagnold (1954) and Savage & Sayed (1984), and the ‘kinetic’ theory of Jenkins & Savage (1983). The stresses were found to be weakly dependent on the volume concentration up to approximately 0.5, and strongly dependent above this concentration. For flows in which water was the interstitial fluid, the ratio of the shear stress to the normal stress was slightly higher (than in air), and the stresses at lower shear rates were found to be more nearly linearly related to the shear rate. It is suggested that these effects are contributed to by the viscous dampening of grain motions by the water. The second type of flow was distinguished by the existence of an internal boundary above which the granular material deformed rapidly, but below which the granular material remained rigidly locked in place. The thickness of the shearing layer was measured to be between 5 and 15 grain diameters. The stress ratio at the bottom of the shearing layer was found to be nearly constant, suggesting the internal boundary is a consequence of the immersed weight of the shearing grains, and may be described by a Coulomb yield criterion. A scaled concentration is proposed to compare similar data obtained using different-sized materials or different apparatus. An intercomparison of the two types of flow studied, along with a comparison between the present experiments and those of Bagnold (1954) and Savage & Sayed (1984), suggests that the nature of the boundaries can have a significant effect upon the dynamics of the entire flow.

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16

Krupička, Jan, Václav Matoušek, Tomáš Picek i Štěpán Zrostlík. "Validation of laser-penetration- and electrical-conductivity-based methods of concentration measurement in flow with intense transport of coarse sediment". EPJ Web of Conferences 180 (2018): 02048. http://dx.doi.org/10.1051/epjconf/201818002048.

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Lack of experimentally determined information on inner structure of flows carrying large amount of coarse sediment is an important limitation for development and validation of appropriate mathematical models. Measurement of local flow properties is particularly difficult in case of coarse sediment due to specific features associated with high ratio of the sediment size to the flow depth. This paper focusses on two methods of evaluation of vertical concentration profiles in the flow of a mixture of plastic grains and water in a laboratory flume. The first one was proposed by B. Spinewine et al. in 2011 and it is based on the relation between concentration of solids and the depth of penetration of a laser stripe to the flow, which is evaluated from a high speed camera record. The second method is based on well-known relation between the concentration and electrical conductivity of a mixture sensed by immersed probe. A sensitivity analysis of both the methods is performed to show the most crucial parameters affecting accuracy of the results. The methods are validated on data measured in fluidization cell with controlled particle concentration. Presented results on flow show limitations and potential of the methods for laboratory studies on liquid-granular flow.

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17

Nordlund, Å., i R. F. Stein. "Solar Magnetoconvection". Symposium - International Astronomical Union 138 (1990): 191–211. http://dx.doi.org/10.1017/s0074180900044144.

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As a prelude to discussing the interaction of magnetic fields with convection, we first review some general properties of convection in a stratified medium. Granulation, which is the surface manifestation of the major energy carrying convection scales, is a shallow phenomenon. Below the surface, the topology changes to one of filamentary cool downdrafts, immersed in a gently ascending isentropic background. The granular downflows merge into more widely separated downdrafts, on scales of mesogranulation and super-granulation.The local topology and time evolution of the small scale, kilo Gauss, network and facular magnetic field elements are controlled by convection on the scale of granulation. The topology and time evolution of larger scale magnetic field concentrations are controlled by the hierarchical structure of the horizontal components of the large scale velocity field. In sunspots, the small scale magnetic field structure determines the energy balance, the systematic flows and the waves. Below the surface, the small scale structure of the magnetic field may change drastically, with little observable effect at the surface. We discuss results of some recent numerical simulations of sunspot magnetic fields, and some mechanisms that may be relevant in determining the topology of the sub-surface magnetic field. Finally, we discuss the role of active region magnetic fields in the global solar dynamo.

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18

Tenneti, Sudheer, Mohammad Mehrabadi i Shankar Subramaniam. "Stochastic Lagrangian model for hydrodynamic acceleration of inertial particles in gas–solid suspensions". Journal of Fluid Mechanics 788 (12.01.2016): 695–729. http://dx.doi.org/10.1017/jfm.2015.693.

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The acceleration of an inertial particle in a gas–solid flow arises from the particle’s interaction with the gas and from interparticle interactions such as collisions. Analytical treatments to derive a particle acceleration model are difficult outside the Stokes flow regime, but for moderate Reynolds numbers (based on the mean slip velocity between gas and particles) particle-resolved direct numerical simulation (PR-DNS) is a viable tool for model development. In this study, PR-DNS of freely-evolving gas–solid suspensions are performed using the particle-resolved uncontaminated-fluid reconcilable immersed-boundary method (PUReIBM) that has been extensively validated in previous studies. Analysis of the particle velocity variance (granular temperature) equation in statistically homogeneous gas–solid flow shows that a straightforward extension of a class of mean particle acceleration models (drag laws) to their corresponding instantaneous versions, by replacing the mean particle velocity with the instantaneous particle velocity, predicts a granular temperature that decays to zero, which is at variance with the steady particle granular temperature that is obtained from PR-DNS. Fluctuations in particle velocity and particle acceleration (and their correlation) are important because the particle acceleration–velocity covariance governs the evolution of the particle velocity variance (characterized by the particle granular temperature), which plays an important role in the prediction of the core annular structure in riser flows. The acceleration–velocity covariance arising from hydrodynamic forces can be decomposed into source and dissipation terms that appear in the granular temperature evolution equation, and these have already been quantified in the Stokes flow regime using a combination of kinetic theory closure and multipole expansion simulations. From PR-DNS data we show that the fluctuations in the particle acceleration that are aligned with fluctuations in the particle velocity give rise to a source term in the granular temperature evolution equation. This approach is used to quantify the hydrodynamic source and dissipation terms of granular temperature from PR-DNS results for freely-evolving gas–solid suspensions that are performed over a wide range of solid volume fraction ($0.1\leqslant {\it\phi}\leqslant 0.4$), Reynolds number based on the slip velocity between the solid and the fluid phase ($10\leqslant \mathit{Re}_{m}\leqslant 100$) and solid-to-fluid density ratio ($100\leqslant {\it\rho}_{p}/{\it\rho}_{f}\leqslant 2000$). The straightforward extension of drag law models does not give rise to any source in the granular temperature due to hydrodynamic effects. This motivates the development of better Lagrangian particle acceleration models that can be used in Lagrangian–Eulerian formulations of gas–solid flow. It is found that a Langevin equation for the increment in the particle velocity reproduces PR-DNS results for the stationary particle velocity autocorrelation in freely-evolving suspensions. Based on the data obtained from the simulations, the functional dependence of the Langevin model coefficients on solid volume fraction, Reynolds number and solid-to-fluid density ratio is obtained. This new Lagrangian particle acceleration model reproduces the correct steady granular temperature and can also be adapted to gas–solid flow computations using Eulerian moment equations.

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19

Dbouk, Talib, i S. Amir Bahrani. "Modeling of buoyancy-driven thermal convection in immersed granular beds". International Journal of Multiphase Flow 134 (styczeń 2021): 103471. http://dx.doi.org/10.1016/j.ijmultiphaseflow.2020.103471.

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20

Sun, Yunhui, Wentao Zhang, Yi An, Qingquan Liu i Xiaoliang Wang. "Experimental investigation of immersed granular collapse in viscous and inertial regimes". Physics of Fluids 33, nr 10 (październik 2021): 103317. http://dx.doi.org/10.1063/5.0067485.

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21

He, Kang, Huabin Shi i Xiping Yu. "Effects of interstitial water on collapses of partially immersed granular columns". Physics of Fluids 34, nr 2 (luty 2022): 023306. http://dx.doi.org/10.1063/5.0079468.

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Drame, Aboubacar Sidiki, Li Wang i Yanping Zhang. "Granular Stack Density’s Influence on Homogeneous Fluidization Regime: Numerical Study Based on EDEM-CFD Coupling". Applied Sciences 11, nr 18 (18.09.2021): 8696. http://dx.doi.org/10.3390/app11188696.

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FLUENT and EDEM were applied to simulate liquid–solid coupling in a 3D homogenous fluidization. The dynamics of destabilization of the granular material immersed by homogeneous fluidization were observed. The effect of initial packing density of granular stack and fluidization rate on the fluidization’s transient regime, the configuration of particles in the fluidized bed and the variation of bed height were analyzed and discussed. According to the results, there was an original observation of a strong impact of the initial density of an initially static granular stack on the transient fluidization regime. Depending on the material initial volume fraction, there was a difference in grain dynamics. For an initially loose stack, a homogeneous turbulent fluidization was observed, whereas for an initially dense stack, there was a mass takeoff of the stack. The propagation of wave porosity instability, from the bottom to the top of the stack with fast kinetics that decompacted the medium, followed this mass takeoff.

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23

Liu, Ping, Xianwen Ran, Qi Cheng, Wenhui Tang, Jingyuan Zhou i Raphael Blumenfeld. "Locomotion of Self-Excited Vibrating and Rotating Objects in Granular Environments". Applied Sciences 11, nr 5 (25.02.2021): 2054. http://dx.doi.org/10.3390/app11052054.

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Many reptiles, known as ‘sand swimmers’, adapt to their specific environments by vibrating or rotating their body. To understand these type of interactions of active objects with granular media, we study a simplified model of a self-excited spherical object (SO) immersed in the granular bed, using three-dimensional discrete element method (DEM) simulations. Modelling the vibration by an oscillatory motion, we simulate the longitudinal locomotion of the SO in three modes: transverse vibration, rotation around different axes, and a combination of both. We find that the mode of oscillation in y direction coupled with rotation around x-axis is optimal in the sense that the SO rises fastest, with periodic oscillations, in the z direction while remaining stable at the initial x position. We analyze the physical mechanisms governing the meandering up or down and show that the large oscillations are caused by an asynchronous changes between the directions of oscillation and rotation. We also observed that the SO’s rising rate is sensitive to three parameters: the oscillation amplitude, the oscillation frequency, f, and the rotation angular velocity, Ω. We report the following results. 1. When the frequencies of the rotation and transverse motion are synchronised, SO rises when Ω<0 and sinks when Ω>0; the average rising/sinking rate is proportional to |Ω|. 2. The rising rate increases linearly with the oscillation amplitude. 3. There exists a critical oscillation frequency, above and below which the rising mechanisms are different. Our study reveals the range of parameters that idealized ‘swimmers’ need to use to optimize performance in granular environments.

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Amarsid, L., J. Y. Delenne, P. Mutabaruka, Y. Monerie, F. Perales i F. Radjai. "Viscoinertial regime of immersed granular flows". Physical Review E 96, nr 1 (5.07.2017). http://dx.doi.org/10.1103/physreve.96.012901.

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Lacaze, Laurent, Joris Bouteloup, Benjamin Fry i Edouard Izard. "Immersed granular collapse: from viscous to free-fall unsteady granular flows". Journal of Fluid Mechanics 912 (9.02.2021). http://dx.doi.org/10.1017/jfm.2020.1088.

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26

Gauthier, Georges, i Philippe Gondret. "Compaction of liquid immersed granular packings by small upward flows". Physical Review Fluids 4, nr 7 (19.07.2019). http://dx.doi.org/10.1103/physrevfluids.4.074308.

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27

Garzó, Vicente. "Towards a better understanding of granular flows". Journal of Fluid Mechanics 968 (26.07.2023). http://dx.doi.org/10.1017/jfm.2023.494.

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Understanding the transport of particles immersed in a carrier fluid (bedload transport) is still an exciting challenge. Among the different types of gas–solid flows, when the dynamics of solid particles is essentially dominated by collisions between them, kinetic theory can be considered as a reliable tool to derive continuum approaches from a fundamental point of view. In a recent paper, Chassagne et al. (J. Fluid Mech., vol. 964, 2023, A27) proposed a two-fluid model based on modifications to a classical kinetic theory model (Garzó & Dufty, Phys. Rev. E, vol. 59, 1999, pp. 5895–5911). First, in contrast to the classical model, the model proposed by Chassagne et al. takes into account the interparticle friction not only in the radial distribution function but also through an effective restitution coefficient in the rate of dissipation term of granular temperature. As a second modification, at the top of the bed where the volume fraction is quite small, the model accounts for the saltation regime in the continuum framework. The theoretical results derived from the model agree with discrete simulations for moderate and high densities and they are also consistent with experiments. Thus, the model proposed by Chassagne et al. (J. Fluid Mech., vol. 964, 2023, A27) helps provide a better understanding of the combined impact of friction and inelasticity on the macroscopic properties of granular flows.

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Goddard, J. D. "Material Instability in Rapid Granular Shear Flow". MRS Proceedings 627 (2000). http://dx.doi.org/10.1557/proc-627-bb4.1.

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ABSTRACTThis is a survey of recent theoretical work on shear flow instabilities of dry granular media in the Bagnold or “grain-inertia” régime. Attention is devoted to steady homogeneous unbounded simple shear, with the goal of identifying material (constitutive) instabilities arising from the coupling of stress to granular concentration and temperature fields. Such instabilities, the dissipative analogs of thermodynamic phase transitions, are familiar in numerous branches of the mechanics of materials.The current interest is motivated in part by the “dissipative clustering” found in various particle-dynamics (“DEM”) simulations of granular systems. Since particle clustering may invalidate standard gas kinetic theory, it is pertinent to ask whether hydrodynamic models based on such theories may themselves exhibit clustering instability.The present article is based largely on a recent review (Goddard and Alam 1999), which provides a unified linear-stability treatment for rapid granular flow, as well for slow flow of mobile particles immersed in viscous liquids. The analysis is based on a “short-memory” response of various fluxes to perturbations on steady uniform states, a feature characteristic of the most popular constitutive models for granular flow. In the absence of gravity, previous theoretical analyses reveal transverse “layering” and spanwise “corrugations” as possible forms of material instability (Alam and Nott 1998)Based on current theoretical findings, further work is recommended, including the exploration of the effects of gravity and of stress relaxation, both of which are likely to be important in real granular flows.

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Cui, Kahlil F. E., Gordon G. D. Zhou i Lu Jing. "Viscous Effects on the Particle Size Segregation in Geophysical Mass Flows: Insights From Immersed Granular Shear Flow Simulations". Journal of Geophysical Research: Solid Earth 126, nr 8 (sierpień 2021). http://dx.doi.org/10.1029/2021jb022274.

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Vowinckel, Bernhard, Kunpeng Zhao, Rui Zhu i Eckart Meiburg. "Investigating cohesive sediment dynamics in open waters via grain-resolved simulations". Flow 3 (2023). http://dx.doi.org/10.1017/flo.2023.20.

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Cohesive particulate flows play an important role in environmental fluid dynamics, as well as in a wide variety of civil and process engineering applications. However, the scaling laws, constitutive equations and continuum field descriptions governing such flows are currently less well understood than for their non-cohesive counterparts. Grain-resolved simulations represent an essential tool for addressing this shortcoming, along with theoretical investigations, laboratory experiments and field studies. Here we provide a tutorial introduction to simulations of fine-grained sediments in viscous fluids, along with an overview of some representative insights that this approach has yielded to date. After a brief review of the key physical concepts governing van der Waals forces as the main cohesive effect for subaqueous sediment suspensions, we discuss their incorporation into particle-resolved simulations based on the immersed boundary method. We subsequently describe simulations of cohesive particles in several model turbulent flows, which demonstrate the emergence of a statistical equilibrium between the growth and break-up of aggregates. As a next step, we review the influence of cohesive forces on the settling behaviour of dense suspensions, before moving on to submerged granular collapses. Throughout the article, we highlight open research questions in the field of cohesive particulate flows whose investigation may benefit from grain-resolved simulations.

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Poulain, P., A. Le Friant, A. Mangeney, S. Viroulet, E. Fernandez-Nieto, M. Castro Diaz, M. Peruzzetto i in. "Performance and limits of a shallow-water model for landslide-generated tsunamis: from laboratory experiments to simulations of flank collapses at Montagne Pelée (Martinique)". Geophysical Journal International, 6.12.2022. http://dx.doi.org/10.1093/gji/ggac482.

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Summary We investigate the dynamics and deposits of granular flows and the amplitude of landslide-generated water waves using the HySEA depth-averaged shallow-water numerical model, both at laboratory and field scales. We evaluate the different sources of error by quantitatively comparing the simulations with (i) new laboratory experiments of granular collapses in different conditions (dry, immersed, dry flow entering water) and slope angles and (ii) numerical simulations made with the SHALTOP code that describes topography effects better than most depth-averaged landslide-tsunami models. For laboratory configurations, representing the limits of the shallow-water approximation in such models, we show that topography and non-hydrostatic effects are crucial. When topography effects are accounted for empirically—by artificially increasing the friction coefficient and performing non-hydrostatic simulations—the model is able to reproduce the granular mass deposit and the waves recorded at gauges located at a distance of more than 2–3 times the characteristic dimension of the slide with an error ranging from 1 per cent to 25 per cent depending on the scenario, without any further calibration. Taking into account this error estimate, we simulate landslides that occurred on Montagne Pelée volcano, Martinique, Lesser Antilles as well as the generated waves. Multiple collapse simulations support the assumption that large flank collapses on Montagne Pelée likely occurred in several successive sub-events. This result has a strong impact on the amplitude of the generated waves and thus on the associated hazards. In the context of the ongoing seismic volcanic unrest at Montagne Pelée volcano, we calculate the debris avalanche and associated tsunamis for two potential flank-collapse scenarios.

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Polanía, Oscar, Miguel Cabrera, Mathieu Renouf i Emilien Azéma. "Collapse of dry and immersed polydisperse granular columns: A unified runout description". Physical Review Fluids 7, nr 8 (22.08.2022). http://dx.doi.org/10.1103/physrevfluids.7.084304.

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Coppin, Nathan, Matthieu Constant, Jonathan Lambrechts, Frédéric Dubois i Vincent Legat. "Numerical analysis of the drag on a rigid body in an immersed granular flow". Computational Particle Mechanics, 21.06.2021. http://dx.doi.org/10.1007/s40571-021-00418-w.

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Zhao, Yifeng, Pei Zhang, Liang Lei, Lingwei Kong, Sergio Galindo-Torres i Stan Z. Li. "Metaball-Imaging Discrete Element Lattice Boltzmann Method for fluid-particle system of complex morphologies with settling case study". Physics of Fluids, 18.01.2023. http://dx.doi.org/10.1063/5.0135834.

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Fluid-particle systems are highly sensitive to particle morphologies. While many attempts have been made on shape descriptors and coupling schemes, how to simulate the particle-particle and particle-fluid interactions with a balance between accuracy and efficiency is still a challenge, especially when complex-shaped particles are considered. This study presents a Metaball-Imaging (MI) based Discrete Element Lattice Boltzmann Method (DELBM) for fluid simulations with irregular shaped particles. The major innovation is the MI algorithm to capture the real grain shape for DELBM simulations, where the Metaball function is utilized as the mathematical representation due to its versatile and efficient expressiveness of complex shapes. The contact detection is tackled robustly by gradient calculation of the closest point with a Newton-Raphson based scheme. And the coupling with LBM is accomplished by a classic sharp-interface scheme. As for refiling, a local refiling algorithm based on the bounce back rule is implemented. Validations on three settling experiments of irregular-shaped natural cobblestones indicate the proposed model to be effective and powerful in probing micromechanics of irregular-shaped granular media immersed in fluid systems. The potential of this model on studies of shape-induced physical processes is further investigated with numerical examples on the "drafting, kissing and tumbling" phenomenon of pair particles in various shapes.

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