Marble, Frank E. and Candel, Sebastien M. (1975) Acoustic Attenuation in Fans and Ducts by Vaporization of Liquid Droplets. AIAA Journal, 13 (5). pp. 634-639. ISSN 0001-1452. http://resolver.caltech.edu/CaltechAUTHORS:20101216-132206855
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A cloud of small water droplets in saturated air attenuates acoustic disturbances by viscous drag, heat transfer, and vapor exchange with the ambient gas. The viscous and heat transfer phenomena attenuate at frequencies above 104 Hz for I-J.l droplets. The processes associated with phase exchange attenuate at a much lower frequency that may he controlled by choice of the liquid mass fraction. The strength of this attenuation is proportional to the mass of water vapor in the air, a factor controlled by air temperature. For plane waves, the attenuation magnitude e~ceeds 5 db!m ~t a temperature of 25°C with a cloud of 0.7 J.l radius droplets constituting 1 % of the gas mass. ThiS attenuation mcreases to more than 7 dbjm at frequencies above 1000 Hz where viscous and heat transfer mechanisms contribute significantly. The attenuation of higher order duct modes is strongly increased over the above values, similarly to the attenuation by duct lining. When the droplet cloud occupies only a fraction of the duct height close to the walls, the droplet clond may be up to twice as elfective as the uniform cloud, and a significant saving is possible in the water required to saturate the air and furnish the water droplets.
|Additional Information:||© 1975, by the American Institute of Aeronautics and Astronautics, and reprinted by permission of the copyright owner. Presented as Paper 74-526 at the AIAA 7th Fluid and Plasma Dynamics Conference, Palo Alto, California, June 17-19, 1974; submitted June 24, 1974; revision received November 5, 1974. Supported by U.S. Air Force Grant AFOSR-71 2068.|
|Group:||Guggenheim Jet Propulsion Center|
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|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||20 Dec 2010 18:59|
|Last Modified:||26 Dec 2012 12:46|
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