Effects of Transient Consecutive Cyclic Injection-Suction of a Fluid on the Interfacial Dynamics During a Radial Immiscible Fluid-Fluid Displacement Inside a Hele-Shaw Cell

In the current study, the inabilities resulting from the interaction of two Newtonian immiscible fluids, including water and base oil, during transient consecutive injection-suction in a Hele-Shaw cell, was studied. For injection-suction purposes, base oils with viscosities of 150, 920, and 1506 cP were used. The highest continuous flow rates for three techniques including pseudo- sinusoidal, percussive time-dependent, and constant-flow rate were 10, 20, and 30 mL/min, respectively. The volume of fluid injected or extracted remained consistent across all three methods. The injection-suction process was repeated for five full cycles to analyze the impact of frequency on the outcome. The primary goal was to study how to eliminate interfacial instabilities and restore the circular shape of the fluid-fluid interface after each cycle. It was found that the percussive and constant-flow rate methods were unable to achieve this objective. Results showed that the growth rate of interfacial instabilities was slower with the pseudo-sinusoidal method compared to the other methods. Increasing the flow rate in the constant-flow rate method resulted in more oil packets being created. The pseudo-sinusoidal method did not show instabilities like water droplets, fingers, or oil packets, unlike the constant-flow rate and percussive methods. Overall, the pseudo-sinusoidal method was found to be the most suitable for restoring the fluid-fluid interface to its original stable state. However, increasing the number of cycles could lead to more instabilities, making it harder to return to the initial stable interface.