Acoustic Attenuation by Vaporization of Liquid Droplets -- Application to Noise Reduction in Aircraft Powerplants.
Abstract
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 mechanisms of these processes are analyzed to show that the viscous and heat transfer phenomena attenuate at frequencies above the reciprocal of the Stokes relaxation time, a frequency of about 10,000 Hz for 1-micron droplets. The processes associated with phase exhange attenuate at much lower frequencies; in fact, the characteristic frequency of this attenuation may be controlled by choice of the liquid mass fraction. The strength of the phase exchange attenuation is, however, proportional to the mass of water vapor in the air, a factor controlled by air temperature.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1975
- Accession Number
- ADA009644
Entities
People
- Frank E. Marble
Organizations
- California Institute of Technology