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AIAA Aerospace Sciences Meeting, 2018

作者： Gosse, Ryan Mackintosh, Cameron Vogiatzis, Konstantinos Williams, Charles AFRL/RQHF U.S. Air Force Research Laboratory Wright-Patterson Air Force Base 2210 Eighth Street OH45433 United States DoD HPCMP PETTT/Engility Corp. DoD Supercomputing Resource Center AFRL/RCM U.S. Air Force Research Laboratory Wright-Patterson Air Force Base 2435 Fifth Street OH45433 United States

ISBN: (数字)9781624105241

ISBN: (纸本)9781624105241

Procedures to parametrically represent two- and three-dimensional domains, used in generation of structured meshes for CFD (Computational Fluid Dynamics) simulations, with Bezier surfaces and volumes have been developed. They provide compact data structures, exhibiting several orders of magnitude reduction in size for the same fidelity that can facilitate scalable mesh generation, decomposition and data analysis and eliminate bandwidth saturation. A demonstration of multi-block mesh generation using an example shape pertinent to compressible strong-shock flow simulations is presented. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Mesh generation

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Towards numerical simulation of hypersonic turbulent flows using high order methods

Towards numerical simulation of hypersonic turbulent flows u...

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AIAA Aerospace Sciences Meeting, 2018

作者： Ranjan, Rakesh Vedula, Prakash Vogiatzis, Konstantinos Josyula, Eswar University of Oklahoma School of Aerospace and Mechanical Engineering NormanOK United States Air Force Research Laboratory DoD HPCMP PETTT/Engility Corp DoD Supercomputing Research Center AFRL/RCM Wright-Patterson AFB 2435 Fifth Street OH United States AFRL/RQHF Wright-Patterson AFB Air Force Research Laboratory 2210 Eighth Street OH United States

ISBN: (纸本)9781624105241

The paper presents the development of a high order finite volume flow solver of Navier-Stokes equations with source terms for application to high Mach number nonequilibrium flow simulations. Inviscid fluxes are approximated using a fifth-order accurate Weighted Non-Oscillatory Scheme (WENO) and viscous fluxes are approximated using a fourth-order (central difference) accurate scheme. The code is validated with the exact solution available for the Sod shock tube problem. The new 3D, high-order accurate, parallel solver showed good agreement with the AFRL ANDEE (Aerothermal Nonequlibrium Detailed Energy Exchange) code for a blunt body problem for both ideal gas and real gas at high speed flow conditions. We use the newly developed code to study the Taylor-Green vortex in a periodic box, and present the evolution of flow for translational and vibrational temperatures depicting the energy exchange between these two modes. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Navier Stokes equations

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Parallelization of ANDEE using the UGLIB MPI interface library

Parallelization of ANDEE using the UGLIB MPI interface libra...

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AIAA Information Systems-AIAA Infotech at Aerospace, 2018

作者： Rosenberg, Robert Khine, Yu Yu Vogiatzis, Konstantinos Josyula, Eswar U.S. Navy Research Laboratory Center for Computational Science 4555 Overlook Ave SW WashingtonDC United States U.S. Navy Research Laboratory DoD HPCMP PETTT/Engility Corp. Center for Computational Science 4555 Overlook Ave SW WashingtonDC United States U.S. Air Force Research Laboratory Wright-Patterson Air Force Base DoD HPCMP PETTT/Engility Corp. DoD Supercomputing Research Center AFRL/RCM 2435 Fifth Street OH United States U.S. Air Force Research Laboratory Wright-Patterson Air Force Base AFRL/RQHF 2210 Eighth Street OH United States

ISBN: (纸本)9781624105272

Hybrid parallelization has been enabled for the AFRL hypersonic nonequilibrium flow code ANDEE through the use of the MPI Interface library, UGLIB, and OpenMP directives. ANDEE solves the Navier-Stokes equations with source terms for a reacting multi-species air mixture. The source terms consist of (a) rate of change of species concentration, and (b) energy exchanges between the state-to-state (STS) vibrational quantum energy and the translational energy modes of the select air species. The focus of the study is on the more computationally intensive STS exchanges that account for over 95% of the total CPU time. The speedup results are presented for sample cases with different numbers of quantum energy states. A parallel efficiency greater than 90% was achieved for total chemistry calculations with 10 quantum levels. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Navier Stokes equations

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State-to-state kinetic modeling of select air species in hypersonic nonequilibrium flows 47th

State-to-state kinetic modeling of select air species in hyp...

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47th AIAA Thermophysics Conference, 2017

作者： Josyula, Eswar Suchyta, Casimir J. Vogiatzis, Konstantinos Vedula, Prakash Air Force Research Laboratory AFRL/RQHF Wright-Patterson AFB 2210 Eighth Street OH United States School of Aerospace and Mechanical Engineering University of Oklahoma NormanOK United States Air Force Research Laboratory DoD HPCMP PETTT/Engility Corp DoD Supercomputing Research Center AFRL/RCM Wright-Patterson AFB 2435 Fifth Street OH United States

ISBN: (纸本)9781624104992

A computational fluid dynamics flow solver for five-species air mixture with state to state-to-state kinetics of oxygen and nitrogen was used for assessing the influence of vibrational excitation and dissociation on hypersonic flowfields ranging from Mach 7-20. We consider flows around an axisymmetric forebody geometry using multiquantum vibrational-translation and dissociation rate coefficients from an ab initio database. Output quantities of interest include shock-standoff distance, translational and vibrational temperatures, and population fractions in the quantum energy states. The nonequilibrium vibrational energy distributions were modeled by the master kinetic equation and the population distributions in the quantum energy states of the diatomic molecule evaluated under multiquantum vibrational-translational (VT) transitions. Both a two-temperature model (2T Model) and a state-to-state kinetics (STS) model are used to compare with existing experimental data. The state-to-state kinetics model has better prediction of shock-standoff distance compared to data. At high temperatures, results indicate that multiquantum transitions have a large influence on the macroscopic parameters of the gas flow behind the shock, especially on the temperature profiles and vibrational population distributions on the upper energy levels. © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Flow of gases

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Double-cone flows in nonequilibrium: Comparison of CFD with experimental data 55

Double-cone flows in nonequilibrium: Comparison of CFD with ...

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55th AIAA Aerospace Sciences Meeting

作者： Vogiatzis, Konstantinos Josyula, Eswar Vedula, Prakash Air Force Research Laboratory United States University of Oklahoma United States DoD HPCMP PETTT/Engility Corp. DoD Supercomputing Research Center AFRL/RCM WrightPatterson AFB 2435 Fifth Street OH United States AFRL/RQHF Wright-Patterson AFB 2210 Eighth Street OH United States School of Aerospace and Mechanical Engineering NormanOK United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

High-enthalpy nonequilibrium laminar flows are studied for a 25-55 deg double-cone geometry, using a real-gas multi-species LLTR model (Landau-Teller vibrational relaxation model and Park dissociation model) and a STS (state-to-state) model with the more accurate QCT rates for the O3 system. Surface pressure and heat flux distributions are compared with experimental data obtained at the CUBRC LENS-XX expansion tunnel facility. Several possible causes for previously reported discrepancies between numerical simulations and experiments are identified to understand the role of different nonequilibrium models. However, CFD poorly predicts the peak pressure and heat flux on the surface of the complex shock system and the recirculation region in the separation zone. The STS model with the more accurate rates appears to have a significant influence on the size and location of the separation zone. The study encourages us to include in future studies the STS approach for other species in the air mixture. © 2017, American Institute of Aeronautics and Astronautics Inc. All rights reserved.

关键词： Computational Fluid Dynamics Heat Flux Distribution Freestream Conditions Hypersonic Flows Enthalpy Perfect Gas Vibrational Energy Shock Layers Energy Exchange Mechanisms Oblique Shock

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A QM/MM equation-of-motion coupled-cluster approach for predicting semiconductor color-center structure and emission frequencies

arXiv

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arXiv 2017年

作者： Lutz, Jesse J. Duan, Xiaofeng F. Burggraf, Larry W. ORISE fellow residing at Department of Engineering Physics Air Force Institute of Technology Wright-Patterson Air Force Base OH45433 United States Air Force Research Laboratory DoD Supercomputing Resource Center Wright-Patterson Air Force Base OH45433 United States Air Force Institute of Technology Wright-Patterson Air Force Base OH45433 United States

Valence excitation spectra were computed for deep-center silicon-vacancy defects in 3C, 4H, and 6H silicon carbide (SiC) and comparisons were made with literature photoluminescence measurements. Optimizations of nuclear geometries surrounding the defect centers were performed within a Gaussian basis-set framework using many-body perturbation theory or density functional theory (DFT) methods, with computational expenses minimized by a QM/MM technique called SIMOMM. Vertical excitation energies were subsequently obtained by applying excitation-energy, electronattached, and ionized equation-of-motion coupled-cluster (EOMCC) methods, where appropriate, as well as time-dependent (TD) DFT, to small models including only a few atoms adjacent to the defect center. We consider the relative quality of various EOMCC and TD-DFT methods for (i) energy-ordering potential ground states differing incrementally in charge and multiplicity, (ii) accurately reproducing experimentally measured photoluminescence peaks, and (iii) energy-ordering defects of different types occurring within a given polytype. The extensibility of this approach to transition-metal defects is also tested by applying it to silicon-substituted chromium defects in SiC and comparing with measurements. It is demonstrated that, when used in conjunction with SIMOMM-optimized geometries, EOMCC-based methods can provide a reliable prediction of the ground-state charge and multiplicity, while also giving a quantitative description of the photoluminescence spectra, accurate to within 0.1 eV of measurement for all cases considered. Copyright © 2017, The Authors. All rights reserved.

关键词： Ground state

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Role of high fidelity nonequilibrium modeling in laminar and turbulent flows for high speed isr missions 46

Role of high fidelity nonequilibrium modeling in laminar and...

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46th AIAA Thermophysics Conference, 2016

作者： Vogiatzis, Konstantinos Josyula, Eswar Vedula, Prakash Air Force Research Laboratory United States University of Oklahoma United States DoD HPCMP PETTT/Engility Corp. DoD Supercomputing Research Center Wright-Patterson AFB AFRL/RCM 2435 Fifth Street OH United States AFRL/RQHF Wright-Patterson AFB 2210 Eighth Street OH United States School of Aerospace and Mechanical Engineering NormanOK United States

ISBN: (数字)9781624104350

ISBN: (纸本)9781624104350

High-enthalpy laminar flows as well as turbulent boundary layer flows pertaining to high-speed ISR missions are investigated. Test cases consisting of laminar flow past cylinder-flare, hemisphere cylinder, a representative long body and wall bounded (channel) geometries at high Mach numbers were studied using a realgas multi-species Lumped Landau-Teller Relaxation (LLTR) and a Discrete State Kinetic Relaxation (DSKR) models. Direct numerical simulations (DNS) of turbulence are performed for low Mach number compressible channel ideal gas flow. In all cases the refractive index of air field was calculated, the OPD (optical path difference) along a nominal sensor path of a given aperture size was derived. Surface pressure and heat flux distributions for the cylinder-flare geometry compared reasonably well with experimental data. Laminar OPDs exhibit a tilt aberration with a positive gradient in the flow direction while in case of turbulent flows the integral length scale of the flow begins to dominate the OPD spatial behavior resulting in higher order aberrations. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All right reserved.

关键词： Flow of gases

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Multiple objective Evolution Strategies using Data Envelopment Analysis

Multiple objective Evolution Strategies using Data Envelopme...

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Portland International Conference on Management of Engineering and Technology (PICMET)

作者： James V. Lill Timothy Anderson Department of Defense Supercomputing Resource Center Air Force Research Laboratory Ohio USA Department of Engineering and Technology Management Portland State University Portland Oregon USA

ISBN: (纸本)9781479917679

Often in science and engineering we are faced with complicated nonlinear problems in optimization that involve simultaneously minimizing or maximizing various non-commensurate quantities. For example, a basic task in design engineering or technology management is to balance suitable measures of performance against the cost. We present a simplified approach for performing multiple objective optimization by combining standard single objective Evolution Strategies with Data Envelopment Analysis. This latter method employs linear programming to compute an L1 distance of a given solution from the Pareto frontier defined by the evolving population of solutions, or from a related frontier defined by DEA. This quantity is then used in a fitness function. Real variable linear programs must be solved for the optimization of convex problems, while the solution of mixed integer linear programs is required to optimize general non-convex problems. This hybrid method yields highly converged results with good coverage of the Pareto frontier when applied to a standardized suite of multiple objective problems. Several current applications will be discussed that employ a massively parallel program (MOES) written in C and MPI that runs on supercomputers. This material was assigned a clearance of CLEARED, Case Number 88ABW-2015-0638.

关键词： Optimization Sociology Statistics Evolutionary computation Standards Pins Convergence

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A Density Functional Theory Investigation on the Properties of Supramolecular Catalysts for Photoinitiated Electron Collection

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Procedia Computer Science 2013年 18卷 779-786页

作者： Xiaofeng Duan Ruth Pachter Karen J. Brewer Barry L. Farmer Air Force Research Laboratory Materials & Manufacturing Directorate Wright-Patterson Air Force Base Ohio USA 45433 Air Force Research Laboratory DoD Supercomputer Resource Center Wright-Patterson Air Force Base Ohio USA 45433 Virginia Polytechnic Institute and State University Blacksburg Virginia USA 24061

In this work we investigated by density functional theory (DFT)/time-dependent DFT (TDDFT) supramolecular complexes for photoinitiated electron collection, in particular [{(bpy) 2 Ru(dpp)} 2 RhCl 2 ] 5+ and related catalysts derived by variation of the ligand/metal. The electron collection in this class of catalysts enables hydrogen production or DNA cleavage, among other applications. Changes in excitation energies upon variation of the ligand/metal were mostly consistent with experiment, and within the expected TDDFT accuracy, thus enabling their use as the basis for further analysis. Indeed, the consistency observed between the predicted excitation energy and the bridging ligand's reduction potential can assist in catalyst design for electron collection. Calculated fragment orbital energies could explain, in part, changes in the propensity towards photocleavage of DNA.

关键词： Mixed-metal supramolecular complex Density functional theory Time dependent density functional theory Electronic spectrum Electron transfer

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Oxygen‐Atom Defects In 6H Silicon Carbide Implanted Using 24‐ MeV O3+ Ions Measured Using Three‐Dimensional Positron Annihilation Spectroscopy System (3DPASS)

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AIP Conference Proceedings 2011年第1期1336卷 458-462页

作者： Christopher S. Williams Xiaofeng F. Duan James C. Petrosky Larry W. Burggraf aAir Force Institute of Technology AFIT/ENP 2950 Hobson Way Wright‐Patterson Air Force Base OH 45433 bAir Force Research Laboratory’s (AFRL) Department of Defense Supercomputing Resource Center (DSRC) Wright‐Patterson Air Force Base OH 45433

Three dimensional electron‐positron (e−‐e+) momentum distributions were measured for single crystal 6H silicon carbide (SiC); both virgin and having implanted oxygen‐atom defects. 6H SiC samples were irradiated by 24‐ MeV O3+ ions at 20 particle‐nanoamps at the Sandia National laboratory’s Ion Beam Facility. O3+ ions were implanted 10.8 μm deep normal to the (0001) face of one side of the SiC samples. During positron annihilation measurements, the opposite face of the 254.0‐μm thick SiC samples was exposed to positrons from a 22Na source. This technique reduced the influence on the momentum measurements of vacancy‐type defects resulting from knock‐on damage by the O3+ ions. A three‐dimensional positron annihilation spectroscopy system (3DPASS) was used to measure e−‐e+ momentum distributions for virgin and irradiated 6H SiC crystal both before and following annealing. 3DPASS simultaneously measures coincident Doppler‐broadening (DBAR) and angular correlation of annihilation radiation (ACAR) spectra. DBAR ratio plots and 2D ACAR spectra are presented. Changes in the momentum anisotropies relative to crystal orientation observed in 2D ACAR spectra for annealed O‐implanted SiC agree with the local structure of defect distortion predicted using Surface Integrated Molecular Orbital/Molecular Mechanics (SIMOMM). Oxygen atoms insert between Si and C atoms increasing their separation by 0.9 Å forming a Si‐O‐C bond angle of ∼150°.

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