Liquid sheet instability in the presence of acoustic forcing

Head-on impingement of two similar laminar liquid jets forms a thin circular liquid sheet which subsequently disintegrates into drops. This study looks at the effect of sinusoidal acoustic disturbance on the break-up of the liquid sheet and is motivated by the use of impinging jet atomization in liquid propellant rocket engines where previous studies reveal a coupling between the atomization process and the unsteady pressure fluctuations. In the present work, liquid sheet formed by impinging two collinear water jets is subjected to acoustic waves of varying frequency, resembling the pressure oscillations inside the combustion chamber of a liquid propellant rocket engine. Experiments were carried out for stable (smooth) as well as flapping regime of the sheet for 500<We<1300, where We =pvd 2d 0/σ is the Weber number and denotes the ratio of the inertial forces to the surface tension forces. Experiments show that for a given Weber number the sheet responds to a set of specific frequencies lying within the range of 100-600 Hz with the frequency set varying with We.