Dynamic fluid interface displacement and prediction of air entrainment

The problem of the deformation of a quiescent air/liquid interface by a plunging solid surface is considered in the context of a differential force balance of the type used in withdrawal theory. Interfacial deformation and air entrainment which eventually arises at high speeds are discussed in terms of three separate regions: where the dynamic contact angle, ?, is >90°, 90° > ? > 180°, and ? ? 180°. This latter condition leads to the development of a dimensionless correlation between Weber and Bond numbers correlating air entrainment data which were found to be in substantial agreement with the experimental results. The theoretical and experimentally measured profiles also showed good agreement, particularly for viscosities up to 6.77 P and dynamic contact angles less than 180°, for surface tensions in the range 34 < p < 65 dyn·cm^-1. © 1977.