Two-dimensional liquid sheet in transverse subsonic airflow

Abstract

Flow dynamics of a two-dimensional liquid sheet injected transversely into a subsonic airstream was comprehensively investigated. An injector with an aspect ratio of 90 and a thickness of 0.35 mm was used to produce the two-dimensional liquid flow. Experimental visualizations were used to identify the main features of the liquid sheet in crossflow. Tests were conducted for a wide range of flow conditions to achieve a complete understanding of the flow physics. Experiments revealed that the sheet flow developed an expanded shape that was absent in conventional liquid jets in crossflow. This newly found structure was named as inflated sheet. Regimes of two-dimensional liquid sheet flows were categorized into: biconvex, enclosed inflated sheet, open inflated sheet, bag breakup/sheet rupture, and multimode breakup. A mapping of the flow was suggested to identify the transition from one regime into another. Furthermore, the main parameters of the liquid sheets including height, trajectory, and breakup point were measured and their dependency on the momentum ratio and Weber number was investigated. Results showed that different stages of inflated sheet development directly influenced the trajectory and height of the liquid sheet. A power-law empirical correlation was suggested to predict the trajectory of the liquid sheet. Also, a finite difference scheme was used to calculate the growth rate of the liquid sheet height. It was demonstrated that the sheet height increased more rapidly with the decrease of momentum ratio. Proper orthogonal decomposition method was applied to the flow visualizations and dominant frequencies of bags were identified and compared at different flow conditions.