ESTIMATION OF THE BREAKUP LENGTH FOR THE ANNULAR AND THE ROUND LIQUID JET USING LINEAR INSTABILITY ANALYSIS

A linear instability analysis of an inviscid annular liquid sheet emanating from an
atomizer subjected to inner and outer swirling air streams and a non-swirl round liquid jet has been
carried out. The dimensionless dispersion equation that governs the instability was derived and
was solved by Numerical method to investigate the effects of the liquid-gas swirl orientation on
the maximum growth rate and its corresponding unstable wave number that produces the finest
droplets. To understand the effect of air swirl orientation with respect to liquid swirl direction, four
possible combinations with both swirling air streams with respect to the liquid swirl direction have
been considered. Results show that at low liquid swirl Weber number a combination of co-inner
air stream and counter-outer air stream has the largest most unstable wave number and shortest
breakup length. The combination of inner and the outer air stream co-rotating with the liquid has
the highest growth rate. Also, the results for round liquid jet and planar liquid sheet show that the
linear theory accurately predicts the variation in breakup length with jet velocity.