Dynamics of Annular Liquid Sheets Using Feature Correlation Velocimetry (FCV)

Abstract

Liquid sheets find relevance in atomization point of view owing to its effect on the droplet distribution. As a general thumb rule, coarser droplets are formed from thicker sheets relative to finer droplets from thinner liquid sheets upon disintegration. Experimental quantification of the dynamics of liquid sheets has been a challenge over a long period. Imaging and subsequent post-processing have been successful in quantifying the velocity of liquid sheets. Towards this line, a non-intrusive method called Feature correlation velocimetry has been successful in determining the velocity of liquid sheets. The technique relies on the advection of short wavelength corrugations formed on the surface of liquid sheets when interacted upon by ambient gas. The present article gives a detailed report on the procedure followed in FCV analysis of an annular liquid sheet by demonstrating the technique on the swirling liquid sheet exiting a Gas Centered Swirl Co-axial injector. The technique gives spatio-temporal values of the velocities over the range of images considered. An estimate of the sheet thickness can also be obtained from the flow rates based on the velocities obtained from FCV analysis. FCV has the added advantage that it provides an insight into the unsteady behavior of liquid sheets.