The velocity and shape of convected elongated liquid drops in narrow gaps

The motion and shape of a liquid drop through another continuous liquid phase (conveying phase) in a Hele-Shaw cell with two different apertures were investigated experimentally. Eight different liquid–liquid systems were tested. In all cases, the continuous phase was more viscous and wetted the bounding walls. In the capillarity-dominated region, the irregular shape of the discontinuous phase changed with time and distance, with much lower velocity than that of the conveying phase. At higher capillary number, three different shapes of stabilized elongated drops were observed. The conditions that lead to the appearance of stabilized elongated drops are discussed. In contrast to gas–liquid systems, the velocity of these stabilized elongated drops was 2 to 4.7 times higher than that of conveying liquid. Two new correlations are derived from dimensionless analysis and the experimental data to predict the elongated drop shape and velocity as a function of the dimensionless parameters governing the system.