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Showing 1 to 13 of 13 for “"CMFD"”.
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An Asynchronous Ensemble-Averaging Approach to CMFD Source Acceleration: Rearchitecting Monte Carlo Reactor Simulation Paradigms for the Exasacle Computing Age
… ensemble averaged Coarse Mesh Finite Difference (CMFD) simulation strategy in order to improve parallel efficiency on HPC systems while also addressing other issues surrounding Monte Carlo methods including fission source stationarity, real variance calculations, and nonlinear coupling schemes. …
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A low order acceleration scheme for solving the neutron transport equation
… to capture more angular effects compared with CMFD. Two variations of the LOO method, together with the CMFD method, are implemented in the OpenMOC framework, which is a 2D MOC solver written to solve the 2D heterogeneous reactor problems. Based on the test cases performed in this work, LOO …
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Monte Carlo and thermal hydraulic coupling using low-order nonlinear diffusion acceleration
… by using coarse mesh finite difference (CMFD), a nonlinear diffusion acceleration method. CMFD was implemented in the continuous-energy MC code OpenMC. When employing this technique, the number of inactive generations was reduced by a factor of 10. Realistic reactor calculations also …
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The Investigation and Application of Alternative Strategies for LC/MS based Bioanalytical Research
… of a prototype ceramic micro-fluidic device (CMFD) and optimized MS source was carried out. The CMFD was packed with sub 2 μm bridged ethyl hybrid (BEH) chromatographic particles that could withstand operating pressures of up to 12,000 psi. The MS source was built to operate in both positive …
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Transient method of characteristics via the Adiabatic, Theta, and Multigrid Amplitude Function methods
… of these methods. We began by deriving the CMFD-accelerated MOC algorithm in 2D steady state form and examining the effects of various MOC and CMFD parameters on eigenvalue convergence. The C5G7 problem showed similar acceleration performance for 2, 4, and 7 CMFD energy group structures. …
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Improvements and applications of the Uniform Fission Site method in Monte Carlo
… method, Coarse Mesh Finite Difference (CMFD) acceleration. Both techniques have been implemented into OpenMC, a continuous energy Monte Carlo code. The UFS method uses weights to alter the number of neutrons born at a fission site. It operates on a superimposed mesh, in which each mesh …
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Advanced application of the discrete generalized multigroup method and recondensation to reactor analysis
… tested against Coarse Mesh Finite Difference (CMFD) acceleration. For extremely expensive transport calculations, SEAM was able to outperform CMFD, resulting in speed-ups of 20-45 relative to the normal power iteration calculation. Additionally, to address the growing interest in Krylov based …
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Reactor Core Isolation Cooling Pump Performance in Multiphase Conditions
… A Computational Multiphase Fluid Dynamics (CMFD) simulation was developed herein for implementation in STAR-CCM+. This simulation studied the RCIC pump performance and degradation due to changes in turbine performance and heat up of the Suppression Pool. As the RCIC pump and turbine are …
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Acceleration methods for Monte Carlo particle transport simulations
… Similar to Coarse Mesh Finite Difference (CMFD), the other acceleration method evaluated in this thesis, LOO parameters are constructed from Monte Carlo tallies. The solutions to the LOO equations are then used to update Monte Carlo fission sources. This thesis deploys independent …
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Development of high fidelity methods for 3D Monte Carlo transient analysis of nuclear reactors
… and accuracy. The coarse mesh finite difference (CMFD) diffusion operator is employed as the low-order solver in Monte Carlo transient analysis for the first time. The CMFD diffusion operator is attractive due to its potential to increase the time step size between the computationally expensive …
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Application of the polynomial chaos expansion to multiphase CFD : a study of rising bubbles and slug flow
… namely computational multiphase fluid dynamics (CMFD) simulations. We consider the problem of how to efficiently propagate uncertainties in the model inputs (e.g., fluid properties, such as density, viscosity, etc.) through a computationally demanding model. The challenge is chiefly a matter of …
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A study of Taylor bubbles in vertical and inclined slug flow using multiphase CFD with level set
… 3D Computational Multiphase Fluid Dynamics (CMFD) with Interface Tracking Methods (ITMs) where the interface is tracked with a Level-Set method implemented in the commercial code TransAT®. In the literature, the Taylor bubble velocity is modeled based on two different contributions: (i) the …
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Full core 3D neutron transport simulation using the method of characteristics with linear sources
… ray tracing, Coarse Mesh Finite Difference (CMFD) acceleration, linear track-based source approximations, and scalable domain decomposition. Transport-corrected cross-sections are used to account for anisotropic without needing to store angular-dependent sources. Additionally, significant …