Trajectory Measurements of a Horizontally Oriented Buoyant Jet in a Coflow Using Filtered Rayleigh Scattering
Publication: Journal of Aerospace Engineering
Volume 30, Issue 1
Abstract
The filtered Rayleigh scattering technique was implemented to discern the mechanisms associated with trajectory and mixing characteristics of buoyant jets in the presence of a coflow. A continuous wave laser in conjunction with a high-speed camera and a molecular filter constituted the equipment needed to obtain near-field concentration measurements of a carbon dioxide jet within a coflow of air. The arrangement enabled carbon dioxide concentration measurements with and without the coflow at a sampling rate of 400 Hz. The time-averaged results demonstrate the significance that adding the coflow has on increasing the mixing rate, thus reducing the impact of the buoyant jet by flattening the jet trajectory. The effects of various flow parameters such as the jet velocity, the jet to coflow velocity ratio, the relative velocity between the jet and the coflow, and the Froude number on the jet trajectory are studied. The downward trajectory of the carbon dioxide jet, absent a coflow, was well correlated with the Froude number. However, the addition of the coflow led to a substantial impact on the jet trajectory, reducing its buoyant effects due to a combination of increased momentum and, likely, the mixing rate. Further increases in the coflow, including the relative magnitude of the coflow, had a lesser impact. Mixing characteristics and time-dependent jet motion were captured.
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Acknowledgments
The authors would also like to thank Jake Schmidt of Spectral Energies, LLC for his contribution in the setup of the laser diagnostic systems and Jay Anderson and John Hixenbaugh at AFIT for their support in setting up the experiment. The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government.
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© 2016 American Society of Civil Engineers.
History
Received: Aug 24, 2015
Accepted: Apr 14, 2016
Published online: Jul 19, 2016
Discussion open until: Dec 19, 2016
Published in print: Jan 1, 2017
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