The largest diameter of falling drop in the up-gas flow

This study aimed to investigate the largest diameter of falling drop in the up-gas flow. Due to gravity, the falling drop is common in nature and industry. Drop breakup in the airflow is referred to as secondary atomization, found in numerous practical applications. Critical Weber number is the key dimensionless number marking the beginning of drop breakup. Herein, we explain the different critical Weber numbers between the free-fall raindrops breakup and secondary atomization based on the Rayleigh-Taylor (RT) instability. The theoretical criterion of largest raindrop size is proposed by RT wave number model. In addition, we suggest a map of falling drop size regions, which can well explain the phenomena of the super-large raindrop. The current study is also helpful in the remission of drop entrainment in the washing tower.