336 research outputs found

    A Review on Contact and Collision Methods for Multi-body Hydrodynamic problems in Complex Flows

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    Modeling and direct numerical simulation of particle-laden flows have a tremendous variety of applications in science and engineering across a vast spectrum of scales from pollution dispersion in the atmosphere, to fluidization in the combustion process, to aerosol deposition in spray medication, along with many others. Due to their strongly nonlinear and multiscale nature, the above complex phenomena still raise a very steep challenge to the most computational methods. In this review, we provide comprehensive coverage of multibody hydrodynamic (MBH) problems focusing on particulate suspensions in complex fluidic systems that have been simulated using hybrid Eulerian-Lagrangian particulate flow models. Among these hybrid models, the Immersed Boundary-Lattice Boltzmann Method (IB-LBM) provides mathematically simple and computationally-efficient algorithms for solid-fluid hydrodynamic interactions in MBH simulations. This paper elaborates on the mathematical framework, applicability, and limitations of various 'simple to complex' representations of close-contact interparticle interactions and collision methods, including short-range inter-particle and particle-wall steric interactions, spring and lubrication forces, normal and oblique collisions, and mesoscale molecular models for deformable particle collisions based on hard-sphere and soft-sphere models in MBH models to simulate settling or flow of nonuniform particles of different geometric shapes and sizes in diverse fluidic systems.Comment: 37 pages, 12 Figure

    Size and thermal effects on sedimentation behaviors of two spheres

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    Gas-solid flows are commonly found in nature, as well as in industries. In such flows the size of the solid particles generally is not uniform. In addition, usually there is heat transfer between solid particles and gas flows. The hydrodynamics and heat transfer both make the behavior of gas-solid flows extremely complicated. In order to reveal these effects, in this paper three cases: (1) two isothermal, (2) two hot and (3) two cold spherical particles with various size ratios are investigated using lattice Boltzmann method-immersed boundary (LB-IB). It is observed that, for the first time, the tumbling duration of both two hot particles and two cold particles settling in vertical channel, is prolonged with size ratio increasing. The differences of threshold size ratio among the three cases are significant and the threshold size ratio of two hot particles is the largest one. Especially, it is found that heat transfer affects critically the interaction of two hot particles with low size ratios. In addition, against particle size ratio increasing, heat transfer effects on the interaction between two non-identical particles become weak

    Direct numerical simulations of particle sedimentation with heat transfer using the Lattice Boltzmann method

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    In most realistic gas–solid flow, the difference of particles’ temperature is significant. The heat transfer induced by temperature difference between particles will influence the behavior of gas–solid flow critically. In order to deepen our insights into this important topic, in this work three typical cases: (1) double hot particles, (2) double cold particles, and (3) one hot and one cold particle, are investigated with the aid of direct numerical simulation of the Lattice Boltzmann method. A comprehensive comparison is carried out between them and some new interesting phenomena are observed. Our results show that thermal convection between particles will influence their behaviors significantly

    Liquid fluidization with cylindrical particles : highly resolved simulations

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    Particle interaction with binary-fluid interfaces in the presence of wetting effects

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    In this paper, we present an Eulerian-Lagrangian methodology to simulate the interaction between a fluid-fluid interface and a solid particle in the presence of wetting effects. The target physical problem is represented by ternary phase systems in which a solid phase and a drop phase interact inside an incompressible Newtonian carrier fluid. The methodology is based on an Eulerian-Lagrangian approach that allows for the numerical solution of the Continuity and Navier-Stokes equations by using a pseudo-spectral method, whereas the drop phase is modelled by the Phase Field Method, in which a smooth transition layer represented by an hyperbolic function is considered both across the solid-fluid interface and across the drop-fluid interface. Finally, the solid phase is described in the form of a virtual force using the Direct Forcing Immersed Boundary approach. The properties of the immersed solid phase (including wetting effects), the deformability of the drops and the characteristics of the carrier fluid flow are the main controlling parameters. To simulate a ternary phase system, the solid phase is coupled to the binary-fluid phase by introducing a single well potential in the free-energy density functional, which can also control the solid surface wetting property. The capabilities of the methodology are proven by examining first 2D and 3D validation cases in which a solid particle is settling in a quiescent fluid. Then, the interaction of solid particles with a binary-fluid interface and the effects of surface wetting on the submergence of a quasi-buoyant body are discussed. Finally, the equilibrium configuration for a solid particle interacting with an equally-sized drop at different contact angles and the relative rotation of two solid particles bridged by a drop are examined in the case the interaction is induced by shear fluid flow deformations on the drop interface

    Shear thickening and history-dependent rheology of monodisperse suspensions with finite inertia via an immersed boundary lattice Boltzmann method

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    This the pre-print of an article submitted to International Journal of Multiphase Flow,Volume 125, April 2020, 103205. The final published version is available at http://dx.doi.org/10.1016/j.ijmultiphaseflow.2019.103205Three-dimensional direct numerical simulations of dense suspensions of monodisperse spherical particles in simple shear flow have been performed at particle Reynolds numbers between 0.1 and 0.6. The particles translate and rotate under the influence of the applied shear. The lattice Boltzmann method was used to solve the flow of the interstitial Newtonian liquid, and an immersed boundary method was used to enforce the no-slip boundary condition at the surface of each particle. Short range spring forces were applied between colliding particles over sub-grid scale distances to prevent overlap. We computed the relative apparent viscosity for solids volume fractions up to 38% for several shear rates and particle concentrations and discuss the effects of these variables on particle rotation and cluster formations. The apparent viscosities increase with increasing particle Reynolds number (shear thickening) and solids fraction. As long as the particle Reynolds number is low (0.1), the computed viscosities are in good agreement with experimental measurements, as well as theoretical and empirical equations. For higher Reynolds numbers, we find much higher viscosities, which we relate to slower particle rotation and clustering. Simulations with a sudden change in shear rate also reveal a history (or hysteresis) effect due to the formation of clusters. We quantify the changes in particle rotation and clustering as a function of the Reynolds number and volume fraction

    A numerical study of particle settling in power–law fluids using lattice – Boltzmann method

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    Sedimentation of individual particles immersed in non-Newtonian fluid is of great industrial interest. Specifically in the oil and gas industry, cuttings generated from the drilling process must be constantly removed in order to properly clean the drill bit region. Thus, cuttings sedimentation must be avoided so that additional complications such as drill blocking and an unwanted operational stop are avoided. In this way, the drilling fluid must be carefully designed so that the it can fulfill these and others specifications. Therefore, it is of great importance to understand the dynamics of particles sedimentation in drilling muds. In this work, a numerical solution for particle settling in a non-Newtonian fluid is presented. The problem consists of a 2D particle released from rest in a quiescent non-Newtonian media within a fixed container. The fluid viscous behavior is represented by a Power-low expression. The aim of the present work was to develop a program able to adequately represent particle motion immersed in Power-law fluid. Based on the literature review, the problem was solved via a direct force immersed boundary- lattice Boltzmann method and its implementation was done via FORTRAN programming language. The Power-law effect was incorporated in the code by means of the adaptive viscosity method. Through verification problems, it was shown that the developed program was able to satisfactorily represent the particle settling dynamics in Newtonian and Power-Law fluids. A parametric study was then performed varying the particle diameter, d, Power-law index, n and particle/fluid density ratio, ρr. In general, regardless of the d and ρr combination, an increase of shear-thinning behavior leads to higher settling velocities. Results were then written in dimensionless form in such a way that results for the generalized particle Reynolds number, Repl;T , and the drag coefficient, CD;T , experienced by the particle at its terminal velocity, are based only on the Power-law index and on the generalized Archimedes number Arpl.Fundação de Apoio à Educação, Pesquisa e Desenvolvimento Científico e Tecnológico da Universidade Tecnológica Federal do Paraná (FUNTEF-PR)Sedimentação de partículas imersas em fluidos não newtonianos é de grande interesse industrial. Especificamente na indústria de petróleo, os cascalhos oriundos do processo de perfuração da rocha devem ser constantemente removidos de forma a limpar adequadamente a região da broca. Sendo assim, a sedimentação de cascalhos deve ser evitada de forma que complicações adicionais como o bloqueio da broca e uma parada operacional não programada sejam evitadas. Dessa forma, as propriedades reológicas do fluido de perfuração devem ser cuidadosamente arranjadas para que o fluido possa cumprir essas, dentre outras, funções. Portanto, é de grande importância entender a dinâmica da sedimentação de partículas em fluidos de perfuração. Neste trabalho, uma solução numérica para investigação da sedimentação de partículas em fluidos não newtonianos foi proposta. O problema consiste em uma partícula 2D liberada a partir do repouso em um fluido não-newtoniano representado por uma expressão de lei de potência. O objetivo do presente trabalho foi desenvolver um programa capaz de representar adequadamente o movimento de partículas imersas em um fluido Power-law. Com base na revisão da literatura, o problema foi resolvido através do método lattice-Boltzmann acoplado ao método da fronteira imersa e sua implementação foi feita via linguagem FORTRAN. O efeito Power-law foi incorporado ao programa através do método da viscosidade adaptativa. Por meio de problemas de verificação, foi comprovado que o programa desenvolvido foi capaz de representar satisfatoriamente a dinâmica de sedimentação de partículas em fluidos Newtonianos e em fluidos Power-Law. Um estudo paramétrico foi então realizado variando o diâmetro das partículas, d, o índice de lei de potência, n e razão de densidades partícula / fluido, ρr. Em geral, independentemente da combinação de d e ρr, um aumento do comportamento pseudoplásico leva a maiores velocidades de sedimentação. Os resultados foram então escritos na forma adimensional, de tal forma que o número de Reynolds generalizado, Repl;T e o coeficiente de arrasto, CD;T , experimentados pela partícula em sua velocidade terminal , pudessem ser escritos em função de n e do número de Arquimedes generalizado, Arpl

    Suspension of flexible cylinders in laminar liquid flow

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