Papers & Reports 2021

Teams from the NASA Ames Research Centers (ARC) and Langley Research Center (LaRC) have been working on validating their computational fluid dynamics (CFD) results for the Boeing Mach 0.80 Transonic Truss-Braced Wing (TTBW) configuration. Experimental data used for the validation were gathered from a test conducted of a 4.5% scale Mach 0.80 TTBW model in the NASA Ames Research Center 11- by 11-Foot Transonic Wind Tunnel.
Improvements in Simulating a Mach 0.80 Transonic Truss-Braced Wing Configuration using the Spalart-Allmaras and k-ω SST Turbulence Models,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

Predictions using the Launch Ascent and Vehicle Aerodynamics (LAVA) Unstructured and Structured Curvilinear solvers for the Biconvex and C608 geometries are compared in support of the 3rd AIAA Sonic Boom Prediction workshop. Description of the mesh generation techniques and numerical methods are provided along with a comparison of nearfield and far-field predictions with available experimental data as well as other workshop submissions.
Structured Overset and Unstructured Grid Simulations for the Third AIAA Sonic Boom Prediction Workshop,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

We propose a new method to optimally deform high-order meshes using an adjoint elasticity solver. Mesh quality measures based on the norm of the Jacobian matrix and the metric tensor are compared against the determinant of the scaled Jacobian, as quantities of interest (QoI) for the optimization problem. We optimize the spatially varying material properties used in the elasticity equations, namely Young's modulus and Poisson's ratio, with a particular emphasis on the most deformed elements.
An Adjoint Elasticity Solver for High-Order Mesh Deformation,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

Wall-modelled Large Eddy Simulations (WMLES) of the NASA Common Research Model (CRM) at transonic conditions and various angles of attacks leading up to and including shock-induced flow separation are performed using the LAVA computational framework. The simulations are shown to accurately predict the lift curve slope and the onset of separation characterized by the break in the pitching moment.
Transonic lift and drag predictions using Wall-Modelled Large Eddy Simulations2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data.
High-Fidelity Simulations of HyMETS Arc-Jet Flows for PICA-N Modeling,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

This study explores the feasibility of using small surface-normal jets near the flap trailing edge as active aerodynamic load control on the high-lift Common Research Model wing/body configuration. Chimera Grid Tools are utilized to generate structured curvilinear overset grids, and the Reynolds-averaged Navier-Stokes solver OVERFLOW is employed to solve for the flow-field around the geometry. The so-called microjet is initially employed across both the inboard and the outboard flaps on the pressure-side near the trailing edge.
Surface-Normal Active Flow Control for Lift Enhancement and Separation Mitigation for High-Lift Common Research Model,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

Arc-jets are essential facilities used in the research, development and evaluation of thermal protection systems for hypersonic vehicles since they can reproduce the high-enthalpy environments seen during planetary entry. A test campaign is underway in the Hypersonic Materials Environmental Test System arc-jet, in support of the oncoming Mars 2020 mission to screen the response of the PICA-NuSil system. High-fidelity thermochemical non-equilibrium computational fluid dynamics simulations have been carried out to assist the test campaign by simulating the complete test matrix for the facility.
Jet Noise Prediction with Large-Eddy Simulation for Chevron Nozzle Flows,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

Simulation results are presented for all cases from the Third AIAA Sonic Boom Prediction Workshop. An inviscid, embedded-boundary Cartesian-mesh flow solver is used in conjunction with adjoint-based mesh adaptation to compute nearfield pressure signatures. Specialized techniques are applied to maximize accuracy and minimize cost on Cartesian meshes.
Cartesian Mesh Simulations for the Third AIAA Sonic Boom Prediction Workshop,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

Our current state-of-the-art computer simulations allow us to build 3D dynamical and radiation models of F-type stars from physical first principles. Using the stellar interior’s structure from the MESA stellar evolution code as initial conditions, we generate models of main-sequence stars with the mass from 1.4 Msun to 2 Msun for various metallicity composition, in the range of [Fe/H] from -0.3 to 0.2.
3D Realistic Modeling of Main-Sequence Stars with Shallow Outer Convection ZoneBulletin of the American Astronomical Society, vol. 53, issue 1, January 11, 2021

The Transiting Exoplanet Survey Satellite (TESS) recently completed its initial two-year, near all-sky survey, identifying over 79 exoplanets and over 2000 exoplanet candidates. We discuss the performance and behavior of the data products generated by the TESS Science Processing Operations Center (SPOC) at NASA Ames Research Center and highlight the new 20-sec data mode and the 10-min FFIs.
Upping the Ante: The TESS Mission Shortens Full Frame Images to 10 Minutes and Introduces a Twenty-Second Data Collection ModeBulletin of the American Astronomical Society, vol. 53, issue 1, January 11, 2021

We present an overview of the single- and multiple-sector results of the Science Processing Operations Center (SPOC) transit search in the primary Transiting Exoplanet Survey Satellite (TESS) mission. TESS was designed to survey bright stars in the greater Solar neighborhood in search of transiting exoplanets. Data were acquired at a 2-minute cadence for 16,000-20,000 pre-selected target stars in each 28-day observation sector and processed in the SPOC pipeline at NASA Ames Research Center.
Primary Mission Threshold Crossing Events in the TESS SPOC Transit SearchBulletin of the American Astronomical Society, vol. 53, issue 1, January 11, 2021

Traditional adjoint variables grow exponentially for turbulent chaotic flows. Most proposed methods (for example. ensemble adjoint, shadow-based, and unstable-subspace-based approaches, etc.) are computationally prohibitive for practical problems. In the current paper, we evaluate a stabilization approach for the adjoints of turbulent flows, which is computationally cheap compared to the previously mentioned methods.
Stabilization of the Adjoint for Turbulent Flows,2021 AIAA SciTech Forum, Virtual Event, January 11-21, 2021

We analyze the evolution of shock waves in high-resolution 3D radiative MHD simulations of the quiet Sun and their synthetic emission characteristics. The simulations model the dynamics of a 12.8 × 12.8 × 15.2 Mm quiet-Sun region (including a 5.2 Mm layer of the upper convection zone and a 10 Mm atmosphere from the photosphere to corona) with an initially uniform vertical magnetic field of 10 G, naturally driven by convective flows.
Connecting Atmospheric Properties and Synthetic Emission of Shock Waves Using 3D RMHD Simulations of the Quiet SunThe Astrophysical Journal, vol. 909, no. 1, March 3, 2022

A method of fine pointing of laser beams by using laser arrays has been developed. The telescope system combines a lens system and a VCSEL/Photodetector Array. In computer simulations, it is applied to CubeSats that use body pointing. Computer simulations of this fine pointing capability have been applied previously to CubeSats in the OCSD program. In this paper, computer simulations of laser pointing using this telescope design are applied to CubeSats in LLO, at 100 km.
Fine Pointing of Laser Beams by Using Laser Arrays for Applications to CubeSatsProceedings of the 2021 SPIE LASE, Volume 11678, Free-Space Laser Communications XXXIII, March 6-12, 2021

A considerable amount of effort has been done to quantify the initial effects of an asteroid impact on Earth. However, delayed downstream and downwind effects will propagate, and disturb areas not immediately affected by the initial impact. This white paper addresses the need for models to anticipate and predict delayed effects on regional areas.
Planetary Defense Preparedness: Identifying the Potential for Post-asteroid Impact Time Delayed and Geographically Displaced HazardsBulletin of the American Astronomical Society, vol. 53, issue 4, March 18, 2021

Viscous vortex layers subject to a more general uniform strain are considered. They include Townsend's steady solution for plane strain (corresponding to a parameter a = 1), in which all the strain in the plane of the layer goes toward vorticity stretching, as well as Migdal's recent steady asymmetric solution for axisymmetric strain (a = 1/2), in which half of the strain goes into vorticity stretching.
Viscous Vortex Layers Subject to More General Strain and Comparison to Isotropic TurbulencePhysics of Fluids, vol. 33, issue 3, March 26, 2021

Various characteristics of small surface-normal jets (microjets) located on a flap’s pressure-side near the trailing edge are investigated as an active aerodynamic load control technology for multi-element high-lift systems. Two-dimensional computational studies are carried out to investigate the sensitivity of microjet aerodynamic effectiveness to configuration. Initially, the effects of microjet location and width are explored.
Microjet Configuration Sensitivities for Active Flow Control on Multi-Element High-Lift SystemsAIAA Journal of Aircraft, vol. 58, no. 4, July 2021

Various characteristics of small surface-normal jets (microjets) located on a flap’s pressure-side near the trailing edge are investigated as an active aerodynamic load control technology for multi-element high-lift systems. Two-dimensional computational studies are carried out to investigate the sensitivity of microjet aerodynamic effectiveness to configuration. Initially, the effects of microjet location and width are explored.
Microjet Configuration Sensitivities for Active Flow Control on Multi-Element High-Lift SystemsAIAA Journal of Aircraft, vol. 58, no. 4, July 2021

The June 2, 2018 impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve.
The Impact and Recovery of Asteroid 2018 LAMeteoritics & Planetary Science, vol. 56, issue 4, April 2021

Asteroid risk assessments, such as those produced using NASA's probabilistic asteroid impact risk (PAIR) model, have typically estimated radiation using nuclear-based engineering-level models. However, large uncertainties have remained in how well such models represent asteroid airburst radiation and in the luminous efficiency parameter that is used to represent how much of the asteroid entry energy contributes to thermal damage. To investigate these thermal damage modeling assumptions and sensitivities, this study compares results of a 2005 model, which has been used in impact risk assessments, with results of a new higher-fidelity asteroid entry radiation model.
Comparison of Thermal Radiation Damage Models and Parameters for Impact Risk Assessment7th IAA Planetary Defense Conference, Vienna, Austria, April 26-30, 2021

This presentation expands upon the probabilistic asteroid impact risk assessments being performed as part of the 2021 PDC hypothetical impact exercise, focusing on key aspects of blast damage modeling uncertainties and sensitivities. We review the current modeling and simulation approaches employed in the current assessment, compare the relative levels of uncertainty stemming from each main element of the problem, and highlight any notable trends and sensitivities for the current scenario case.
Probabilistic Blast Damage Modeling Uncertainties and Sensitivities7th IAA Planetary Defense Conference, Vienna, Austria, April 26-30, 2021

Most of the research on the effects of an intermediate-sized asteroid impact or air burst have focused on immediate damage caused by the shock wave and the thermal radiation. Our focus is to quantify additional effects that could disrupt a larger geographical area than the initial blast. We classify these effects as either downwind or downstream. Some of these effects may occur within hours while others may extend to months, adding to the economic and social cost of the impact event.
Asteroid Impacts - Downwind and Downstream Effects7th IAA Planetary Defense Conference, Vienna, Austria, April 26-30, 2021

The PDC 2021 hypothetical impact exercise poses an interesting challenge to traditional threat assessment methods since it combines a potentially large impactor with minimal warning time. With large uncertainty in the early observational data, this case presents a particular problem for high-fidelity simulation techniques since many of the key input parameters are simply unknown. In this work, we show how recent advances in Bayesian inference and probabilistic risk assessment can be used to develop specific impactors that facilitate high-fidelity simulation in spite of the early uncertainty.
High-Fidelity Blast Modeling of Impact from Hypothetical Asteroid 2021 Pdc7th IAA Planetary Defense Conference, Vienna, Austria, April 26-30, 2021

Dutch-roll motions caused by sudden gusts are studied for a typical advanced air mobility vehicle. The selected lift+cruise configuration consists of a fuselage with high wing powered by lifting and pushing propellers. Flow is modeled using the Navier–Stokes equations. A procedure is developed to embed the Dutch-roll motion equations in an overset grid topology along with rotating blades. (Full paper requires login.)
Dutch-Roll Stability Analysis of an Air Mobility Vehicle Using Navier-Stokes EquationsAIAA Journal of Aeronautics and Astronautics, vol. 59, no. 10, October 2021

A detailed numerical study of harmonically pitching airfoils of NACA00 series is presented here. Based on the analysis of the computational fluid dynamics (CFD) results, a hypothesis is made that a simple data model can capture the dynamics of the airfoils in pitch. The data model is based on the c_l−α (lift coefficient–angle of attack) hysteresis loops that retain generic geometrical characteristics for a wide range of reduced frequency, k, encountered in flutter in transonic flows for all the NACA00 airfoils considered.
Resolving Pitching Airfoil Transonic Aerodynamics by Computational Fluid Dynamics Data ModelingJournal of Fluids Engineering, vol. 143, issue 9, September 2021

The complexity of the highly dynamical atmospheric layers of the Sun in the presence of inhomogeneous magnetic fields makes it challenging to correctly interpret observations from space and ground-based instruments. In particular, the center-to-limb variations of spectro-polarimetric properties may lead to significant misinterpretations of helioseismic and magnetic observables. To address these challenges and study the physical processes behind observations of various types, we use 3D MHD radiative models, which reproduce the dynamics and observational properties with high-degree realism.
Influence of Center-to-Limb Effects on Observations of the Solar AtmosphereBulletin of the American Astronomical Society, vol. 53, issue 6, June 18, 2021

In this study, we extract the deep features and investigate the compression of the Mg II k spectral line profiles observed in quiet Sun regions by NASA's IRIS satellite. The data set of line profiles used for the analysis was obtained on April 20th, 2020, at the center of the solar disc, and contains almost 300,000 individual Mg II k line profiles after data cleaning.
Compression of Solar Spectroscopic Observations: a Case Study of Mg II k Spectral Line Profiles Observed by NASA's IRIS SatelliteInternational Conference on Content-Based Multimedia Indexing, Lille, France, June 28-30, 2021

Solar Energetic Particle events (SEPs) are among the most dangerous transient phenomena of solar activity. As hazardous radiation, SEPs may affect the health of astronauts in outer space and adversely impact current and future space exploration. In this paper, we consider the problem of daily prediction of Solar Proton Events (SPEs) based on the characteristics of the magnetic fields in solar Active Regions (ARs), preceding soft X-ray and proton fluxes, and statistics of solar radio bursts.
Prediction of Solar Proton Events with Machine Learning: Comparison with Operational Forecasts and "All-Clear" PerspectivesarXiv:2107.03911 [astro-ph.SR], July 8, 2021

Detection of Earth-mass planets requires measurements of radial velocity with extreme precision. To capture the tiny disturbances caused by a planet's motion, it is necessary to understand and characterize the host star’s turbulent dynamics in order to apply proper filtering to the observational data. We take advantage of current computational and technological capabilities to develop 3D realistic models of the stellar subsurface convection and atmospheres and thereby estimate the photospheric jitter.
3D Modeling of Solar-Type Stars to Characterize Stellar JitterPresented at the TESS Science Conference II, August 2-6, 2021

Precision asteroseismology data from Kepler and TESS provide a unique opportunity to investigate the interior structure of stars at various stages of stellar evolution. Detection of mixed acoustic-gravity oscillation modes has opened perspectives for probing the properties of energy-generating cores. We present direct asteroseismic inversions using the method of optimally localized averages, which effectively eliminates the surface effects and attempts to resolve the stellar core structure.
Probing Stellar Cores by Asteroseismic InversionsPresented at the TESS Science Conference II, August 2-6, 2021

The Revised TESS Habitable Zone Catalog identified the 2-min TESS target stars that were observed for sufficient duration over consecutive primary mission sectors to unambiguously capture a transit signature of planets orbiting in the Habitable Zone (HZ). We employ the Combined Differential Photometric Precision computed at 15 pulse durations in the Science Processing Operations Centertransit searches of the primary mission light curves to estimate the signal-to-noise ratio associated with transiting terrestrial planets in the HZ of the Catalog stars.
Detectability of Transiting Terrestrial Planets in the Habitable Zone with TESSPresented at the TESS Science Conference II, August 2-6, 2021

A dramatic increase in observational data from NASA's Kepler, K2, and TESS missions and supporting ground-based observatories have opened new opportunities to investigate the internal structure, dynamics, and evolution of stars and their atmospheres. We present 3D radiative MHD simulations for several main-sequence stars with masses from 1.4 to 1.5 Msun. The simulations are performed using the "StellarBox" code developed for modeling stellar turbulent convection and atmospheres with a high degree of realism.
Dynamics and Structure of Main-Sequence Stars with Shallow Convection ZonesPresented at the TESS Science Conference II, August 2-6, 2021

The past eighteen months have seen a number of important changes for the TESS Science Processing Operations Center (SPOC) and our archival data products as TESS embarked upon its first extended mission. First, the SPOC developed and deployed a new 20-sec cadence pipeline, promising to unveil exciting new astrophysics at these short timescales for up to 1000 targets per observing sector. We also developed an FFI light curve pipeline that creates light curves and associated data products for up to 160,000 targets in each sector and archive these as High-Level Science Products at the Mikulski Archive for Space Telescopes.
TESS Science Processing Operations Center Pipeline Status and UpdatesPresented at the TESS Science Conference II, August 2-6, 2021

The aerodynamic design and fuel burn performance of a Mach 0.78 strut-braced-wing regional jet is investigated through aerodynamic shape optimization based on the Reynolds-averaged Navier-Stokes equations. Conceptual-level multidisciplinary design optimization is first performed to size the strut-braced-wing aircraft for a design mission similar to the Embraer E190-E2, with a design range of 3,100 nmi at a maximum capacity of 104 passengers, and a maximum payload of 30,200 lb.
Aerodynamic Optimization of a Transonic Strut-Braced-Wing Regional Aircraft Based on the Reynolds-Averaged Navier-Stokes EquationsAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

An unsteady body-force rotor model utilizing integral velocity sampling is developed for Cartesian meshes with a focus on accurate performance predictions. In this approach, the rotors are modeled as body-force source terms, and integral sampling is used to define the local freestream velocity vector. (Full paper requires login.)
Integral Velocity Sampling for Unsteady Rotor Models on Cartesian MeshesAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

A non-intrusive uncertainty quantification method is applied to computational analysis of supersonic, low-boom aircraft. The mean and standard deviation statistics of the pressure waveforms and loudness metrics are evaluated through use of numerical quadrature. (Full paper requires login.)
Uncertainty Estimates for Sonic-Boom Pressure Signatures and Loudness CarpetsAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

A multidisciplinary design optimization methodology to directly minimize the ground-level noise generated by a supersonic aircraft's sonic boom is presented. A gradient-based optimizer is coupled with a Cartesian Euler flow solver and an atmospheric propagation tool to forge a unique design capability. (Full paper requires login.)
Adjoint-Based Minimization of X-59 Sonic Boom Noise Via Control SurfacesAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

The ability of CFD simulations to serve as a surrogate for wind tunnel testing at high supersonic speeds has been evaluated for a sub-scale model of the Co-Optimization Blunt-body Re-entry Analysis-Mid-lift-to-drag Rigid Vehicle (CobraMRV) human Mars entry vehicle concept. The vehicle was tested at the Unitary Plan Wind Tunnel (UPWT) at the NASA Langley Research Center under flow conditions and surface control configurations relevant to the entry stage of a flight mission. (Full paper requires login.)
Evaluation of CFD Predictions of Cobra-MRV Control Surface Effectiveness at the NASA Langley Unitary Plan Wind TunnelAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

This paper is a joint effort between the National Aeronautics and Space Administration (NASA) Ames and Langley research centers to assess the capability of modern Computational Fluid Dynamic (CFD) codes to accurately simulate experimental force and moment loads on the core stage rocket and Solid Rocket Boosters (SRBs) during the SRBs' separation from a Block 1B configuration Space Launch System (SLS) exploration-class launch vehicle test article within a supersonic wind tunnel.
CFD Analysis of Space Launch System Solid Rocket Booster Separation within the Langley Unitary Plan Wind TunnelAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

This work addresses preconditioning approaches for an implicit high-order solver framework applied to multiple physics. The solver is based on a space-time spectral element method and matrix-free Newton-Krylov solver developed at NASA over the recent years. Within this context, most preconditioning methods are impractical, as the computational time and memory requirements scale poorly with increasing polynomial orders.
Efficient preconditioning of a high-order solver for multiple physicsAIAA Aviation 2021 Forum, Virtual Event, August 2-6, 2021

A perspective on CFD/CSD-based time accurate computational aeroelasticity (CCA) is presented by a researcher who has been actively pursuing this research area since its beginning in late 70s. Discusses the use of terminology focusing on differences between the time accurate coupling and loose coupling methods in CCA. Highlights the misplaced interpretation of tight coupling. Need for time accurate CCA is illustrated with an example that compares CCA results with wind tunnel data that could not be computed using the linear aerodynamic theory. The paper provides a guideline for newcomers to the ever growing CCA research field.
Perspective on CFD/CSD-Based Computational Aeroelasticity during 1977–2020Journal of Aerospace Engineering, vol. 34, issue 6, November 2021

A parallel computational method for simulating fluid–structure interaction problems involving large, geometrically nonlinear deformations of thin shell structures is presented and validated. A compressible Navier-Stokes solver utilizing a higher-order finite difference immersed boundary method is coupled with a geometrically nonlinear computational structural dynamics solver employing the mixed interpolation of tensorial components formulation for thin triangular shell elements.
An Immersed Boundary Fluid–Structure Interaction Method for Thin, Highly Compliant Shell StructuresJournal of Computational Physics, vol. 438, August 1, 2021

The entropy split method is based on the physical entropies of the thermally perfect gas Euler equations. The Euler flux derivatives are approximated as a sum of a conservative portion and a non-conservative portion in conjunction with summation-by-parts (SBP) difference boundary closure recently proved that the entropy split method is entropy conservative and stable. The current work is our first attempt to derive a high order conservative numerical flux for the non-conservative portion of the entropy splitting of the Euler flux derivatives.
Construction of Conservative Numerical Fluxes for the Entropy Split MethodCommunications on Applied Mathematics and Computation, August 24, 2021

This paper presents first-of-a-kind measurements, and complementary computations, of the flow through the propulsion system of a boundary layer ingesting, twin-engine advanced civil transport aircraft configuration. The experiments were carried out in the NASA Langley 14- by 22-foot Subsonic Tunnel, using a 1:11 scale model of the D8 “double-bubble” aircraft with electric ducted fans providing propulsive power.
Inlet Flow Distortion in an Advanced Civil Transport Boundary Layer Ingesting Engine InstallationASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, vol. 1, June 7-11, 2021

Artificial intelligence is expected to revolutionize all areas of space operations in the coming years. The most advanced space systems will possess the ability to adapt and improve performance over time, or online learning. This work presents a novel framework that uses the highly researched artificial intelligence paradigm, reinforcement learning, to perform online learning.
Bridging Reinforcement Learning and Online Learning for Spacecraft Attitude ControlJournal of Aerospace Information Systems, vol. 19, no. 1, January 2022

Artificial intelligence is expected to revolutionize all areas of space operations in the coming years. The most advanced space systems will possess the ability to adapt and improve performance over time, or online learning. This work presents a novel framework that uses the highly researched artificial intelligence paradigm, reinforcement learning, to perform online learning.
Structured and Unstructured Simulations for the Third AIAA Sonic Boom Prediction WorkshopJournal of Aircraft, vol. 58, no. 3, May 2022

We present a robust, highly accurate, and efficient positivity- and boundedness-preserving diffuse interface method for the simulations of compressible gas-liquid two-phase flows with the five-equation model by Allaire et al. using high-order finite difference weighted compact nonlinear scheme (WCNS) in the explicit form. The equation of states of gas and liquid are given by the ideal gas and stiffened gas laws respectively.
A Positivity-Preserving High-Order Weighted Compact Nonlinear Scheme for Compressible Gas-Liquid FlowsJournal of Computational Physics, vol. 444, November 1, 2021

The Geostationary Lightning Mapper (GLM) instrument onboard the GOES 16 and 17 satellites has been shown to be capable of detecting bolides (bright meteors) in Earth’s atmosphere. Due to its large, continuous field of view and immediate public data availability, GLM provides a unique opportunity to detect a large variety of bolides, including those in the 0.1 to 3 m diameter range and complements current ground-based bolide detection systems, which are typically sensitive to smaller events. We present a machine learning-based bolide detection and light curve generation pipeline being developed at NASA Ames Research Center as part of NASA’s Asteroid Threat Assessment Project (ATAP).
An Automated Bolide Detection Pipeline for GOES GLMIcarus, vol. 368, November 1, 2021

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 (EPRV) measurements. The required precision of these measurements necessitates 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 and its Effects on the Stellar Spectrum for More Precise Radial Velocity MeasurementsPresented at the International Astronomical Union Symposia, France, November 8-12, 2021

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 (EPRV) measurements. The required precision of these measurements necessitates 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.
Feasibility of Running Singularity Containers with Hybrid MPI on NASA High-End Computing Resources3rd International Workshop on Containers and New Orchestration Paradigms for Isolated Environments in HPC, November 2021

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

The Surface Biology and Geology (SBG) mission is one of the core missions of NASA’s Earth System Observatory (ESO). SBG will acquire high resolution solar-reflected spectroscopy and thermal infrared observations at a data rate of ~10 TB/day and generate products at ~75 TB/day. As the per-day volume is greater than NASA’s total extant airborne hyperspectral data collection, collecting, processing/re- processing, disseminating, and exploiting the SBG data presents new challenges. To address these challenges, we are developing a prototype science pipeline and a full-volume global hyperspectral synthetic data set to help prepare for SBG’s flight.
Progress in Developing a Prototype Science Pipeline and Full-Volume, Global Hyperspectral Synthetic Data Sets for NASA’s Earth System Observatory’s Upcoming Surface, Biology and Geology MissionPresented at the AGU 2021 Fall Meeting, New Orleans, LA, December 13-17, 2021