Influence of an adjacent droplet on fluid convection inside an evaporating droplet of binary mixture

• Internal convection of a droplet is influenced by a neighboring droplet.
• Neighboring droplet affects the concentration and velocity field inside the droplet.
• Flow pattern shows asymmetric behavior in the presence of an adjacent droplet.
• Influence of the adjacent droplet depends on the separation distance of droplets.

We study the fluid convection inside two adjacent evaporating droplets of binary mixture. Micro-PIV technique has been used to measure the velocity field inside the droplet. The experimental observation on internal convection inside droplet has been explained using the simulation results of evaporative flux distribution and concentration field inside the droplet. The interaction between the two adjacent evaporating droplets has been studied by varying the separation distance between the two droplets. Evaporation from the droplet induces buoyancy driven Rayleigh convection inside the droplet. Fluid convection inside a single droplet shows a symmetrical flow pattern with two recirculating bubbles in X–Z and Y–Z wall normal planes. This behavior is attributed to the symmetric evaporative flux distribution on the droplet surface and the resulting symmetric concentration field inside the droplet. Presence of an adjacent evaporating droplet leads to asymmetric evaporative flux distribution on the droplet surface due to the influence of the neighboring droplet on the free stream mass fraction. This asymmetric evaporative flux distribution on the droplet surface results in asymmetric concentration field inside the droplet. As a result, the fluid convection in two droplets configuration shows asymmetric flow pattern with one recirculation bubble in X–Z wall normal plane and two recirculation bubbles in Y–Z wall normal plane.

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