Thermally delayed drop coalescence

The Marangoni flows generated in the air layer beneath a cold drop resist its coalescence with a warm bath.

We present the results of a combined experimental and theoretical study of drop coalescence in the presence of an initial temperature difference between a drop and a bath of the same liquid. We characterize experimentally the dependence of the residence time before coalescence on the temperature difference for silicone oils with different viscosities. The observed dependence is rationalized theoretically through consideration of the thermocapillary flows generated within the drop, the bath and the intervening air layer.

See paper: Geri, M., Keshavarz, B., McKinley, G.H. and Bush, J.W.M. (2017)