Journal articles on the topic 'Particle-wall collision model'
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Lin, J. H., and K. C. Chang. "Particle Dispersion Simulation in Turbulent Flow Due to Particle-Particle and Particle-Wall Collisions." Journal of Mechanics 32, no. 2 (August 19, 2015): 237–44. http://dx.doi.org/10.1017/jmech.2015.63.
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AbstractSimulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm of collision pair among particles is developed. It is found that the effects of inter-particle collisions on particle dispersion cannot be negligible when the ratio of the mean free time of particle to the mean particle relaxation time of particle is less or equal to O(10). In addition, the wall roughness extent plays an important role in the simulation of particle-wall collisions particularly for cases with small mass loading ratios.
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ARDEKANI, A. M., and R. H. RANGEL. "Numerical investigation of particle–particle and particle–wall collisions in a viscous fluid." Journal of Fluid Mechanics 596 (January 17, 2008): 437–66. http://dx.doi.org/10.1017/s0022112007009688.
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The dynamics of particle–particle collisions and the bouncing motion of a particle colliding with a wall in a viscous fluid is numerically investigated. The dependence of the effective coefficient of restitution on the Stokes number and surface roughness is analysed. A distributed Lagrange multiplier-based computational method in a solid–fluid system is developed and an efficient method for predicting the collision between particles is presented. A comparison between this method and previous collision strategies shows that the present approach has some significant advantages over them. Comparison of the present methodology with experimental studies for the bouncing motion of a spherical particle onto a wall shows very good agreement and validates the collision model. Finally, the effect of the coefficient of restitution for a dry collision on the vortex dynamics associated with this problem is discussed.
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Derevich, I. V. "Probabilistic model of a particle-rough wall collision." Journal of Applied Mechanics and Technical Physics 40, no. 5 (September 1999): 989–94. http://dx.doi.org/10.1007/bf02468487.
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Zenit, Roberto, and Melany L. Hunt. "Mechanics of Immersed Particle Collisions." Journal of Fluids Engineering 121, no. 1 (March 1, 1999): 179–84. http://dx.doi.org/10.1115/1.2821999.
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The present work investigates the mechanics of particle collisions submerged in a liquid using a simple pendulum experiment. Particle trajectories for different particles in water are measured using a high-speed digital camera and the magnitude of the collision is recorded using a high-frequency-response pressure transducer at the colliding surface. The particle deceleration occurs at distances less than half a particle diameter from the wall. The measured collision impulse increases with impact velocity and particle mass. Comparisons are drawn between the measured pressures and the predictions of basic impact mechanics assuming a perfectly elastic collision. A control-volume model is proposed that accounts for the fluid inertia and viscosity. When a particle approaches a planar surface or another particle, the fluid is squeezed prior to contact, reducing the initial kinetic energy and decelerating the particle. The pressure profile is integrated over the surface of the particle to obtain a force that is a function of the initial particle Reynolds number, Reo, and the ratio of the densities of the particle and fluid phases, ρp/ρf. The model predicts a critical Stokes number at which the particle reaches the wall with zero velocity. Comparisons between the proposed model and the experimental measurements show qualitative agreement.
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Lin, Jian-Hung, and Keh-Chin Chang. "A Modeling Study on Particle Dispersion in Wall-Bounded Turbulent Flows." Advances in Applied Mathematics and Mechanics 6, no. 06 (December 2014): 764–82. http://dx.doi.org/10.4208/aamm.2014.m533.
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AbstractThree physical mechanisms which may affect dispersion of particle’s motion in wall-bounded turbulent flows, including the effects of turbulence, wall roughness in particle-wall collisions, and inter-particle collisions, are numerically investigated in this study. Parametric studies with different wall roughness extents and with different mass loading ratios of particles are performed in fully developed channel flows with the Eulerian-Lagrangian approach. A low-Reynolds-numberk–εturbulence model is applied for the solution of the carrier-flow field, while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. It is shown that the mechanism of inter-particle collisions should be taken into account in the modeling except for the flows laden with sufficiently low mass loading ratios of particles. Influences of wall roughness on particle dispersion due to particle-wall collisions are found to be considerable in the bounded particle–laden flow. Since the investigated particles are associated with large Stokes numbers, i.e., larger thanO(1), in the test problem, the effects of turbulence on particle dispersion are much less considerable, as expected, in comparison with another two physical mechanisms investigated in the study.
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Kempe, Tobias, and Jochen Fröhlich. "Collision modelling for the interface-resolved simulation of spherical particles in viscous fluids." Journal of Fluid Mechanics 709 (August 23, 2012): 445–89. http://dx.doi.org/10.1017/jfm.2012.343.
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AbstractThe paper presents a model for particle–particle and particle–wall collisions during interface-resolving numerical simulations of particle-laden flows. The accurate modelling of collisions in this framework is challenging due to methodological problems generated by interface approach and contact as well as due to the greatly different time scales involved. To cope with this situation, multiscale modelling approaches are introduced avoiding excessive local grid refinement during surface approach and time step reduction during the surface contact. A new adaptive model for the normal forces in the phase of ‘dry contact’ is proposed, stretching the collision process in time to match the time step of the fluid solver. This yields a physically sound and robust collision model with modified stiffness and damping determined by an optimization scheme. Furthermore, the model is supplemented with a new approach for modelling the tangential force during oblique collisions which is based on two material parameters: a critical impact angle separating rolling from sliding and the friction coefficient for the sliding motion. The resulting new model is termed the adaptive collision model (ACM). All proposed sub-models only contain physical parameters, and virtually no numerical parameters requiring adjustment or tuning. The new model is implemented in the framework of an immersed boundary method but is applicable with any spatial and temporal discretization. Detailed validation against experimental data was performed so that a general and versatile model for arbitrary collisions of spherical particles in viscous fluids is now available.
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Zhang, Xia, and Lixing Zhou. "A second-order moment particle–wall collision model accounting for the wall roughness." Powder Technology 159, no. 2 (November 2005): 111–20. http://dx.doi.org/10.1016/j.powtec.2005.07.005.
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Cheng, Jiarui, Yihua Dou, Ningsheng Zhang, Zhen Li, and Zhiguo Wang. "A New Method for Predicting Erosion Damage of Suddenly Contracted Pipe Impacted by Particle Cluster via CFD-DEM." Materials 11, no. 10 (September 28, 2018): 1858. http://dx.doi.org/10.3390/ma11101858.
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A numerical study on the erosion of particle clusters in an abrupt pipe was conducted by means of the combined computational fluid dynamics (CFD) and discrete element methods (DEM). Furthermore, a particle-wall extrusion model and a criterion for judging particle collision interference were developed to classify and calculate the erosion rate caused by different interparticle collision mechanisms in a cluster. Meanwhile, a full-scale pipe flow experiment was conducted to confirm the effect of a particle cluster on the erosion rate and to verify the calculated results. The reducing wall was made of super 13Cr stainless steel materials and the round ceramsite as an impact particle was 0.65 mm in diameter and 1850 kg/m3 in density. The results included an erosion depth, particle-wall contact parameters, and a velocity decay rate of colliding particles along the radial direction at the target surface. Subsequently, the effect of interparticle collision mechanisms on particle cluster erosion was discussed. The calculated results demonstrate that collision interference between particles during one cluster impact was more likely to appear on the surface with large particle impact angles. This collision process between the rebounded particles and the following particles not only consumed the kinetic energy but also changed the impact angle of the following particles.
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BOURGADE, JEAN-PIERRE. "A COUPLED SPHERICAL HARMONICS EXPANSION MODEL FOR CONFINED PARTICLES." Mathematical Models and Methods in Applied Sciences 14, no. 08 (August 2004): 1133–65. http://dx.doi.org/10.1142/s021820250400357x.
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Our goal in this paper is to derive from a kinetic setting a diffusion model for the transport of charged particles trapped in a surface potential. The so-obtained model is derived through a diffusion approximation, as we assume the thermalization to be governed by particle-wall collisions. In order to take into account the possible inelasticity of such collisions, we introduce a nonlocal (in energy) collision operator on the boundary. At the macroscopic scale, this results in a coupled (in energy) Spherical Harmonics Expansion (SHE) model. The model is both formally and rigorously derived from the kinetic equation, and existence is obtained as a by-product of the derivation.
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Gui, Nan, Xingtuan Yang, Jiyuan Tu, and Shengyao Jiang. "A generalized particle-to-wall collision model for non-spherical rigid particles." Advanced Powder Technology 27, no. 1 (January 2016): 154–63. http://dx.doi.org/10.1016/j.apt.2015.12.002.
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Roisman, I. V., and C. Tropea. "Impact of a crushing ice particle onto a dry solid wall." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2183 (November 2015): 20150525. http://dx.doi.org/10.1098/rspa.2015.0525.
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This is a theoretical study about ice particle impact onto a rigid wall. It is motivated by the need to model the process of ice crystal accretion or damage caused by an ice particle impacts. A quasi-one-dimensional model of ice particle impact and deformation is developed. Spherical, cylindrical and conical shapes of the ice crystals are analysed. The model is able to predict particle residual height, the force produced by impact and the collision duration. The theoretical predictions agree well with the available experimental data.
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Vigolo, D., I. M. Griffiths, S. Radl, and H. A. Stone. "An experimental and theoretical investigation of particle–wall impacts in a T-junction." Journal of Fluid Mechanics 727 (June 20, 2013): 236–55. http://dx.doi.org/10.1017/jfm.2013.200.
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AbstractUnderstanding the behaviour of particles entrained in a fluid flow upon changes in flow direction is crucial in problems where particle inertia is important, such as the erosion process in pipe bends. We present results on the impact of particles in a T-shaped channel in the laminar–turbulent transitional regime. The impacting event for a given system is described in terms of the Reynolds number and the particle Stokes number. Experimental results for the impact are compared with the trajectories predicted by theoretical particle-tracing models for a range of configurations to determine the role of the viscous boundary layer in retarding the particles and reducing the rate of collision with the substrate. In particular, a two-dimensional model based on a stagnation-point flow is used together with three-dimensional numerical simulations. We show how the simple two-dimensional model provides a tractable way of understanding the general collision behaviour, while more advanced three-dimensional simulations can be helpful in understanding the details of the flow.
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Ji, Shi Ming, J. L. Xu, Li Zhang, Ming Sheng Jin, Y. H. Yang, and Y. Wang. "Motion Model and Numerical Simulation of Fluid and Abrasive Particle in Near Wall Region." Materials Science Forum 626-627 (August 2009): 237–42. http://dx.doi.org/10.4028/www.scientific.net/msf.626-627.237.
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The paper discusses the near wall region of soft abrasive particle flow in weak force finish machining method. Turbulent flow morphology in near wall region of rectangular channel with different viscosity is numerically simulated and compared. Through the analysis of kinetic equation of abrasive particle, the abrasive particle motion trace of different diameter in turbulent flow with different viscosity is simulated and compared. The result reveals the condition under which the fluids with different viscosity can form Turbulent flow is different. The greater the viscosity is, the greater the velocity needed is. Also the quantitative relation of velocity and flow volume is available to determine the pump parameter in abrasive particle flow machining. Fluid at wall has pressure and shear stress on work piece. The greater the viscosity and velocity is, the greater the wall pressure and shear stress is. So it is helpful to make material removal on work piece surface. But the greater the viscosity is, the greater the velocity attenuation of abrasive particle is. Abrasive particle mainly move along the flow direction with the movement of fluid. The velocity attenuation of larger diameter abrasive particle is much than the smaller particle but the latter can maintain greater velocity in a longer distance favorable for collision with the work piece surface salient.
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Li, Xiaobai, Melany L. Hunt, and Tim Colonius. "A contact model for normal immersed collisions between a particle and a wall." Journal of Fluid Mechanics 691 (December 1, 2011): 123–45. http://dx.doi.org/10.1017/jfm.2011.461.
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AbstractThe incompressible Navier–Stokes equations are solved numerically to predict the coupled motion of a falling particle and the surrounding fluid as the particle impacts and rebounds from a planar wall. The method is validated by comparing the numerical simulations of a settling sphere with experimental measurements of the sphere trajectory and the accompanying flow field. The normal collision process is then studied for a range of impact Stokes numbers. A contact model of the liquid–solid interaction and elastic effect is developed that incorporates the elasticity of the solids to permit the rebound trajectory to be simulated accurately. The contact model is applied when the particle is sufficiently close to the wall that it becomes difficult to resolve the thin lubrication layer. The model is calibrated with new measurements of the particle trajectories and reproduces the observed coefficient of restitution over a range of impact Stokes numbers from 1 to 1000.
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Ozolins, Ansis, and Uldis Strautins. "SIMPLE MODELS FOR WALL EFFECT IN FIBER SUSPENSION FLOWS." Mathematical Modelling and Analysis 19, no. 1 (February 20, 2014): 75–84. http://dx.doi.org/10.3846/13926292.2014.893263.
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Jeffery's equation describes the dynamics of a non-inertial ellipsoidal particle immersed in a Stokes liquid and is used in various models of fiber suspension flow. However, it is not valid in close neighbourhood of a rigid wall. Geometrically impossible orientation states with the fiber penetrating the wall can result from this model. This paper proposes a modification of Jeffery's equation in close proximity to a wall so that the geometrical constraints are obeyed by the solution. A class of models differing in the distribution between the translational and rotational part of the response to the contact is derived. The model is upscaled to a Fokker–Planck equation. Another microscale model is proposed where recoiling from the wall upon the collision is permitted. Numerical examples illustrate the dynamics captured by the models.
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Daghooghi, Mohsen, and Iman Borazjani. "A kinematics-based model for the settling of gravity-driven arbitrary-shaped particles on a surface." PLOS ONE 16, no. 2 (February 9, 2021): e0243716. http://dx.doi.org/10.1371/journal.pone.0243716.
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A discrete model is proposed for settling of an arbitrary-shaped particle onto a flat surface under the gravitational field. In this method, the particle dynamics is calculated such that (a) the particle does not create an overlap with the wall and (b) reaches a realistic equilibrium state, which are not guaranteed in the conventional discrete element methods that add a repulsive force (torque) based on the amount of overlap between the particle and the wall. Instead, upon the detection of collision, the particle’s kinematics is modified depending on the type of contact, i.e., point, line, and surface types, by assuming the contact point/line as the instantaneous center/line of rotation for calculating the rigid body dynamics. Two different stability conditions are implemented by comparing the location of the projection of the center of mass on the wall along gravity direction against the contact points to identify the equilibrium (stable) state on the wall for particles with multiple contact points. A variety of simulations are presented, including smooth surface particles (ellipsoids), regular particles with sharp edges (cylinders and pyramids) and irregular-shaped particles, to show that the method can provide the analytically-known equilibrium state.
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Lixing, Zhou, and Zhang Xia. "Simulation of sudden-expansion and swirling gas-particle flows using a two-fluid particle-wall collision model with consideration of the wall roughness." Acta Mechanica Sinica 20, no. 5 (October 2004): 447–54. http://dx.doi.org/10.1007/bf02484266.
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Pan, Heng, Robert G. Landers, and Frank Liou. "Dynamic Modeling of Powder Delivery Systems in Gravity-Fed Powder Feeders." Journal of Manufacturing Science and Engineering 128, no. 1 (July 11, 2005): 337–45. http://dx.doi.org/10.1115/1.2120778.
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This paper presents an approach for modeling powder delivery system dynamics in low flow rate applications. Discrete particle modeling (DPM) is utilized to analyze the motion of individual powder particles. In DPM, an irregular bouncing model is employed to represent the powder dispersion in the powder delivery system induced by non-spherical particle-wall collisions. A three-dimensional friction collision model is utilized to simulate the interactions between particles and the powder delivery system walls. The modeling approach is experimentally verified and simulation studies are conducted to explore the effect of powder delivery system mechanical design parameters (i.e., tube length, diameter, and angle, number of tubes and meshes, and mesh orientation and size) on the powder flow dynamics. The simulation studies demonstrate that the powder delivery system dynamics can be modeled by a pure transport delay coupled with a first order system.
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Goswami, Partha S., and V. Kumaran. "Particle dynamics in the channel flow of a turbulent particle–gas suspension at high Stokes number. Part 2. Comparison of fluctuating force simulations and experiments." Journal of Fluid Mechanics 687 (October 6, 2011): 41–71. http://dx.doi.org/10.1017/jfm.2011.295.
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AbstractThe particle and fluid velocity fluctuations in a turbulent gas–particle suspension are studied experimentally using two-dimensional particle image velocimetry with the objective of comparing the experiments with the predictions of fluctuating force simulations. Since the fluctuating force simulations employ force distributions which do not incorporate the modification of fluid turbulence due to the particles, it is of importance to quantify the turbulence modification in the experiments. For experiments carried out at a low volume fraction of $9. 15\ensuremath{\times} 1{0}^{\ensuremath{-} 5} $ (mass loading is 0.19), where the viscous relaxation time is small compared with the time between collisions, it is found that the gas-phase turbulence is not significantly modified by the presence of particles. Owing to this, quantitative agreement is obtained between the results of experiments and fluctuating force simulations for the mean velocity and the root mean square of the fluctuating velocity, provided that the polydispersity in the particle size is incorporated in the simulations. This is because the polydispersity results in a variation in the terminal velocity of the particles which could induce collisions and generate fluctuations; this mechanism is absent if all of the particles are of equal size. It is found that there is some variation in the particle mean velocity very close to the wall depending on the wall-collision model used in the simulations, and agreement with experiments is obtained only when the tangential wall–particle coefficient of restitution is 0.7. The mean particle velocity is in quantitative agreement for locations more than 10 wall units from the wall of the channel. However, there are systematic differences between the simulations and theory for the particle concentrations, possibly due to inadequate control over the particle feeding at the entrance. The particle velocity distributions are compared both at the centre of the channel and near the wall, and the shape of the distribution function near the wall obtained in experiments is accurately predicted by the simulations. At the centre, there is some discrepancy between simulations and experiment for the distribution of the fluctuating velocity in the flow direction, where the simulations predict a bi-modal distribution whereas only a single maximum is observed in the experiments, although both distributions are skewed towards negative fluctuating velocities. At a much higher particle mass loading of 1.7, where the time between collisions is smaller than the viscous relaxation time, there is a significant increase in the turbulent velocity fluctuations by ${\ensuremath{\sim} }1$–2 orders of magnitude. Therefore, it becomes necessary to incorporate the modified fluid-phase intensity in the fluctuating force simulation; with this modification, the mean and mean-square fluctuating velocities are within 20–30 % of the experimental values.
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Kartushinsky, Alexander, and Efstathios E. Michaelides. "Gas–Solid Particle Flow in Horizontal Channels: Decomposition of the Particle-Phase Flow and Interparticle Collision Effects." Journal of Fluids Engineering 129, no. 6 (November 13, 2006): 702–12. http://dx.doi.org/10.1115/1.2734202.
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This paper examines the turbulent flow of heavy particles in horizontal channels and pipes. Calculations for the fluid are performed within an Eulerian frame of reference, while the particulate phase is considered as several continuous polydisperse media, each constituting a separate phase. The interparticle collisions include two mechanisms: collisions with sliding friction and collisions without sliding friction. The collisions of particles are accounted for, by collisions due to the difference in the average and fluctuating velocities of the several particulate fractions. This work introduces an original model for the closure for the mass and momentum equations based on the collisions as well as an original description of the particle motion in a horizontal channel, by introducing the decomposition of the particle-phase motion into two types of particle phases: falling and rebounding particles. The decomposition allows the correct calculation of the influence of the wall on the motion of particles.
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Niazi Ardekani, M., P. Costa, W. P. Breugem, F. Picano, and L. Brandt. "Drag reduction in turbulent channel flow laden with finite-size oblate spheroids." Journal of Fluid Mechanics 816 (February 28, 2017): 43–70. http://dx.doi.org/10.1017/jfm.2017.68.
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We study suspensions of oblate rigid particles in a viscous fluid for different values of the particle volume fractions. Direct numerical simulations have been performed using a direct-forcing immersed boundary method to account for the dispersed phase, combined with a soft-sphere collision model and lubrication corrections for short-range particle–particle and particle–wall interactions. With respect to the single-phase flow, we show that in flows laden with oblate spheroids the drag is reduced and the turbulent fluctuations attenuated. In particular, the turbulence activity decreases to lower values than those obtained by accounting only for the effective suspension viscosity. To explain the observed drag reduction, we consider the particle dynamics and the interactions of the particles with the turbulent velocity field and show that the particle–wall layer, previously observed and found to be responsible for the increased dissipation in suspensions of spheres, disappears in the case of oblate particles. These rotate significantly slower than spheres near the wall and tend to stay with their major axes parallel to the wall, which leads to a decrease of the Reynolds stresses and turbulence production and so to the overall drag reduction.
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ZENIT, R., and M. L. HUNT. "The impulsive motion of a liquid resulting from a particle collision." Journal of Fluid Mechanics 375 (November 25, 1998): 345–61. http://dx.doi.org/10.1017/s0022112098002596.
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When two particles collide in a liquid, the impulsive acceleration due to the rebound produces a pressure pulse that is transmitted through the fluid. Detailed measurements were made of the pressure pulse and the motion of the particles by generating controlled collisions with an immersed dual pendulum. The experiments were performed for a range of impact velocities, angles of incidence, and distances between the wall and the pairs of particles. The radiated fluid pressure was measured using a high-frequency-response pressure transducer, and the motion of the particles was recorded using a high-speed digital camera. The magnitude of the impulse pressure was found to scale with the particle velocity, the particle diameter and the density of the fluid. Additionally, a model is proposed to predict the impulse field in the fluid based on the impulse pressure theory. The model agrees well with the experimental measurements.
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Ardekani, M. Niazi, and L. Brandt. "Turbulence modulation in channel flow of finite-size spheroidal particles." Journal of Fluid Mechanics 859 (November 26, 2018): 887–901. http://dx.doi.org/10.1017/jfm.2018.854.
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Finite-size particles modulate wall-bounded turbulence, leading, for the case of spherical particles, to increased drag also owing to the formation of a particle wall layer. Here, we study the effect of particle shape on the turbulence in suspensions of spheroidal particles at volume fraction $\unicode[STIX]{x1D719}=10\,\%$ and show how the near-wall particle dynamics deeply changes with the particle aspect ratio and how this affects the global suspension behaviour. Direct numerical simulations are performed using a direct-forcing immersed boundary method to account for the dispersed phase, combined with a soft-sphere collision model and lubrication corrections for short-range particle–particle and particle–wall interactions. The turbulence reduces with the aspect ratio of oblate particles, leading to drag reduction with respect to the single-phase flow for particles with aspect ratio ${\mathcal{A}}{\mathcal{R}}\leqslant 1/3$, when the significant reduction in Reynolds shear stress is more than the compensation by the additional stresses, induced by the solid phase. Oblate particles are found to avoid the region close to the wall, travelling parallel to it with small angular velocities, while preferentially sampling high-speed fluid in the wall region. Prolate particles also tend to orient parallel to the wall and avoid its vicinity. Their reluctance to rotate around the spanwise axis reduces the wall-normal velocity fluctuation of the flow and therefore the turbulence Reynolds stress, similar to oblates; however, they undergo rotations in wall-parallel planes which increase the additional solid stresses due to their relatively larger angular velocities compared to the oblates. These larger additional stresses compensate for the reduction in turbulence activity and lead to a wall drag similar to that of single-phase flows. Spheres on the other hand, form a layer close to the wall with large angular velocities in the spanwise direction, which increases the turbulence activity in addition to exerting the largest solid stresses on the suspension, in comparison to the other studied shapes. Spherical particles therefore increase the wall drag with respect to the single-phase flow.
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Quintero, Brian, Santiago Laín, and Martin Sommerfeld. "Derivation and validation of a hard-body particle-wall collision model for non-spherical particles of arbitrary shape." Powder Technology 380 (March 2021): 526–38. http://dx.doi.org/10.1016/j.powtec.2020.11.032.
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Pan, Yadi, Shuya Shan, Yao Wei, Feng Ji, Jinping Weng, Yulan Tian, and Jin Qian. "Study on the fiber fouling in drying exhaust heat utilization of wood industry." E3S Web of Conferences 38 (2018): 01003. http://dx.doi.org/10.1051/e3sconf/20183801003.
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Based on the viscoelastic and creep deformation properties, a new deposition mechanism model for slender wood fiber particles in wast heat utilization is proposed in this paper. And the equivalent sphere method is used to describe the particle feature size in the model. With the proposed deposition model of flexible slender particles, the critical criteria are obtained. The influence of particle size, aspect ratio and damping factor on particle deposition has been investigated. The results indicate that particle deposition increases with the particle size decrease, aspect ratio and damping factor increase. According to the present deposition model, a coupling simulation with FLUENT and EDEM method was carried out for the flow field of fiber drying tail gas in heat piping exchanger, which indicated that particle deposition mainly occurred at the central windward area of fin due to the direction changer and the magnitude decrease of collision velocity between fiber particles and wall. Experiment of heat recovery of drying tail gas revealed that using the H fin tubes instead of rectangular fin tubes can greatly relieve the deposition of wood fiber particles, which provided a useful way to save energy in wood industries.
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Chinappi, M., and E. De Angelis. "Confined dynamics of a single DNA molecule." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1944 (June 13, 2011): 2329–36. http://dx.doi.org/10.1098/rsta.2011.0096.
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The effect of a slit-like confinement on the relaxation dynamics of DNA is studied via a mesoscale model in which a bead and spring model for the polymer is coupled to a particle-based Navier–Stokes solver (multi-particle collision dynamics). The confinement is found to affect the equilibrium stretch of the chain when the bulk gyration radius is comparable to or smaller than the channel height and our data are in agreement with the ( R g,bulk / h ) 1/4 scaling of the polymer extension in the wall tangential direction. Relaxation simulation at different confinements indicates that, while the overall behaviour of the relaxation dynamics is similar for low and strong confinements, a small, but significant, slowing of the far-equilibrium relaxation is found as the confinement increases.
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Dong, Yunshan, Zongliang Qiao, Fengqi Si, Bo Zhang, Cong Yu, and Xiaoming Jiang. "A Novel Method for the Prediction of Erosion Evolution Process Based on Dynamic Mesh and Its Applications." Catalysts 8, no. 10 (September 30, 2018): 432. http://dx.doi.org/10.3390/catal8100432.
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Particle erosion is a commonly occurring phenomenon, and it plays a significantly important role in service life. However, few simulations have replicated erosion, especially the detailed evolution process. To address this complex issue, a new method for establishing the solution of the erosion evolution process was developed. The approach is introduced with the erosion model and the dynamic mesh. The erosion model was applied to estimate the material removal of erosion, and the dynamic mesh technology was used to demonstrate the surface profile of erosion. Then, this method was applied to solve a typical case—the erosion surface deformation and the expiry period of an economizer bank in coal-fired power plants. The mathematical models were set up, including gas motion, particle motion, particle-wall collision, and erosion. Such models were solved by computational fluid dynamics (CFD) software (ANSYS FLUENT), which describes the evolution process of erosion based on the dynamic mesh. The results indicate that: (1) the prediction of the erosion profile calculated by the dynamic mesh is in good agreement with that on-site; (2) the global/local erosion loss and the maximum erosion depth is linearly related to the working time at the earlier stage, but the growth of the maximum erosion depth slows down gradually in the later stage; (3) the reason for slowing down is that the collision point trajectory moves along the increasing direction of the absolute value of θ as time increases; and (4) the expiry period is shortened as the ash diameter increases.
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Ye, Huilin, Zhiqiang Shen, and Ying Li. "Interplay of deformability and adhesion on localization of elastic micro-particles in blood flow." Journal of Fluid Mechanics 861 (December 19, 2018): 55–87. http://dx.doi.org/10.1017/jfm.2018.890.
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The margination and adhesion of micro-particles (MPs) have been extensively investigated separately, due to their important applications in the biomedical field. However, the cascade process from margination to adhesion should play an important role in the transport of MPs in blood flow. To the best of our knowledge, this has not been explored in the past. Here we numerically study the margination behaviour of elastic MPs to blood vessel walls under the interplay of their deformability and adhesion to the vessel wall. We use the lattice Boltzmann method and molecular dynamics to solve the fluid dynamics and particle dynamics (including red blood cells (RBCs) and elastic MPs) in blood flow, respectively. Additionally, a stochastic ligand–receptor binding model is employed to capture the adhesion behaviours of elastic MPs on the vessel wall. Margination probability is used to quantify the localization of elastic MPs at the wall. Two dimensionless numbers are considered to govern the whole process: the capillary number $Ca$, denoting the ratio of viscous force of fluid flow to elastic interfacial force of MP, and the adhesion number $Ad$, representing the ratio of adhesion strength to viscous force of fluid flow. We systematically vary them numerically and a margination probability contour is obtained. We find that there exist two optimal regimes favouring high margination probability on the plane $Ca{-}Ad$. The first regime, namely region I, is that with high adhesion strength and moderate particle stiffness; the other one, region II, has moderate adhesion strength and large particle stiffness. We conclude that the existence of optimal regimes is governed by the interplay of particle deformability and adhesion strength. The corresponding underlying mechanism is also discussed in detail. There are three major factors that contribute to the localization of MPs: (i) near-wall hydrodynamic collision between RBCs and MPs; (ii) deformation-induced migration due to the presence of the wall; and (iii) adhesive interaction between MPs and the wall. Mechanisms (i) and (iii) promote margination, while (ii) hampers margination. These three factors perform different roles and compete against each other when MPs are located in different regions of the flow channel, i.e. near-wall region. In optimal region I, adhesion outperforms deformation-induced migration; and in region II, the deformation-induced migration is small compared to the coupling of near-wall hydrodynamic collision and adhesion. The finding of optimal regimes can help the understanding of localization of elastic MPs at the wall under the adhesion effect in blood flow. More importantly, our results suggest that softer MP or stronger adhesion is not always the best choice for the localization of MPs.
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Filipovic, N., M. Kojic, and A. Tsuda. "Modelling thrombosis using dissipative particle dynamics method." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1879 (July 2008): 3265–79. http://dx.doi.org/10.1098/rsta.2008.0097.
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Aim . Arterial occlusion is a leading cause of cardiovascular disease. The main mechanism causing vessel occlusion is thrombus formation, which may be initiated by the activation of platelets. The focus of this study is on the mechanical aspects of platelet-mediated thrombosis which includes the motion, collision, adhesion and aggregation of activated platelets in the blood. A review of the existing continuum-based models is given. A mechanical model of platelet accumulation onto the vessel wall is developed using the dissipative particle dynamics (DPD) method in which the blood (i.e. colloidal-composed medium) is treated as a group of mesoscale particles interacting through conservative, dissipative, attractive and random forces. Methods . Colloidal fluid components (plasma and platelets) are discretized by mesoscopic (micrometre-size) particles that move according to Newton's law. The size of each mesoscopic particle is small enough to allow tracking of each constituent of the colloidal fluid, but significantly larger than the size of atoms such that, in contrast to the molecular dynamics approach, detailed atomic level analysis is not required. Results . To test this model, we simulated the deposition of platelets onto the wall of an expanded tube and compared our computed results with the experimental data of Karino et al . ( Miscrovasc. Res. 17 , 238–269, 1977). By matching our simulations to the experimental results, the platelet aggregation/adhesion binding force (characterized by an effective spring constant) was determined and found to be within a physiologically reasonable range. Conclusion . Our results suggest that the DPD method offers a promising new approach to the modelling of platelet-mediated thrombosis. The DPD model includes interaction forces between platelets both when they are in the resting state (non-activated) and when they are activated, and therefore it can be extended to the analysis of kinetics of binding and other phenomena relevant to thrombosis.
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Mansoor, M. M., J. O. Marston, J. Uddin, G. Christopher, Z. Zhang, and S. T. Thoroddsen. "Cavitation structures formed during the collision of a sphere with an ultra-viscous wetted surface." Journal of Fluid Mechanics 796 (May 5, 2016): 473–515. http://dx.doi.org/10.1017/jfm.2016.229.
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We investigate the inception of cavitation and resulting structures when a sphere collides with a solid surface covered with a layer of non-Newtonian liquid having a kinematic viscosity of up to ${\it\nu}_{0}=20\,000\,000$ cSt. We show the existence of shear-stress-induced cavitation during sphere approach towards the base wall (i.e. the pressurization stage) in ultra-viscous films using a synchronized dual-view high-speed imaging system. For the experimental parameters employed, liquids having viscoelastic properties of $De\geqslant O(1)$ are shown to enable sphere rebound without any prior contact with the solid wall. Cavitation by depressurization (i.e. during rebound) in such non-contact cases is observed to onset after a noticeable delay from when the minimum gap distance is reached. Also, the cavities created originate from remnant bubbles, being the remains of the primary bubble entrapment formed by the lubrication pressure of the air during film entry. Cases where physical contact occurs (contact cases) in 10 000 cSt ${\leqslant}{\it\nu}_{0}\leqslant 1000\,000$ cSt films produce cavities attached to the base wall, which extend into an hourglass shape. In contrast, strikingly different structures occur in the most viscous liquids due to the disproportionality in radial expansion and longitudinal extension along the cavity length. Horizontal shear rates calculated using particle image velocimetry (PIV) measurements show the apparent fluid viscosity to vary substantially as the sphere approaches and rebounds away from the base wall. A theoretical model based on the lubrication assumption is solved for the squeeze flow in the regime identified for shear-induced cavity events, to investigate the criterion for cavity inception in further detail.
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Shi, Ruifang, Jianzhong Lin, Hailin Yang, and Mingzhou Yu. "Distribution of non-spherical nanoparticles in turbulent flow of ventilation chamber considering fluctuating particle number density." Applied Mathematics and Mechanics 42, no. 3 (February 11, 2021): 317–30. http://dx.doi.org/10.1007/s10483-021-2707-8.
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AbstractThe Reynolds-averaged general dynamic equation (RAGDE) for the nanoparticle size distribution function is derived, including the contribution to particle coagulation resulting from the fluctuating concentration. The equation together with that of a turbulent gas flow is solved numerically in the turbulent flow of a ventilation chamber with a jet on the wall based on the proposed model relating the fluctuating coagulation to the gradient of mean concentration. Some results are compared with the experimental data. The results show that the proposed model relating the fluctuating coagulation to the gradient of mean concentration is reasonable, and it is necessary to consider the contribution to coagulation resulting from the fluctuating concentration in such a flow. The changes of the particle number concentration M0 and the geometric mean diameter dg are more obvious in the core area of the jet, but less obvious in other areas. With the increase in the initial particle number concentration m00, the values of M0 and the standard deviation of the particle size σ decrease, but the value of dg increases. The decrease in the initial particle diameter leads to the reduction of M0 and σ, and the increase in dg. With the increase in the Reynolds number, particles have few chances of collision, and hence the coagulation rate is reduced, leading to the increase in M0 and σ, and the decrease in dg.
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Li, Liqun, Yichen Huang, Chunyu Zou, and Wang Tao. "Numerical Study on Powder Stream Characteristics of Coaxial Laser Metal Deposition Nozzle." Crystals 11, no. 3 (March 12, 2021): 282. http://dx.doi.org/10.3390/cryst11030282.
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A 3D model was established to accurately simulate the internal and external powder stream characteristics of the coaxial discrete three-beam nozzle for laser metal deposition. A k-ε turbulence model was applied in the gas flow phase, and powder flow was coupled to the gas flow by a Euler-Lagrange approach as a discrete phase model. The simulated powder stream morphology was in good agreement with the experimental results of CCD and high-speed camera imaging. The simulation results showed that the length, diameter and shrinkage angle of the powder passage in the nozzle have different effects on the velocity and convergence characteristics of the powder stream. The influence of different particle size distribution and the inner laser shielding gas on the powder stream were also discussed in this study. By analyzing the powder stream caused by different incident directions of powder passage, and the collision process between powder and the inner wall, the basic principle of controlling powder stream convergence was obtained.
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Ji, Shi Ming, J. Q. Zhong, Da Peng Tan, and Y. W. Chi. "Research of Distribution and Dynamic Characteristic of Particle Group in the Structural Flow Passage." Key Engineering Materials 499 (January 2012): 271–76. http://dx.doi.org/10.4028/www.scientific.net/kem.499.271.
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Because of the liquid phase’s driving action, particles would be collided the surface and impacted with each other in the flow passage, the surface will be machined though the continuous action of impact force and friction force. The finishing results of structural surface is related to the collision frequency and the pressure, abrasion situation in different area of the structural surface can be analyzed obviously by investigating dynamic characteristic and distribution of particle group. Based on coupled wave theory of liquid-solid two phases flow, using mixture model which belongs to Euler-Euler multiphase flow model and realizable turbulence model, turbulence effects of liquid-solid two-phase flow in the wall is numerical simulated and some parameters such as turbulent velocity and turbulent energy are calculated with different particles concentration in the flow passage which has V-shaped texture and semicircular cross-section. The simulation results show that the disorder degree of turbulence can be improved by assembling V-shaped constrained component, because V-shaped passage is benefit of eddy current’s generation. As the concentration of particles being enhanced, the velocity of particle would be increased in a certain range, turbulence energy reduces gradually, fluctuation margin of particle volume fraction is smaller and smaller, and curves of every kind of parameters change as continuous oscillation, area of surface corresponded with crest of the curve. The concentration of particles should be selected properly and different particles distribution and finishing performance would be obtained with different particles concentration.
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Aretxabaleta, Xabier M., Marina Gonchenko, Nathan L. Harshman, Steven Glenn Jackson, Maxim Olshanii, and Grigory E. Astrakharchik. "The Dynamics of Digits: Calculating Pi with Galperin’s Billiards." Mathematics 8, no. 4 (April 2, 2020): 509. http://dx.doi.org/10.3390/math8040509.
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In Galperin billiards, two balls colliding with a hard wall form an analog calculator for the digits of the number π . This classical, one-dimensional three-body system (counting the hard wall) calculates the digits of π in a base determined by the ratio of the masses of the two particles. This base can be any integer, but it can also be an irrational number, or even the base can be π itself. This article reviews previous results for Galperin billiards and then pushes these results farther. We provide a complete explicit solution for the balls’ positions and velocities as a function of the collision number and time. We demonstrate that Galperin billiard can be mapped onto a two-particle Calogero-type model. We identify a second dynamical invariant for any mass ratio that provides integrability for the system, and for a sequence of specific mass ratios we identify a third dynamical invariant that establishes superintegrability. Integrability allows us to derive some new exact results for trajectories, and we apply these solutions to analyze the systematic errors that occur in calculating the digits of π with Galperin billiards, including curious cases with irrational number bases.
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Zhao, Wandong, Ying Zhang, Wenqiang Shang, Zhaotai Wang, Ben Xu, and Shuisheng Jiang. "Simulation of droplet impacting a square solid obstacle in microchannel with different wettability by using high density ratio pseudopotential multiple-relaxation-time (MRT) lattice Boltzmann method (LBM)." Canadian Journal of Physics 97, no. 1 (January 2019): 93–113. http://dx.doi.org/10.1139/cjp-2018-0126.
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In this paper, a pseudopotential high density ratio (DR) lattice Boltzmann model was developed by incorporating multi-relaxation-time collision matrix, large DR external force term, surface tension adjustment external force term, and solid–liquid pseudopotential force. It was found that the improved model can precisely capture the two-phase interface at high DR. Besides, the effects of initial Reynolds number, Weber number, solid wall contact angle (CA), ratio of obstacle size to droplet diameter (χ1), and ratio of channel width to droplet diameter (χ2) on the deformation and breakup of a droplet when impacting on a square obstacle were investigated. The results showed that with the Reynolds number increasing, the droplet will fall along the obstacle and then spread along both sides of the obstacle. Furthermore, by increasing Weber number, the breakup of the liquid film will be delayed and the liquid film will be stretched to form an elongated ligament. With decreasing of the wettability of solid particle (CA → 180°), the droplet will surround the obstacle and then detach from the obstacle. When χ1 is greater than 0.5, the droplet will spread along both sides of the obstacle quickly; otherwise, the droplet will be ruptured earlier. Furthermore, when χ2 decreases, the droplet will spread earlier and then fall along the wall more quickly; otherwise, the droplet will expand along both sides of the obstacle. Moreover, increasing the hydrophilicity of the microchannel, the droplet will impact the channel more rapidly and infiltrate the wall along the upstream and downstream simultaneously; on the contrary, the droplet will wet downstream only.
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KELBALIEV, Gudrat Isfandiyar ogly, Sakit Rauf ogly RASULOV, and Niyaz Gadym ogly VALIEV. "Mathematical modeling of sedimentation processes and surfacing of solids, droplets and bubbles in an isotropic turbulent flow." NEWS of the Ural State Mining University, no. 4 (December 20, 2020): 123–45. http://dx.doi.org/10.21440/2307-2091-2020-4-123-145.
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Relevance. The problems of separation, stratification and classification of disperse systems that constitute the base of sedimentation and phase displacement are determined by hydrodynamic structure and direction of the flow, physical interaction of forces of different nature of the systems, diffusion transport and deposition in turbulent flows, physical and chemical properties of the particles themselves and the carrier medium and many other factors. Appears the necessity of development of the model of solid spherical particles deposition from a volume with small values of number Re under the condition of absence of effects of interaction of particles and model of constrained deposition from the concentrated disperse flow. The consideration of expressions for determination of effective viscosity of the dispersed system taking into account the concentration of particles in the flow and models of particle deposition from isotropic turbulent flow taking into account the scale of turbulence and specific energy of dissipation. This, in turn, is associated with the determination of the coefficient of resistance for deformable particles (droplets and bubbles), which is used in the model of deposition velocity and surfacing of droplets and bubbles for different numbers of Weber and Morton. Purpose of work. The purpose of this study is an analytical review of all kinds of sedimentation (deposition), separation and stratification of dispersed systems and model representations of their description in different flow conditions. Methodology. To solve given problem, it is necessary to analyze all the effects associated with particle migration, deposition and separation. An essential role in deposition and migration is determined by the forces of resistance, which depend on the number of Reynolds, shape and size, as well as physical and chemical properties of the particles and the corresponding environment. Results. The study of particle deposition in an isotropic turbulent flow for different scales of turbulence in pipes and channels allowed to express the deposition rate through the main parameters of turbulence – specific energy dissipation, scale of turbulence and viscosity of the medium. The deposition and formation of a dense layer of particles on the inner surface of the pipes has a significant influence on all parameters of substance transfer (mass, heat and pulse) and on hydrodynamic stability of the flow. It has been found that the deposition of polydisperse particles is characterized by the size inconstancy or the function of their size distribution, which is related to the confinement of deposition, collision and interaction of particles among themselves. Conclusions. It is concluded that the nature of deposition of particles from the polydisperse turbulent flow is significantly different from their free deposition from the volume. As the result of dispersed particle deposition on the walls of pipes and canals, the following mechanisms and models are distinguished: free-inertial, which is based on the principle of free inertial ejection of particles to the wall; elevating-migration, which binds the deposition of particles with their elevating migration (Magnus effect); convection-inertial, which binds the deposition rate of particles with inertial effects; efficient-diffusion; turbulent-migration, where turbulent migration of particles to the wall is considered as the driving force of deposition. Particle deposition and formation of a dense layer of particles on the inner surface of the pipes has a significant impact on the hydrodynamic flow and heat-mass transfer. Particle deposition and formation of a dense layer of particles on the inner surface of the pipes has a significant impact on the hydrodynamics of the flow and heat and mass transfer. All proposed models are compared with available experimental data, which confirms their effectiveness and adequacy.
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Bhonsale, Satyajeet, Lewis Scott, Mojtaba Ghadiri, and Jan Van Impe. "Numerical Simulation of Particle Dynamics in a Spiral Jet Mill via Coupled CFD-DEM." Pharmaceutics 13, no. 7 (June 23, 2021): 937. http://dx.doi.org/10.3390/pharmaceutics13070937.
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Spiral jet mills are ubiquitous in the pharmaceutical industry. Breakage and classification in spiral jet mills occur due to complex interactions between the fluid and the solid phases. The study of these interactions requires the use of computational fluid dynamics (CFD) for the fluid phase coupled with discrete element models (DEM) for the particle phase. In this study, we investigate particle dynamics in a 50-mm spiral jet mill through coupled CFD-DEM simulations. The simulations showed that the fluid was significantly decelerated by the presence of the particles in the milling chamber. Furthermore, we study the particle dynamics and collision statistics at two different operating conditions and three different particle loadings. As expected, the particle velocity was affected by both the particle loading and operating pressure. The particles moved slower at low pressures and high loadings. We also found that particle–particle collisions outnumbered particle–wall collisions.
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DE ALCANTARA BONFIM, O. F. "FERMI ACCELERATION IN A PERIODICALLY DRIVEN FERMI–ULAM MODEL." International Journal of Bifurcation and Chaos 22, no. 06 (June 2012): 1250140. http://dx.doi.org/10.1142/s0218127412501404.
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The dynamics of a particle bouncing between two harmonically vibrating walls is analyzed in the context of the static wall approximation. Fermi acceleration is observed for a wide range of the ratio between the frequencies of the oscillating walls and their relative phases. However, no acceleration is observed if the frequency ratio is an integer. In the phase versus frequency-ratio diagram, the region in which Fermi acceleration is observed is separated by an upper and lower boundary. At the lower boundary, after a large number of collisions, the particle average velocity increases with the square-root of the number of collisions (n) with the walls. Between the lower and upper boundaries, the particle average velocity behaves as V(n) ~ nβ, with β in the interval [0.5, 1.0]. Below and near the lower boundary, the average particle velocity initially grows with the number of collisions until it eventually reaches a plateau. In this region, for a fixed frequency ratio, the velocity of the particle exhibits scaling properties over a range of the relative phases of the vibrating walls. Inelastic collisions with the walls cause suppression of the Fermi acceleration inside the previously accelerating region and lead to the particle velocity exhibiting scaling properties with respect to changes in the coefficient of restitution.
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Kumar, Amit, Rafael G. Henríquez Rivera, and Michael D. Graham. "Flow-induced segregation in confined multicomponent suspensions: effects of particle size and rigidity." Journal of Fluid Mechanics 738 (December 13, 2013): 423–62. http://dx.doi.org/10.1017/jfm.2013.592.
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AbstractThe effects of particle size and rigidity on segregation behaviour in confined simple shear flow of binary suspensions of fluid-filled elastic capsules are investigated in a model system that resembles blood. We study this problem with direct simulations as well as with a master equation model that incorporates two key sources of wall-normal particle transport: wall-induced migration and hydrodynamic pair collisions. The simulation results indicate that, in a mixture of large and small particles with equal capillary numbers, the small particles marginate, while the large particles antimarginate in their respective dilute suspensions. Here margination refers to localization of particles near walls, while antimargination refers to the opposite. In a mixture of particles with equal size and unequal capillary number, the stiffer particles marginate while the flexible particles antimarginate. The master equation model traces the origins of the segregation behaviour to the size and rigidity dependence of the wall-induced migration velocity and of the cross-stream particle displacements in various types of collisions. In particular, segregation by rigidity, especially at low volume fractions, is driven in large part by heterogeneous collisions, in which the stiff particle undergoes larger displacement. In contrast, segregation by size is driven mostly by the larger wall-induced migration velocity of larger particles. Additionally, a non-local drift-diffusion equation is derived from the master equation model, which provides further insights into the segregation behaviour.
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Devenish, B. J., D. C. Swailes, Y. A. Sergeev, and V. N. Kurdyumov. "A PDF model for dispersed particles with inelastic particle–wall collisions." Physics of Fluids 11, no. 7 (July 1999): 1858–68. http://dx.doi.org/10.1063/1.870048.
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Stefanovic, Predrag, Dejan Cvetinovic, Goran Zivkovic, Simeon Oka, and Pavle Pavlovic. "Numerical modeling of disperse material evaporation in axisymmetric thermal plasma reactor." Thermal Science 7, no. 1 (2003): 63–99. http://dx.doi.org/10.2298/tsci0301063s.
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A numerical 3D Euler-Lagrangian stochastic-deterministic (LSD) model of two-phase flow laden with solid particles was developed. The model includes the relevant physical effects, namely phase interaction, panicle dispersion by turbulence, lift forces, particle-particle collisions, particle-wall collisions, heat and mass transfer between phases, melting and evaporation of particles, vapour diffusion in the gas flow. It was applied to simulate the processes in thermal plasma reactors, designed for the production of the ceramic powders. Paper presents results of extensive numerical simulation provided (a) to determine critical mechanism of interphase heat and mass transfer in plasma flows, (b) to show relative influence of some plasma reactor parameters on solid precursor evaporation efficiency: 1 - inlet plasma temperature, 2 - inlet plasma velocity, 3 - particle initial diameter, 4 - particle injection angle a, and 5 - reactor wall temperature, (c) to analyze the possibilities for high evaporation efficiency of different starting solid precursors (Si, Al, Ti, and B2O3 powder), and (d) to compare different plasma reactor configurations in conjunction with disperse material evaporation efficiency.
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Sheikh Mamoo, Mohammad, Ataallah Soltani Goharrizi, and Bahador Abolpour. "CFD SIMULATION OF EROSION BY PARTICLE COLLISION IN U-BEND AND HELICAL TYPE PIPES." Journal of the Serbian Society for Computational Mechanics 14, no. 2 (December 30, 2020): 1–13. http://dx.doi.org/10.24874/jsscm.2020.14.02.01.
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Erosion caused by solid particles in curve pipes is one of the major concerns in the oil and gas industries. Small solid particles flow with a carrier liquid fluid and impact the inner wall of the piping, valves, and other equipment. These components face a high risk of solid particle erosion due to the constant collision, which may result in equipment malfunctioning and even failure. In this study, the two-way coupled Eulerian-Lagrangian method with the Oka erosion and Grant and Tabakoff particle-wall rebound models approach is employed to simulate the liquid-solid flow in U-bend and helical pipes using computational fluid dynamics. The effects of operating parameters (inlet fluid velocity and temperature, particle density and diameter, and mass flow rate) and design parameters (mean curvature radius/pipe diameter ratio) are investigated on the erosion of these tubes walls. It is obtained that increasing the fluid velocity and temperature, particle mass flow and particle density increase the penetration rate, particle diameter affects the rate of penetration, and increasing mean curvature radius/pipe diameter ratio decreases the rate of penetration.
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Ray, M., F. Chowdhury, A. Sowinski, P. Mehrani, and A. Passalacqua. "An Euler-Euler model for mono-dispersed gas-particle flows incorporating electrostatic charging due to particle-wall and particle-particle collisions." Chemical Engineering Science 197 (April 2019): 327–44. http://dx.doi.org/10.1016/j.ces.2018.12.028.
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Burnard, David J., and William D. Griffiths. "A Model of Inclusion Behaviour in Liquid Aluminium." Materials Science Forum 765 (July 2013): 92–96. http://dx.doi.org/10.4028/www.scientific.net/msf.765.92.
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Inclusions in castings are particularly damaging as crack initiators, causing failure in service. It is therefore desirable to attempt to remove them prior to their entry into the casting. In this work the behaviour of inclusions was studied using a computer simulation to predict the movement of particles in flowing liquid metal. The computer simulation was created by a combination of Computational Fluid Dynamics (CFD) and Discrete Element Modelling (DEM), to try to predict the agglomeration characteristics of inclusions in liquid Al alloy in a launder system. The model was tailored to simulate dispersed particles in a fluid, where particle collisions with each other and with side walls are significant. The launder model had a wall or baffle placed along its length to investigate its effect on trapping inclusions, results from the model showing particle distribution.
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CROIZET, C., and R. GATIGNOL. "BOLTZMANN-LIKE MODELLING OF A SUSPENSION." Mathematical Models and Methods in Applied Sciences 12, no. 07 (July 2002): 943–64. http://dx.doi.org/10.1142/s0218202502001970.
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This paper deals with the presentation of a kinetic model for a suspension of identical hard spheres. Considering that the collisions between particles are instantaneous, binary, inelastic and taking the diameter of the spheres into account, a Boltzmann equation for the dispersed phase is proposed. It allows one to obtain the conservation of mass and momentum as well as, for slightly inelastic collisions, an H-theorem which conveys the irreversibility of the evolution. The problem of the boundary conditions for the Boltzmann equation is then introduced. From an anisotropic law of rebound characterizing the inelastic and non-punctual impact of a particle to the wall, a parietal behavior for the first moments of the kinetic equation is deduced.
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Zhao, Rui-Jie, You-Long Zhao, De-Sheng Zhang, Yan Li, and Lin-Lin Geng. "Numerical Investigation of the Characteristics of Erosion in a Centrifugal Pump for Transporting Dilute Particle-Laden Flows." Journal of Marine Science and Engineering 9, no. 9 (September 3, 2021): 961. http://dx.doi.org/10.3390/jmse9090961.
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Erosion in centrifugal pumps for transporting flows with dilute particles is a main pump failure problem in many engineering processes. A numerical model combining the computational fluid dynamics (CFD) and Discrete Element Method (DEM) is applied to simulate erosion in a centrifugal pump. Different models of the liquid-solid inter-phase forces are implemented, and the particle-turbulence interaction is also defined. The inertial particles considered in this work are monodisperse and have finite size. The numerical results are validated by comparing the results with a series of experimental data. Then, the effects of particle volume fraction, size, and shape on the pump erosion are estimated in the simulations. The results demonstrate that severe erosive areas are located near the inlet and outlet of the pressure side of the impeller blade, the middle region of the blade, the corners of the shroud and hub of the impeller adjoining to the pressure side of the blade, and the volute near the pump tongue. Among these locations, the maximum erosion occurs near the inlet of the pressure side of the blade. Erosion mitigation occurs under the situation where more particles accumulate in the near-wall region of the eroded surface, forming a buffering layer. The relationship between the particle size and the erosion is nonlinear, and the 1 mm particle causes the maximum pump erosion. The sharp particles cause more severe erosion in the pump because both the frequency of particle-wall collisions and the impact angle increase with the increasing sharpness of the particle.
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Fan, Jinchao, Benchun Yao, Yi Hao, Shimin Zhang, and Xiaoxiao Zhu. "Numerical Simulation of Slurry flow in horizontal pipe based on CFD-DEM." MATEC Web of Conferences 306 (2020): 01007. http://dx.doi.org/10.1051/matecconf/202030601007.
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In this paper, we propose a novel pipeline cleaning method utilizing slurry. The reason why slurry can be used for pipeline cleaning is that the collisions between the particles and the contaminant in the pipe wall can enhance the cleaning effect. A slurry with polypropylene particles embedded in water is used to cleaning a horizontal pipe is conducted to realize this method. Because the flow characteristics of the slurry is crucial for the cleaning process, it is valuable to conduct a simulation and investigate the influence of several different factors including the convey velocity and the particle size. A 3D CFD-DEM model has been established. The indicators including pressure loss, particle accumulation level at the top of the pipe are choses to characterize the slurry flow and the influence of convey velocity and particle size has been investigated accordingly. In addition, an effective method is proposed to determine the critical convey velocity for each size of the particle.
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Panelli, Mario, Davide Morfei, Beniamino Milo, Francesco D’Aniello, and Francesco Battista. "Axisymmetric Hybrid Plasma Model for Hall Effect Thrusters." Particles 4, no. 2 (June 18, 2021): 296–324. http://dx.doi.org/10.3390/particles4020026.
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Hall Effect Thrusters (HETs) are nowadays widely used for satellite applications because of their efficiency and robustness compared to other electric propulsion devices. Computational modelling of plasma in HETs is interesting for several reasons: it can be used to predict thrusters’ operative life; moreover, it provides a better understanding of the physical behaviour of this device and can be used to optimize the next generation of thrusters. In this work, the discharge within the accelerating channel and near-plume of HETs has been modelled by means of an axisymmetric hybrid approach: a set of fluid equations for electrons has been solved to get electron temperatures, plasma potential and the discharge current, whereas a Particle-In-Cell (PIC) sub-model has been developed to capture the behaviour of neutrals and ions. A two-region electron mobility model has been incorporated. It includes electron–neutral/ion collisions and uses empirical constants, that vary as a continuous function of axial coordinates, to take into account electron–wall collisions and Bohm diffusion/SEE effects. An SPT-100 thruster has been selected for the verification of the model because of the availability of reliable numerical and experimental data. The results of the presented simulations show that the code is able to describe plasma discharge reproducing, with consistency, the physics within the accelerating channel of HETs. A small discrepancy in the experimental magnitude of ions’ expansion, due probably to boundary condition effects, has been found.
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Timmermans, C. J., R. J. Rosado, and D. C. Schram. "An Investigation of Non-Equilibrium Effects in Thermal Argon Plasmas." Zeitschrift für Naturforschung A 40, no. 8 (August 1, 1985): 810–25. http://dx.doi.org/10.1515/zna-1985-0804.
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The parameters and transport properties of a wall stabilized argon arc (40-200 A) at atmospheric pressure with diameters of 5 and 8 mm are studied by spectroscopy and interferometry. The plasma is assumed to be partial local thermal equilibrium and this assumption is verified with the aid of a collisional-radiative model. The departures from Saha-equilibrium of the argon neutral ground state are found to be associated with particle diffusion and the escape of recombination radiation. The measurement of the total excitation rate, from the ground level, including direct ionization, of neutral argon is in reasonable agreement with the literature value.
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Sun, Baojiang, Hengfu Xiang, Hao Li, and Xiangfang Li. "Modeling of the Critical Deposition Velocity of Cuttings in an Inclined-Slimhole Annulus." SPE Journal 22, no. 04 (February 6, 2017): 1213–24. http://dx.doi.org/10.2118/185168-pa.
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Summary A coupled computational-fluid-dynamics/discrete-element-method (CFD/DEM) theory is developed to simulate the transportation of cuttings in an inclined-slimhole annulus. In this theory, the liquid phase is governed by the Eulerian continuum equation and the Navier-Stokes momentum-conservation equation. The collisions between particle and wall, between particle and drillstring, and among particles are treated as the spring-damping system, and the particle-contact model is then established. The particle-governing equation based on Newton's second law is established by analyzing the forces on the particles. The CFD/DEM theory is developed by analyzing the forces on the dispersed particles per unit volume, which is the source term in the coupling. Using this CFD/DEM coupling algorithm, cuttings transportation in slimhole drilling is investigated, and the particle velocity and distributions are calculated. The calculated annular cuttings concentration is in good agreement with experimental data from the literature (Kim et al. 2014). The effects of the annular-fluid velocity, angle of inclination, cuttings concentration in feeding, and rotation speed of the drillstring on the annular cuttings concentration are also investigated. A correlation of critical deposition velocity has been proposed by use of dimensional analysis and nonlinear regression analysis. The correlation of annular cuttings concentration is also concluded. The new method proposed in this work is of great significance to hole-cleaning calculation and hydraulic-parameter design in slimhole drilling.