In this paper we show that while drops from all size ranges coalesce on packing surfaces, secondary drops are also produced during drop detachment from all packing surfaces and the net coalescence rate for secondary drops is low.
The factors which govern the sizes of these secondary drops are discussed and empirical relationships are presented.
There are computed: minimal Weber number when the drop begins to flatten, degree of flattening, critical Weber number and secondary drops diameter.
Secondary drops were produced from protruding columns of liquid which were formed at both the front and rear of the drops.
It is apparent that such low effluent concentrations from gravity separators can only be realized, in general, if the finest drops in a dispersion, secondary drops (drops with diameters less than 100 μm), coalesce and are separated from the continuous phase.
At ∣Δθ∣⪡1, the spectrum of transmission (without mode conversion) represents a nearly periodic group of abrupt dips to zero and a modulated group of secondary drops increasing with growing 2N2, whereas the general spectral background is close to unity.
In contrast to the shear-thinning cases, it exhibits a plug flow prior to necking, an almost step-change approach to pinch-off of a "torpedo" shaped drop following the onset of necking, and a much smaller neck length; no secondary drops are formed.
Our principal conclusions are that the maximum size of secondary drops produced on packing surfaces is independent of the nature of the packing material, and that this drop size can be expressed as a simple function of the physical properties of the dispersion.
Differences in personal and disease characteristics will be compared between participants completing the study, those who fulfill the inclusion criteria but decline participation (primary drop-out), and those who participate in parts of the study but for various reasons end participation (secondary drop-out).
