Coalescence and separation in binary collisions of liquid drops

TLDR

The study experimentally investigates binary collisions of water drops across size ratios 1, 0.75, and 0.5, Weber numbers 1–100, and all impact parameters, and presents theoretical models predicting reflexive and stretching separations. The experiments reveal two distinct separating collision modes—reflexive for near head‑on impacts and stretching for large impact parameters—and delineate their boundaries with coalescence.

Abstract

An extensive experimental investigation of the binary collision dynamics of water drops for size ratios of 1. 0.75, and 0.5, for the Weber-number range of 1 to 100, and for all impact parameters is reported. Two different types of separating collisions, namely reflexive and stretching separations, are identified. Reflexive separation is found to occur for near head-on collisions, while stretching separation occurs for large-impact-parameter collisions. The boundaries between both of the separating collisions and coalescence collision are found experimentally. Theoretical models for predictions of the reflexive and stretching separation are also given.