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Turbulence phenomena at free surfaces
Author(s) -
Davies J. T.
Publication year - 1972
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690180131
Subject(s) - turbulence , mass transfer , mechanics , absorption (acoustics) , wake , eddy , surface roughness , flow (mathematics) , mass transfer coefficient , surface finish , free surface , chemistry , materials science , optics , thermodynamics , physics , composite material
Gas absorption by eddies at the free surface of a strongly turbulent liquid is interpreted quantitatively in terms of the Levich approach. The mass transfer coefficient is calculated to vary as Re to a relatively high power (1.3 to 1.5). Experiments on free turbulent jets of liquids in gas are in general accord with this theory. For turbulent films of liquids flowing over large roughness elements in “wake‐interference” flow, the turbulence is anomalously efective in promoting gas absorption. Traces of surface‐active agents suppress the surface renewal. This is analyzed theoretically: the results compare favorably with gas‐absorption for stirred cells and flow experiments over smooth plates. For “wake‐interference” flow over rough plates, the reduction in the rate of gas absorption by surface‐active material is more pronounced than predicted for ordinary turbulence. But even in the presence of a surface‐active agent, the roughness still gives an advantage in mass transfer rates as compared with smooth plates.