Study on the effect of wall roughness on the flow characteristics of liquid film in airflow

During the flight, water flows under the action of shear force to form the overflow liquid film and freezes to form overflow ice. Overflow ice will change the aerodynamic shape of the aircraft and affect the safety and stability. In this paper, the three-dimensional structure of the liquid film in airflow was measured transiently with the digital image projection technology. The effects of different flat wall roughnesses, airflow velocities, and liquid film flow rates on the flow characteristics of the liquid film were analyzed. The experimental results show that the lower the wall roughness, the more pronounced the liquid film contraction toward the central axis. When the liquid flow rate drops to 0.228 l/min, the continuous liquid film transforms into rivulets on the surface of a large contact angle or low roughness. The average thickness of the liquid film on the flat is greater than that on the rough flat at low airflow velocity and low liquid flow rate, but smaller than that on the rough flat at high airflow velocity and high liquid flow rate. The wave near the inlet has an obvious acceleration process, and after reaching the peak speed, it gradually decreases and stabilizes near a certain value. The smoother the surface, the faster the acceleration of the wave at the inlet, and the greater the final stable wave speed.