The breakup and atomization of a liquid jet by a high velocity turbulent gas stream is known as airblast atomization (Lefebvre, 1989). In liquid propellant rocket engines for instance liquid oxygen is atomized by a high speed annular hydrogene gas jet. Because of these important practical applications a relatively large number of investigations have considered this problem but have to a large extent been limited to measuring the drop size at a certain distance downstream of the nozzle, as afunction of the flow parameters at the nozzle exit. The correlation of the drop size, expressed for instance by the Sauter mean diameter D{sub}32, with gas velocity is of the form D{sub}32～U{sup}-b with b ranging from 0.8 to 1.4 and even 2. Variousattempts have been made to explain such a power law (see Lasheras et al, 1998). The other important quantities are the spreading rate of the spray and the liquid intact or potential cone. length. The latter has generally been correlated with theaerodynamic Weber number and the liquid Reynolds number (Arai et al., 1985). When the Weber number is large, a more relevant parameter in liquid jet breakup is the gas to liquid momentum flux ratio M = ρ{sub}gU{sub}g{sup}2/ρ{sub}1U{sub}1{sup}2(Hopfinger and Lasheras, 1994; Rehab et al., 1997). It has been demonstrated (Raynal, 1997) that in a certain range of M the liquid cone length is independent of Weber number and varies as M{sup}(-1/2). One of the open questions is the drop size resulting from the primary breakup.
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