Gas phase turbulence effect over the hydrodynamics of the solid phase in Euler-Euler sub-grid modeling of rapid gas-solid flows

• Grant number: 11/11278-4
• Support Opportunities: Scholarships abroad - Research
• Start date: November 01, 2011
• End date: October 31, 2012
• Field of knowledge: Engineering - Chemical Engineering - Chemical Process Industries
• Principal Investigator: Christian Lea Coelho da Costa Milioli
• Grantee: Christian Lea Coelho da Costa Milioli
• Host Investigator: Sankaran Sundaresan
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Institution abroad: Princeton University, United States

Abstract

Rapid gas-solid flows in circulating fluidized beds are multiphase, highly heterogeneous, turbulent, reactive and multi-scale. All the scales in the flow intensely interact with each other, highly affecting all the mass and energy transfer, and reaction rates in the process. Those characteristics impose refined mathematical models that are strongly based on computational fluid mechanics. However, the computational processing capabilities, both present and in the foreseeable future, are far bellow that required for resolving all the scales in the flow. Therefore, large scale simulations (LSS) are performed in coarse numerical meshes, which require sub-grid modeling for recovering filtered information. A common procedure for generating sub-grid models consists of performing sub-grid simulations (SGS) applying Euler-Euler formulations (two-fluid modeling) in small domains under periodic boundary conditions. This line of research has been practiced at the University of Princeton since the 90's, under the command of Professor Sankaran Sundaresan. In gas-solid flows the SGS simulations are referred to as highly resolved simulations, since numerical meshes are practiced that are refined enough to capture all the scales of cluster sizes that develop. This, however, does no happen for the gas phase, whose inferior turbulent scales are filtered for their sizes fall orders of magnitude bellow the mesh resolutions that are computationally viable. The literature shows that gas turbulence can, in fact, affect the effective hydrodynamics of the particulate motion in gas-solid flows. The extension at which this happens is, however, an open question. In Euler-Euler sub-grid simulations gas phase turbulence is usually disregarded. In this project such effect is to be accounted for by introducing additional modeling for the turbulent kinetic energy of the gas phase. It is intended to consider an additional conservative transport equation and closures for the turbulent kinetic energy of the gas phase; to implement it into the Euler-Euler open source numerical code MFIX; and to perform computational experiments for studying the effects of gas turbulence over drag and over the hydrodynamic effective behavior of the solid phase. (AU)