Hydrodynamic interactions suppress deformation of suspension drops in Poiseuille flow

Abstract

Evolution of a suspension drop entrained by Poiseuille flow is studied numerically at a low Reynolds number. A suspension drop is modelled by a cloud of many non-touching particles, initially randomly distributed inside a spherical volume of a viscous fluid which is identical to the host fluid outside the drop. Evolution of particle positions and velocities is evaluated by the accurate multipole method corrected for lubrication, implemented in the hydromultipole numerical code. Deformation of the drop is shown to be smaller for a larger volume fraction. At high concentrations, hydrodynamic interactions between close particles significantly decrease elongation of the suspension drop along the flow in comparison to the corresponding elongation of the pure-fluid drop. Owing to hydrodynamic interactions, the particles inside a dense-suspension drop tend to stay for a long time together in the central part of the drop; later on, small clusters occasionally separate out from the drop, and are stabilized by quasi-periodic orbits of the constituent non-touching particles. Both effects significantly reduces the drop spreading along the flow. At large volume fractions, suspension drops destabilize by fragmentation, and at low volume fractions, by dispersing into single particles.

Hydrodynamic segregation in a bidisperse colloidal suspension in microchannel flow: A theoretical study

“…Only physical features, which are not included in the Stokes equations, such as direct particle-particle contacts due to surface roughness, 20 thermal motion, or residual inertia [21][22][23] can break the kinematic reversibility and induce cross-streamline migration in dense suspensions. But also, deformable objects such as a semiflexible polymers, [24][25][26][27] emulsion droplets, 28,29 and red blood cells [30][31][32] show cross-streamline migration. A recent experiment by Pine et al 33 demonstrates violation of kinematic reversibility for a particle suspension in an oscillating Couette device above a threshold value for density and amplitude.…”

Axial dispersion of suspended sediments in vertical upward pipe flow

“…This expected dependency on solids volume fraction is not present for dissolved matter. Sadlej et al (2010) used numerical simulations of particle drops in a Poiseuille flow at low Reynolds numbers to show how hydrodynamic interactions influence the axial dispersion of the particle drops. The simulations show that the larger the initial volume fraction, the smaller the axial dispersion, with approximately a factor two difference in axial dispersion between the c v ¼ 5% case and the c v ¼ 50% case.…”

Lung Deposition Analyses of Inhaled Toxic Aerosols in Conventional and Less Harmful Cigarette Smoke: A Review

“…A “cloud” is defined as a very larger number of particles surrounded by clear fluid [112,113,114,115,116,117,118,119,120,121,122,123,124,125,126]. A cloud of droplets can be treated as a single droplet ( i.e.…”

“…As shown in Figure 6(a)–(d), the general cloud evolution during, say, sedimentation can be separated into four phases [122,123,124,125,126,127,128,129]: The initial acceleration phase: the cloud accelerate to its maximum velocity, during which the particles circulate in a toroidal vortex (Hill’s vortex) inside the cloud, in a manner similar to the heavy fluid inside a droplet descending in a lighter fluid. Chaotic fluctuations due to the particle-particle and particle-flow interactions will cause some particles to start cross the boundary of the closed surfaces (see Figure 6(a)).…”