Papers & Reports 2024

A scoping study is being conducted on the air supply for a microjet-based active flow control (AFC) system on a twin-turbofan commercial transport airplane. Microjets provide circulation control using small surface-normal pneumatic jets located near the trailing edge of a lifting surface such as a wing or flap. In this study, microjets are considered for installation in the flaps of the high-lift version of the Common Research Model (CRM-HL).
Scoping of an Air Supply Configuration for Active Flow Control on a Commercial Transport Airplane High-Lift System34th Congress of the International Council of the Aeronautical Sciences (ICAS), Florence, Italy,

Solar activity is a primary factor determining the state of the Earth’s space environment, geomagnetic and ionospheric disturbances, and radiation hazards. In the current state of knowledge, machine learning (ML) methods provide essential tools for processing data, investigating relationships among various physical properties and characteristics, uncovering hidden connections, and predicting hazardous solar events. To facilitate ML-ready data preparation and access, we have developed an interactive database of solar flares integrating the most essential datasets.
Development of Solar Flare and Energetic Particle Prediction PortalXXXII IAU General Assembly, Cape Town, South Africa, August 6-15, 2024.

Ingenuity has sustained an astonishing 72 flights on Mars. The little helicopter proved that non-terrestrial powered flight is possible, even on planets with thin atmospheres. Future planetary rotorcraft will be bigger and heavier to accomplish new scientific and exploratory goals. This work evaluates the effectiveness of existing numerical simulation models in predicting the severity of this phenomenon for planetary rotorcraft.
Comparing Planetary Helicopter Brownout Observations With Numerical Predictions for IngenuityAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

A physics-based moving-body unsteady Reynolds Averaged Navier-Stokes based method for predicting the onset of transonic buffet is described. Four test cases of varying complexity are chosen to evaluate the approach; an ONERA OAT15A supercritical airfoil, a NACA0012 airfoil, the NASA High-Speed Common Research Model, and the Boeing SUGAR Phase V Transonic Truss Braced Wing.
Evaluation of a Physics-Based Unsteady RANS Method for Buffet Onset PredictionAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

The unstructured Voronoi mesher currently being developed within the Launch, Ascent, and Vehicle Aerodynamicssoftware framework at NASA Ames Research Center is described in detail. The discussions include, but are not limited to, the strategies used in the seeding and smoothing phases to ensure a high-quality mesh for Wall-Modeled Large-Eddy Simulations, the methods behind the cell clipping algorithm responsible for conforming the mesh to a complex geometry, and the approach to create a global mesh from the distinct Voronoi cells.
LAVA Voronoi Mesher for Wall-Modeled Large-Eddy SimulationsAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

This paper presents an investigation into the potential benefits of a boundary layer ingestion aft fuselage propulsion system, or tail-cone thruster, when applied to two transport category aircraft: a conventional tube-and-wing configuration based on the NASA Common Research Model and a transonic truss-braced wing configuration.
Aeropropulsive Assessment of a BLI Tail-Cone Thruster Propulsion System for the NASA Common Research Model and a Transonic Truss-Braced Wing ConfigurationAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

The CFD solver OVERFLOW was used to simulate the CobraMRV undergoing supersonic retropropulsion (SRP) in the Langley Unitary Plan Wind Tunnel as part of a CFD and wind-tunnel integration effort. Selection of numerical methods and resulting comparisons to selected tunnel conditions of interest are detailed.
Comparison of OVERFLOW Computational and Experimental Results of the CobraMRV Mars Entry Vehicle Concept During Supersonic RetropropulsionAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

Simulations of unsteady supersonic retropropulsion flow over a Hypersonic Inflatable Aerodynamic Decelerator blunt-body vehicle were performed using the OVERFLOW Computational Fluid Dynamics solver. High-fidelity flow solver techniques, including Detached Eddy Simulation turbulence modeling and Adaptive Mesh Refinement, were employed to obtain improved realism in CFD predictions.
Comparison of OVERFLOW Computational and Experimental Results for a Blunt Mars Entry Vehicle Concept During Supersonic RetropropulsionAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

Traditional Reynolds-averaged Navier-Stokes grid methods applied to aerodynamic shape optimization can struggle with the deformation of surface and volume grids at component intersections, such as at wing-fuselage junctions. To overcome this, we propose an approach which utilizes curvilinear overset grids for the discretization of the domain, with the presence of the body modeled using an immersed boundary method.
Towards Aerodynamic Shape Optimization Using an Immersed Boundary Overset Grid MethodAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

The goal of this work is to quantify uncertainty in the level of noise reaching the ground from supersonic aircraft at cruise conditions. To cope with uncertainty in the state of the atmosphere, the temperature and relative humidity profiles are parameterized using a Karhunen-Loeve expansion based on a novel formulation involving dew point temperature.
Acoustic Signature Uncertainty Quantification for Quiet Supersonic AircraftAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

Fluid-structure interaction simulations have the potential to accelerate the certification process of parachute systems for interplanetary robotic exploration missions while helping to mitigate risks by covering a wider range of scenarios than can be flight tested. The Launch, Ascent, and Vehicle Aerodynamics team is working toward actualizing this potential by further developing the capability to perform such fluid-structure interaction simulations and validating it with the best supersonic parachute flight test data available.
Fluid-Structure Interaction Simulations Of Supersonic Parachute Inflation: Model SensitivitiesAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

A series of scale-resolving simulations of flow over the ONERA OAT15A airfoil have been performed at an angle of attack of 3.5 degrees, just past the onset of buffet. The focus of this study is to document the sensitivity of the wall-modeled large eddy simulation methodology for curvilinear structured overset grids within the Launch, Ascent, and Vehicle Aerodynamics framework to mesh spacing, mesh distribution, and domain size.
Wall-Modeled Large Eddy Simulations of Transonic Buffet Over a Supercritical AirfoilAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

The development of innovative open-rotor propulsion systems that meet performance, fuel efficiency, and noise standards for commercial use depends significantly on the availability of reliable and computationally efficient tools for aerodynamic performance and noise prediction. This investigation demonstrates the capability of the structured curvilinear overset grid Computational Fluid Dynamics solver within the Launch, Ascent, and Vehicle Aerodynamics framework to predict the aerodynamic and aeroacoustic characteristics of a Contra-Rotating Open Rotor propulsion system under various sideslip angles.
Exploring the Impact of Sideslip Angle on Acoustic Predictions of an Open Rotor System Using Scale-Resolving SimulationsAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

We investigate the utility of adjoint-based error estimates for sonic boom farfield simulations governed by solutions of the augmented Burgers' equation. Solution of this nonlinear system uses operator splitting with a second-order finite volume discretization in space and second-order Runge-Kutta time marching, while the absorption and molecular relaxation are solved using second-order central differencing.
Discretization Error Estimation and Control for Farfield Acoustic SignaturesAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

Automation of overset structured surface mesh generation has recently been accomplished by the creation of face, edge, and node meshes based on Boundary Representation solids as the geometry input. The current work continues the automation effort in overset volume mesh generation and domain connectivity based on the auto-generated surface meshes.
Advances in Automation of Overset Structured Volume Mesh Generation and Domain ConnectivityAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

The effects of laminar-to-turbulent transition modeling in the Spalart-Allmaras and Langtry-Menter’s shear stress transport turbulence models are explored through high-fidelity simulations of the XV-15 rotor in hover. Using NASA’s OVERFLOW solver, solutions on grids of varying resolutions with a range of collective angle configurations are compared alongside experimental data.
Effect of Transition Modeling on the XV-15 Hovering Rotor FlowsAIAA Aviation Forum and Ascend 2024, Las Vegas, NV, July 29-August 2, 2024.

A detailed analysis of transonic aerodynamics of a pitching conceptual Boeing Truss-Braced Wing (TBW) section has been carried out at various Mach numbers at a typical reduced frequency, k = 0.15. A new important flow feature of hysteresis loop cross-over has been discovered through the analysis of the hysteresis loops.
Machine Learning of Unsteady Transonic Aerodynamics of a Pitching Truss-Braced Wing SectionAerospace Science and Technology, vol. 152, September 2024.

The NASA Source Diagnostic Test (SDT) campaign experimental data is used for validation of a sliding mesh technique recently implemented within the Launch, Ascent, and Vehicle Aerodynamics computational framework for time-accurate simulation of rotating fans. The far-field acoustics are analyzed in this work, building upon the aerodynamic validation studies previously published in Part I.
Fan Noise Predictions of the NASA Source Diagnostic Test Using Unsteady Simulations With LAVA Part II – Tonal and Broadband Noise Assessment30th AIAA/CEAS Aeroacoustics Conference, Rome, Italy, June 4-7, 2024.

Results from ongoing research on jet noise prediction using wall-modeled large eddy simulations (WMLES) conducted within the Launch Ascent and Vehicle Aerodynamics (LAVA) computational framework are presented. The study primarily focuses on the aeroacoustic implications of multi-stream nozzle configurations with internal mixing generated by the addition of both internal and external plug geometries.
Noise Prediction of Multi-Stream Internally Mixed Jets With External and Internal Pligs Using Large-Eddy Simulation30th AIAA/CEAS Aeroacoustics Conference, Rome, Italy, June 4-7, 2024.

Risk assessment studies of local asteroid hazards traditionally simulate the physics of meteors with engineering models tailored to analyze tens-of-millions of scenarios. However, these simplified approaches still need to solve time-dependent ODEs to model the entry process and the resulting ground damage. To improve computational efficiency, we propose in this paper an orthogonal approach based on machine learning models to predict the size of damaged areas given a list of entry parameters.
Machine Learning for the Prediction of Local Asteroid DamagesActa Astronautica, vol. 219, June 2024.

To create early warning capabilities for upcoming Space Weather disturbances, we have selected a dataset of 61 emerging active regions, which allows us to identify characteristic features in the evolution of acoustic power density to predict continuum intensity emergence. For our study, we have utilized Doppler shift and continuum intensity observations from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO).
Predicting the Emergence of Solar Active Regions Using Machine LearningarXiv:2402.08890 [astro-ph.SR], February 14, 2024.

This paper describes a building-block approach for high-fidelity computational fluid dynamic simulations of NASA’s Lift+Cruise (L+C) Vertical Take-off and Landing (VTOL) concept vehicle. The Reynolds-Averaged Navier-Stokes equations are solved on overset structured grids using OVERFLOW. Overset meshes are generated using recently developed automated meshing tools. A baseline study is initially performed on the vehicle fuselage with wings and tails. Vehicle components such as pylons and gears are then added individually and together to study incremental component aerodynamic effects. Results from this study are also used to demonstrate the capabilities of the automatic meshing tools for performing rapid computational analyses.
Computational Aerodynamic Study of the Lift+Cruise VTOL Concept Vehicle ComponentsTransformative Vertical Flight 2024, Santa Clara, CA, February 6-8, 2024.

This paper discusses the validation of the ascent surface pressure database developed using Computational Fluid Dynamics (CFD) for the Space Launch System (SLS) Program with Artemis I flight data from the ascent phase of flight. The ascent phase begins shortly after the vehicle clears the launch tower and extends to the first staging event. This work compares sensor data from the successful Artemis I flight to point pressures extracted from the implemented surface pressure database for Artemis I and other available CFD data sets.
Validation of SLS Ascent CFD Surface Pressure Databases Using Artemis I Flight DataAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

This paper presents an update to the conceptual design of the NASA Subsonic Single Aft Engine (SUSAN) Electrofan transport aircraft---a 180 passenger, Mach 0.785 hybrid-electric regional jet with an economy range of 750 nmi and a design range of 2,500 nmi. Investigated in this work is the system level sizing and analysis of the SUSAN Electrofan when accounting for system level trades related to its electrified aircraft propulsion (EAP) systems.
Conceptual Design of the Hybrid-Electric Subsonic Single Aft Engine (SUSAN) Electrofan Transport AircraftAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

Wall-modeled large-eddy simulation (WMLES) methods have been used to perform increasingly practical physics based simulations where resolving turbulent structures is important, including those involving the NASA High-Lift Common Research Model geometry. However, the results obtained from these numerical campaigns are typically quite sensitive to choices pertaining to the flux formulation, in addition to the mesh topology and resolution used. The current study seeks to partially alleviate the flux sensitivity by proposing a formulation based on an existing non-dissipative kinetic energy and entropy preserving flux combined with carefully constructed dissipation to achieve stability.
Wall-Modeled Large-Eddy Simulations of a Swept WingAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

The flow past the Boeing Transonic Truss-Braced Wing (TTBW) aircraft is simulated with a Hybrid Reynolds-Averaged Navier-Stokes Large-Eddy Simulations (HRLES) turbulence modeling approach to study transonic buffet onset and evaluate the predictive capability of the numerical approach. All simulations used structured overset curvilinear grids for the free-air configuration, with all simulations performed using the Launch, Ascent, and Vehicle Aerodynamics (LAVA) computational framework.
Simulating Transonic Buffet Aerodynamics for the Boeing Transonic Truss-Braced Wing AircraftAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

A supervised deep learning approach is coupled with heuristic convergence criteria to construct a classification model for detecting the completion (convergence) of computational fluid dynamics (CFD) simulations. Heuristic convergence criteria alone are not always sufficient and more complex decisions are often left to a human analyst. The proposed approach leverages heuristic convergence criteria as well as two deep neural network (DNN) models, one binary and one multi-class, to improve the efficiency and consistency of convergence classification across a wide range of flight regimes.
Deep Neural Network Based Convergence Classification for Computational Fluid DynamicsAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

The development of breakthrough open-rotor propulsion systems that meet performance, fuel efficiency, and noise requirements for commercial viability relies heavily on the availability of reliable and computationally efficient aerodynamic performance and noise prediction tools. This investigation showcases the proficiency of the structured curvilinear overset grid Computational Fluid Dynamics solver implemented in the Launch Ascent and Vehicle Aerodynamics framework for predicting the aerodynamic and aeroacoustic characteristics of a Contra-Rotating Open Rotor propulsion system.
Scale Resolving Simulations of Contra Rotating Open Rotor Noise PredictionAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

A scoping study was conducted on the air supply of a microjet-based active flow control (AFC) system on a twin-turbofan commercial transport airplane. Microjets provide direct lift-control in the linear regime of the lift curve using small surface-normal pneumatic jets located near the trailing edge of a lifting surface such as a wing or flap.
Scoping of an Air Supply System for Active Flow Control on a Commercial Transport AirplaneAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.

This work presents a method to generate line loads that are consistent with integrated force and moment constraints, while also following the statistical distribution underlying known line load data. The motivation for this method is to address a particular problem that can arise during the pre-flight analysis of an ascent vehicle. That problem is constructing separate databases, for line loads and integrated aerodynamic coefficients, that contain different data and thus different amounts of quantified uncertainty.
Statistically Consistent Dispersion of Line Loads to Uncertain Integrated Forces and MomentsAIAA SciTech 2024 Forum, Orlando, FL, January 8-12, 2024.