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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Wetting of a partially immersed compliant rod

The force on a solid rod partially immersed in a liquid is commonly used to determine the liquid-vapor surface tension by equating the measured force required to remove the rod from the liquid to the vertical component of the liquid-vapor surface tension. Here, we study how this process is affected when the rod is compliant. For equilibrium, we enforce force and configurational energy balance, including contributions from elastic energy. We show that, in general, the contact angle does not equal that given by Young's equation. If surface stresses are tensile, the strain in the immersed part of the rod is found to be compressive and to depend only on the solid-liquid surface stress. The strain in the dry part of the rod can be either tensile or compressive, depending on a combination of parameters that we identify. We provide results for compliant plates partially immersed in a liquid under plane strain and plane stress. Our results can also be used to extract solid surface stresses from such experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Double echo symmetry-based REDOR and RESPDOR pulse sequences for proton detected measurements of heteronuclear dipolar coupling constants

1 H{X} symmetry-based rotational echo double resonance pulse sequences (S-REDOR) and symmetry-based rotational echo saturation pulse double resonance (S-RESPDOR) solid-state NMR experiments have found widespread application for 1 H detected measurements of difference NMR spectra, dipolar coupling constants, and internuclear distances under conditions of fast magic angle spinning (MAS). In these experiments the supercycled $\text{R4}^2_1 (\text{SR4}^2_1)$ symmetry-based recoupling pulse sequence is typically applied to the 1 H spins to reintroduce heteronuclear dipolar couplings. However, the timing of $\text{SR4}^2_1$ and other symmetry-based pulse sequences must be precisely synchronized with the rotation of the sample, otherwise, the evolution of 1 H CSA and other interactions will not be properly refocused. For this reason, significant distortions are often observed in experimental dipolar dephasing difference curves obtained with S-REDOR or S-RESPDOR pulse sequences. Here we introduce a family of double echo (DE) S-REDOR/S-RESPDOR pulse sequences that function in an analogous manner to the recently introduced $t_1$-noise eliminated (TONE) family of dipolar heteronuclear multiple quantum coherence (D-HMQC) pulse sequences. Through numerical simulations and experiments the DE S-REDOR/S-RESPDOR sequences are shown to provide dephasing difference curves similar to those obtained with S-REDOR/S-RESPDOR. However, the DE sequences are more robust to the deviations of the MAS frequency from the ideal value that occurs during typical solid-state NMR experiments. In this work, the DE sequences are shown to provide more reliable 1 H detected dipolar dephasing difference curves for nuclei such as 15 N (with isotopic labelling), 183 W and 35 Cl. The double echo sequences are therefore recommended to be used in place of conventional S-REDOR/S-RESPDOR sequences for measurement of weak dipolar coupling constants and long-range distances.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1982

Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster

A total of 59 tail first drops were made. Model entry conditions simulated full scale vertical velocities of approximately 75 to 110 ft/sec with horizontal velocities up to 45 ft/sec and impact angles to + or - 10 deg. These tests were conducted at scaled atmospheric pressures (1.26 psia or 65 mm.Hg). The model, test program, test facility, test equipment, instrumentation system, data reduction procedures, and test results are described.

Source record↗
DOE OSTI2016

Optical CT imaging of solid radiochromic dosimeters in mismatched refractive index solutions using a scanning laser and large area detector

Purpose: The practical use of the PRESAGE® solid plastic dosimeter is limited by the inconvenience of immersing it in high-viscosity oils to achieve refractive index matching for optical computed tomography (CT) scanning. The oils are slow to mix and difficult to clean from surfaces, and the dosimeter rotation can generate dynamic Schlieren inhomogeneity patterns in the reference liquid, limiting the rotational and overall scan speed. Therefore, it would be beneficial if lower-viscosity, water-based solutions with slightly unmatched refractive index could be used instead. The purpose of this work is to demonstrate the feasibility of allowing mismatched conditions when using a scanning laser system with a large acceptance angle detector. A fiducial-based ray path measurement technique is combined with an iterative CT reconstruction algorithm to reconstruct images. Methods: A water based surrounding liquid with a low viscosity was selected for imaging PRESAGE® solid dosimeters. Liquid selection was optimized to achieve as high a refractive index as possible while avoiding rotation-induced Schlieren effects. This led to a refractive index mismatch of 6% between liquid and dosimeters. Optical CT scans were performed with a fan-beam scanning-laser optical CT system with a large area detector to capture most of the refracted rays. A fiducial marker placed on the wall of a cylindrical sample occludes a given light ray twice. With knowledge of the rotation angle and the radius of the cylindrical object, the actual internal path of each ray through the dosimeter can be calculated. Scans were performed with 1024 projections of 512 data samples each, and rays were rebinned to form 512 parallel-beam projections. Reconstructions were performed on a 512 × 512 grid using 100 iterations of the SIRT iterative CT algorithm. Proof of concept was demonstrated with a uniformly attenuating solution phantom. PRESAGE® dosimeters (11 cm diameter) were irradiated with Cobalt-60 irradiator to achieve either a uniform dose or a 2-level “step-dose” pattern. Results: With 6% refractive index mismatching, a circular field of view of 85% of the diameter of a cylindrical sample can be reconstructed accurately. Reconstructed images of the test solution phantom were uniform (within 3%) inside this radius. However, the dose responses of the PRESAGE® samples were not spatially uniform, with variations of at least 5% in sensitivity. The variation appears as a “cupping” artifact with less sensitivity in the middle than at the periphery of the PRESAGE® cylinder. Polarization effects were also detected for these samples. Conclusions: The fiducial-based ray path measurement scheme, coupled with an iterative reconstruction algorithm, enabled optical CT scanning of PRESAGE® dosimeters immersed in mismatched refractive index solutions. However, improvements to PRESAGE® dose response uniformity are required.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Strength, deformation, and the fcc–hcp phase transition in condensed Kr and Xe to the 100 GPa pressure range

The rare gas solids exhibit systematic differences in crystal structure, phase transition conditions, bond strength, and other physical properties. The physical properties of heavy rare gas solids krypton and xenon are modified by the martensitic phase transition from face-centered cubic to hexagonal close packed structure over a broad pressure range. Crystal structure, strength, and plastic deformation of krypton and xenon have been investigated at 300 K using compression in the diamond-anvil cell with synchrotron angle-dispersive x-ray diffraction and complementary ruby fluorescence spectroscopy for Xe. Stacking faults indicative of the fcc–hcp phase transition are observed at pressures at and above 1.23 ± 0.05 and 1.9 ± 0.6 GPa in Kr and Xe, respectively. The transition remains incomplete in both solids to pressures greater than 100 GPa. Strength determined from stress measurements in Pt and ruby standards at pressures up to 111 GPa and complemented by observations of strain and texture measurements obtained by x-ray diffraction in the radial geometry to 100 GPa indicates similar or higher strength than Ar at all conditions, with significant stiffening at 15–20 GPa. Radial diffraction data reveal the persistence of broad highly textured fcc diffraction lines to 101 GPa in Xe, suggesting that the axial measurements may underestimate the metastable persistence of the fcc phase due to biased sampling of hcp crystallites resulting from preferred crystallite orientation. Kr and Xe are compared with He, Ne, and Ar for a systematic understanding of physical properties and phase equilibria of rare gas solids.

Compressive stress↗
DOE OSTI2021

Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77 Se and 113 Cd Solid-State NMR Spectroscopy

Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113 Cd and 77 Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113 Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe 3 O, CdSe 2 O 2 , and CdSeO 3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113 Cd– 113 Cd and 77 Se– 77 Se and heteronuclear 113 Cd– 77 Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77 Se{ 113 Cd} scalar heteronuclear multiple quantum coherence ( J -HMQC) experiments were used to selectively measure one-bond 77 Se– 113 Cd scalar coupling constants ( 1 J ( 77 Se, 113 Cd)). With knowledge of 1 J ( 77 Se, 113 Cd), heteronuclear 77 Se{ 113 Cd} spin echo ( J -resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. Furthermore, the J -resolved experiments directly confirmed that major Cd and Se surface species have CdSe 2 O 2 and SeCd 4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Highly collimated monoenergetic target-surface electron acceleration in near-critical-density plasmas

Optimized-quality monoenergetic target surface electron beams at MeV level with low normalized emittance (0.03π mm mrad) and high charge (30 pC) per shot have been obtained from 3 TW laser-solid interactions at a grazing incidence. The 2-Dimension particle-in-cell simulations suggest that electrons are wake-field accelerated in a large-scale, near-critical-density preplasma. It reveals that a bubble-like structure as an accelerating cavity appears in the near-critical-density plasma region and travels along the target surface. A bunch of electrons are pinched transversely and accelerated longitudinally by the wake field in the bubble. The outstanding normalized emittance and monochromaticity of such highly collimated surface electron beams could make it an ideal beam for fast ignition or may serve as an injector in traditional accelerators.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Unraveling Gibbsite Transformation Pathways into LiAl-LDH in Concentrated Lithium Hydroxide

The intercalation of lithium (Li+) ions into metallic hydroxides (e.g. gibbsite, Al(OH)3) facilitates the synthesis of layered double hydroxides. Caustic environments, such as in lithium hydroxide (LiOH) solutions, present additional pathways beyond the intercalation of ions, specifically dissolution/precipitation processes. Herein, the phase transformation Al(OH)3 to lithium aluminum hydroxide dihydrate, Li[Al(OH)3)]2OH•2H2O in partially deuterated LiOH solutions is tracked through multinuclear, magic angle spinning, high-field nuclear magnetic resonance spectroscopy (27Al and 6Li MAS-NMR) , X-ray diffraction, and scanning electron microscopy of harvested solids. At high magnetic fields (19.975 T), 27Al MAS-NMR enabled detection and quantification of the reactive interface between Al(OH)3 and Li[Al(OH)3)]2OH•2H2O. 6Li MAS-NMR spectra collected on the harvested solids exhibited exchange mediated narrowing as the reaction time progressed, consistent with transport of Li+ ions between the interface and the bulk Li[Al(OH)3)]2OH•2H2O. Complimentary in-situ 27Al MAS-NMR at lower magnetic fields (7.046 T) utilized unique rotors capable of simultaneous resolution of solution and solid state Al-species in caustic environments. The reaction between Al(OH)3 (0.5 M) and LiOH (3 M) initially exhibited greater dissolution and formation of Al(OH)4- than the precipitation. Over several hours, the supersaturated Al(OH)4- solution precipitated Li[Al(OH)3)]2OH•2H2O. Simultaneous, in-situ observations of the solid component tracked the formation of Li[Al(OH)3)]2OH•2H2O evident by an increase in signal and narrowing of the Oh resonance. These results provides insight into Al precipitation in alkaline media with applications ranging from the reduction of Al content in Hanford site, high-level radioactive waste (HLRW) to the precipitation of LDH materials for application as catalyst materials, drug delivery devices, and ion-ion exchangers.

Graham, Trenton R.↗
DOE OSTI2024

Opportunities and new developments for the study of surfaces and interfaces in soft condensed matter at the SIRIUS beamline of Synchrotron SOLEIL

The SIRIUS beamline of Synchrotron SOLEIL is dedicated to X-ray scattering and spectroscopy of surfaces and interfaces, covering the tender to mid-hard X-ray range (1.1–13 keV). The beamline has hosted a wide range of experiments in the field of soft interfaces and beyond, providing various grazing-incidence techniques such as diffraction and wide-angle scattering (GIXD/GIWAXS), small-angle scattering (GISAXS) and X-ray fluorescence in total reflection (TXRF). SIRIUS also offers specific sample environments tailored for in situ complementary experiments on solid and liquid surfaces. Recently, the beamline has added compound refractive lenses associated with a transfocator, allowing for the X-ray beam to be focused down to 10 µm × 10 µm while maintaining a reasonable flux on the sample. This new feature opens up new possibilities for faster GIXD measurements at the liquid–air interface and for measurements on samples with narrow geometries.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

SU-E-P-24: Simplified EDW Profile Measurements Using Two Commonly Available Detector Arrays

Purpose: Enhanced dynamic wedge (EDW) profiles are needed as part of the commissioning of a treatment planning system. This work compares the acquisition of EDW profiles using a linear diode array (LDA) with two commonly used detector arrays available in the clinics, with the goal of identifying the simplest approach for these measurements. Methods: The measurements of EDW profiles were performed on a Varian TrueBeam linear accelerator for 6, 10, and 18 MV photon beams for all seven wedge angles at four depths. The measurements were done using the LDA 99 in Blue Phantom2 (IBA Dosimetry), and IC Profiler and MapCHECK2 (Sun Nuclear) in solid water phantoms. The water phantom was set up at 100 cm SSD, whereas the two other devices were set up at 75 cm due to the size limitations of the devices. The largest possible field size was used. The average and maximum percentage differences were examined within the central 90% of the field and in the penumbra. Results: Dose profiles measured with IC Profiler were in a good agreement with LDA 99 data. The average percentage difference within the field did not exceed 0.5% for all energies. MapCHECK2 measurements matched well with LDA 99 for 10 and 18 MV (within 0.3%) with discrepancies of up to 1.4% observed for the 6 MV beam. The maximum percentage differences for both devices in the penumbra exhibited larger variations than LDA 99 results due to differences in detector spacing and high dose gradient, as expected. Conclusion: Common linac QA devices such as IC Profiler or MapCHECK2 provide EDW beam profile data of reasonable accuracy as compared to measurements performed using a linear diode array in a water phantom, saving the expense and time involved in acquiring and setting up a LDA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-145: Beam Characteristics of Flattening Filter Free Beams Including Low Dose Rate Setting

Purpose: In commissioning of volumetric modulated arc therapy (VMAT), it is necessary to evaluate the beam characteristics of various dose rate settings with potential to use. The aim of this study is to evaluate the beam characteristics of flattened and flattening filter free (FFF) including low dose rate setting. Methods: We used a Varian TrueBeam with Millennium 120 MLC. Both 6 and 10 MV beams with or without flattening filter were used for this study. To evaluate low-dose rate FFF beams, specially-designed leaf sequence files control out-of-field MLC leaf pair at constant dose rate ranging from 80 to 400 MU/min. For dose rate from 80 MU/min to the maximum usable value of all energies, beam output were measured using ionization chamber (CC04, IBA). The ionization chamber was inserted into water equivalent phantom (RT3000-New, R-tech), and the phantom was set with SAD of 100cm. The beam profiles were performed using the 2D diode array (Profiler2, Sun Nuclear). The SSD was set to 90cm and a combined 30cmx30cmx9cm phantom which consisted of solid water slabs was put on the device. All measurement were made using 100MU irradiation for 10cmx10cm jaw-defined field size with a gantry angle of 0°. Results: In all energies, the dose rate dependences with beam output and variation coefficient were within 0.2% and 0.07%, respectively. The flatness and symmetry exhibited small variations (flatness ≤0.1 point and symmetry≤0.3 point at absolute difference). Conclusion: We had studied the characteristics of flattened and FFF beam over the 80 MU/min. Our results indicated that the beam output and profiles of FFF of TrueBeam linac were highly stable at low dose rate setting.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1953

Transient temperature distributions in simple conducting bodies steadily heated through a laminar boundary layer

An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero. The appropriate heat-conduction equations are solved by an iteration method, the zeroeth-order terms describing the situation in the limit of small time. The method is presented and the solutions are calculated to three orders which are sufficient to give reasonably accurate results when the forward edge has attained one-half the total temperature rise (nose half-rise time). Flight Mach number and air properties occur as parameters in the result. Approximate expressions for the extent of the conduction region and nose half-rise times as functions of the parameters of the problem are presented. (author)

Parker, Hermon M↗
NASA NTRS1993

Macroscopic electric charge separation during hypervelocity impacts: Potential implications for planetary paleomagnetism

The production of transient magnetic fields by hypervelocity meteoroid impact has been proposed to possibly explain the presence of paleomagnetic fields in certain lunar samples as well as across broader areas of the lunar surface. In an effort to understand the lunar magnetic record, continued experiments at the NASA Ames Vertical Gun Range allow characterizing magnetic fields produced by the 5 km/s impacts of 0.32-0.64 cm projectiles over a broad range of impact angles and projectile/target compositions. From such studies, another phenomenon has emerged, macroscopic electric charge separation, that may have importance for the magnetic state of solid-body surfaces. This phenomenon was observed during explosive cratering experiments, but the magnetic consequences of macroscopic electric charge separation (as opposed to plasma production) during explosion and impact cratering have not, to our knowledge, been explored before now. It is straightforward to show that magnetic field production due to this process may scale as a weakly increasing function of impactor kinetic energy, although more work is needed to precisely assess the scaling dependence. The original intent of our experiments was to assess the character of purely electrostatic signals for comparison with inferred electrostatic noise signals acquired by shielded magnetic sensors buried within particulate dolomite targets. The results demonstrated that electrostatic noise does affect the magnetic sensors but only at relatively short distances (less than 4 cm) from the impact point (our magnetic studies are generally performed at distances greater than approximately 5.5 cm). However, to assess models for magnetic field generation during impact, measurements are needed of the magnetic field as close to the impact point as possible; hence, work with an improved magnetic sensor design is in progress. In this paper, we focus on electric charge separation during hypervelocity impacts as a potential transient magnetic field production mechanism in its own right.

Crawford, D. A.↗
NASA NTRS1993

Solid state laser

A wavelength-tunable, injection-seeded, dispersion-compensated, dispersively-pumped solid state laser includes a lasing medium; a highly reflective mirror; an output coupler; at least one isosceles Brewster prism oriented to the minimum deviation angle between the medium and the mirror for directing light of different wavelengths along different paths; means for varying the angle of the highly reflective mirror relative to the light from at least one Brewster angle for selecting a predetermined laser operating wavelength; a dispersion compensation apparatus associated with the lasing medium; a laser injection seeding port disposed between the dispersion compensation apparatus and one of the mirror and coupler and including a reflective surface at an acute non-Brewster angle to the laser beam for introducing a seed input; a dispersion compensation apparatus associated with the laser medium including opposite chirality optical elements; the lasing medium including a pump surface disposed at an acute angle to the laser beam to define a discrete path for the pumping laser beam separate from the pumped laser beam.

Rines, Glen A.↗
DOE OSTI2020

Negatively Charged Lipids Exhibit Negligible Effects on the Water Repellency of Montmorillonite Films

Amphiphilic molecules can alter the wettability of soil minerals. To determine how the headgroup chemistry of amphiphiles determines these effects, we investigate a system of the clay montmorillonite with long-chain phospholipids. We use phosphatidylglycerol (PG) phospholipids to contrast with our previous work using phosphatidylethanolamine lipids (PE). Zwitterionic PE lipids can sorb to the negatively-charged montmorillonite surface, whereas negatively-charged PG lipids cannot. Employing a suite of techniques from molecular dynamics, atomic force microscopy, fluorescence microscopy, and contact angle measurements, we define sample characteristics from molecular scale structure to the macroscopic wettability. We find that PG lipids do not significantly alter montmorillonite wetting characteristics, such as the contact angle, flow viscosity, and the characteristic timescale for droplet imbibition. In comparing PE and PG lipid/clay films, we find that, among the phospholipids compared, they must have three characteristics in order to change clay/lipid film wettability: they must bind to the mineral surface, be solid at room temperature, and have a relatively continuous distribution throughout the film.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Rapid acquisition of data dense solid-state CPMG NMR spectral sets using multi-dimensional statistical analysis

The development of multi-dimensional statistical methods has been demonstrated on variable contact time (VCT) 29 Si{ 1 H} cross-polarization magic angle spinning (CP/MAS) data sets collected using Carr–Purcell–Meiboom–Gill (CPMG) type acquisition. These methods utilize the transformation of the collected 2D VCT data set into a 3D data set and use tensor-rank decomposition to extract the spectral components that vary as a function of transverse relaxation time ( T 2 ) and CP contact time. The result is a data dense spectral set that can be used to reconstruct CP/MAS spectra at any contact time with a high signal to noise ratio and with an excellent agreement to 29 Si{ 1 H} CP/MAS spectra collected using conventional acquisition. These CPMG data can be collected in a fraction of time that would be required to collect a conventional VCT data set. Here, we demonstrate the method on samples of functionalized mesoporous silica materials and show that the method can provide valuable surface specific information about their functional chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

The interface character distribution of cold-rolled and annealed duplex stainless steel

The interface character distributions (ICDs) of cold-rolled and annealed duplex stainless steel specimens, previously solid-solution-heated (SHT) at 1573 K and 1323 K, are investigated using electron backscatter diffraction (EBSD) and five-parameter analysis (FPA). For the δ-ferrite phase, high concentrations of low angle grain boundaries (LAGBs) are developed, and the boundary planes are predominantly oriented on (111). High angle grain boundaries (HAGBs) with misorientations ranging from 50{sup o} to 60° are mostly pure tilt boundaries, and the boundary planes are primarily located on (112). For the austenite phase, very high density of coherent twin boundaries are introduced, implying that the boundary planes are exactly oriented on (111). The phase boundary character distribution (PBPD) appears to be connected with the K-S and N-W orientation relationships (ORs) terminating on (110) {sub F}‖(111) {sub A} and (110){sub F}‖(hkl){sub A}, respectively. - Highlights: •Five-parameter analysis was used to determine interface character distribution. •ICD results of statistical meaning were achieved. •Initial microstructure has a significant effect on ICD. •Low and high angle GBs in δ phase prefer in (111) and (112) planes, respectively. •K-S phase boundaries terminate on (110){sub F}‖(111){sub A} while N-W ones on (110){sub F}‖(hkl){sub A}.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Unsteady pressures on a NACA 64A010 airfoil - Experimental and theoretical results

Transonic testing of an NACA 64A010 airfoil at the Ohio State University Aero-Astro Research Laboratory is described, and results of fixed angle of attack and pitch oscillation experiments are discussed. The operating range was Mach 0.20 to 1.07 with available total pressures of 140,000 N/m2 to 620,000 N/m2. The airfoil model was mounted on roller bearings installed in the solid sidewalls of the tunnel test section. The equipment included transducers to measure unsteady pressures, and static pressure taps obtaining steady-state data. The data gathered at Mach 0.8 gave an indication of the influence of the natural shock instability and shock-induced flow separation on the unsteady pressures, with the location of the peak disturbance level shifting forward in the comparison of 0 to 2 deg pitch angle data. The oscillating airfoil data is examined in terms of harmonic content and the in-phase and out-of-phase components. It is concluded that the experimental data has good qualitative comparison with methods accounting for shock interaction.

Davis, J. A.↗