Exponential scaling in early-stage agglomeration of adhesive particles in turbulence

Abstract

We carry out direct numerical simulation together with an adhesive discrete element method calculation (DNS-DEM) to investigate agglomeration of particles in homogeneous isotropic turbulence (HIT). We report an exponential-form scaling for the size distribution of early-stage agglomerates, which is valid across a wide range of particle inertia and inter-particle adhesion values. Such scaling allows one to quantify the state of agglomeration using a single scale parameter. An agglomeration kernel is then constructed containing the information of agglomerate structures and the sticking probability. An explicit relationship between the sticking probability and microscale particle properties is also proposed based on the scaling analysis of the equation for head-on collisions. Our results extend Smoluchowski's theory to the condition of non-coalescing solid adhesive particles and can reproduce DNS-DEM results with a simple one-dimensional simulation.

Deagglomeration of cohesive particles by turbulence

“…Meanwhile, it has no noticeable change in the breakup time . This is not surprising as fluid torque acting on each particle , , is proportional to the dynamic viscosity , which is added to the right-hand side of (2.6) according to (Chen, Li & Marshall 2019) where is the fluid rotation rate vector. While such effects are known to be important for liquid–solid suspensions, the dynamic viscosity is typically two orders of magnitudes smaller in gas-solid flows.…”

“…The numerical implementation of JKR model is based on Chen et al. (2019). For both values of , the JKR model predicts a slightly larger rate of breakup than the DMT models ( versus 1523 for and 598 versus 570 for ), and the breakup times are in reasonable agreement for all cases ( versus 0 for and 220 versus 225 for ).…”

Collision-induced breakage of agglomerates in homogenous isotropic turbulence laden with adhesive particles

“…For solid micron particles immersed in turbulence, various complicated particle-scale interactions, such as van der Waals attraction (Israelachvili 2011; Chen, Li & Marshall 2019 a ), capillary force (Royer et al 2009) and electrostatic forces (Jones 2005; Steinpilz et al 2020), lead to the formation of agglomerates. On the other hand, breakage of agglomerates also happens due to the flow stress (Higashitani, Iimura & Sanda 2001; Bäbler, Morbidelli & Bałdyga 2008) and collisions of other particles (Liu & Hrenya 2018).…”

“…The kernel functions are further extended to reflect the influence of particle inertia, identifying the effect of preferential concentration (Squires & Eaton 1991; Saw et al 2008; Balachandar & Eaton 2010; Tagawa et al 2012) leading to an inhomogeneous particle distribution and sling or caustic effects (Falkovich, Fouxon & Stepanov 2002; Wilkinson, Mehlig & Bezuglyy 2006; Pumir & Wilkinson 2016) which cause inertial particles to collide with large velocity differences. Recent studies also suggest that complicated interparticle interactions, including elastic repulsion (Bec, Musacchio & Ray 2013; Voßkuhle et al 2013), electrostatic interactions (Lu et al 2010; Lu & Shaw 2015) and van der Waals adhesion (Kellogg et al 2017; Chen et al 2019 a ), give rise to non-trivial collision phenomenon that cannot be predicted from the ghost collision approximation, where particles can pass through each other without any modification to their trajectories.…”

Migration and agglomeration of adhesive microparticle suspensions in a pressure‐driven duct flow

“…Moreover, the mechanical properties of the particles, including mass density, elastic modulus, friction coefficient, and so on also play important roles in the interparticle collision and thus can influence the agglomeration. Most of the previous studies focus on the dynamic evolution of the agglomerates, include the size evolution, the fractal dimension, the collision efficiency, as well as the breakage . Experimental investigation on the detailed mechanism of agglomeration, especially for submicron particles, is still a challenging problem .…”