Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Kent E. Wardle Project Name: SepCFD Division: CSE Project title: CFD Simulation of Separations Processes Associated funding: - DOE-NE Nuclear Energy Advanced Modeling and Simulation (NEAMS) Program - DOE-NE Fuel Cycle Research and Development (FCR&D) Program Other Systems: - MCS Cosmea Linux Cluster (limited use for development and debugging) - MCS Full-disclosure (SiCortex 5832) - local 8-core workstation for meshing, postprocessing, and small-scale development Science: This project uses the open-source CFD package OpenFOAM (www.opencfd.co.uk) which is based on the finite volume solution method of the Navier-Stokes equations on arbitrary polyhedral, unstructured meshes for computational fluid dynamics simulations. OpenFOAM is capable of simulation of a wide range of physics and the focus in this project is on simulation of turbulent, multi-phase (liquid-liquid and liquid-liquid-air) mixing and separation. The specific application of interest is for liquid-liquid extraction processes employed in recycling of used nuclear fuel. In addition, a small portion of the project seeks to explore advanced CFD methods using a finite-element based unstructured, lattice Boltzmann simulation method. This is promising technique which can bridge the gap between molecular and continuum scales and can potentially allow much more efficient computational scaling than traditional CFD techniques. Project description: This project seeks to apply the open-source CFD package OpenFOAM to simulation of the complex, multiphase flow in liquid-liquid separations devices used for processing nuclear fuel via solvent extraction with a particular focus on simulations of the flow in the annular centrifugal contactor (www.mcs.anl.gov/~wardle/contactorSketch.png). For such processes, complex physical phenomena including free surface flow and liquid-liquid droplet breakup and coalescence must be incorporated. Accurate simulation of such physics requires fine meshes to resolve phase boundaries as well as efficient computational performance to enable transient simulations spanning several seconds of flow time despite the very small time steps that are required (~10-6 s). The specific simulation techniques to be used for the OpenFOAM simulations are based on the Volume of Fluid (VOF) method with Large Eddy Simulation (LES) of turbulence. Additional multiphase simulation methods will also be explored. The code package OpenFOAM uses a C++ object-oriented framework with dynamically linked libraries and high-level solvers to enable the user to write custom solvers and combine various physics models and equations enabling the evaluation of unique combinations of models such as are required for the development of advanced liquid-liquid mixing simulation capability as targeted in this work. Work during FY11 will focus on three-phase (liquid-liquid-air) simulations of the coupled mixing zone and separation zone of the annular centrifugal contactor (see contactor sketch link above). Here is an example of the type of simulations that have been conducted to date and will be built upon as part of this work: www.mcs.anl.gov/~wardle/4vpoly05base_BRC-side-15fps.avi. This simulation shows the turbulent mixing of water (blue), oil (red), and air (cyan) in the annular mixing region of a centrifugal contactor and was performed on ~2000 processors on MCS's SiCortex system. During FY10, large simulations for water-air and water-oil-air flow in a coupled model of the mixing and separating zone were conducted using a the VoF-based multiphase solver. A snapshot from the two-phase water-air simulation showing the flow of water in the contactor as seen from above is shown here: www.mcs.anl.gov/~wardle/fullExt-over-woExts.png. Analysis of the three-phase simulation is ongoin g and will provide valuable insight and provide a basis for the development of advanced multiphase models that will take place during FY11. The results of this work will also be included in a future paper currently being prepared. In addition to this full-scale, liquid-liquid simulation effort, during FY10 a focused project on exploration of a specific design feature of a commercially available contactor design was also conducted with the support of this project allocation. These results will be the core of another paper now in preparation and will also provide valuable direction for improving performance of contactors of this design to places such as Savannah River where they are in use. This project will support nuclear fuel cycle simulations efforts under DOE-NE as well as potential collaborations with DOE-EM sites such as Savannah River where centrifugal contactors and other multiphase separators are in use. The simulations performed here will also support ongoing FY11 experimental work in CSE led by the PI aimed at obtaining detailed multiphase measurements in an engineering-scale annular centrifugal contactor using electrical tomographic techniques. It is hoped that this experimental effort can provide data for validation of advanced multiphase CFD models. Aside from the work outlined above, one additional component of this project seeks to explore 'advanced' CFD techniques which may be more inherently suited to massive-scale parallel computations. One such advanced method is based on an unstructured method for solution of the discrete Boltzmann Equation along with a free-energy based multiphase simulation technique. This method does not require a global pressure solve and depends primarily on nearest neighbor information allowing it to exhibit more ideal parallel scaling. While to-date many of these simulations have been done on other systems (e.g. full-disclosure), a small fraction of the project allocation may also be used for this developmental effort. This project has one PI (Wardle) and may have at most 1-2 additional participating researchers, collaborators, or students. Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 600000 Justification: The OpenFOAM code has been found to scale quite well on a number of different computational systems. The Volume of Fluid technique combined with the fine mesh resolution required for droplet and interface tracking necessitate simulation timesteps on the order of microseconds. As such, typical runs require about 100 wall hours for every 1 second of simulated flow time. On Fusion with more recent versions of the code with minor enhancements, we have observed that this can be reduced to ~50 hours/1 second of flow. A plot showing a comparison of the scaling (strong) of a characteristic OpenFOAM simulation (VOF interFoam solver) for a relatively small-size problem (530K tetrahedral cells) is posted here: www.mcs.anl.gov/~wardle/scaling_ann3d_530K_cosmeaFdSurveyorFusion.png. Note that the number of processors has been scaled to 2.0Ghz equivalents. OpenFOAM performs quite well on Fusion. During FY10 work, a number of runs using polyhedral meshes on the order o f 1M cells were done on as many as 128 processors. As new solvers are used the scaling may need to be explored again to ensure the optimum number of processors are used to efficiently use the project allocation. Thank You, The LCRC Accounts System