Numerical analysis of two hollow drops simultaneously impacting a wet surface

Abstract

The impingement behaviors of two hollow drops or two continuous dense drops simultaneously impacting a thin liquid film were analyzed numerically using a three-dimensional coupled level-set and volume-of-fraction method. The findings indicate the formation of a counter-jet during the simultaneous impact of two hollow drops, whereas a relatively stable residual film is formed during the impingement of two continuous dense drops. This counter-jet generates heat-transfer blind spots in the case of simultaneous impact by hollow drops, leading to the easy splitting of the residual liquid film. The heat around the blind spot region is difficult to release due to flow stagnation and the squeezing of the initial cold liquid film to the symmetric point. These findings indicate that more focus should be placed on the uniformity of heat transfer in realistic applications involving drop impingement. Finally, analyses of pressure gradient and flow separation revealed the formation process of the counter-jet and central liquid sheet. The findings are valuable for guiding industrial technical practice.