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Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2004, Volume14

99 pages

Issue price - $85.00

MODELING THE PRIMARY BREAKUP OF HIGH-SPEED JETS

Rolf Reitz
University of Wisconsin Madison

ABSTRACT

A new jet primary breakup model is proposed and applied to high-speed jets to predict the primary breakup characteristics. The liquid jet is modeled by discrete blobs. Initial conditions, such as jet diameter, injection velocity, and initial disturbances on the liquid jet, are provided by a nozzle flow model to reflect the effects of nozzle internal flow. The breakup characteristics of the jet are calculated by tracking the wave growth on the surface of each liquid blob using a one-dimensional Eulerian approach. Novel initial and periodic boundary conditions are applied to the computational domain that allow consideration of the unstable growth of complex initial disturbances. The surface structure of a blob is decomposed into a combination of waves with different wavelengths and is expressed in a Fourier series using a fast Fourier transform (FFT). The drops that are stripped from the surface are calculated from the surface wavelengths and amplitudes, as indicated by the Fourier coefficients. A multilayer drop-stripping model is proposed and multidimensional effects are included by reflecting the surface structure in the axial direction into the peripheral direction, as suggested by high-speed jet experiments that show that surface wavelengths are approximately isotropic. The new breakup model has been implemented in the multidimensional KIVA computational fluid dynamics (CFD) code to simulate spray atomization. The breakup model has been used to predict drop size, jet breakup length, and spray liquid penetration length. Comparisons with experimental data indicate that the new breakup model significantly improves spray predictions over standard atomization models that are based on linear jet stability theories.