Research Keywords: computing in chemical engineering; polymers; fluid mechanics; rheology; molecular simulation; computational fluid dynamics; process modeling.
Chemical processes and materials are often governed by complex dynamics spanning a broad spectrum of length and time scales. Non-trivial coupling between them makes the prediction of material properties or process outcome highly challenging, for which intuition can often be misleading. We use high-performance computers and combine a range of numerical tools -- including computational fluid dynamics (CFD) and molecular dynamics (MD) -- to simulate these systems and investigate their underlying dynamics, from the molecular scale up to the continuum level. Simulation results are combined with theories and data analytics for in-depth insight not available from experiments, which advances our fundamental knowledge in areas such as polymer physics, fluid dynamics, and physical chemistry.
We also strive to develop scientific computing as a mainstream tool in industrial development. Working with various partners and collaborators, we keep on refining our modeling capability for more reliable predictions of process outcome and materials properties. Recent and ongoing projects include the modeling of fluid flow, mixing, and reactive processes and computational molecular engineering for the formulation development of polymer materials.
Current research projects are organized around the following theme areas.
Multiscale molecular modeling of polymer materials
Polymer materials are not only ubiquitous in our everyday life, their characteristics -- high flexibility, light weight, high manufacturing speed (and low cost), functionalizability, etc. -- also make them potential solutions to some of the greatest challenges our society faces. Indeed, many new materials designed for applications in energy, the environment and biomedicine involve polymers. Properties of polymer materials are determined not only by the chemical structure of the monomers but also by their configuration and dynamics at the scales of segments and entire chains. To capture these scales, we take a holistic approach and combine fully-resolved atomistic simulation with coarse-grained molecular models. Our goal is to build a bottom-up approach for the molecular design of materials with controlled morphology and targeted properties.
Energy conservation/drag reduction in flow turbulence
When flow in a pipe transitions from the laminar state to turbulence, its friction drag increases abruptly: energy dissipation in turbulent flows is much larger. Regulating flow turbulence for energy conservation is thus of immense technical significance. It has been well established that dissolving a minute amount of polymers can substantially reduce the turbulent friction drag. Despite decades of research, answers to many questions in this area remain elusive. We use high-performance computers to systematically investigate the mechanisms behind experimental observations. Building on this understanding, new approaches will be developed to achieve high-levels of drag reduction without polymer additives.
Dynamics and rheology of polymer liquids
Polymer liquids -- solutions and melts -- are found in numerous settings including the processing of most polymer materials. When polymer dynamics are coupled with flow motion, many interesting phenomena can occur, understanding of which can be of great practical significance. On the one hand, polymer chains can be strongly deformed by the flow: as a result, conditions of polymer processing can largely determine the structure and properties of the final products. On the other hand, polymers also change the rheological properties of the fluid, which often results in flow behaviors drastically different than what we see in simple Newtonian fluids. Combing our expertise in molecular modeling and complex fluid flow simulation, we investigate polymer fluid behaviors at both small and large scales.