OUR PASSION LIES HERE
Research Themes
▎ Polymer Materials | Polymer Dynamics and Rheology | Structure-Property Relationships | Sustainability
▎ Fluid Mechanics | Turbulent Flows | Viscoelastic Fluids | Computational Fluid Dynamics
▎ Digital Manufacturing | Process Modeling | Process Design and Development
▎ Scientific Computing | Experiments | Modeling | Theory | Data Science
The Xi Research Group takes its core knowledge in polymer physics, fluid mechanics, and chemical engineering fundamentals and applies it to a broad spectrum of research topics, from fundamental research in flow turbulence and polymer dynamics to applied research in the development of sustainable and smart materials manufacturing processes.
Current research projects are organized around the following theme areas.
▊ Numerical simulation of flow turbulence in Newtonian and viscoelastic fluids
Fluid flow in a pipe or channel turns turbulent when its flow rate surpasses a certain threshold. With this transition, fluid mixing is significantly enhanced but the energy consumption for fluid transportation also sharply increases. Modern computer simulation techniques can faithfully reproduce the detailed, time-dependent flow fields that are otherwise hard to measure in experiments. The simulation results, however, still contain an overwhelming amount of information, owing to the intrinsic complexity of turbulent dynamics, from which meaningful physical theories cannot be straightforwardly derived. Researchers rely heavily on subjective visual inspection and intuitive arguments for understanding turbulence. We envision a different approach in which physical narratives can be built on the objective analysis of flow fields. Towards that goal, we are developing methods for extracting flow structure objects, such as vortices, from turbulent flow fields and analyze their statistics and life-time evolution.
Another passion of us is to study how the dynamics of polymer molecules interact with turbulence. Dissolving a small amount of long-chain polymers makes a fluid viscoelastic. Viscoelastic fluids show many unusual flow behaviors. In turbulent flows, these fluids often require much less energy to be pushed down, e.g., the pipeline, which is known as the turbulent drag reduction phenomenon. We combine numerical simulation with detailed flow field analysis to reveal the fundamental physics behind the complex phenomenology.
▊ Sustainable polymer manufacturing for a zero-plastic-waste future
Plastics are among the most impactful inventions in our industrialized society. Meanwhile, their prevalence has also irreversibly changed our relationship with the environment. As chemical engineers, we were credited for the convenience that plastics has brought upon our life, we are now also responsible for re-inventing a plastic industry that can co-exist with a happy environment.
Our group aim to develop technologies for plastics production that will minimize the amount of plastic wastes ending up in the environment. Our efforts are split into two routes. The first is to enable more recycled plastics to re-enter the production line for a circular plastics economy. Our immediate focus is on PVC, which is notoriously difficult to recycle and reprocess. Vinyl (PVC) products containing a substantial portion of recycled ingredients are known to show inferior performance. In our lab, we are developing technologies that will allow more recycled PVC to be used in the production of new plastics without sacrificing the product quality. The second route searches for biodegradable materials to replace synthetic plastics. Food and beverage packaging, containers, and grocery bags made of such materials will break down in the natural environment without leaving a permanent footprint. In both routes, we work closely with the plastics industry across North America to quickly bring these technologies to manufacturing facilities.
▊ Multiscale molecular modeling for the dynamics and properties of polymer materials
Molecular simulation is a powerful tool that helps us understand the behaviors of a material and predict its properties based on the interactions between its most basic constituents – molecules and atoms. Polymers are a fascinating class of materials whose properties are determined not only by their chemical structures, but also by their molecular conformations and dynamics at a broad range of length and time scales. Molecular simulation holds great promise for unpacking the nontrivial dynamics and complex structure-property relationships of polymer materials. However, fully capturing the vast scales involved in polymer dynamics is computationally prohibitive. We are interested in techniques that allow us to combine and integrate models at different levels for this challenge. With such models, we are especially interested in understanding, and eventually predicting, dynamical properties of polymer materials, such as their mechanical strength, transport coefficients, and rheology.
▊ Digital manufacturing process design enabled by modeling and data science
Chemical manufacturing processes are generally composed of a series of unit operations, each of which has a complex set of design and operating parameters to determine for the whole process to meet its production targets. Development of such processes usually starts from the experimentation of each unit operation at the lab scale, which is then scaled up to larger facilities in a step-wise manner. Intrinsic scale-dependence of the chemical and physical processes involved makes the process outcome highly unpredictable during the scale-up. Repeated trials and errors are often required, leading to high development cost and prolonged development cycles.
We work closely with industrial partners, especially in the pharmaceutical and polymer manufacturing sectors, to integrate process modeling into their design practice. First-principles-based and data-driven models are often combined to predict the outcome of process alteration and scale-up, which will guide the parameter selection and reduce the number of trials at the new set-up. In the long run, the same digital process design approach will also enable the manufacturers to quickly adapt to new products and new processes with minimal cost and production interruption. Such a new paradigm will be critical for meeting the manufacturing challenges of tomorrow.
BEHIND US
Partners
Our research is enabled by the facilities at the following organizations:
