Thermocapillary migration of a compound droplet on a substrate

We present a numerical study of the thermal migration of a compound droplet attached to a horizontal substrate. The different constant temperatures are applied to the left and right boundaries of the computational domain. The compound droplet contains one inner core. The problem is solved by using a front-tracking technique associated with the finite difference method. The investigated parameters include the radius ratio (R-io) of the inner droplet and the equivalent radius of the outer droplet (R-io varied in the range of 0.2 to 0.7), the viscosity ratio (mu(om)) of the outer to middle fluids (mu(om) varied in the range of 0.1 to 2.4), and the static contact angle theta(e) (theta(e )varied in the range of 60(degrees) to 120(degrees)). The results reveal that the inner droplet drives the compound droplet towards the hot region as its radius is sufficiently large (R-io >= 0.6). The compound droplet moves towards the cold region as the value of R-io is less than 0.6. Increasing the viscosity of the outer fluid (by increasing mu(om)) or theta(e) causes the compound droplet to move towards the hot region. The trajectory of the centroid of the inner droplet is also investigated.(c) 2023 Elsevier Masson SAS. All rights reserved.

Automated summary

In this study, the thermal migration of a compound droplet attached to a horizontal substrate is numerically investigated. The results show that the size of the inner droplet, viscosity ratio, and static contact angle can influence the movement direction of the compound droplet.