Numerical study on the sedimentation of single and multiple slippery particles in a Newtonian fluid

Abstract

The dynamics of a single or a group of slippery spheres settling under gravity in a Newtonian fluid is studied numerically. We focus particularly on the effect of particle surface slip on the sedimentation behavior. The flows containing moving slippery spheres are solved by a three-dimensional lattice Boltzmann model where a kinetic boundary condition is used to handle the slip phenomenon at the curved particle surface. The method is first validated by simulating the slip flow in a cylindrical tube, and the no-slip flows around one and two spheres settling in a container. The hydrodynamic behaviors of one, two and multiple slippery spheres settling under gravity are then investigated. The results for a single sphere show that the surface slip makes the sphere fall faster than a no-slip particle and the wall correction factor decreases as the level of particle-surface slip is increased, indicating a drag reduction caused by the slip condition. For two settling spheres, when the no-slip particle is placed below the slip one, the two spheres will enter into the kissing phase earlier; on the contrary, deploying the no-slip particle above the slip one, the DKT process does not occur beyond a critical slip level and initial gap distance. If the two spheres are both slippery, the settling dynamics are similar to the no-slip case, but the time duration of the kissing phase decreases. As for the sedimentation of multiple spheres, it is found that the initial geometric arrangement has a significant impact on the sedimentation behavior. In general, slippery spheres in a cluster will experience larger fluctuations in the vertical velocity and position in the accelerated-falling stage, and smaller fluctuations in the decelerated-falling stage.

Discrete fluidization of dense monodisperse emulsions in neutral wetting microchannels

“…We perform numerical simulations based on a two-species lattice Boltzmann (LB) model, with suitable pseudo-potential interactions. Recently, the LB method has become a very efficient and powerful simulation method for complex flows [29][30][31][32][33][34][35][36][37][38][39][40] . The LB equation takes the form [41][42][43][44] :…”

Numerical and experimental study of the motion of a sphere in a communicating vessel system subject to sloshing

“…Several authors appeal to the settling of a sphere as an initial validation for their fluid-structure interaction numerical schemes. [9][10][11]13,55,56 Following the analysis presented by Ref. 11, the settling of a spherical particle of radius 7.5 mm (rp) and density ρs = 1250 kg/m 3 is studied.…”

“…The embedded and immersed methods represent the contours of objects as nonconforming geometric entities inside the fluid discretization, i.e., the body boundaries cross the faces of the grid. 7,8 Embedded strategies can be combined with different numerical methods for solving the fluid flow, e.g., lattice Boltzmann methods [9][10][11] and Navier-Stokes classic solvers. [12][13][14][15] When a fluidfluid interface or a free surface appears, the flow solver has to be extended, e.g., via a level-set method 2,3 or a volume-of-fluid approach.…”

Numerical study on slip flow using the discrete unified gas-kinetic scheme

“…Numerical studies on slip boundaries have been developed for decades. Sbragaglia et al (2006), Toschi and Succi (2005), Succi (2002), Guo et al (2014, 2007a, 2007b, 2008a, 2011), Tao and Guo (2015), Tao et al (2016), Tao and Guo (2017) and Tao et al (2017) established the slip boundary model using the lattice Boltzmann method (LBM). However, their slip boundary models are not suitable for the liquid slip flow because the Knudsen number related to slip parameters cannot accurately describe the characteristics of liquid flow.…”