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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Additional Investigations of Ice Shape Sensitivity to Parameter Variations

A second parameter sensitivity study was conducted at the NASA Glenn Research Center's Icing Research Tunnel (IRT) using a 36 in. chord (0.91 m) NACA-0012 airfoil. The objective of this work was to further investigate the feasibility of using ice shape feature changes to define requirements for the simulation and measurement of SLD and appendix C icing conditions. A previous study concluded that it was feasible to use changes in ice shape features (e.g., ice horn angle, ice horn thickness, and ice shape mass) to detect relatively small variations in icing spray condition parameters (LWC, MVD, and temperature). The subject of this current investigation extends the scope of this previous work, by also examining the effect of icing tunnel spray-bar parameter variations (water pressure, air pressure) on ice shape feature changes. The approach was to vary spray-bar water pressure and air pressure, and then evaluate the effects of these parameter changes on the resulting ice shapes. This paper will provide a description of the experimental method, present selected experimental results, and conclude with an evaluation of these results.

Miller, Dean R.↗
NASA NTRS1974

A scale model wind tunnel study of dispersion in the Cleveland area. Laboratory simulation of lake breeze effects on diffusion from ground level emissions

A wind tunnel simulation of the diffusion patterns in a sea breeze was attempted. The results indicate that the low level onshore flow was well simulated for neutral, stable, unstable, and elevated inversion conditions. Velocity, turbulence, shear stress, and temperature data were taken, and the spread of emissions from ground level sources was investigated. Comparison is made with theoretical predictions by E. Inoue and with the open, homogeneous plane field results of Pasquill. Agreement with the predictions by Inoue is good, and the comparison with Pasquill's results shows that the wind tunnel flows are shifted two categories towards more stable. The discrepancy may be explained as a matter of averaging time.

Hoydysh, W. G.↗
NASA NTRS2002

Boundary Layer Transition on Slender Cones in Conventional and Low Disturbance Mach 6 Wind Tunnels

An experimental investigation was conducted on a 5-degree half-angle cone and a 5-degree half-angle flared cone in a conventional Mach 6 wind tunnel to examine the effects of facility noise on boundary layer transition. The influence of tunnel noise was inferred by comparing transition onset locations determined from the present test to that previously obtained in a Mach 6 low disturbance quiet tunnel. Together, the two sets of experiments are believed to represent the first direct comparison of transition onset between a conventional and a low disturbance wind tunnel using a common test model and transition detection technique. In the present conventional hypersonic tunnel experiment, separate measurements of heat transfer and adiabatic wall temperatures were obtained on the conical models at small angles of attack over a range of Reynolds numbers, which resulted in laminar, transitional, and turbulent flow. Smooth model turbulent heating distributions are compared to that obtained with transition forced via discrete surface roughness. The model nosetip radius was varied to examine the effects of bluntness on transition onset. Despite wall to total temperature differences between the transient heating measurements and the adiabatic wall temperature measurement, the two methods for determining sharp cone transition onset generally yielded equivalent locations. In the 'noisy' mode of the hypersonic low disturbance tunnel, transition onset occurred earlier than that measured in the conventional hypersonic tunnel, suggesting higher levels of freestream acoustic radiation relative to the conventional tunnel. At comparable freestream conditions, the transition onset Reynolds number under low disturbance conditions was a factor of 1.3 greater than that measured on flared cone in the LaRC conventional hypersonic tunnel and a factor of 1.6 greater that the flared cone run in the low disturbance tunnel run 'noisy'. Navier-Stokes mean flow computations and linear stability analysis were conducted to assess the experimental results and have indicated N factors associated with sharp flared cone transition onset to be approximately a factor of 2 lower than that inferred from the corresponding low disturbance tunnel measurements.

Horvath, Thomas J.↗
NASA NTRS1985

Numerical study of three-dimensional turbulent flow interactions between blockage models and wind tunnels including longitudinally slotted test sections

A spatial forward-marching approach is applied to compute three-dimensional turbulent flows for several blockage models in free flight, in a solid wall wind tunnel, and in a wind tunnel with longitudinal slots in the test section. The effects of area blockage in the tunnel, model growth and tunnel wall boundary layers, and of the slots are included. The large blockage models are found to have significant wall interference effects which can be reduced by the slots. The effects of the latter are confined to the region near the tunnel wall. Model/wall interference effects are not limited to the effects of area blockage; in particular, boundary layer profile shapes for a wind tunnel model in a tunnel are different from shapes for a model in free flight even when slots are used. This indicates that the flow responds differently in these two cases with the same pressure gradient.

Lin, S.-J.↗
NASA NTRSDate not supplied

Rotor Performance Predictions of a Next Generation Mars Science Helicopter

Since Ingenuity took flight and proved aerial capabilities on Mars, the horizon for rotorcraft on the Red Planet has only expanded. One proposed future Martian rotorcraft is the Mars Science Helicopter (MSH). The MSH is a hexacopter capable of carrying scientific payloads. As a part of its joint development by NASA Ames Research Center (ARC) and the Jet Propulsion Laboratory (JPL), key MSH rotor components will be tested inside the in-development Reduced Atmospheric Pressure Testing Of Rotors (RAPTOR) wind tunnel in the Planetary Aeolian Laboratory (PAL) at NASA ARC. In preparation for the test, the Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM) analysis was utilized to predict the aerodynamic performance for one MSH hexacopter isolated rotor. This paper provides an overview of the planned experiments involving the MSH reference blades, as well as CHARM pretest predictions of rotor performance in hover and forward flight. Additionally, the interference effects of wind tunnel walls on rotor performance will be evaluated to inform the test matrix of the upcoming test in the RAPTOR tunnel.

MHS↗
NASA NTRS1946

Altitude-Wind-Tunnel Investigation of Performance of Several Propellers on YP-47M Airplane at High Blade Loading: Curtiss 838-1C2-18R1 Four-Blade Propeller - 2

An investigation was conducted in the Cleveland altitude wind tunnel to determine the performance of a Curtiss propeller with four 838-lC2-lSRl blades on a YP-47M airplane at high blade loadings and engine powers. The study was made for a range of power coefficients between 0.30 and 1.00 at free-stream Mach numbers of 0.40 and 0.50. The results of the force measurements indicate primarily the trend of propeller efficiency for changes in power coefficient or advance-diameter ratio, inasmuch as corrections for the effects of tunnel-wall constriction on the installation have not been applied. Slip-stream pressure surveys across the propeller disk are presented to illustrate blade thrust load distribution for several operating conditions. At a free-stream Mach number of 0.40, nearly constant peak efficiencies were obtained at power coefficients from 0.30 to 0.70. A change in power coefficient from 0.70 to 0.90 reduced the peak efficiency about 5 percent. Blade stall at the tip sections became evident for a power coefficient of 0.91 when the advance-diameter ratio was reduced to 1.87. At a free-stream Mach number of 0.50, the highest propeller efficiencies were obtained for power coefficients from 0.80 to 1.00 at advance-diameter ratios above 2.90. At advance-diameter ratios below 2.90, the highest efficiencies were obtained for power coefficients of 0.60 and 0.70. The envelope of the efficiency curves decreased about 12 percent between advance-diameter ratios of 2.60 and 4.20. Local compressibility effects became evident for a power coefficient of 0.40 when the advance-diameter ratio was decreased to 1.75.

Wallner, Lewis E.↗
NASA NTRS1986

Failure analysis of a large wind tunnel compressor blade

A failure analysis was performed to establish the cause of a 2014-T6 aluminum compressor rotor blade failure in a large NASA-Ames wind tunnel. Metallurgical failure analysis by light photography, fractographic SEM examinations, and fatigue experiments showed that a 0.13-mm-deep scratch in the shank of the blade had acted as an initiation site for a fatigue crack, which subsequently grew by Stage II fatigue before occurrence of the final fracture by unstable crack growth. Studies of modal deformation plots and blade FEM analysis indicated that Mode-3 was the most likely mode responsible for the resonance condition which produced the vibration loading that effected crack growth. Tunnel measurements data showed that the crack growth was controlled by both the tunnel resonance and the dampening from the crack itself.

Hampton, Roy W.↗
NASA NTRS1988

Viscous effects on the resonance of a slotted wind tunnel using finite elements

Prompted by the fact that wind tunnel flutter and oscillatory airload measurements are affected by acoustic vibration mode coupling when the model frequency lies near a wind tunnel resonance frequency, a numerical method has been developed for design sensitivity analysis. Solid curves represent the resonant frequency for the slot, without considering the slot's viscosity. While the viscosity effect decreases with increasing slot width, the viscosity effect also decreases as the slot width approaches zero.

Lee, IN↗
NASA NTRS1978

Unsteady two dimensional airloads acting on oscillating thin airfoils in subsonic ventilated wind tunnels

The numerical calculation of unsteady two dimensional airloads which act upon thin airfoils in subsonic ventilated wind tunnels was studied. Neglecting certain quadrature errors, Bland's collocation method is rigorously proved to converge to the mathematically exact solution of Bland's integral equation, and a three way equivalence was established between collocation, Galerkin's method and least squares whenever the collocation points are chosen to be the nodes of the quadrature rule used for Galerkin's method. A computer program displayed convergence with respect to the number of pressure basis functions employed, and agreement with known special cases was demonstrated. Results are obtained for the combined effects of wind tunnel wall ventilation and wind tunnel depth to airfoil chord ratio, and for acoustic resonance between the airfoil and wind tunnel walls. A boundary condition is proposed for permeable walls through which mass flow rate is proportional to pressure jump.

Fromme, J.↗
NASA NTRS2015

Reducing the Effect of Transducer Mount Induced Noise on Aeroacoustic Wind Tunnel Testing Data with a New Transducer Mount Design

Flight vehicle aeroacoustic environments induced during transonic and supersonic flight are usually predicted by subscale wind tunnel testing utilizing high frequency miniature pressure transducers. In order to minimize noise induced by the measurement itself, transducer flush mounting with the model surface is very important. The National Aeronautics and Space Administration (NASA) has accomplished flushness in recent testing campaigns via use of a transducer holder that can be machined and sanded. A single hole in the holder allows the flow medium to interact with the transducer diaphragm. Noise is induced by the resulting cavity however, and is a challenge to remove in post-processing. A new holder design has been developed that minimizes the effects of this transducer mount induced noise (XMIN) by reducing the resonance amplitude or increasing its resonance frequency beyond the range of interest. This paper describes a test conducted at the NASA/George C. Marshall Space Flight Center Trisonic Wind Tunnel intended to verify the effectiveness of this design. The results from this test show that this new transducer holder design does significantly reduce the influence of XMIN on measured fluctuating pressure levels without degrading a transducer's ability to accurately measure the noise external to the model.

Herron, Andrew J.↗
DOE OSTI2021

Effective Dielectric Passivation Scheme in Area-Selective Front/Back Poly-Si/SiOx Passivating Contact Solar Cells

Despite the high efficiencies reached by heavily doped poly-Si/SiO x passivating contact solar cells, challenges like the high front parasitic absorption still limit their performance. Previously, we showed a wet etching technique using self-aligned metal grids to remove the front poly-Si in the non-metallized region. Here, we focus on the effective dielectric passivation on this tunneling oxide/n + in-diffused region. The effect of poly-Si thickness was studied to balance between the passivation quality and the current gain. We then compared various dielectric passivation schemes using SiN x , Al 2 O 3 , and stacks thereof via injection-level dependent lifetime and the transfer length method. We demonstrate a SiN x /Al 2 O 3 stack yielded the best passivation performance within device process limitation and obtained an improved front/back poly-Si/SiO x passivating contact device, with a short circuit current density of 41.8 mA/cm 2 and an efficiency of 21.8%.

anisotropic wet etching↗
NASA NTRS1995

The NASA Langley 16-Foot Transonic Tunnel: Historical Overview, Facility Description, Calibration, Flow Characteristics, and Test Capabilities

The Langley 16-Foot Transonic Tunnel is a closed-circuit single-return atmospheric wind tunnel that has a slotted octagonal test section with continuous air exchange. The wind tunnel speed can be varied continuously over a Mach number range from 0.1 to 1.3. Test-section plenum suction is used for speeds above a Mach number of 1.05. Over a period of some 40 years, the wind tunnel has undergone many modifications. During the modifications completed in 1990, a new model support system that increased blockage, new fan blades, a catcher screen for the first set of turning vanes, and process controllers for tunnel speed, model attitude, and jet flow for powered models were installed. This report presents a complete description of the Langley 16-Foot Transonic Tunnel and auxiliary equipment, the calibration procedures, and the results of the 1977 and the 1990 wind tunnel calibration with test section air removal. Comparisons with previous calibrations showed that the modifications made to the wind tunnel had little or no effect on the aerodynamic characteristics of the tunnel. Information required for planning experimental investigations and the use of test hardware and model support systems is also provided.

Capone, Francis J.↗
NASA NTRS2009

Navier-Stokes Simulation of a Heavy Lift Slowed-Rotor Compound Helicopter Configuration

Time accurate numerical simulations were performed using the Reynolds-averaged Navier-Stokes (RANS) flow solver OVERFLOW for a heavy lift, slowed-rotor, compound helicopter configuration, tested at the NASA Langley 14- by 22-Foot Subsonic Tunnel. The primary purpose of these simulations is to provide support for the development of a large field of view Particle Imaging Velocimetry (PIV) flow measurement technique supported by the Subsonic Rotary Wing (SRW) project under the NASA Fundamental Aeronautics program. These simulations provide a better understanding of the rotor and body wake flows and helped to define PIV measurement locations as well as requirements for validation of flow solver codes. The large field PIV system can measure the three-dimensional velocity flow field in a 0.914m by 1.83m plane. PIV measurements were performed upstream and downstream of the vertical tail section and are compared to simulation results. The simulations are also used to better understand the tunnel wall and body/rotor support effects by comparing simulations with and without tunnel floor/ceiling walls and supports. Comparisons are also made to the experimental force and moment data for the body and rotor.

Allan, Brian G.↗
NASA NTRS2018

Quantum Machine Learning

Quantum computing promises an unprecedented ability to solve intractable problems by harnessing quantum mechanical effects such as tunneling, superposition, and entanglement. The Quantum Artificial Intelligence Laboratory (QuAIL) at NASA Ames Research Center is the space agency's primary facility for conducting research and development in quantum information sciences. QuAIL conducts fundamental research in quantum physics but also explores how best to exploit and apply this disruptive technology to enable NASA missions in aeronautics, Earth and space sciences, and space exploration. At the same time, machine learning has become a major focus in computer science and captured the imagination of the public as a panacea to myriad big data problems. In this talk, we will discuss how classical machine learning can take advantage of quantum computing to significantly improve its effectiveness. Although we illustrate this concept on a quantum annealer, other quantum platforms could be used as well. If explored fully and implemented efficiently, quantum machine learning could greatly accelerate a wide range of tasks leading to new technologies and discoveries that will significantly change the way we solve real-world problems.

Biswas, Rupak↗
NASA NTRS1995

Computational Modeling of the Ames 11-Ft Transonic Wind Tunnel in Conjunction with IofNEWT

Technical advances in Computational Fluid Dynamics have now made it possible to simulate complex three-dimensional internal flows about models of various size placed in a Transonic Wind Tunnel. TWT wall interference effects have been a source of error in predicting flight data from actual wind tunnel measured data. An advantage of such internal CFD calculations is to directly compare numerical results with the actual tunnel data for code assessment and tunnel flow analysis. A CFD capability has recently been devised for flow analysis of the NASA/Ames 11-Ft TWT facility. The primary objectives of this work are to provide a CFD tool to study the NASA/Ames 11-Ft TWT flow characteristics, to understand the slotted wall interference effects, and to validate CFD codes. A secondary objective is to integrate the internal flowfield calculations with the Pressure Sensitive Paint data, a surface pressure distribution capability in Ames' production wind tunnels. The effort has been part of the Ames IofNEWT, Integration of Numerical and Experimental Wind Tunnels project, which is aimed at providing further analytical tools for industrial application. We used the NASA/Ames OVERFLOW code to solve the thin-layer Navier-Stokes equations. Viscosity effects near the model are captured by Baldwin-Lomax or Baldwin-Barth turbulence models. The solver was modified to model the flow behavior in the vicinity of the tunnel longitudinal slotted walls. A suitable porous type wall boundary condition was coded to account for the cross-flow through the test section. Viscous flow equations were solved in generalized coordinates with a three-factor implicit central difference scheme in conjunction with the Chimera grid procedure. The internal flow field about the model and the tunnel walls were descretized by the Chimera overset grid system. This approach allows the application of efficient grid generation codes about individual components of the configuration; separate minor grids were developed to resolve the model and overset onto a main grid which discretizes the interior of the tunnel test section. Individual grid components axe not required to have mesh boundaries joined in any special way to each other or to the main tunnel grid. Programs have been developed to rotate the model about the tunnel pivot point and rotation axis, similar to that of the tunnel turntable mechanism for adjusting the pitch of the physical model in the test section.

Djomehri, M. Jahed↗
NASA NTRS1946

Altitude-Wind-Tunnel Investigation of Performance of Several Propellers on YP-47M Airplane at High Blade Loadings: Hamilton Standard 6507A-2 Four- and Three-Blade Propellers - 6

An altitude-wind-tunnel investigation has been made to determine the performance of Hamilton Standard 6507A-2 four-blade and three-blade propellers on a YP-47M airplane at high blade loadings and high engine powers. Characteristics of the four-blase propeller were obtained for a range of power coefficients from 0.10 to 1.00 at free-stream Mach numbers of 0.20, 0.30, 0.40. Characteristics of the three-blade propeller were obtained for a range of power coefficients from 0.30 to 1.00 at a free-stream Mach number of 0.40. Results of the force measurements indicate primarily the trend of propeller efficiency for changes in power coefficient or advance-diameter ratio because no corrections for the effects of tunnel-wall constriction on the installation were applied. Slipstream surveys are presented to illustrate blade thrust load distribution for certain operating conditions. Within the range of advance-diameter ratios investigated at each free-stream Mach number, the efficiency of the four-blade propeller decreased as the power coefficient was increased from 0.10 to 1.00. For the three-blade propeller, nearly constant maximum efficiencies were obtained for power coefficients from 0.32 to 0.63 at advance-diameter ratios between 1.90 and 3.00. In general, for conditions below the stall and critical tip Mach number, the maximum thrust load shifted from the inboard sections toward the tip sections as the power coefficient was increased or as the advance-diameter ratio was decreased. For conditions beyond the stall or critical tip Mach number, losses in thrust occurred on the outboard blade sections owing to flow break-down; the thrust load increased slightly on the inboard sections.

Saari, Martin J.↗