Experimental study of the shape and motion of flattened drops in a Hele-Shaw Cell

> The motion and shape of a flattened drop and bubble through another continuous liquid phase (conveying phase) are investigated experimentally, using a narrow gap HeleShaw cell. Seven different liquid-liquid systems were tested. In all cases the continuous phase was the more viscous wetting phase. A number of observations on the shape and motion of the elongated flattened drops are noted and discussed. In the capillaritydominated (Ca<1.69×10-6) region, the irregular shape of the discontinuous phase drops changed with time and position, and the drop velocity was much lower than that of the conveying phase. Three different shapes of stabilized elongated drops were observed at higher Capillary numbers. The conditions that lead to the appearance of stabilized elongated drops are discussed. The velocities of these stabilized elongated flattened drops were 2 to 4.7 times higher than that of the conveying liquid. A correlation to predict the elongated flattened drop shape as a function of the dimensionless parameters governing the system is developed based on the experimental results.