A Comparison of Classical Atomization Models against Current Experimental Measurements within a Zero-Dimensional Framework

A Comparison of Classical Atomization Models against Current Experimental Measurements within a Zero-Dimensional Framework

Presented at :

ILASS Americas, 17th Annual Conference on Liquid Atomization and Spray Systems, Arlington, VA, May 2004

Authors:

R. O. Grover, Jr. and D. N. Assanis
Department of Mechanical Engineering, University of Michigan
A. M. Lippert, General Motors R&D and Planning

Abstract:

Two classical secondary atomization models commonly used in multidimensional computational fluid dynamics (CFD) codes were evaluated against single droplet experimental measurements. The Taylor Analogy Breakup (TAB) and Kelvin-Helmholtz (KH) instability models were compared to measurements of breakup time ranging from the bag to the catastrophic breakup regimes (Pilch & Erdman 1987, Dai & Faeth 2001), drop size in the bag (Chou & Faeth 1998) and shear (Hsiang & Faeth 1993, Faeth, et al. 1995, Chou, et al. 1997) breakup regimes, and drag coefficient evolution in the bag breakup regime (Chou & Faeth 1998). Droplets having a liquid-to-gas density ratio greater than 751 and Oh < 0.1 were studied. The applicability of these submodels over a range of We was investigated and the most sensitive constants within these models identified; appropriate ranges were also determined for physical accuracy. Furthermore, an evaluation of two different numerical approaches, namely abrupt (TAB) versus continuous stripping (KH), was undertaken over the range of breakup regimes considered. The comparison was conducted within a zero-dimensional (0D) single droplet framework capable of replicating unsteady momentum boundary conditions. Included in the 0D code was a simplified drag model, which updates the relative velocity and drag coefficient of the drop at each timestep, assuming a constant ambient flow field. The results revealed that suitable bounds on key model constants could be identified to estimate breakup time, drop size, or drag coefficient, individually, for a specific regime; however, the simultaneous prediction of all three led to inherent tradeoffs between different regimes and between drop size and breakup time predictions.

Paper: P2004_03.PDF