The orientation distribution of nonspherical aerosol particles within a cloud

The orientation distribution of non-spherical particles within a cloud was studied. Theoretically, the subject was treated for a general laminar flow of immediate as well as weak and strong character, and for a turbulent flow whose Kolmogoroff scale was much larger than the particles themselves. The laminar flow served as one realization for the turbulent field within the cloud. It is found that the orientation distribution function in a laminar medium is generally structured with a preferred orientation while that of the turbulent medium is random on the average but with a significant dispersion. Experimentally, a horizontal wind tunnel was erected for orientation measurements; it was equipped with a dedicated hot-wire computerized system for turbulence characterization, which was shown to conform to the determinations of Laufer. Light scattering signals were used as the orientation-gauge.