When polymers are added to a solvent, even in very dilute solutions, they markedly change the behavior of the fluid in intriguing ways, such as reducing the drag force of flow past objects. Polymer-induced drag reduction in marine transport applications can result in 20-25% decrease in frictional energy losses and can thus have a major impact on society in the form of reduced fuel consumption and carbon dioxide emissions. However, the changes induced in the time-varying three-dimensional fluid dynamics are often counter-intuitive and poorly understood. In some configurations, the polymeric solution can introduce new flow instability mechanisms that would not be possible in typical fluids; yet in other regimes, the same forces can also have the seemingly opposite effect of mitigating the energetic eddying motions of turbulence. Direct imaging of the evolution of turbulent flow structures is needed, and it requires a technique with very high resolution and sensitivity. The research plan to achieve this goal is tightly coupled with an education and outreach plan that includes both curriculum development and supplemental lectures and interactive lab demonstrations for Engineering Innovation through summer programs for high-school and college-level STEM students at both universities.
The research involves detailed experiments using a unique imaging system to probe how a polymeric jet injected into a surrounding Newtonian fluid becomes unstable. These visualizations will enable a detailed characterization of the mixing between the polymeric jet and the surrounding fluid and the amplification rate of jet instability. The results from the experiments will be complemented by first-of-their-kind measurement-infused simulations of the same configuration. By directly integrating the measurements into the simulations, computations will probe the exact same flow and provide all the additional details that cannot be measured directly in the laboratory. The coupled results from both the experiments and simulations will provide an unprecedented view of the mechanisms through which polymer solutions alter turbulent flow instabilities. Ultimately, such insights will explain how molecular parameters such as chain extensibility and flow elasticity control polymer drag reduction and help guide selection of novel biopolymer sourced additives that can serve as cheap and environmentally friendly substitutes for traditional drag reduction agents such as synthetic polymers derived from hydrocarbon resources.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.