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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Final Report for Collaborative Project: Sensitivity of Atmospheric Parametric Formulations to Regional Mesh Refinement in Global Climate Simulations Using CESM-HOMME

In this project we analyze climate simulations using the Community Earth System Model (CESM) in order to determine the modeled response and sensitivity to horizontal resolution. Simple aqua-planet configurations were used to provide a clean comparison of the response to resolution in CESM. This enables us to easily examine all aspects of the model sensitivity to resolution including mean quantities, variability and physical parameterization tendencies: the chief reflection of resolution sensitivity. An extension to the global resolution sensitivity study is the examination of regional grid refinement where resolution changes are prescribed in a single global simulation. We examine the relevance of the global resolution sensitivity results as applied to these regional refinement simulations. In particular we examine how variations in the grid resolution, centered on different parts of the globe, lead to differences in the parameterized response and the potential to generate residual circulations as a result. Given the potential to generate this resolution sensitivity we examine simple modifications to the parameterized physics that are able to moderate any residual circulations. Finally, we transfer the framework to the standard AMIP configuration to examine the resolution sensitivity in the presence of compounding effects such as land-sea distributions, orography and seasonal variation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

The MCNP6 Book On Unstructured Mesh Geometry: User's Guide for MCNP 6.2.1

Los Alamos National Laboratory’s (LANL) Monte Carlo N-Particle R (MCNP R ) transport code has a more general geometry capability than has been available in most combinatorial geometry codes [1]. In addition to the capability of combining several predefined geometric bodies, as in a combinatorial scheme, MCNP6 [2] gives the user the added flexibility of defining geometric regions from all the first and second degree surfaces of analytical geometry and elliptical tori and then combining them with Boolean operators. This decades-old constructive solid geometry (CSG) capability has been well-tested and verified. However, it has long been recognized that as the model complexity increases, this process of describing the geometry is difficult, tedious, time-consuming, and error prone[3, 4, 5]. Consequently, innovators have taken on the task of developing a better way to construct geometries, not only in MCNP6, but other particle transport codes as well

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Interactive Mesh Generation and Comparison Tools for Nuclear Energy Advanced Modeling & Simulation Phase I. Final Report

The promise of computer simulations for nuclear reactor designs is the opportunity to speed up the design process while also improving safety, providing more detail and higher fidelity, reducing cost, minimizing schedule risk, and avoiding many other potential problems; because simulations have the potential to be much less expensive and time-consuming than traditional development – where scale models and physical tests require construction and long lead times – it is possible to consider more alternatives and complete more comprehensive assessments before the design is finalized and constructed. As more design scenarios are studied by simulation, the speed that simulations promise is only available as long as bottlenecks are addressed for these scenarios. A frequent bottleneck is the amount of human labor required to describe the shape of the objects being designed and decompose the shape into simple elements, such as hexahedra, that are small enough to capture the physical phenomena of interest without being so small that even fast computers cannot perform the simulation in a reasonable amount of time. Recently, techniques for creating all-hexahedral decompositions have been developed, but they require some human input. Many simulation codes prefer all-hexahedral decompositions, so we proposed to evaluate the feasibility of these techniques on nuclear reactor geometries to see whether they required too much human input to be commercially viable. Our study concluded that they can be made viable with some additional software tools to reduce the amount of user input required.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗