Two-phase flow turbulence in swirling sprays from a coaxial atomizer

Overview & Synopsis

The present investigation focuses on the turbulent characteristics of swirling/non-swirling sprays from a coaxial atomizer. The probability distribution functions of the velocity fluctuation are found to narrow their range with an increase in swirl, for the axial, radial, and tangential components. The centerline gas jet velocity close to the nozzle is observed to be higher in the presence of spray than without it, and while the opposite is true far away from the nozzle. When considering the carrier phase, the axial velocity fluctuations show self-similar radial profiles independently of the spray parameters. The droplets, on the other hand, display off-center maxima, except for low-swirling sprays, at a high gas-to-liquid dynamic pressure ratio M. On the contrary, only the latter conditions have off-centered maxima for the droplet radial velocity fluctuations. Although an expected self-similarity is observed for the Reynolds stress term uv for the gas phase, the droplet covariance is found to increase with swirl. The behaviors of the other terms, including the gas Reynolds stresses and the droplet covariances, are also characterized in detail, along variations of M and swirl in particular. Furthermore, the gas flow's integral time scale is observed to increase, while the dissipation rate decreases with an increase in swirl. The computation of the local Stokes number highlights the difficulty in finding adequate seeding material to faithfully be tracers of such high-speed sprays. This comprehensive database of spray turbulence can serve in future spray models.