Extinction-sedimentation inversion technique for measuring size distribution of artificial fogs

Area of Science:

• Atmospheric Science
• Optical Physics
• Particle Characterization

Background:

• Accurate measurement of artificial fog particle size distribution is crucial.
• Traditional sampling methods can disturb particle states, leading to inaccurate data.
• A non-invasive technique is needed to preserve particle integrity during measurement.

Purpose of the Study:

• To develop and describe a new method for measuring the size distribution of artificial fog particles.
• To ensure the natural state of fog particles is not disturbed during measurement.
• To provide a direct inversion method for obtaining particle size distribution from optical depth data.

Main Methods:

• Fog particles settle in quiet air within an enclosure.
• A parallel light beam measures optical depth (tau) as a function of time (t).
• An analytic function fit to the tau(t) decay curve is inverted to yield particle size distribution n(r).

Main Results:

• The described method successfully measures artificial fog particle size distribution.
• Experimental results from artificial fogs are presented as an example.
• Forward-scattering corrections were analyzed to minimize experimental error.

Conclusions:

• The developed method offers a non-invasive approach for fog particle size analysis.
• Direct inversion of optical depth decay provides accurate particle size distribution.
• Optimizing experimental design can minimize errors from forward scattering.