Discrete Particle Modeling of Dense Multiphase Flows

      Dense dispersed flow has been identified as a complex system, which consists of a large number of finite solid particles, gaseous bubbles or liquid droplets that are convected by a laminar or turbulent flow of a continuous fluid. Of significance are the ongoing research efforts to develop numerical models and to understand the flow behavior of such complex system. Several models at different resolution scale levels have been formulated, among which the discrete particle model (DPM) shows a great potential to unearth the system complexity for its merit of modeling the dispersed phase in a natural way.

      During my PhD study I developed a 2D hard-sphere discrete particle/bubble model and coupled it to computational fluid dynamics. Later I solved several difficulties in 3D code development, including the accurate void fraction calculation under unstructured grid and the implicit two-phase coupling algorithm. I also proposed an efficient particle collision handling algorithm which allows a full 3D simulation of gas-particle systems having several millions of particles without parallel computing. The developed 3D DPM code has been integrated into the commercial CFD software FLUENT by user-defined functions. The code has been validated through a comprehensive comparison to the experiments and can capture many important characteristics of gas-solid fluidization systems, such as bubbling, spouting, particle clustering and core-annulus flow structures under specific operating conditions.

      I have a great interest in developing numerical models and have gained a lot experiences in scientific computation, especially in high performance computing since I worked as a research assistant on the project of meso-scale air pollution modeling at the Hong Kong Polytechnic University. My research goal is to develop an efficient, versatile and robust 3D-DPM code that can be used to study the dispersed multiphase systems. This relies not only on programming skills but also on a thorough understanding of the physics inside, such as all kinds of interactions taking place in a dispersed system. The latter actually helps a lot on designing numerical algorithms. My future research mainly focuses on the following topics

1)  3D-DPM code development for simulation of bubbly flow with free surface

2)  Three-phase flow and particle-scale heat transfer in fluidized bed by DPM simulations

3)  Particle mixing and segregation in granular flows

      In this poster session, I will present my recent work on the 3D parallel DPM code development under TeraGrid and LONI HPC environment. By designing a specific interface, the developed parallel code can run separately for granular flow simulation or corporate with the CFD solver for dispersed gas-solid flow simulation based on the user's demand. Both MPI and multithreading techniques are adopted in the code development. The parallel code is scalable up to 128 CPUs.

Post-doctoral advisor

K. Nandakumar, Gordon A. and Mary Cain endowed chair professor, Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803

Selected publications

[1] Wu C.L., Berrouk A. S., Nandakumar K., Three-dimensional discrete particle model for gas-solid fluidized beds on unstructured mesh. Chemical Engineering Journal 152: 514-529, 2009

[2] Wu C. L., Zhan J.M., Li Y.S., Lam K.S., Berrouk A.S., Accurate void fraction calculation for three-dimensional discrete particle model for gas-solid fluidized bed on unstructured mesh, Chemical Engineering Science 64:1260-1266, 2009.

[3] Wu C. L., Berrouk A. S., Nandakumar K., An efficient chained-hash-table strategy for collision handling in hard-sphere discrete particle modeling, Powder Technology 197: 58-67, 2010

[4] Wu C. L., Yang Y., Wong S.L., Alvin Lai C. K., A new mathematical model for irradiance field prediction of Upper-Room Ultraviolet Germicidal Systems, Journal of Hazardous Materials 189: 173-185, 2011

[5] Wu C.L., Zhan J.M., Li Y.S., Lam K.S., Dense particulate flow model on unstructured mesh, Chemical Engineering Science 61:5726-5741, 2006