(3ek) Multi-Scale Modeling of Mechanics and Transport in Complex Particulate Materials

Particulate materials like powders, colloids and suspensions are ubiquitously found in various industries such as pharmaceutical, consumer products and renewable energy. Despite common occurrence, their mechanics during processing, and transport through them in deployed devices, are poorly understood on a fundamental level, particularly in far from equilibrium conditions. A key scientific challenge is to identify particle-scale mechanisms that govern macroscopic properties (e.g., rheology, structure, transport) of particulate materials, and provide predictions for their response to various processing and operational conditions. A combination of computer simulations and applied mathematical methods can provide the required tools to tackle this challenge. Computer simulations can be used to elucidate particle-scale mechanisms for a specific material response at small length and time scales, and applied mathematical techniques such as continuum and phase-field modeling can be used to upscale this knowledge towards predictive models at larger length and time scales.

During my graduate research with Prof. Timothy Fisher at Purdue University, I developed computational methods to study rheology, mechanics and transport in granular materials. I simulated creep in packings of polyhedral particles, and identified how local non-affine mechanics drive macroscale plasticity, with relevance to processing of cement and concrete, and additive manufacturing. These findings also provided fundamental insights into the mechanics of amorphous materials. I also demonstrated how thermal transport occurs through composites of polyhedral nanoparticles, with relevance to materials development in thermoelectric devices and batteries.

In my research as a postdoctoral fellow with Dr. Gary Grest at Sandia National Laboratories, I am developing tensorial constitutive models for non-equilibrium flow-arrest transitions in granular materials through discrete element simulations. Such models can aid in the prediction of intermittent clogging of powder flows in industrial processing and the development of particulate materials with targeted rheology, thus reducing waste and downtimes. In another project, I am simulating particulate processing of lithium-ion battery electrodes with complex inter-particle interactions towards providing materials predictions for optimized battery performance.

My future research program will build upon my prior research experiences, and will initially focus on the following three themes:

Mesostructure control in solid-state batteries for enhanced transport. Solid-state batteries are dense compacts of electrode and electrolyte particles along with conductive carbon nanoparticles. Computer simulations will be used to accurately model their processing that involves compaction of particulate materials. Statistical methods will be used to characterize mesostructural and electrochemical transport heterogeneity through these materials. Data science techniques will be used to develop statistical correlations between particle properties, processing mechanics and battery performance.

Constitutive modeling of granular materials with complex interactions in complex flows. Common industrial granular materials like cement and pharmaceutical powders contain particles with complex shapes flowing in complex flow fields. The interactions between particles is often a combination of cohesion and complex tribology. However, current constitutive models for granular flows are limited to spherical particles with simple frictional interactions in simple shear flow fields. Particle-based simulations will be used to simulate granular flows with models for cohesive and complex tribological interactions between aspherical particles in shear, extensional and mixed flow fields. Using techniques from representation theory, constitutive rheological models will be developed that connect microstructural features of flow to continuum description of the material. The calibration of particle interaction models will provide opportunities for collaboration with experimental research groups.

Modeling evaporation of particulate materials partially saturated by fluids. Partially-saturated particulate materials in fluids are formulated during industrial processing involving drying and solidification, such as in additive manufacturing and wet granulation technology. However, there is a lack of fundamental understanding of particle dynamics during drying and its influence on material structure upon drying. A combination of phase-field modeling and particle-based simulations will be used to model capillary stress and simulate resulting particle dynamics, with an aim to develop continuum models for structural evolution during drying.

Teaching Interests:

During my PhD, I had the unique opportunity to assist in teaching an undergraduate laboratory course on Heat Transfer, a master's course entitled Nanoscale Heat Transfer, and a doctoral course entitled Numerical Methods in Heat, Mass and Momentum Transfer. For the master's course, I also aided the course instructor in designing the course, drafting the course textbook and creating Wolfram CDF tools as computational aids in a flipped classroom environment. My extensive and diverse teaching responsibilities to a diverse student group were an enriching experience that I thoroughly enjoyed, and I look forward to my role as a teacher in the future.

My research and educational experience has well-equipped me to teach Thermodynamics, Fluid Mechanics, Transport Phenomena and Mass Transfer at undergraduate and graduate levels. In addition, I propose to develop two courses for senior undergraduate and graduate students. The first course entitled Introduction to Granular Materials will expose students to the fascinating world of granular materials along with their importance in nature and industry. The second course entitled Computational Methods for Complex Fluids will provide a review of advanced computational methods in modeling and simulation of complex fluids.