CCS and Power Systems

Crosscutting Research - University Training and Research

Implementation and Refinement of a Comprehensive Model for Dense Granular Flows

Performer: Princeton University

Project No: FE0006932

Program Background and Project Benefits

Dense granular flows are ubiquitous in both natural and industrial processes. They manifest three different flow regimes—commonly referred to as the quasi-static, inertial, and intermediate regimes—each of which exhibits its own dependencies on solids volume fraction, shear rate, and particle-level properties. The differences in these regimes can be attributed to microscale phenomena, with quasi-static flows being dominated by enduring frictional contacts between grains, inertial flows by grain collisions, and intermediate flows by a combination of the two. Existing constitutive models for the stress tend to focus on one or two regimes at a time. Recent research at Princeton University (Princeton) has centered on a rheological model for dense granular flows that captures stresses in all three regimes under steady-shear conditions and the transitions among them.

Since the inception of the Department of Energy (DOE) National Energy Technology Laboratory (NETL) University Coal Research (UCR) Program in 1979, the primary objectives have been to (1) improve understanding of the chemical and physical processes involved in the conversion and utilization of coal in an environmentally acceptable manner; (2) maintain and upgrade the coal research capabilities and facilities of U.S. colleges and universities; and (3) support the education of students in the area of coal science.

As part of the UCR Program, NETL has partnered with Princeton in a project that will continue and advance the development of dense granular flow simulations to enable better understanding of the chemical and physical processes involved in the conversion and utilization of coal.

The nonlinear continuum model developed at Princeton predicts stresses in all three of the aforementioned dense granular flow regimes and is a promising candidate for predicting flow behaviors in industrially relevant flows, which will enhance the ability to interrogate the dense phase flow behavior in large-scale processes. This research in combination with other modeling efforts are targeting improved accuracy and predictive capability of system and flow behavior which will lead to better process design and reduced cost associated with scale up advanced technologies that include complex flow regimes.

Goal and Objectives

The goal of this project is to implement and validate a new rheological model for dense granular phase in MFIX while continuing to improve it to capture more complex flow behavior. Specific objectives planned to accomplish this goal include (1) implementing in MFIX the steady-shear rheological model developed; performing MFIX simulations of various test problems such as hopper, bin, chute, and Couette flows using this rheological model in conjunction with the no-slip and partial slip boundary conditions already available in MFIX; and comparing the results against experimental and DEM simulation data; (2) developing improved wall boundary conditions for the particle phase that can be applied in all three regimes of flow and implementing them in MFIX; examining the effect of refined boundary conditions on flow characteristics in the test problems previously mentioned; and (3) developing the rheological model to allow for dynamic evolution of the stresses, making appropriate modifications to the MFIX implementation, and conducting appropriate validation tests.

Project Details