Masters Theses

Date of Award

8-1989

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Roy J. Schulz

Committee Members

R. A. Crawford

Abstract

The following thesis is an experimental and theoretical study on the flow field downstream of a cylindrical body aligned with a low Mach number air stream with liquid mass ejecting from the base of the body. The objectives of this study are two-fold: one, to modify a single-phase flow model of a flow field downstream of a cylindrical body to include liquid mass ejection at the base of the body; and two, to gather experimental data of such a flow field enabling an evaluation of the model to be performed. Experimental data from previous work were gathered which measured the total mass concentrations of the liquid and its vapor in the two-phase flow at 12 and 41 X/D downstream of the cylindrical body which measured 2.5 inches in diameter and 5 inches in length. Droplet diameters of the liquid spray were also measured at 72 X/D downstream of the body. Additional data were gathered on the pressures at the base of the body with no liquid mass ejection taking place. All data were taken in an air stream of Mach number 0.4 or less. These data were used to evaluate the computer model which used the local homogeneous flow (LHF) approximation theory, described by Faeth in Reference 1, to model the ejected liquid spray. The LHF theory assumes that the liquid spray is a continuum phase (dense gas) transported like heat or IV concentration in the mixing process. Local density thus represents a mixture density lying between the liquid and freestream gas densities, and whose value depends on the local liquid mass fraction.

The LHF model evaluation showed that the overall model uncertainty for the predicted liquid mass fractions at the centerline was on the order of 150 percent. The model invariably overestimated the diameters of the spray at 12 X/D and almost invariably underestimated the spray diameters at 41 X/D. The spray diameters at 12 X/D were overestimated by the model by as much as 150 percent, and were underestimated at 41 X/D by as much as 45 percent. The base pressure coefficients predicted by the model with no liquid ejection at the base were overestimated by 200 percent, but were constant for the range of tunnel air velocities used in the test as they should be.

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