Collision statistics and settling velocity of inertial particles in homogeneous turbulence from high-resolution DNS under two-way momentum coupling

How does two-way coupling modify particle settling and the role of multiscale preferential sweeping?

“…It is worth emphasizing that we see this significant enhancement even for the low volume fraction considered in this study Φ v = 1.5 × 10 −5 , where the effect of 2WC on the global flow statistics is negligible (see tables 2 and 3). This suggests, in agreement with the previous studies of Bosse et al (2006), Monchaux & Dejoan (2017) and Rosa et al (2021), that in modelling atmospheric particle transport where Φ v is often small, the effects of 2WC on particle settling may not be negligible.…”

“…This potential justification is also hinted at in Maxey & Patel (2001). In addition to this potential justification, we also use this aforementioned method of enforcing a zero mean fluid velocity at each time step in order to be able to meaningfully compare our results with those of the previous studies by Bosse et al (2006), Monchaux & Dejoan (2017) and Rosa et al (2021).…”

“…2006; Dejoan 2011; Monchaux & Dejoan 2017; Rosa et al. 2021) have indeed shown that , implying . Experimental studies in the laboratory (Aliseda et al.…”

“…Moreover, many recent works (e.g. Rosa et al 2021) used high-order schemes for the interpolation of the fluid velocity at the particle position combined with low-order schemes for the computation of the coupling term. Since this introduces errors in the energy balance of the system (Sundaram & Collins 1996), we employ the same B-spline polynomial basis of degree 7 (that uses 8 points in each direction) for interpolation of the velocity field and computation of the coupling term C.…”

“…Finally, following previous works (Bosse et al 2006;Monchaux & Dejoan 2017;Rosa et al 2021), at each time step we set to zero the average fluid velocity in the direction of gravity. This is equivalent to applying a mean vertical pressure gradient (Bosse et al 2006;Monchaux & Dejoan 2017;Rosa et al 2021) without which the total kinetic energy in the flow would grow without bound due to the finite settling velocity of the particles continuously injecting kinetic energy into the flow. While introduced in Maxey & Patel (2001) and used for 2WC simulations by Bosse et al (2006) to remedy the numerical issue that arises for an unbounded flow, its physical validity could be called into question.…”