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Pierce, Flint

Publications and source records attributed to Pierce, Flint.

36 records · Page 2
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DOE OSTI2017

Fuego/Scefire MPMD Coupling L2 Milestone Executive Summary

This milestone campaign was focused on coupling Sandia physics codes SIERRA low Mach module Fuego and RAMSES Boltzmann transport code Sceptre(Scefire). Fuego enables simulation of low Mach, turbulent, reacting, particle laden flows on unstructured meshes using CVFEM for abnormal thermal environments throughout SNL and the larger national security community. Sceptre provides simulation for photon, neutron, and charged particle transport on unstructured meshes using Discontinuous Galerkin for radiation effects calculations at SNL and elsewhere. Coupling these ”best of breed” codes enables efficient modeling of thermal/fluid environments with radiation transport, including fires (pool, propellant, composite) as well as those with directed radiant fluxes. We seek to improve the experience of Fuego users who require radiation transport capabilities in two ways. The first is performance. We achieve this through leveraging additional computational resources for Scefire, reducing calculation times while leaving unaffected resources for fluid physics. This approach is new to Fuego, which previously utilized the same resources for both fluid and radiation solutions. The second improvement enables new radiation capabilities, including spectral (banded) radiation, beam boundary sources, and alternate radiation solvers (i.e. Pn). This summary provides an overview of these achievements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Rubble Fire Multi-Phase Model Development

This report presents multi-phase modeling approaches that are developed for simulating rubble fire scenarios similar to a large-scale rubble pool fire test at Sandia National Laboratories using composite materials and jet fuel. The rubble pool fire test burnt oddly shaped combustible solid objects submerged in liquid fuel. As an intermediate step toward a full scale rubble fire simulation, various model improvement tasks were performed. For modeling solid decomposition, a multi-step degradation model was used for canonical verification problems and the Chemical Percolation for Devolatilization (CPD) approach was implemented. Capabilities of Lagrangian particle approach has been extended such that a group of particles may represent a solid bulk. For gas-liquid interface, the volume of fluid (VOF) technique was implemented and relevant physics were added. The developed tools offer a potential for simulating three-phase (gas, liquid, and solid) combustion applications.

42 ENGINEERING↗
DOE OSTI2016

NSRD-11: Computational Capability to Substantiate DOE-HDBK-3010 Data.

Safety basis analysts throughout the U.S. Department of Energy (DOE) complex rely heavily on the information provided in the DOE Handbook, DOE - HDBK - 3010, Airborne Release Fractions/Rates and Respirable Fractions for Nonreactor Nuclear Facilities, to determine radionuclide source terms. In calculating source terms, analysts tend to use the DOE Handbook's bounding values on airborne release fractions (ARFs) and respirable fractions (RFs) for various categories of insults (representing potential accident release categories). This is typically due to both time constraints and the avoidance of regulatory critique. Unfortunately, these bounding ARFs/RFs represent extremely conservative values. Moreover, they were derived from very limited small-scale bench/laboratory experiments and/or from engineered judgment. Thus, the basis for the data may not be representative of the actual unique accident conditions and configurations being evaluated. The goal of this research is to develop a more accurate and defensible method to determine bounding values for the DOE Handbook using state-of-art multi-physics-based computer codes. This enables us to better understand the fundamental physics and phenomena associated with the types of accidents in the handbook. In this year, this research included improvements of the high-fidelity codes to model particle resuspension and multi-component evaporation for fire scenarios. We also began to model ceramic fragmentation experiments, and to reanalyze the liquid fire and powder release experiments that were done last year. The results show that the added physics better describes the fragmentation phenomena. Thus, this work provides a low-cost method to establish physics-justified safety bounds by taking into account specific geometries and conditions that may not have been previously measured and/or are too costly to perform.

54 ENVIRONMENTAL SCIENCES↗