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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Computational Analysis of X-57 Rate Derivatives and Comparison to Wind Tunnel Data

Rate derivates of the wind tunnel model of X-57 were evaluated using hysteresis from computational fluid dynamics simulation and compared with that computed using the wind tunnel experimental data. To accomplish the task, hysteresis of the pitch, roll, and yaw oscillations were produced numerically using two different CFD solvers: STARCCM+ and Launch Ascent and Vehicle Analysis. The rate derivatives were computed using same parameter identification technique on CFD-based and wind tunnel-based hysteresis data. Results show CFD-based pitch rate derivatives have large error, up to 73%, while the lateral and direction derivates compared well with errors within 5% with respect to the that computed using the wind tunnel data. This may be due to lack of wind tunnel wall and sting model in the CFD simulation as well as lack of wall correction in the wind tunnel data which has larger impact on pitch than lateral and directional oscillations. Geometrical features such as the shape, slope of extremities, and enclosed area were compared between CFD-based and wind tunnel-based hysteresis. Results show that area enclosed by the hysteresis had largest influence on the accuracy of the computed rate derivatives given that shape of the hysteresis were roughly equivalent.

Seung Y. Yoo↗
DOE OSTI2022

Controlled Hysteresis of Conductance in Molecular Tunneling Junctions

The problem this paper addresses is the origin of the hysteretic behavior in two-terminal molecular junctions made from an EGaIn electrode and self-assembled monolayers of alkanethiolates terminated in chelates (transition metal dichlorides complexed with 2,2'-bipyridine; BIPY-MCl 2 ). The hysteresis of conductance displayed by these BIPY-MCl 2 junctions changes in magnitude depending on the identity of the metal ion (M) and the window of the applied voltage across the junction. The hysteretic behavior of conductance in these junctions appears only in an incoherent (Fowler–Nordheim) tunneling regime. When the complexed metal ion is Mn(II), Fe(II), Co(II), or Ni(II), both incoherent tunneling and hysteresis are observed for a voltage range between +1.0 V and –1.0 V. When the metal ion is Cr(II) or Cu(II), however, only resonant (one-step) tunneling is observed, and the junctions exhibit no hysteresis and do not enter the incoherent tunneling regime. Using this correlation, the conductance characteristics of BIPY-MCl 2 junctions can be controlled. Furthermore, this voltage-induced change of conductance demonstrates a simple, fast, and reversible way (i.e., by changing the applied voltage) to modulate conductance in molecular tunneling junctions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Dramatic effect of electrode type on tunnel junction based molecular spintronic devices

A new class of molecular spintronic devices can be fabricated by chemically bonding magnetic molecular channels to the electrodes of a prefabricated tunnel junction with exposed side edges. Prior experimental studies showed that the cyanide-bridged octametallic molecular cluster, [(pzTp)FeIII(CN)3]4[NiII(L)]4¬[O3SCF3]4 [(pzTp) = tetra(pyrazol-1-yl)borate; L = 1-S(acetyl)tris(pyrazolyl)decane] molecule impact depended on the type of metallic electrodes used in the tunnel junction testbed. Experimental magnetization and transport studies showed a dramatic difference in molecule response on tunnel junctions with different combinations of metallic electrodes. Transport via paramagnetic molecular channels on a tunnel junction involving paramagnetic and ferromagnetic metal electrodes was dramatically different than the suppressed current state observed on tunnel junctions involving two ferromagnetic electrodes. We conducted theoretical studies to understand the experimental data and explore a wide range of electrode materials on tunnel junction-based molecular spintronics devices (TJMSD). Here, we report a Monte Carlo simulation study that focuses on understanding the effect of electrodes on the magnetic and physical properties of TJMSD. A 3D Heisenberg model of cross-junction-shaped TJMSD was used for the simulation study. We studied the effects of ferromagnetic, paramagnetic, and antiferromagnetic electrode materials. This study provides insights for designing and understanding futuristic molecular spintronics devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Time-Resolved Observation of Hole Tunneling in van der Waals Multilayer Heterostructures

We reported a time-resolved study of quantum-mechanical tunneling of holes between two MoSe 2 monolayers that are separated by a monolayer WS 2 energy barrier. Four-layer heterostructures of MoSe 2 /WS 2 /MoSe 2 /graphene, as well as control samples, were fabricated by mechanical exfoliation and dry transfer techniques. To time-resolve the hole tunneling process, an ultrashort laser pulse was used to excite electrons and holes in both MoSe 2 layers. Here, by utilization of the graphene layer to eliminate carriers in the third MoSe 2 layer, the first MoSe 2 layer is selectively populated with the holes, which then tunnel to the third MoSe 2 layer. By monitoring decay of the hole population with an ultrashort probe pulse, we measure a hole tunneling time of about 20 ps, which is found to slightly increase with the injected carrier density. Besides the fundamental interests of real-time observation of the quantum-mechanical tunneling effect across a nanometer barrier, these results provide quantitative understanding on tunneling mechanisms of charge transfer in van der Waals heterostructures, which is useful for designing sophisticated van der Waals multilayer heterostructures.

36 MATERIALS SCIENCE↗
NASA NTRS2015

Aeroelastic Analysis of a Flexible Wing Wind Tunnel Model with Variable Camber Continuous Trailing Edge Flap Design

This paper presents data analysis of a flexible wing wind tunnel model with a variable camber continuous trailing edge flap (VCCTEF) design for drag minimization tested at the University of Washington Aeronautical Laboratory (UWAL). The wind tunnel test was designed to explore the relative merit of the VCCTEF concept for improved cruise efficiency through the use of low-cost aeroelastic model test techniques. The flexible wing model is a 10%-scale model of a typical transport wing and is constructed of woven fabric composites and foam core. The wing structural stiffness in bending is tailored to be half of the stiffness of a Boeing 757-era transport wing while the torsional stiffness is about the same. This stiffness reduction results in a wing tip deflection of about 10% of the wing semi-span. The VCCTEF is a multi-segment flap design having three chordwise camber segments and five spanwise flap sections for a total of 15 individual flap elements. The three chordwise camber segments can be positioned appropriately to create a desired trailing edge camber. Elastomeric material is used to cover the gaps in between the spanwise flap sections, thereby creating a continuous trailing edge. Wind tunnel data analysis conducted previously shows that the VCCTEF can achieve a drag reduction of up to 6.31% and an improvement in the lift-to-drag ratio (L=D) of up to 4.85%. A method for estimating the bending and torsional stiffnesses of the flexible wingUWAL wind tunnel model from static load test data is presented. The resulting estimation indicates that the stiffness of the flexible wing is significantly stiffer in torsion than in bending by as much as 9 to 1. The lift prediction for the flexible wing is computed by a coupled aerodynamic-structural model. The coupled model is developed by coupling a conceptual aerodynamic tool Vorlax with a finite-element model of the flexible wing via an automated geometry deformation tool. Based on the comparison of the lift curve slope, the lift prediction for the rigid wing is in good agreement with the estimated lift coefficients derived from the wind tunnel test data. Due to the movement of the VCCTEF during the wind tunnel test, uncertainty in the lift prediction due to the indicated variations of the VCCTEF deflection is studied. The results show a significant spread in the lift prediction which contradicts the consistency in the aerodynamic measurements, thus suggesting that the indicated variations as measured by the VICON system may not be reliable. The lift prediction of the flexible wing agrees very well with the measured lift curve for the baseline configuration. The computed bending deflection and wash-out twist of the flexible wing also match reasonably well with the aeroelastic deflection measurements. The results demonstrate the validity of the aerodynamic-structural tool for use to analyze aerodynamic performance of flexible wings.

Wind Tunnel↗
NASA NTRS2016

Wind Tunnel Model Design for Sonic Boom Studies of Nozzle Jet with Shock Interactions

NASA and Industry are performing vehicle studies of configurations with low sonic boom pressure signatures. The computational analyses of modern configuration designs have matured to the point where there is confidence in the prediction of the pressure signature from the front of the vehicle, but uncertainty in the aft signatures with often greater boundary layer effects and nozzle jet pressures. Wind tunnel testing at significantly lower Reynolds numbers than in flight and without inlet and nozzle jet pressures make it difficult to accurately assess the computational solutions of flight vehicles. A wind tunnel test in the NASA Ames 9- by 7-Foot Supersonic Wind Tunnel from Mach 1.6 to 2.0 will be used to assess the effects of shocks from components passing through nozzle jet plumes on the sonic boom pressure signature and provide datasets for comparison with CFD codes. A large number of high-fidelity numerical simulations of wind tunnel test models with a variety of shock generators that simulate horizontal tails and aft decks have been studied to provide suitable models for sonic boom pressure measurements using a minimally intrusive pressure rail in the wind tunnel. The computational results are presented and the evolution of candidate wind tunnel models is summarized and discussed in this paper.

Wind↗
NASA NTRS2016

Computational Role of Tunneling in a Programmable Quantum Annealer

Quantum tunneling is a phenomenon in which a quantum state tunnels through energy barriers above the energy of the state itself. Tunneling has been hypothesized as an advantageous physical resource for optimization. Here we present the first experimental evidence of a computational role of multiqubit quantum tunneling in the evolution of a programmable quantum annealer. We developed a theoretical model based on a NIBA Quantum Master Equation to describe the multi-qubit dissipative cotunneling effects under the complex noise characteristics of such quantum devices.We start by considering a computational primitive, the simplest non-convex optimization problem consisting of just one global and one local minimum. The quantum evolutions enable tunneling to the global minimum while the corresponding classical paths are trapped in a false minimum. In our study the non-convex potentials are realized by frustrated networks of qubit clusters with strong intra-cluster coupling. We show that the collective effect of the quantum environment is suppressed in the critical phase during the evolution where quantum tunneling decides the right path to solution. In a later stage dissipation facilitates the multiqubit cotunneling leading to the solution state. The predictions of the model accurately describe the experimental data from the D-WaveII quantum annealer at NASA Ames. In our computational primitive the temperature dependence of the probability of success in the quantum model is opposite to that of the classical paths with thermal hopping. Specially, we provide an analysis of an optimization problem with sixteen qubits,demonstrating eight qubit cotunneling that increases success probabilities. Furthermore, we report results for larger problems with up to 200 qubits that contain the primitive as subproblems.

hard problems↗
NASA NTRS2015

SMART Rotor Wind Tunnel Test Report

The Boeing Company, Mesa Arizona, has been developing smart material actuated rotor technology (SMART) under in-house, DARPA (Defense Advanced Research Projects Agency), NASA and Army funding. A whirl tower test of the SMART active flap rotor system was successfully conducted at the remote test facility (RTF) in Mesa, Arizona, in 2003. Under DARPA and NASA funding, the SMART rotor system was tested in the NASA Ames National Full Scale Aerodynamic Complex (NFAC) 40- by 80-Foot Wind Tunnel in 2008. The DARPA program objectives were to demonstrate the active flap impact on rotor acoustics in forward flight and establish a validation database for noise prediction tools. Under NASA funding, additional wind tunnel tests were conducted, with the objective to demonstrate and quantify vibration, noise, and performance improvements.Wind tunnel testing was successfully and safely concluded, meeting all high priority objectives. The authority, effectiveness, and reliability of the flap actuation system were demonstrated in 65 hours of testing at up to 155 knots and 7,700 pound thrust. Validation data was successfully acquired for four test conditions; blade loads were too high for the high speed condition. The effectiveness of the flap for noise and vibration control was demonstrated conclusively, with results showing significant reductions in BVI (Blade-Vortex Interaction) and in-plane noise as well as vibratory hub loads. The impact of the flap on control power and rotor smoothing was also demonstrated. Data evaluating any benefits in aerodynamic performance and impact on flight controls were acquired, but will need more detailed evaluation. Both open loop control and closed loop feedback control, using continuous time and higher harmonic controllers, were applied.The purpose of the Test Report is to provide a comprehensive document that describes the preparation for and conduct of the wind tunnel test and summarizes the processing and evaluation of wind tunnel test data for the DARPA and the NASA portion of the test. An overview of the wind tunnel test and results can be found in Reference 1. Details on the testing and results for BVI noise, in-plane noise, and vibrations can be found in References 2-4, respectively. These references are four papers, presented at the American Helicopter Society Annual Forum in 2009. A brief description of the delivered electronic data is provided in Reference 5.

Rotor↗
NASA NTRS2019

Acoustic Testing of the Tiltrotor Test Rig in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel

The Tiltrotor Test Rig (TTR) was tested in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel from 2017 to 2018. The primary goal of the test was to understand the operational capabilities of the TTR, while also acquiring research data, including acoustic data. Four microphones were placed around the TTR: two on the wind tunnel floor and two on struts. Acoustic measurements of the TTR rotor were acquired to 1) understand the acoustic testing capabilities of the TTR in the NFAC 40- by 80-FootWind Tunnel, 2) compare to previous XV-15 rotor acoustic data acquired in the NFAC 80- by 120-Foot Wind Tunnel, and 3) provide data for future validation studies. A data quality study revealed that the NFAC 40- by 80-Foot Wind Tunnel is an adequate acoustic environment to test the TTR rotor. For a given thrust and advance ratio, a shaft angle sweep was performed and acoustic measurements were compared against 1996 and 1999 XV-15 data in the NFAC 80- by 120-Foot Wind Tunnel; differences between the three tests are discussed.

40- by 80-FootWind Tunnel↗
NASA NTRSDate not supplied

Comparisons of CFD Simulations of Icing Wind Tunnel Clouds with Experiments Conducted at the NASA Propulsions Systems Laboratory

This paper evaluates simulation predictions against experimental test data of icing clouds that were produced during 2018 ice crystal icing physics tests conducted at the NASA Propulsion Systems Laboratory icing wind tunnel. Aero-thermal and cloud parameters are set and known upstream at the tunnel inlet and spray system, but change as the cloud and air thermodynamically interact as the flowing masses reach the tunnel test section. Utilizing the ANSYS Fluent Discrete Phase Model function, 3D computational fluid dynamics (CFD) simulations were performed, capturing the thermodynamic interactions between the test parameters, and providing predictions of the aero thermal and cloud conditions at the tunnel test section. Simulation predictions were compared with test data that were measured at the tunnel exit plane. Evaluations focused on the cloud concentration (total water content), humidity content, and air temperature. CFD simulation predictions showed areas of agreement and disagreement. Simulations showed that cloud concentration profiles at the test section are strongly related to the initial spray nozzle pattern used at the tunnel inlet. Experimental data suggest that greater dispersion of the cloud occurred as the simulated cloud predicted areas of high and low cloud concentration compared to test data profiles. Simulations, however, captured the magnitude and location of the change in humidity content and the change in air temperature due to the presence of the cloud reasonably well, when compared to test data. This result would suggest that while the ANSYS simulation did not fully predict the spreading of the cloud as measured during experiment, it did capture evaporation and the molecular movements of air and vapor relatively well.

CFD↗
NASA NTRSDate not supplied

Comparisons of CFD Simulations of Icing Wind Tunnel Clouds with Experiments Conducted at the NASA Propulsions Systems Laboratory

This paper evaluates simulation predictions against experimental test data of icing clouds that were produced during 2018 ice crystal icing physics tests conducted at the NASA Propulsion Systems Laboratory icing wind tunnel. Aero-thermal and cloud parameters are set and known upstream at the tunnel inlet and spray system, but change as the cloud and air thermodynamically interact as the flowing masses reach the tunnel test section. Utilizing the ANSYS Fluent Discrete Phase Model function, 3D computational fluid dynamics (CFD) simulations were performed, capturing the thermodynamic interactions between the test parameters, and providing predictions of the aero thermal and cloud conditions at the tunnel test section. Simulation predictions were compared with test data that were measured at the tunnel exit plane. Evaluations focused on the cloud concentration (total water content), humidity content, and air temperature. CFD simulation predictions showed areas of agreement and disagreement. Simulations showed that cloud concentration profiles at the test section are strongly related to the initial spray nozzle pattern used at the tunnel inlet. Experimental data suggest that greater dispersion of the cloud occurred as the simulated cloud predicted areas of high and low cloud concentration compared to test data profiles. Simulations, however, captured the magnitude and location of the change in humidity content and the change in air temperature due to the presence of the cloud reasonably well, when compared to test data. This result would suggest that while the ANSYS simulation did not fully predict the spreading of the cloud as measured during experiment, it did capture evaporation and the molecular movements of air and vapor relatively well.

CFD↗
NASA NTRSDate not supplied

Comparison of Wind-Tunnel and Flight Unsteady Pressure Environments for the Ares I-X Flight Test Vehicle

Wind-tunnel testing of highly-instrumented rigid models is the current standard for the estimation of unsteady environments acting on a launch vehicle during ascent. However, uncertainties are present in how well these constant condition wind-tunnel data model the unsteady environments for a full-scale launch vehicle during accelerating flight. The Ares I-X wind-tunnel and flight tests provided rich data sets for comparative analysis that have been used to develop answers to the question of tunnel-to-flight validity and uncertainty. In this paper, additional comparisons are presented for the unsteady pressure data acquired during wind-tunnel and flight testing to describe current methods that are used to evaluate preflight predictions. Utilizing these methods to generate ensembles of flight-comparable realizations from wind-tunnel data is shown to yield fluctuating magnitudes and spectra that compare well with flight data for the Ares I-X flight test vehicle throughout the transonic flight regime.

buffet↗
NASA NTRSDate not supplied

Comparison of Wind-Tunnel and Flight Unsteady Pressure Environments for the Ares I-X Flight Test Vehicle

Wind-tunnel testing of highly-instrumented rigid models is the current standard for the estimation of unsteady environments acting on a launch vehicle during ascent. However, uncertainties are present in how well these constant condition wind-tunnel data model the unsteady environments for a full-scale launch vehicle during accelerating flight. The Ares I-X wind-tunnel and flight tests provided rich data sets for comparative analysis that have been used to develop answers to the question of tunnel-to-flight validity and uncertainty. In this paper, additional comparisons are presented for the unsteady pressure data acquired during wind-tunnel and flight testing to describe current methods that are used to evaluate preflight predictions. Utilizing these methods to generate ensembles of flight-comparable realizations from wind-tunnel data is shown to yield fluctuating magnitudes and spectra that compare well with flight data for the Ares I-X flight test vehicle throughout the transonic flight regime.

buffet↗
NASA NTRS2022

X-59 Sonic Boom Test Results from the NASA Glenn 8- by 6-Foot Supersonic Wind Tunnel

A wind tunnel test was conducted to investigate near-field sonic boom pressure signatures from a model of the X-59 Low-Boom Flight Demonstrator aircraft. A 1.62%-scale model of the aircraft in the C612A configuration was fabricated for the wind tunnel test, which took place in the NASA Glenn 8- by 6-Foot Supersonic Wind Tunnel in September and October 2021. The model had provisions for two different mounting options: a swept blade strut that attached at the top of model ahead of the inlet, and rear-entry sting that was made as one piece with a dummy nacelle, and which had a 2”-long cylindrical segment aft of the nozzle exit before tapering up in size. The blade strut allowed for a clean aft end of the model for evaluation of the shocks from that region, while the sting avoided the significant distortions of the flow and shocks from the blade strut along the top of the model. Both the sting and the strut had adapters that attached to a force balance. The model had alternate parts for ±0.5° deflections of the flaps, ailerons, and stabilator, and ±1° deflections of the T-tail horizontal surface. Off-body static pressure measurements of the flow field below the model were made by use of a pressure rail which had 420 orifices along its tip. The model was positioned at various heights from the rail by vertical movement of the wind tunnel strut, and at various longitudinal stations relative to the rail by means of a linear actuator mounted between the tunnel strut and the balance. The longitudinal positioning allowed multiple pressure signatures to be obtained along different portions of the rail. These signatures were aligned by accounting for the model longitudinal movement and then averaged to take out the effects of tunnel flow distortions and the interference of the rail flow field and shocks on the model pressure signatures. The test was run at approximate Mach numbers of 1.36, 1.4, and 1.47, and the model was set at various angles of attack and roll relative to the rail. Plots of the model signatures for all the variations of Mach number, model angles, control deflections, and height relative to the rail are provided throughout the report. Repeatability was generally very good and gave confidence in the quality of the measurements. The signatures measured at various heights from the rail provided insight into the aging of the model shocks as they propagated from 1.2 to 3 body lengths from the model. Off-track signatures up to 45° from centerline obtained by rolling the model gave indications of the shock flow fields across the width of the sonic boom carpet. The deflections of the various control surfaces allowed assessment of the boom sensitivity to the control surface movements.

Sonic boom↗
NASA NTRS2023

X-59 Sonic Boom Test Results from the NASA Glenn 8- by 6-Foot Supersonic Wind Tunnel

A wind tunnel test was conducted to investigate near-field sonic boom pressure signatures of the X-59 Low-Boom Flight Demonstrator aircraft. A 1.62%-scale model of the aircraft was fabricated for the wind tunnel test, which took place in the NASA Glenn 8- by 6-Foot Supersonic Wind Tunnel in September and October 2021. The model had provisions for being mounted by a swept blade strut that attached at top of model ahead of the inlet, or by a rear-entry sting that held the model at the location of the nacelle. The model had alternate parts for ±0.5° deflections of the flaps, ailerons, and stabilator, and ±1° deflections of the T-tail. Off-body static pressure measurements of the flow field below the model were made on a pressure rail which had 420 orifices along its tip. The model was positioned at various heights from the rail by vertical movement of the tunnel strut, and at various longitudinal stations relative to the rail by means of a linear actuator mounted between the wind tunnel strut and the balance. Spatial averaging of model pressure signatures acquired over a range of longitudinal positions reduced the effects of tunnel flow distortions and the interference of the rail flow field and shocks on the model pressure signatures. The test was run at approximate Mach numbers of 1.36, 1.4, and 1.47, and the model was set at various angles of attack and roll relative to the rail. Plots of the model signatures for representative variations of Mach number, model angles, control deflections, and height relative to the rail are provided throughout the report. Repeatability was generally very good and gave confidence in the quality of the measurements. The signatures measured at various heights from the rail provided insight into the aging of the model shocks as they propagated from 1.2 to 3 body lengths from the model. Off-track signatures up to 45° from centerline obtained by rolling the model gave indications of the shock flow fields across the width of the sonic boom carpet. The deflections of the various control surfaces allowed assessment of the boom sensitivity to the control surface movements.

Sonic boom↗
NASA NTRSDate not supplied

Wind Tunnel Wall Interference Investigation of an Aspect Ratio13.5 Common Research Model using FUN3D

This paper presents a computation study of an aspect ratio 13.5 wind tunnel scale CommonResearch Model (CRM) inside a transonic wind tunnel using FUN3D CFD solver. The transonicwind tunnel is a slotted-test-section with 16 ft×16 ft test section wind tunnel. The simulationsare conducted under free-air, closed slots, and open slots conditions. The wind tunnel wallinterference effects are analyzed based on the simulations. The wall interference effects will beused to calibrate the aerodynamic database generated by VSPAERO solver for the real-timedrag optimization and maneuver load alleviation study of the wind tunnel scale CRM model.

CFD↗
NASA NTRSDate not supplied

Uncertainty Improvement in the NASA Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel

Within the past decade, a measurement uncertainty analysis (MUA) team was assembled at the NASA Glenn Research Center to assist the wind tunnel characterization team with quantification of uncertainty estimates for variables of interest in wind tunnels and test cells across the center. The initial analysis performed by the team was conducted on the 8- by 6- Foot Supersonic Wind Tunnel using results from the 1996/97 full calibration test entry. These MUA results were published in 2016 which included recommendations for methods to improve the uncertainty estimates for various variables of interest, such as changes to regression models, tunnel operation philosophy, and instrumentation choices. The wind tunnel characterization team utilized the proposed methods in 2019 during a full characterization test entry. Following publication of the 2019 test section characterization results, the MUA team pursued an update to the uncertainty estimates for the facility, which validated previous recommendations and revealed significantly reduced systematic uncertainties across most variables of interest. Inclusion of within-test repeat points in the 2019 test entry allowed for higher fidelity estimates of random uncertainty to be generated, as well. This collaboration between the facility, wind tunnel characterization, and MUA teams serves as an example of the data quality benefits that can be achieved through rigorous analysis of the sources of uncertainty in a ground-test facility.

Uncertainty↗
NASA NTRSDate not supplied

Uncertainty Improvement in the NASA Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel

Within the past decade, a measurement uncertainty analysis (MUA) team was assembled at NASA Glenn Research Center to assist the wind tunnel characterization team with quantification of uncertainty estimates for variables of interest in wind tunnels and test cells across the center. The initial analysis performed by the team was conducted on the 8- by 6-Foot Supersonic Wind Tunnel using results from the 1996/97 full calibration test entry. These MUA results were published in 2016 which included recommendations for methods to improve the uncertainty estimates for various variables of interest, such as changes to regression models, tunnel operation philosophy, and instrumentation choices. The wind tunnel characterization team utilized the proposed methods in 2019 during a full characterization test entry. Following publication of the 2019 test section characterization results, the MUA team pursued an update to the uncertainty estimates for the facility, which validated previous recommendations and revealed significantly reduced systematic uncertainties across most variables of interest. Inclusion of within-test repeat points in the 2019 test entry allowed for higher fidelity estimates of random uncertainty to be generated, as well. This collaboration between the facility, wind tunnel characterization, and MUA teams serves as an example of the data quality benefits that can be achieved through rigorous analysis of the sources of uncertainty in a ground-test facility.

Uncertainty↗