1. Robust Grid-based environment for large scale lattice-Boltzmann simulations Maddalena Venturoli Matt Harvey Peter Coveney Giovanni Giupponi Jonathan Chin Robin Pinning Andrew Porter Steven Pickles AHM 2005

2. Scientific motivation: flow in porous media Study multiphase fluid flow in porous media using realistic geometries from XMT data resolution of 4.9  m full data set ~ 800 3 voxels Large scale simulations

3. Fluid represented by one particle distribution function on a lattice, discrete velocities Time evolution: advection and collision. Conserves mass and momentum: recovers Navier-Stokes equation Multiphase: local (nearest neighbour) force to take into account interactions with other components (coupling constant) Shan-Chen model Lattice-Boltzmann method Color coding

4. Advantages Easy to implement and “embarrassingly” parallel: only local interactions Scales as N (number of lattice sites) Complex boundary conditions can be treated by simple rules Fluid/fluid interfaces emerge from the dynamic binary/ternary (surfactants) miscible/immiscible fluids linear parallel performance up to 1024 CPUs (gold star at HPCx) Grid enabled for computational steering and visualization Checkpointing facility, platform independent format Lattice-Boltzmann code: LB3D (CCS-UCL) (performance steering and job migration)

5. Parameter space exploration Two-phase fluid: coupling constant (miscibility/surface tension) Mixture composition Rock wettability Flow rate Monitor evolution of interfaces as function of time Computational steering and visualization increasing rock wettability increasing water concentration

6. RealityGrid steering library Real-time interaction with running applications Relatively easy to implement in existing codes Dynamic attach/detach Pause/Resume/Stop Parameter steer/monitor: Qt-steerer, Web portal (EPCC), PDA Checkpointing Job migration/restart (checkpoint tree)

7. RealityGrid infrastructure

8. Creating a robust Grid environment: a user perspective Portability issues Security and certification Globus related issues Implementation of a local Registry at UCL UKLight connectivity Visualization (security issues) Co-allocation of resources Now easier to bring new users “up-and-running” (ex.LAMMPS)

10. Bentheimer: permeability vs system size

11. Multiphase flow generalized Darcy’s law J = flux, X = force, S = saturation k = relative permeability binary immiscible mixture oil/water colour label red/blue rock (3d) is water wet

12. Results: relative permeabilities LB simulationsExperimental data SPEJ, 1998 256 3 run on NCSA

13. Drainage 512 3 data set, simulations run on 256 procs at HPCx

14. Contact: m.venturoli@ucl.ac.uk http://www.realitygrid.org