Controlling complex fluid displacement flows in confined geometry

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The movement of one fluid by another fluid in confined geometry is one of the most common processes in Nature. These interesting flows also have many industrial applications, for example, in the field of energy, particularly in the petroleum industry (e.g., in oil and gas exploration, extraction and transportation), manufacturing (e.g., coating flows, co-extrusion), biomedical applications (e.g., digestion, clearing of mucus plugs in alveoli) and food processing (e.g., biofilm removal, cleaning of processing machinery). The fluids involved frequently exhibit various interesting complex rheological features such as shear-thinning, shear-thickening, viscoelastic, viscoplastic and thixotropic effects. These displacement flows are often vulnerable to well-known instabilities that may develop at the fluid-fluid interface, which depending on the situation may be undesirable or desirable. This sparks a significant research question: How can one control and manipulate complex fluid displacement flows, e.g., by hindering/triggering interfacial instabilities to achieve desired flow patterns and behaviours? Relevant to this question, our long-term research goal is to develop comprehensive controlling strategies to manipulate the advancement and penetration of complex fluids into one another, hinder/trigger the associated instabilities, induce/deter certain pattern formations, and maximize/minimize the resulting mixing. This enables one to precisely predict and design behaviours of multi-fluid flows in relevant systems, reducing concomitant negative impacts associated to unpredictability and uncontrollability of these flows. In the short-term, motivated by a number of recent studies that propose controlling strategies for simple (Newtonian) fluid displacement flows, we will extend three controlling strategies for complex (non-Newtonian) fluid displacement flows through studying: