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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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Bubble dynamics and nucleate pool boiling heat transfer on microporous copper surfaces
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Combined stability analysis of phase-field dynamic fracture and shear band localization
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Incipient dynamic recrystallization and adiabatic shear bands in Ti?7Al studied via in situ X-ray di
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Comparative excited state dynamics of metallo meso-(4-fluoro-2,6-dimethyl-phenyl) porphyrins
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Monitoring water content dynamics of biological soil crusts
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Mutations in PBP2 from ceftriaxone-resistant Neisseria gonorrhoeae alter the dynamics of the [beta]3
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Towards a circular economy for PET bottle resin using a system dynamics inspired material flow model
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An efficient quasi-3D particle tracking-based approach for transport through fractures with application to dynamic dispersion calculation
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A coupled ordinates method for solution acceleration of rarefied gas dynamics simulations
Non-equilibrium rarefied flows are frequently encountered in a wide range of applications, including atmospheric re-entry vehicles, vacuum technology, and microscale devices. Rarefied flows at the microscale can be effectively modeled using the ellipsoidal statistical Bhatnagar–Gross–Krook (ESBGK) form of the Boltzmann kinetic equation. Numerical solutions of these equations are often based on the finite volume method (FVM) in physical space and the discrete ordinates method in velocity space. However, existing solvers use a sequential solution procedure wherein the velocity distribution functions are implicitly coupled in physical space, but are solved sequentially in velocity space. This leads to explicit coupling of the distribution function values in velocity space and slows down convergence in systems with low Knudsen numbers. Furthermore, this also makes it difficult to solve multiscale problems or problems in which there is a large range of Knudsen numbers. In this paper, we extend the coupled ordinates method (COMET), previously developed to study participating radiative heat transfer, to solve the ESBGK equations. In this method, at each cell in the physical domain, distribution function values for all velocity ordinates are solved simultaneously. This coupled solution is used as a relaxation sweep in a geometric multigrid method in the spatial domain. Enhancements to COMET to account for the non-linearity of the ESBGK equations, as well as the coupled implementation of boundary conditions, are presented. The methodology works well with arbitrary convex polyhedral meshes, and is shown to give significantly faster solutions than the conventional sequential solution procedure. Acceleration factors of 5–9 are obtained for low to moderate Knudsen numbers on single processor platforms.