K-1114 Experimental Study on Instability of a Radial Liquid Sheet

Abstract

The laminar-turbulent transition process in a liquid sheet is investigated by linear instability analysis and laser measurement. A radial liquid film flow is generated by a water discharge through a small gap formed between the end of a nozzle and the flat surface of a disk. The liquid film flow spreads radially on the disk, flowing from the disk edge into the still air as a liquid sheet. Sudden laminar-turbulent transition occurs in the liquid sheet when the Reynolds number exceeds a critical value, resulting in the perforation and the disintegration of the liquid sheet. In this flow, a disturbance wave(D wave) is appeared before the transition. The frequency of D wave is measured with a laser. The measured frequency agrees with the frequency in which a disturbance grows most rapidly because of an inflectional velocity profile in the sheet. This agreement shows the transition is due to the inflectional instability.