Outstanding Poster Award on our averaging method study in 1st International Conf on Energy and Environment

It is a great honor to receive an Outstanding Poster Award on our averaging method work.

Refs:

1. Q. F. Hou, Z. Y. Zhou, J. S. Curtis, A. B. Yu. How to generate valid local quantities of particle-fluid flows for establishing constitutive relations. AIChE Journal, 65 (2019) e16690.
2. Y. L. Wu, Q. F. Hou, A. B. Yu. Linking discrete particle simulation to continuum properties of the gas fluidization of cohesive particles. Submitted (2019).

[Paper accepted] How to generate valid local quantities of particle-fluid flows for establishing constitutive relations

Q.F. Hou, Z.Y. Zhou, J.S. Curtis, A.B. Yu. How to generate valid local quantities of particle-fluid flows for establishing constitutive relations. AIChE Journal, Accepted (2019).

https://aiche.onlinelibrary.wiley.com/doi/10.1002/aic.16690

How to Generate Valid Local Quantities of Particle-fluid Flows for Establishing Constitutive Relations

Qinfu Hou,^1* Zongyan Zhou,¹ Jennifer S. Curtis² and Aibing Yu^1,3*

¹ARC Research Hub for Computational Particle Technology, Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

²College of Engineering, University of California at Davis, One Shields Ave, Davis, CA 95616, USA

³Centre for Simulation and Modelling of Particulate Systems, Southeast University - Monash University Joint Research Institute, Suzhou 215123, PR China

Abstract

There are continuum and discrete approaches to describe granular flows. A continuum approach relies on local average quantities which can be derived through an averaging method based on a discrete approach. But the selection of averaging domain and the validity of local quantities for constitutive relations are not well established, particularly for transient particle-fluid flows. Here, it is demonstrated that converged local quantities can be achieved on an averaging domain with proper spatial and temporal sizes. Furthermore, the relation between solid pressure and solid volume fraction is established, agreeing qualitatively to all the existing monotonic ones in the literature. But it is quantitatively different, showing a bifurcation at a high solid volume fraction, which is essentially linked to the variation of short and enduring contacts among particles with flow state and solid volume fraction. This bifurcation must be properly recognized in developing constitutive relations for granular materials.

Keywords: particle-fluid flow, fluidized beds, averaging method, constitutive relation, solid pressure

[The relations between solid pressure Ps and solid volume fraction εs in fluidized and moving beds. Scattered circle and triangular symbols are from the averaging method with Lt = 180 and Lp = 3. ]

[Paper online] Micromechanical modeling and analysis of different flow regimes in gas fluidization

Micromechanical modeling and analysis of different flow regimes in gas fluidization
Q.F. Hou, Z.Y. Zhou, A.B. Yu
Abstract
The micromechanics of different particle-fluid flow regimes, such as fixed, expanded and fluidized beds, in gas fluidization is investigated for group A and B powders. To establish the connection between macroscopic and microscopic descriptions of complex particle-fluid flows, focus is given to the following two aspects: the formation of a stable expanded bed in relation to the interparticle cohesive, sliding and rolling frictional forces, and the correlation between coordination number (CN) and porosity (ε). The method employed is the combined approach of three-dimensional (3D) discrete element method (DEM) and two-dimensional (2D) computational fluid dynamics. The results show that compared to 2D DEM, 3D DEM is more reliable in investigating the micromechanics of granular media, although both can capture key features of different flow regimes. The roles of various forces between particles and between particles and fluid are examined, and the origin of different flow regimes is discussed. It is shown that the cohesive force is critical to the formation of a static expanded bed, while the sliding and rolling frictional forces also play a role here. The criterion for bed expansion is analyzed at bulk and particle scales, and the deficiency at a bulk scale is identified. CN, as a key measure of local structure, is analyzed. It is found that the CN-ε relationship for group A powders has a transitional point between the expanded and fluidized bed flow regimes at a bulk scale, unlike group B powders. A new phase diagram is established in terms of CN-ε relationship that has two branches representing expanded and fluidized (bed) states, which corresponds to the one in terms of interparticle forces.

Highlights
► Flow regimes such as fixed, expanded and fluidized beds are numerically reproduced.
► The effects of various forces is analysed corresponding to different flow regimes.
► The contacts among particles and associated flow structures are studied in details.
► A new phase diagram is established to describe the flow regimes.

Keywords
Fluidization; Computational fluid dynamics; Discrete element method; Granular materials; Microstructure; Simulation

http://www.sciencedirect.com/science/article/pii/S0009250912005568?v=s5

A brief review paper of averaging methods in press: linking micro- and macro-properties of particulate flows

Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application
H.P. Zhu^a, Z.Y. Zhou^b, Q.F. Hou^b and A.B. Yu^b, , 
In Press, Corrected Proof, Available online 12 June 2011

^a School of Engineering, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia

^b Laboratory for Simulation and Modelling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia

Received 8 September 2010;  

revised 11 January 2011;  

accepted 11 January 2011.  

Available online 12 June 2011. 

Abstract

Two approaches are widely used to describe particle systems: the continuum approach at macroscopic scale and the discrete approach at particle scale. Each has its own advantages and disadvantages in the modelling of particle systems. It is of paramount significance to develop a theory to overcome the disadvantages of the two approaches. Averaging method to link the discrete to continuum approach is a potential technique to develop such a theory. This paper introduces an averaging method, including the theory and its application to the particle flow in a hopper and the particle-fluid flow in an ironmaking blast furnace.

Zhu, H.P., Zhou, Z.Y., Hou, Q.F., Yu, A.B., 2011. Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application. Particuology 9, 342-357.

A co-authored paper in Chinese Science Bulletin (CSB): Averaging method of particulate systems

H. P. Zhu, Q. F. Hou, Z. Y. Zhou, A. B. Yu. Averaging method of particulate systems and its application to particle-fluid flow in a fluidized bed. Chin Sci Bull 54(2009) 4309-4317.

http://dx.doi.org/10.1007/s11434-009-0500-0

ABSTRACT: A particulate system can be described through the discrete approach at the microscopic level or through the continuum approach at the macroscopic level. It is very significant to develop the method to link the two approaches for the development of models allowing a better understanding of the fundamentals of particulate systems. Several averaging methods have been proposed for this purpose in the past, but they mainly focused on cohesionless particle systems. In this work, a more general averaging method is proposed by extending it for cohesionless particle systems. The application of the method to the particle-fluid flow in a gas fluidized bed is studied. The density, velocity and stress of this flow are examined. A detailed discussion has been conducted to understand the dependence of the averaged variables on sample size.