According to United Nations, 8 million tonnes of plastic waste is dumped into our oceans every year. The plastic waste doesn't just stay at the top layer, it gets disintegrated into even dangerous micro plastic due to wind and wave action. These micro plastics have been found in deep oceans as well as in the stomachs of deep sea animals. Once the waste turns into micro plastic, it is almost impossible to take it out. The question is ; can we do anything about it? Apart from taking the essential steps of avoiding the use of single-use plastic products, we need to make our plastic waste recycling process more efficient and effective. One of the crucial stages in recycling industry is identification and sorting of plastic of various kinds and contaminants and gravitational settling is often used for this purpose. However, there is a lack in our understanding of how the settling process is affected by various important parameters like inertia, shape and surface irregularities. Due to this reason, there is cross-contamination in recycling making the process highly inefficient. In this project, we shed light into how inertia and surface irregularities affect settling of particles across fluid interfaces. Insights from this work provides framework for making recycling more efficient and effective.

Rapid global scale carbon capture and storage is essential to minimize the global warming. Injection of CO2 into deep, brine-saturated rocks is a commercially proven technique of CO2 sequestration. However, CO2 migrates away from the injection site due to buoyancy and viscous forces, increasing the probability of escape from the injection zone. Capillary trapping, which occurs when CO2 pinches off and becomes immobilized in the pore space by capillary forces, is one of the key processes that successfully limit CO2 plume migration and boost storage capacity in saline aquifers. Capillary trapping is a complex phenomena that is governed not only by the fluids’ interfacial tension, but also by the wettability of the porous media, the inertia of the invading fluid, gravitational and viscous forces, and pore geometry. However, our understanding on the effect of pore geometry and inertia on the capillary trapping is still lacking. In this project, we shed light into how the inertia of the invading fluid and the pore geometry can influence the trapping process. Insights from this work will help optimize the trapping process for efficient CO2 storage.

For many lung diseases, lung transplantation is the only available “cure”. Unfortunately, there are not enough donor organs to supply the demand, and those lungs that are transplanted are at constant risk of rejection necessitating the use of immune suppressants for the remaining life of the recipient. Due to the paucity of suitable donor lungs available, the bioengineering of lungs using the patients’ own cells is being investigated as an alternative. Lung decellularization/recellularization strategies have been hampered by inefficient cell seeding techniques for the airways. It is reasoned that sprayed deposition of live cells in a targeted manner into the airways will facilitate the approach. However, the parameters required for optimizing the spraying strategy are not well defined. The aim of this project is to understand and characterize cell distribution within aerosol sprays and determine how this distribution correlates with short term viability of deposited cells as well as longer term cell differentiation. This project is in collaboration with leading experts from the Department of Medicine at the University of Minnesota. The research findings from this work also have implications for other biofabrication techniques such as 3D bioprinting, as well as the development of in vivo cell therapies for lung injury and disease.

Low-drag events are intriguing, intermittent events in wall-bounded turbulent flows that are a natural target for flow control strategies. Sometimes referred to as hibernating turbulence, these events are described by extended periods (~ 3 eddy turnover times) where the skin friction of the system is considerably lower than its mean value (~ 90% of the mean). Characterization of low-drag events can provide a better understanding of how and why these events manifest. This project aims to characterize these events for moderate Reynolds numbers of Re_τ = 700. We compare direct numerical simulations (DNS) of a turbulent channel flow with experimental data obtained by stereoscopic particle image velocimetry (SPIV) for a turbulent boundary layer at the same friction Reynolds number. We investigate Turbulent characteristics and Reynolds number dependence of the near-wall low-drag events. This work combines expertise in CFD and experiments from the University of Nebraska-Lincoln and the University of Minnesota, respectively.