Modeling the deformation and breakup of a surfactant-coated droplet on a roughness solid surface in shear flow

Abstract

A surfactant-coated droplet attached to a rough wall subjected to shear flow is investigated using a coupled lattice Boltzmann with the finite difference method, where a contact angle hysteresis model is introduced into the method to characterize the surface roughness. The method is first verified by the equilibrium contact angle of a semi-circular droplet setting on the bottom plane. It is then adopted to explore the surfactant role on the droplet motion and deformation on a rough wall with two representative hysteresis windows. For the hysteresis window of (0°, 180°), i.e., the contact line remains pinned, the addition of surfactants first promotes droplet deformation and then hinders droplet deformation with increasing effective capillary number. However, for the hysteresis window of (70°, 110°), the addition of surfactants always promotes droplet motion and deformation. Finally, the surfactant role on droplet breakup is presented. For the hysteresis window of (0°, 180°), the addition of surfactants hinders droplet breakup. However, for the hysteresis window of (70°, 110°), the addition of surfactants promotes droplet breakup.

Mouth breathing, dry air, and low water permeation promote inflammation, and activate neural pathways, by osmotic stresses acting on airway lining mucus

“…Here, α B is a dimensional airway constant (cm 2 mg −1 ) that can be directly determined as described below from published data of ATP secretion following the compression of ciliated epithelial cells in vitro (Button et al , 2013 ). Similar first-order approximate relationships can be expressed for diminution of cilia beat frequency (CBF) and elevation of exhaled breath particles (EBPs) 3 (Edwards et al , 1991 ; Lucassen-Reynders, 1993 ; Deng et al , 2022 ) (see the ).…”

The dynamic behavior of a droplet flows through a constricted splitting channel: a lattice Boltzmann study

“…In this method, the multiple-relaxation-time (MRT) lattice Boltzmann (LB) color-gradient model (Deng et al 2022) is adopted to simulate the immiscible two-phase flows. The wetting boundary condition reported by Xu et al (2017) is adopted to simulate the interaction between the fluid-fluid interface and arbitrary complex geometric walls.…”

“…We adopt the two-dimensional nine-velocity (D2Q9) LB color-gradient model (Deng et al 2022) to simulate the immiscible two-phase flows. The red and blue fluids represent the twophase fluids, and their distribution functions are denoted by f R i and f B i , where the subscript 'i' represents the ith velocity direction.…”

“…The wetting boundary condition adopted in our recently work (Deng et al 2022) is only suitable for the straight wall, it is therefore necessary to adopt a wetting boundary condition applicable to any complex wall. In this work, we adopt the wetting boundary condition suggested by Leclaire et al (2016) and subsequently modified by Xu et al (2017).…”