Dynamic and kinematic characteristics of unsteady motion of a water-in-oil emulsion droplet in collision with a solid heated wall under conditions of convective heat transfer

The paper presents the experimental results of spreading, fingering and corona-like splashing of water-in-oil emulsion droplets based on n-decane, isoparaffin oil and distilled water in the range of Weber numbers We = 100-900, wall temperatures Tw = 20-80 degrees C and in collision with a smooth solid surface. The spreading features and separate convective rolling structures in emulsion droplets are examined at the late stages of wetting. The effect of Tw on the viscous dissipation energy and the maximum spreading coefficient is established. The validity of the assumptions explaining the contradictory behavior of the maximum spreading diameter of emulsion droplets with increasing temperature is studied. The assumption of unstable behavior of the emulsion droplet rim during spreading is proposed. The maximum emulsion corona diameter and height decrease linearly with the Tw growth due to the longer corona lifetime. The maximum corona diameter increases following the power law with increasing the Brinkman number due to an increase in the liquid viscosity and a decrease in Tw. The results help to predict the corona's behavior by determining the relationship between the viscous dissipation of the spreading liquid and the energy transferred to the liquid from the wall due to molecular (thermal) conduction.

Automated summary

This paper presents experimental results on the spreading, fingering, and corona-like splashing of water-in-oil emulsion droplets in collision with a solid surface. The effects of Weber numbers, wall temperatures, and the assumptions explaining the behavior of the maximum spreading diameter of emulsion droplets are examined. The results provide insights into predicting the behavior of the corona based on the relationship between the viscous dissipation of the spreading liquid and the energy transferred to the liquid from the wall.