New technologies such as advanced gas-turbine engines and other advanced engines involve injection of liquids at higher pressures, which can reach levels that are hundreds of times greater than atmospheric pressure. There is a demand for new predictive capabilities to describe the sizes, shapes, and locations of small droplets breaking from the surface during the liquid-stream breakup (atomization) process. This project seeks an explanation of the physical mechanisms and to control of the breakup process and of the resulting spray. Graduate and undergraduate students will conduct the project. Topical development will allow strengthening of various graduate courses in the topic of fluid dynamics and a future third edition of a textbook. Through existing UCI minority support programs, the Principal Investigator and his graduate students can support project work and give public talks on topics of interest.
The project goals are to provide a satisfactory computational analysis of the liquid stream breakup at a supercritical pressure and to determine the important mixing length scales with real-gas equations of state and phase-equilibrium laws. The amount of gases dissolving into the liquid and the new, substantially higher critical pressure will be determined, establishing when two distinct phases exist. Both liquids and gases will be compressible and have variable density at high pressures. The analysis will give predictions of relevant characteristic time and scales (e.g., diffusion times, frequencies, most unstable wavelengths, and growth rates). The sensible enthalpy, as a function of pressure and temperature; transport properties; surface tension; and energies of vaporization will be determined. Three-dimensional Navier-Stokes solutions, with interface tracking through volume-of-fluid or level-set methods, followed by ?2 vorticity-dynamics analysis will explain the sequence of smaller structures that appear in the breakup cascade. This approach will describe and explain the behavior whether the jet breakup is in a two-phase or supercritical gaseous state; in either case, the smaller structures appear. Atomization, at the Reynolds and Weber numbers of practical interest, will be analyzed and properly viewed as transitional turbulence.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
