MicroMesoscopic Modeling of Heterogeneous Chemically Reacting Flows MMMHCRF

Micro-Mesoscopic Modeling of Heterogeneous Chemically Reacting Flows (MMMHCRF) Over Catalytic/Solid Surfaces Presented by Sreekanth Pannala Computing and Computational Science Directorate Computer Science and Mathematics

Goal Develop a multiphysics and multiscale mathematics framework for accurate modeling of heterogeneous reacting flows over catalytic surfaces 2

Flow over a catalyst surface Chemically reactive flow over a surface is a basic building block which is central to many energy-related applications Illustrative benchmark to demonstrate the capability to integrate scales of several orders of magnitude KMC: ~1 QM: ~1 LBM: ~1 m nm mm Lattice Boltzmann (LBM) Kinetic Monte Carlo (KMC)Density Functional Theory (DFT) Closely Reaction coupled barriers Figure adapted from Succi et al. , 2001 3

Approach: KMC–LBM coupling through Compound Wavelet Matrix y y KMC contribution LBM T viqi x t LBM contribution viqi KMC x Fractal projection Actual surface 4 x-y x x Compound Wavelet Matrix (CWM) Construct a CWM from LBM and KMC Use CWM for coupling of mesoscopic and microscopic simulations in time and space Use a Multiple Time Stepping (MTS) algorithm for higher order accuracy in time Use fractal projection to map the surface topographical information to construct the KMC in one less dimension

CWM methodology in work: Transferring information from KMC to LBM Wavelet transformation Micro-information Homogenized KMC properties at next scale Increasing spatial or temporal scales Objective: Develop algorithms to construct projection operators and time integration methods to connect the microscale (e. g. , KMC) and the mesoscale (e. g. , LBM) 5 Homogenization at the level corresponding to LBM, feeding from KMC to LBM The interactions between various physical processes at different scales are encapsulated by CWM and can be employed in control and design of reacting surfaces Time separation between methods and scales simplifies the problem The method recovers the mean field behavior in the macroscopic limit

Recent results* 1 D reaction/diffusion simulation performed at two different length and time scales - Fine (KMC and diffusion equation using finite difference at fine scale) - Coarse (analytical species solution and diffusion equation using finite difference at coarse scale) Reconstructed the fine simulation results to reasonable accuracy using CWM at fraction of cost Method allows for bi-directional transfer of information, i. e. , upscaling and downscaling *Frantziskonis et al. (under review) 6

80 Coarse 60 40 CWM reconstruction Fine 20 0 20 40 60 80 Time, t 100 120 Successfully applied CWM strategy for coupling reaction/diffusion system A very unique, rigorous, and powerful way to bridge temporal and spatial scales for multiphysics/multiscale simulations *Frantziskonis et al. (under review) 7 A(0 k, t) 100 A(0 k, t) Species concentration A(0 k, t) Recent results* 50 40 30 20 10 0 Transferring mean field 100 200 300 Time, t 400 Transferring fine-scale statistics 25 500 100 Time, t 200

Applications Chemical looping combustion (CLC) SCOT (staged combustion with oxygen transfer) Efficient, low-emissions and amenable to CO 2 sequestration CLC adapted for transportation Fibrous substrate for discontinuous fiber substrate The voids found by probing the substrate with a fixed-size sphere are denoted by spheres a a Polyethylene production Important process which uses ~10% of crude petroleum Reactive flows through fibrous media Light-weight, p low-cost and highradiation strength composites z Fuel cell components Gas Scaffolds for phase Gas flow in the biomedical char applications Pyrolysis Coal gasification and combustion 8 New technologies for cleaner and efficient coal combustion a front Not yet reacted coal r Coal particle b z Schematic of burning of coal particle using laser heating in microgravity environment showing the various regimes of combustion [Adapted from Wendt et al. , 2002]

Additional applications: Nuclear fuel coating process Coated fuel particle (small scale) Si-C Kerne l Amorphous C Spouted bed coater (device scale) ~10 -1 m Ballistic zone UO 2 Inner Pyrolitic C Transport reaction zone (~10 -6 -10 -2 s) ~10 -3 m Hopper flow ~10 -3 m • 0. 5 - to 1 -mm particles zone (~s) Inlet gas • Coating encapsulates fission products • Failure rate < 1 in 105 • Quality depends on surface processes at nm length scale and ns time scales 9 Pickup zone (~10 -6 -10 -2 s) • Coating at high temperature (1300– 1500°C) in batch spouted bed reactor for ~104 s • Particles cycle thru deposition and annealing zones where complex chemistry occurs Design challenge: Maintain optimal temperatures, species, residence times in each zone to attain right microstructure of coating layers at nm scale Truly multiscale problem: ~O(13) time scales, ~O(8) length scales Links multiscale mathematics with petascale computing and GNEP

Going forward Extend the methodology to multiple spatial dimensions Couple the KMC with LBM simulator Develop error measures and error control strategies Implement the multiscale framework into highly scalable parallel environment Apply the developed framework to the targeted applications 10 Pannala_MM_0611

The Team Oak Ridge National Laboratory University of Arizona National Energy Technology Laboratory George Frantziskonis Thomas O’Brien Srdjan Simunovic Sudib Mishra Dominic Alfonso Stuart Daw Pierre Deymier Madhava Syamlal Sreekanth Pannala Phani Nukala 11 Ames Laboratory Iowa State University Rodney Fox

ORNL contact Sreekanth Pannala Oak Ridge National Laboratory (865) 574 -3129 pannalas@ornl. gov 12 Pannala_MM_0611 12