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EFFECTS OF SEEDING ON THE CONDENSATION OF ATMOSPHERIC MOISTURE IN NOZZLES.
YALE UNIV NEW HAVEN CONN
When smoke particles of certain inorganic compounds are added to moist air expanding at near sonic speeds in the wind tunnel, they act as heterogeneous nuclei for the condensation of water. Unlike homogeneous condensation, which commences later in the expansion and is characterized by a hump in the static pressure distribution, heterogeneous condensation is so gradual that while it occurs the static pressure values are indistinguishable from those in a dry air expansion. Nevertheless, when the initial humidity exceeds a certain level determined by the flow conditions and the smoke concentration, heterogeneous condensation becomes sufficiently rapid to affect the local humidity, and homogeneous condensation is partially suppressed. This seeding effect can be used to eliminate normal shocks resulting from homogeneous condensation. Since it requires upwards of 10 to the 8th power particlescc, the effect is not shown by the foreign nuclei naturally present in the atmosphere. Author
Rept. no. 5,
See also AD-444 547.