Abstract
•Stretching of elastomer sample causes extension of the droplet axisymmetric at same rate.•Stretching alters the wetting area and height of the droplet.•The size and orientation of circulation structures alter in droplet fluid with stretching.•Maximum flow velocity reduces inside droplet as stretching progresses.•Nusselt and Bond numbers with stretching of elastomer sample.
Heating of a droplet on a stretchable hydrophilic surface is investigated and fluid dynamics in the droplet under the heating load is assessed. Elastomer wafers are considered as the sample material and the fixture is designed and manufactured to assure uniform stretching of the droplet located elastomer surface. Droplet adhesion and possible slipping/sliding of the droplet are evaluated during stretching of the sample surface. Numerical simulations are carried out to predict thermal and flow response of the droplet fluid before and after stretching. The effect of droplet volume on heating enhancement is also included in the numerical simulations. Experiments are carried out using a high-speed recording system towards comparing the flow predictions. Findings reveal that predictions are in agreement with their counterparts of experiments. Stretching of sample surface increases wetting area and lowers height of the droplet while influencing thermal flow structures in the fluid. The Nusselt and the Bond numbers increase with enlarging stretching, which becomes more visible for large droplet volume (80 µl). Hence, stretching corresponding to 80% extension of elastomer surface gives rise to 60% improvement in the Nusselt number.