Papers and Reports

An in-depth performance comparison of an HPE Apollo 9000 system based on the AMD EPYC Rome processors to an HPE SGI 8600-XA730i Gen10 based on Intel Cascade Lake processors using industry standard benchmarks as well as 11 production applications and one mini-application representing a wide range of disciplines. This paper measures and explains differences in: performance of the HPL, HPCG and HPCC benchmarks; performance of STREAM, the memory bandwidth benchmark; node-to-node performance, including a breakdown of computation, communication, and I/O, for 9 production applications on node counts ranging from 1 up to 32.
Performance Evaluation of a Supercomputer Based on AMD Rome and Intel Cascade Lake ProcessorsNAS Technical Report NAS-2022-01, NASA Ames Research Center, Moffett Field, CA (PDF 5.7MB).

Recent progress in the ab-initio modeling of solar magnetoconvection makes it possible to simulate the surface dynamics of solar-type stars with a high degree of realism. These simulations can be used to characterize stellar photospheric disturbances which contaminate the radial velocity signal and limit our capabilities to detect Earth-mass exoplanets. We use the 3D radiative MHD “StellarBox” code to obtain realistic stellar (magneto)convection models and characterize photospheric noise.
Characterization of Stellar Jitter Using 3D Realistic Modeling of Solar-Type StarsBulletin of the American Astronomical Society, vol. 54, issue 6, June 29, 2022

A scheme is presented for the automatic generation of structured overset meshes on geometries that are defined by Boundary Representation (BRep) solids. The surface mesh system consists of face, edge and node meshes corresponding to the three respective basic BRep entity types. A cut-cell method is introduced to improve robustness of the on-geometry determination test for a face mesh grid point.
Automation of Overset Structured Mesh Generation on Boundary Representation GeometriesAIAA AVIATION Forum, Chicago, IL, June 27 - July 1, 2022

A summary of the nine submissions to the Wall-Modeled LES and Lattice-Boltzmann (WMLESLB) Technical Focus Group (TFG) at the 4th High lift Prediction Workshop is provided. The focus of this TFG was to assess the current capabilities of WMLES and Lattice Boltzmann methods on a complex high-lift configuration across a wide range of angles of attack.
HLPW-4/GMGW-3: Wall-Modeled LES and Lattice-Boltzmann Technology Focus Group Workshop SummaryAIAA AVIATION Forum, Chicago, IL, June 27 - July 1, 2022

A new immersed boundary Wall-Modelled Large Eddy Simulation (WMLES) formulation is developed to study high-lift aerodynamics on the NASA High-Lift Common Research Model (HL-CRM). A sequence of Cartesian Octree grids with sizes ranging from 100 Million through 2.02 Billion grid points is utilized to systematically assess grid-sensitivity and convergence for the in-tunnel (QinetiQ) configuration of the model, and remarkable agreement between the immersed boundary and the curvilinear body-aligned WMLES formulations is reported on grids with comparable resolutions.
A Wall-Modeled LES Perspective for the High Lift Common Research Model Using LAVAAIAA AVIATION Forum, Chicago, IL, June 27 - July 1, 2022

An assessment of a Hybrid RANS/LES (HRLES) approach for CL,max prediction is presented for the NASA High-Lift Common Research Model (CRM-HL). Both the free air and the wind tunnel configuration of the CRM-HL are investigated and the results are compared to the QinetiQ wind tunnel experiments and to two other numerical approaches: Reynolds Averaged Navier-Stokes (RANS) and Wall-Modeled Large Eddy Simulations (WMLES).
A Hybrid RANS-LES Perspective for the High Lift Common Research Model Using LAVAAIAA AVIATION Forum, Chicago, IL, June 27 - July 1, 2022

A computational technique has been developed to perform compressible flow simulations involving moving boundaries using an embedded boundary approach within the block-structured adaptive mesh refinement (SAMR) framework of AMReX. We leverage the SAMR capability to obtain quantitatively accurate results whilst using robust, second-order finite volume schemes.
A Moving Embedded Boundary Approach for the Compressible Navier-Stokes Equations in a Block-Structured Adaptive Refinement FrameworkJournal of Computational Physics, vol. 465, September 2022

High-fidelity fluid-structure interaction (FSI) simulations of the ASPIRE SR01 supersonic parachute flight test are performed through the loose coupling of computational fluid dynamics (CFD) and computational structural dynamics (CSD) solvers. The CFD solver employs a Cartesian adaptive mesh refinement (AMR) grid paradigm with a ghost cell immersed boundary method to represent arbitrarily complex geometries, and the CSD solver uses MITC3 triangular shell and Timoshenko beam elements to discretize the parachute canopy and suspension lines.
Fluid-Structure Interaction Simulations of the ASPIRE SR01 Supersonic Parachute Flight TestAerospace Science and Technology, vol. 126, July 2022

A new one-dimensional, inviscid, and vertically integrated disc model with prescribed infall is presented. The flow is computed using a second-order shock-capturing scheme. Included are vertical infall, radial infall at the outer radial boundary, radiative cooling, stellar irradiation, and heat addition at the disc-surface shock.
Protostellar Discs Subject to Infall: A One-Dimensional Inviscid Model and Comparison with ALMA ObservationsMonthly Notices of the Royal Astronomical Society, vol. 514, issue 4, August 2022

A time–distance measurement technique is derived to isolate phase travel time anisotropy caused by subsurface horizontal magnetic fields; a method that uses the measured anisotropy to estimate the field's orientation is also derived. A simulation of acoustic waves propagating in a uniform, inclined magnetic field with solar background structure is used to verify the derived technique.
Detection of Travel Time Anisotropy from Subsurface Horizontal Magnetic FieldsThe Astrophysical Journal, vol. 930, no. 1, April 28, 2022

To reduce the complexity and to reduce the cost of turnaround time of simulating unsteady flows of rotating blades with moving overset grids, a mid-fidelity option is provided in the OVERFLOW computational fluid dynamics analysis to model rotors and propellers as infinitely thin disks. The effect of the flow through the disk is represented by the momentum source terms in the governing Navier-Stokes equations.
Application of Rotor Disk Model in the OVERFLOW CFD CodeNASA Technical Memorandum 2022005496, April 2022

The high-fidelity and reduced order CFD method's validation and analysis are presented for the Multirotor Test Bed. The reduced-order method uses a rotor-disk model in the OVERFLOW CFD code and is an important aspect of this study. A rotor-trim option loosely coupling the Comprehensive code CAMRAD II with the OVERFLOW CFD code is included in the simulation that captures rotor blade aerodynamics, blade and rotor performance, rotor-rotor, and rotor-body interactions.
Multi-Fidelity CFD Simulation of the Multirotor Test BedNASA Technical Memorandum 2022004659, April 2022

Computational heliophysics has shed light on the fundamental physical processes inside the Sun, such as the differential rotation, meridional circulation, and dynamo-generation of magnetic fields. However, despite the substantial advances, the current results of 3D MHD simulations are still far from reproducing helioseismic inferences and surface observations. The reason is the multi-scale nature of the solar dynamics, covering a vast range of scales, which cannot be solved with the current computational resources.
Advances and Challenges in Observations and Modeling of the Global-Sun Dynamics and DynamoarXiv:2203.10721 [astro-ph.SR], March 21, 2022

This white paper is prepared as an effort of the working group "Uniform Semantics and Syntax of Solar Observations and Events" created within the "Towards Integration of Heliophysics Data, Modeling, and Analysis Tools" EarthCube Research Coordination Network, with primary objectives to discuss current advances and identify future needs for the solar research cyberinfrastructure. The white paper summarizes presentations and discussions held during the special working group session at the EarthCube Annual Meeting on June 19th, 2020, as well as community contribution gathered during a series of preceding workshops and subsequent RCN working group sessions.
Revisiting the Solar Research Cyberinfrastructure Needs: A White Paper of Findings and RecommendationsarXiv:2203.09544 [astro-ph.IM], March 17, 2022

Understanding effects driven by rotation in the solar convection zone is essential for many problems related to solar activity, such as the formation of differential rotation, meridional circulation, and others. We present realistic 3D radiative hydrodynamics simulations of solar subsurface dynamics in the presence of rotation in a local domain 80 Mm-wide and 25 Mm deep, located at 30 degrees latitude.
3D Radiative Hydrodynamic Modeling of the Near-Surface Shear Layer in the Solar Convection ZonearXiv:2203.01484 [astro-ph.SR], March 3, 2022

The detection of Earth-size exoplanets is a technological and data analysis challenge. Future progress in Earth-mass exoplanet detection is expected from the development of extreme precision radial velocity measurements. Increasing radial velocity precision requires developing a new physics-based data analysis methodology to discriminate planetary signals from host-star-related effects, taking stellar variability and instrumental uncertainties into account. In this work, we investigate and quantify stellar disturbances of the planet-hosting solar-type star HD121504 from 3D radiative modeling obtained with the StellarBox code.
Modeling Stellar Jitter for the Detection of Earth-Mass Exoplanets via Precision Radial Velocity MeasurementsarXiv:2202.07087 [astro-ph.SR], February 14, 2022

In the present work, we consider the accuracy degradation issues typically encountered by upwind-type schemes in the low-Mach-number regime (Turkel, 1999 [59]) and their treatment using Flux-Preconditioning. ES schemes suffer from the same issues and Flux-Preconditioning can improve their behavior without interfering with entropy-stability.
Entropy-Stable Schemes in the Low-Mach-Number Regime: Flux-Preconditioning, Entropy Breakdowns, and Entropy TransfersJournal of Computational Physics, vol. 456, May 2022

We investigate reactive and non-reactive scattering of hyperthermal beam of gas particles within highly porous carbon-fiber preform using particle-based numerical simulations. High-resolution X-ray tomography images of the microstructure is used to resolve its complex fiber network. The gas–surface interaction is studied at material temperatures up to 2000 K, typical of hypersonic aero-thermal environments.
Gas–Surface Interactions in Lightweight Fibrous Carbon MaterialsComputational Materials Science, vol. 205, April 2022

The NASA USM3D flow solver was used to compute test cases for the Third AIAA Sonic Boom Prediction Workshop (SBPW3). The test cases included a near-field biconvex shock–plume interaction wind tunnel model and the C608 low boom flight demonstrator. Numerical simulations were conducted on the mixed-element and tetrahedral grids provided by the workshop committee, as well as a family of grids generated by an in-house approach known as BoomGrid.
USM3D Simulations for the Third AIAA Sonic Boom Prediction WorkshopJournal of Aircraft, vol. 59, no. 3, May 2022

NASA's Advanced Air Transport Technology (AATT) project is breaching the boundaries of aircraft design in pursuit of eco-friendly solutions that are compatible with urban noise comfort levels. Boundary layer ingesting (BLI) propulsion systems promise to reduce fuel burn with additional potential benefits in noise reduction. Type-II BLI systems of the STARC-ABL type are the subject of a test campaign planned for fiscal year 2022 in the National Transonic Facility (NTF), for which a CRM-based model with a retrofitted tail cone thruster (TCT) has been designed. The present work is a precursor to the NTF test, where the 240 cases planned for the experiment were simulated using the Launch, Ascent, and Vehicle Aerodynamics (LAVA) computational framework.
Computational Aerodynamics Analysis in Support of the CRM Tail Cone Thruster Configuration Wind Tunnel TestAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

The Subsonic Single Aft Engine (SUSAN) Electrofan is a new single-aisle regional jet class transport aircraft being studied by NASA, which benefits from reduced fuel consumption through a reduction in the number of hydrocarbon fuel-burning engines from two to one. This is achieved through a hybrid-electric system architecture, where a series of generators are used to extract power from a fuel-consuming tail cone thruster to drive electric propulsors mounted on the wings. To support the development of these propulsion systems, which involve high levels of propulsion-airframe integration, this paper presents high-fidelity analyses through computational fluid dynamics (CFD) simulations provided by the Launch, Ascent, and Vehicle Aerodynamics (LAVA) framework, which also includes capabilities for modeling the effect of active propulsors.
High-Fidelity Aerodynamic Analysis and Optimization of the SUSAN Electrofan ConceptAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

High-fidelity computational fluid dynamics simulations have been carried out to analyze NASA's quadrotor air taxi concept for urban air mobility. High-order accurate schemes, dual-time stepping, and the delayed detached-eddy simulation model have been employed. The flow solver has been loosely coupled with the rotorcraft comprehensive analysis code. The vehicle simulated is a six-passenger quadrotor for air taxi operations.
High-Fidelity Simulations of a Quadrotor Vehicle for Urban Air MobilityAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

A campaign of wall-modeled large-eddy simulations (WMLES) using structured curvilinear overlapping grids has been performed with the Launch Ascent and Vehicle Aerodynamics (LAVA) computational fluid dynamics (CFD) software to predict jet noise for single-stream axisymmetric round jets. The simulations address the new Prediction Uncertainty Reduction (PUR) technical challenge within the context of NASA's Commercial Supersonic Technology (CST) project.
Wall Modeled Large Eddy Simulations for NASA's Jet Noise Consensus Database of Single-Stream, Round, Convergent JetsAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

This paper reports the results of CFD simulations of the test cases for the AIAA 1st CFD Transition Modeling and Prediction Workshop held at the AIAA Scitech Forum on 21-22 January, 2021 using the NASA solver OVERFLOW. The Langtry-Menter transition model was used in combination with the Shear Stress Transport (SST) turbulence model.
1st AIAA CFD Transition Modeling and Prediction Workshop: OVERFLOW Results for the SST and Langtry-Menter ModelsAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

This paper presents an aircraft configuration trade space exploration for NASA’s SUbsonic Single Aft eNgine (SUSAN) Electrofan, which is a 180 passenger regional class transport aircraft that utilizes electrified aircraft propulsion and advanced propulsion airframe integration technologies to enable reduced fuel consumption and emissions.
Conceptual Exploration of Aircraft Configurations for the SUSAN ElectrofanAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

High-fidelity computational fluid dynamics (CFD) simulations have so far only played exploratory and supporting roles in the study and qualification of parachutes for planetary entry. The last few years have seen the maturation of coupled computational methods that are capable of modeling the complex fluid-structure interactions between a parachute canopy and the supersonic flow in the wake of an entry vehicle in flight conditions.
Fluid-Structure Interaction Simulations of the ASPIRE SR01 Supersonic ParachuteAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

A unified assessment of three turbulence treatments: Reynolds Averaged Navier-Stokes (RANS), Hybrid RANS/LES (HRLES) and Equilibrium Wall-Modelled Large Eddy Simulation (WMLES) is presented for the High-Lift Common Research Model (CRM-HL). For the free-air configuration, steady-state RANS simulations show very accurate drag polar predictions in the low-AoA linear regime.
High-Lift Common Research Model: RANS, HRLES, and WMLES perspectives for CLmax prediction using LAVAAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

A smooth local correlation-based transition model is fully coupled to a RANS-based Newton-Krylov flow solver and discrete-adjoint gradient-based optimization algorithm. The free-transition optimization framework is evaluated using lift-constrained drag minimizations of airfoils at design conditions ranging from light to single-aisle aircraft and an infinite swept wing at design conditions representative of a transonic strut-braced wing aircraft.
Investigation of a Smooth Local Correlation-based Transition Model in a Discrete-Adjoint Aerodynamic Shape Optimization AlgorithmAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

The numerical behaviour of transport-equation-based transition models, including both iterative and grid convergence, is influenced by the source terms. Transition models contain source terms that are large and highly nonlinear, and can be destabilizing in a strong implicit solver. Linearization strategies with varying levels of coupling are evaluated in conjunction with a source-term time step restriction to determine best-practices for solving the SA-sLM2015 smooth local correlation-based transition model in an implicit Newton-Krylov flow solver.
Numerical Behaviour of a Smooth Local Correlation-based Transition Model in a Newton-Krylov Flow SolverAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

Several improvements are made to overlap preservation in the automated approach to generating overset structured meshes. A loosely-coupled boundary condition (LCBC) is introduced to maintain optimal overlap for surface meshes generated from overlapping initial curves. Extension of the LCBC scheme to three-dimensional volume meshing is also presented.
Overlap Preservation Using Loosely-Coupled Boundary Conditions for Body-Fitted Structured Overset GridsAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

Supersonic retro-propulsion (SRP) is a deceleration technology that could enable larger payloads and potentially humans to be brought from space to the surface of Mars safely. Accurate and reliable CFD predictions are needed to help design future Mars entry, descent, and landing (EDL) vehicles due to the cost and limitations of wind tunnel tests. This work demonstrates how high-order scale-resolving simulations on Cartesian adaptive mesh refinement (AMR) grids can provide accurate and reliable time-averaged aerodynamic loads on the vehicle for this challenging flow regime.
Scale-Resolving Simulations of Supersonic Retro-Propulsion Concept For Mars Entry, Descent, and LandingAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

A trade space exploration of a new NASA regional transport aircraft concept called the SUbsonic Single Aft eNgine (SUSAN) Electrofan is presented. The SUSAN concept uses a 20MW Electrified Aircraft Propulsion (EAP) system to enable advance Propulsion Airframe Integration (PAI) in transport category aircraft. This paper presents the status of the trade space exploration; however the concept definition is not finished.
Subsonic Single Aft Engine (SUSAN) Transport Aircraft Concept and Trade Space ExplorationAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022

A wind tunnel model was designed, manufactured, and tested to evaluate the potential of active aerodynamic flow control for multi-element airfoils. The configuration selected for this test is the NLR7301 two-element airfoil and it was tested in the Oran W. Nicks Low-Speed Wind Tunnel at Texas A&M University at a chord Reynolds number of 2.0 million and Mach number of 0.10. This paper presents wind tunnel results for the NLR7301 in the Flap 20 and Flap 30 configurations.
Wind Tunnel Experiment of Microjet-based Flow Control on a Multi-Element High-Lift AirfoilAIAA SciTech 2022 Forum, San Diego, CA, January 3-7, 2022