TUNING THE SPLITTING BEHAVIOR OF LOW-VISCOUS FINGER IN BIFURCATING NETWORK BY SURFACE WETTABILITY

Abstract

This article reports the splitting behavior of low-viscous fingers in a two-dimensional bifurcating network by varying the surface wettability of daughter and subdaughter branches. It assumes that perfluorodecalin displaces linearly to silicon oil in the bifurcating network. The displacement leads to unstable due to their viscosity gaps. Thus a low-viscous finger (LVF)-shaped instability appears on the interface. This study aims to tune the splitting dynamics of LVF by surface wettability of all six branches of the bifurcating network. Three wettability conditions are used-hydrophilic, hydrophobic, and superhydrophobic. The surface wettabilities of all six branches are organized into three pairs, represented by (θ<sub>1</sub>, θ<sub>2</sub>), (θ<sub>3</sub>, θ<sub>4</sub>), and (θ<sub>5</sub>, θ<sub>6</sub>). A series of numerical simulations is carried out by considering four unique wettability configurations of all three pairs, such as (θ<sub>1</sub>, θ<sub>2</sub>), (θ<sub>3</sub>, θ<sub>4</sub>), (θ<sub>5</sub>, θ<sub>6</sub>) ∈ [(78°, 78°); (78°, 118°); (78°, 150°); (150°, 150°)]. The results of the present investigation demonstrate that the LVF may be split either symmetrically or nonsymmetrically in the bifurcating network depending on the surface wettability of all three pairs. The symmetrical splitting behavior of LVF is found when the surface wettability of all three pairs is either hydrophilic (78°, 78°) or superhydrophobic (150°, 150°). In contrast, the nonsymmetrical splitting behavior of LVF is found when the surface wettability of all three pairs is a combination of hydrophilic and hydrophobic (78°, 118°) or hydrophilic and superhydrophobic (78°, 150°). The splitting ratio is found to be one for symmetrical splitting and less than one for nonsymmetrical splitting. The findings of this article will be useful in lung biomechanics and respiratory diseases.