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Observation of a dynamic wetting process using Laser‐Doppler velocimetry
Author(s) -
Mues W.,
Hens J.,
Boiy L.
Publication year - 1989
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.690350912
Subject(s) - wetting , entrainment (biomusicology) , laser doppler velocimetry , contact angle , air entrainment , velocimetry , materials science , line (geometry) , capillary action , optics , composite material , acoustics , physics , medicine , blood flow , geometry , mathematics , rhythm
The purpose of this study is to observe the dynamic wetting process of a slide coater flow ( Ca = 0.16; Re = 14.4; St = 0.0142; Δ eP = 2.5), using a specially‐developed Laser‐Doppler measuring technique. The measurements, carried out with glycerol solutions, reveal that the observed contact line is apparent and that a thin air film is entrained between the web and the liquid surface. The liquid is accelerated along the lower free surface and attains approximately 50% of the web velocity at the apparent contact line. Downstream from the apparent contact line, the liquid is further accelerated along the air film to the web velocity at the real contact line. The apparent contact angle increases with the capillary number Ca and air entrainment occurs at Ca = 0.25.