Collision of elastic drop with thin cylinder

Abstract

The collision of water and elastic liquid drops with a thin cylinder (thread) is studied. The droplet flight trajectory and the cylinder axis are mutually perpendicular. Attention is focused on the difference between collisions of water drops and drops of elastic fluids. In the experiments, the drop diameter was 3 mm, the diameter of horizontal stainless steel cylinders was 0.4 and 0.8 mm. The drops were formed by slowly pumping liquid through a vertical stainless steel capillary with an outer diameter of 0.8 mm, from which droplets were periodically detached under the action of gravity. The droplet velocity before collision was defined by the distance between the capillary cut and the target (cylinder); in experiments, this distance was approximately 5, 10, and 20 mm. The drop velocities before impact are estimated in the range of 0.2-0.5 m/s. The collision process was monitored by high-speed video recording methods with a frame rate of 240 and 960 Hz. The test liquids were water and aqueous solutions of polyacrylamide of molecular weight 11 million and concentrations of 100 and 1000 ppm (PAM-100 and PAM-1k). Experiments have shown that, depending on the drop impact height and polymer concentration, different scenarios of a drop collision with a thin cylinder are possible: a short-term recoil of a drop from an obstacle, a drop flowing around a cylindrical obstacle while maintaining the continuity of the drop, the breakup of a drop into two secondary drops, one of which can continue flight and the other one is captured by the cylinder, or both secondary droplets continue to fly, the drop also can be captured by the cylinder, until the impact of the next drop(s) forces the accumulated drop detach from the cylinder. Numerical modeling satisfactorily reproduces the phenomena observed in the experiment.