Tomographic PIV measurement of internal complex flow of an evaporating droplet with non-uniformly receding contact lines

Abstract

We investigate an internal flow pattern of an evaporating droplet where the contact line non-uniformly recedes. By using tomographic Particle Image Velocimetry, we observe a three-dimensional azimuthal vortex pair that is maintained until the droplet is completely dried. The non-uniformly receding contact line motion breaks the flow symmetry. Finally, a simplified scaling model presents that the mechanical stress along the contact line is proportional to the vorticity magnitude, which is validated by the experimental results.

Non-uniformly receding contact line breaks axisymmetric flow patterns

“…To date, although several experimental and theoretical studies are performed [24,25,26,27], the internal flow field is not investigated, except for our previous study [30]. Here, using tomographic PIV, we obtain a three-dimensional azimuthal vortex pair inside an drying droplet on a SAMs substrate where the contact line partially recedes in time and space, as shown in Fig.…”

“…Here, we use a glass substrate coated with Self Assembled Monolayers (referred to as SAMs). We obtain the three-dimensional azimuthal vortex flow field by means of tomographic PIV, which has been firstly reported in the previous study [30]. Here, we further investigate the experimental results.…”