Chemical Engg. Seminar Series : Dr. Manish Kumar.

Complex dynamics in complex fluids

Biological and industrial fluids are often complex due to the presence of macromolecules, cells, and particles. The flow of these fluids exhibits complex dynamics arising from their intricate microstructures and regulates a broad range of applications in energy, biomedical, and environmental sectors. Elastoinertial turbulence (EIT) is an example of such complex dynamics that emerges in the flow of dilute polymer solutions from the interplay between inertia and elasticity and limits the achievable drag reduction using polymer additives in turbulent flows. Polymeric additives are commonly used in pipeline transport of liquids to reduce pumping costs and in the filling of aircraft tanks to reduce fuel transfer time. They have also been envisioned as a means to enhance the drainage capacity of sewer systems for flood control. In this talk, I will discuss the dynamics of EIT and demonstrate that its dynamics is predominantly composed of a collection of self-similar nested traveling waves, where the most dominant traveling wave originates from a nonlinear wall mode instability and the remaining traveling waves originate from a recursive process. Due to its complexity, EIT is computationally expensive to investigate, creating a bottleneck in the downstream analyses of its dynamics. In the latter part of the talk, I will introduce a framework based on machine learning that enables the development of a reduced-order model of EIT, which accurately captures its dynamics roughly a million times faster than the direct numerical simulation. Such acceleration facilitates downstream analyses, including the investigation of coherent structures and the design of control strategies to suppress EIT to reduce turbulent drag beyond the Maximum Drag Reduction (MDR) limit.