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NASA NTRSDate not supplied

Mixed-element USM3D Contributions to the 4th AIAA High-Lift Prediction Workshop

This paper discusses results of the mixed-element USM3D (USM3D-ME) simulations performed for the 4th AIAA High-Lift Prediction Workshop. The workshop was separated into six Technical Focus Groups to investigate the impact of geometry modeling, grid, and computational methods for predicting high lift flows. This work was performed under the Fixed Grid RANS Technical Focus Group. The primary geometry selected for the workshop was the High-Lift Common Research Model. The performed simulations included a flap deflection study and both a grid refinement study and pitch sweep for the nominal flap deflection configuration. The results show that USM3D-ME RANS solutions, generally, tends to underpredict the lift coefficient and to predict a less negative pitching moment relative to the experimental data. The predicted drag coefficient values agree better with experiment for smaller angles of attack but were observed to be larger than experiment for the largest angle of attack simulated. The results of the grid refinement study demonstrated a lack of grid convergence for the provided grid family. The results of the grid refinement study are consistent with the submissions to the Fixed Grid and Mesh Adaptation Technical Focus Groups. Grid convergence for the provided grid family remains elusive for the international community. A 2D Multielement Airfoil configuration was included to enable a turbulence model verification study, which illustrated favorable agreement between USM3D-ME and the solutions provided by other flow solvers.

CFD↗
NASA NTRSDate not supplied

Mixed-Element USM3D Contributions to the 4th AIAA High-Lift Prediction Workshop

This paper discusses results of the mixed-element USM3D (USM3D-ME) simulations performed for the 4th AIAA High-Lift Prediction Workshop. The workshop was separated into six Technical Focus Groups to investigate the impact of geometry modeling, grid, and computational methods for predicting high lift flows. This work was performed under the Fixed Grid RANS Technical Focus Group. The primary geometry selected for the workshop was the High-Lift Common Research Model. The performed simulations included a flap deflection study and both a grid refinement study and pitch sweep for the nominal flap deflection configuration. The results show that USM3D-ME RANS solutions, generally, tends to underpredict the lift coefficient and to predict a less negative pitching moment relative to the experimental data. The predicted drag coefficient values agree better with experiment for smaller angles of attack but were observed to be larger than experiment for the largest angle of attack simulated. The results of the grid refinement study demonstrated a lack of grid convergence for the provided grid family. The results of the grid refinement study are consistent with the submissions to the Fixed Grid and Mesh Adaptation Technical Focus Groups. Grid convergence for the provided grid family remains elusive for the international community. A 2D Multielement Airfoil configuration was included to enable a turbulence model verification study, which illustrated favorable agreement between USM3D-ME and the solutions provided by other flow solvers.

CFD↗
NASA NTRS1990

Observed mid-to-high latitude interchange of atmospheric angular momentum and some implications

Graphic illustration of midlatitude interchange of atmospheric angular momentum between distant regions is presented. An examination is conducted of the global distribution of atmospheric angular momentum during 1977-1978 and 1982-1983 in order to identify evidence of prominent short-term interchanges of relavitive atmospheric angular momentum between mid and high latitude zones in both hemispheres. Thirty-day detrended angular momentum time series, prepared from the NMC global zonal wind data, are examined in latitude bands. The results confirm that momentum can be selectively redistributed between tropical, temperate, and high latitudes in patterns indicative of the development and dissipation of interacting regions, described variously in studies on the index cycle, seesaws, and telecommunications.

Taylor, H. A., Jr.↗
NASA NTRS1969

A sterilizable high-impact antenna

Rectangular cup antenna withstands indirect impacts up to 10,000g and direct impacts up to 250 ft/sec of impact velocity and provides radiation of selected polarization and beam shape. It has high radiating efficiency, and relatively broad bandwidth.

Woo, K. E.↗
NASA NTRS2007

Criterion for Identifying Vortices in High-Pressure Flows

A study of four previously published computational criteria for identifying vortices in high-pressure flows has led to the selection of one of them as the best. This development can be expected to contribute to understanding of high-pressure flows, which occur in diverse settings, including diesel, gas turbine, and rocket engines and the atmospheres of Jupiter and other large gaseous planets. Information on the atmospheres of gaseous planets consists mainly of visual and thermal images of the flows over the planets. Also, validation of recently proposed computational models of high-pressure flows entails comparison with measurements, which are mainly of visual nature. Heretofore, the interpretation of images of high-pressure flows to identify vortices has been based on experience with low-pressure flows. However, high-pressure flows have features distinct from those of low-pressure flows, particularly in regions of high pressure gradient magnitude caused by dynamic turbulent effects and by thermodynamic mixing of chemical species. Therefore, interpretations based on low-pressure behavior may lead to misidentification of vortices and other flow structures in high-pressure flows. The study reported here was performed in recognition of the need for one or more quantitative criteria for identifying coherent flow structures - especially vortices - from previously generated flow-field data, to complement or supersede the determination of flow structures by visual inspection of instantaneous fields or flow animations. The focus in the study was on correlating visible images of flow features with various quantities computed from flow-field data.

Bellan, Josette↗
NASA NTRS1999

Long-Wavelength Rupturing Instability in Surface-Tension-Driven Benard Convection

A liquid layer with a free upper surface and heated from below is subject to thermocapillary-induced convective instabilities. We use very thin liquid layers (0.01 cm) to significantly reduce buoyancy effects and simulate Marangoni convection in microgravity. We observe thermocapillary-driven convection in two qualitatively different modes, short-wavelength Benard hexagonal convection cells and a long-wavelength interfacial rupturing mode. We focus on the long-wavelength mode and present experimental observations and theoretical analyses of the long-wavelength instability. Depending on the depths and thermal conductivities of the liquid and the gas above it, the interface can rupture downwards and form a dry spot or rupture upwards and form a high spot. Linear stability theory gives good agreement to the experimental measurements of onset as long as sidewall effects are taken into account. Nonlinear theory correctly predicts the subcritical nature of the bifurcation and the selection between the dry spot and high spots.

Swift, J. B.↗
NASA NTRS2005

Optimal Sensor Selection for Health Monitoring Systems

Sensor data are the basis for performance and health assessment of most complex systems. Careful selection and implementation of sensors is critical to enable high fidelity system health assessment. A model-based procedure that systematically selects an optimal sensor suite for overall health assessment of a designated host system is described. This procedure, termed the Systematic Sensor Selection Strategy (S4), was developed at NASA John H. Glenn Research Center in order to enhance design phase planning and preparations for in-space propulsion health management systems (HMS). Information and capabilities required to utilize the S4 approach in support of design phase development of robust health diagnostics are outlined. A merit metric that quantifies diagnostic performance and overall risk reduction potential of individual sensor suites is introduced. The conceptual foundation for this merit metric is presented and the algorithmic organization of the S4 optimization process is described. Representative results from S4 analyses of a boost stage rocket engine previously under development as part of NASA's Next Generation Launch Technology (NGLT) program are presented.

Santi, L. Michael↗
NASA NTRS1993

Mixing model analysis of telescopic lunar spectra

We have analyzed very high quality reflectance spectra of the lunar surface from the University of Hawaii lunar spectral data collection using a spectral mixing model. The spectra analyzed are those of 45 mare sites and 75 highland sites. The spectra were selected on the basis of very high signal to noise ratios based on error bars and point to point scatter, and on quality of removal of telluric water bands. The spectral mixing model used 7 components, not all of which were used in each fit. Four of the components were mineral spectra of the orthopyroxene, a clinopyroxene, an olivine and an anorthite, measured at the Brown University's RELAB. All of the minerals were 45-90 micron splits. Lunar soil contains other components which have the effect of reddening and darkening the soil as well as reducing spectral contrast. In addition, lunar soil contains spectral neutral bright material (likely very fine grained feldspar) which serves to reduce spectral contrast and brighten soils. Early attempts to fit many of the spectra pointed out the need for a component which has a very broad smooth absorption feature centered near 1.1 microns. Glass is a good candidate for this component. For the bright component we used a flat reflectance of 70 percent to represent fine grained feldspar. For the 'glass' component we used a telescopic spectrum of a pyroclastic glass present on the Aristarchus plateau which is characterized by a strong smooth band centered at 1.07 microns. In addition to exhibiting the glass band this spectrum is very red and has a low albedo. On the assumption that the dark component and the red component are agglutinates, which is reasonable but not necessarily true, we sought a dark red component. To derive its properties we modelled the spectrum of an Apollo 16 soil (16xxx) and assumed the dark red component to comprise 60 percent of the soil, appropriate to agglutinate abundance in mature soil. We adjusted the albedo and slope of a straight line representing the dark red component until the contrast and albedo of the model spectrum matched the soil spectrum. The mixing was done after conversion to a single scattering albedo.

Lucey, Paul G.↗
NASA NTRS2008

Providing Goal-Based Autonomy for Commanding a Spacecraft

A computer program for use aboard a scientific-exploration spacecraft autonomously selects among goals specified in high-level requests and generates corresponding sequences of low-level commands, understandable by spacecraft systems. (As used here, 'goals' signifies specific scientific observations.) From a dynamic, onboard set of goals that could oversubscribe spacecraft resources, the program selects a non-oversubscribing subset that maximizes a quality metric. In an early version of the program, the requested goals are assumed to have fixed starting times and durations. Goals can conflict by exceeding a limit on either the number of separate goals or the number of overlapping goals making demands on the same resource. The quality metric used in this version is chosen to ensure that a goal will never be replaced by another having lower priority. At any time, goals can be added or removed, or their priorities can be changed, and the 'best' goal will be selected. Once a goal has been selected, the program implements a robust, flexible approach to generation of low-level commands: Rather than generate rigid sequences with fixed starting times, the program specifies flexible sequences that can be altered to accommodate run time variations.

Rabideau, Gregg↗
NASA NTRS1985

Viking Lander Mosaics of Mars

The Viking Lander 1 and 2 cameras acquired many high-resolution pictures of the Chryse Planitia and Utopia Planitia landing sites. Based on computer-processed data of a selected number of these pictures, eight high-resolution mosaics were published by the U.S. Geological Survey as part of the Atlas of Mars, Miscellaneous Investigation Series. The mosaics are composites of the best picture elements (pixels) of all the Lander pictures used. Each complete mosaic extends 342.5 deg in azimuth, from approximately 5 deg above the horizon to 60 deg below, and incorporates approximately 15 million pixels. Each mosaic is shown in a set of five sheets. One sheet contains the full panorama from one camera taken in either morning or evening. The other four sheets show sectors of the panorama at an enlarged scale; when joined together they make a panorama approximately 2' X 9'.

Morris, E. C.↗
NASA NTRS1987

Effect of long-term thermal aging on coated Celion/LARC-160 composites

Coated and uncoated unidirectional laminates of Celion (Trademark)/LARC-160 graphite/polyimide were thermally aged in air at temperatures of 204, 260, and 316 C for various times up to 15,000 hours. Selected panels were coated with a high temperature coating resin (polyphenyl quinoxaline--PPQ): 1) edges only; 2) top and bottom only; 3)completely; or 4) not at all. Periodically during aging, panels were removed from the ovens, weighed, and short beam shear (SBS) specimens cut from selected locations in the panels. The protective coating did not influence the retention of SBS strength during thermal aging but did not lessen the amount of weight-loss incurred. The integrity of the PPQ coating was completely destroyed during aging at 316 C.

Nelson, James B.↗
NASA NTRS1988

Tip aerodynamics and acoustics test: A report and data survey

In a continuing effort to understand helicopter rotor tip aerodynamics and acoustics, a flight test was conducted by NASA Ames Research Center. The test was performed using the NASA White Cobra and a set of highly instrumented blades. All aspects of the flight test instrumentation and test procedures are explained. Additionally, complete data sets for selected test points are presented and analyzed. Because of the high volume of data acquired, only selected data points are presented. However, access to the entire data set is available to the researcher on request.

Cross, Jeffrey L.↗
NASA NTRS1985

Aerodynamic design considerations for efficient high-lift supersonic wings

A previously developed technique for selecting a design space for efficient supersonic wings is reviewed; this design-space concept is expanded to include thickness and camber effects and is evaluated for cambered wings at high-lift conditions. The original design-space formulation was based on experimental upper-surface and lower-surface normal-force characteristics for flat, uncambered delta wings; it is shown that these general characteristics hold for various thickness distributions and for various amounts of leading-edge camber. The original design-space formulation was also based on the assumption that the combination of Mach number and leading-edge sweep which would produce an equal division of flat-wing lift between the upper and lower surface would also be the proper combination to give the best cambered-wing performance. Using drag-due-to-lift factor as a measure of performance, for high-lift conditions cambered-wing performance is shown to significantly increase as conditions approach the design space; this correlation is demonstrated for both subcritical and supercritical flows.

Miller, D. S.↗
NASA NTRS1973

A high-speed photographic system for flow visualization in a steam turbine

A photographic system was designed to visualize the moisture flow in a steam turbine. Good performance of the system was verified using dry turbine mockups in which an aerosol spray simulated, in a rough way, the moisture flow in the turbine. Borescopes and fiber-optic light tubes were selected as the general instrumentation approach. High speed motion-picture photographs of the liquid flow over the stator blade surfaces were taken using stroboscopic lighting. Good visualization of the liquid flow was obtained. Still photographs of drops in flight were made using short duration flash sources. Drops with diameters as small as 30 micrometers (0.0012 in.) could be resolved. In addition, motion pictures of a spray of water simulating the spray off the rotor blades and shrouds were taken at normal framing rates. Specially constructed light tubes containing small tungsten-halogen lamps were used. Sixteen millimeter photography was used in all cases. Two potential problems resulting from the two-phase turbine flow (attenuation and scattering of light by the fog present and liquid accumulation on the borescope mirrors) were taken into account in the photographic system design but not evaluated experimentally.

Barna, G. J.↗
NASA NTRS2001

High Speed PC Based Data Acquisition and Instrumentation for Measurement of Simulated Low Earth Orbit Thermally Induced Disturbances

The Hubble Space Telescope (HST) Disturbance Verification Test (DVT) was conducted to characterize responses of the Observatory's new set of rigid solar array's (SA3) to thermally induced 'creak' or stiction releases. The data acquired in the DVT were used in verification of the HST Pointing Control System on-orbit performance, post-Servicing Mission 3B (SM3B). The test simulated the on-orbit environment on a deployed SA3 flight wing. Instrumentation for this test required pretest simulations in order to select the correct sensitivities. Vacuum compatible, highly accurate accelerometers and force gages were used for this test. The complexity of the test, as well as a short planning schedule, required a data acquisition system that was easy to configure, highly flexible, and extremely robust. A PC Windows oriented data acquisition system meets these requirements, allowing the test engineers to minimize the time required to plan and perform complex environmental test. The SA3 DVT provided a direct practical and complex demonstration of the versatility that PC based data acquisition systems provide. Two PC based data acquisition systems were assembled to acquire, process, distribute, and provide real time processing for several types of transducers used in the SA3 DVT. A high sample rate digital tape recorder was used to archive the sensor signals. The two systems provided multi-channel hardware and software architecture and were selected based on the test requirements. How these systems acquire and processes multiple data rates from different transducer types is discussed, along with the system hardware and software architecture.

Sills, Joel W., Jr.↗
NASA NTRS2016

Active Flow Control Using Sweeping Jet Actuators on a Semi-Span Wing Model

Wind tunnel experiments were performed using active flow control on an unswept semispan wing model with a 30% chord trailing edge flap to aid in the selection of actuators for a planned high Reynolds number experiment. Two sweeping jet actuator sizes were investigated to determine the influence of actuator size on the active flow control system efficiency. Sweeping jet actuators with orifice sizes of 1 mm x 2 mm and 2 mm x 4 mm were selected because of the differences in actuator jet sweep angle. The parameters that were varied include actuator momentum, freestream velocity, and trailing edge flap deflection angle. Steady and unsteady pressure data, Particle Image Velocimetry data, and force and moment data were acquired to assess the performance of the two actuators. In addition to the wind tunnel experiments, benchtop studies of the actuators were performed to characterize the jets produced by each actuator. Benchtop investigations of the smaller actuator reveal that the jet exiting the actuator has a reduced sweep angle compared to published data for larger versions of this type of actuator. The larger actuator produces an oscillating jet that attaches to the external di↵user walls at low supply pressures and produces the expected sweep angles. The AFC results using the smaller actuators show that while the actuators can control flow separation, the selected spacing of 3.3 cm may be too large due to the reduced sweep angle. In comparison, the spacing for the larger actuators, 6.6 cm, appears to be optimal for the Mach numbers investigated. Particle Image Velocimetry results are presented and show how the wall jets produced by the actuators cause the flow to attach to the flap surface.

Melton, LaTunia Pack↗
NASA NTRS2013

Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10(exp 8) < M/Stellar Mass < or approx. 10(exp 10), obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 < or approx. z < or approx. 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R23 metallicity diagnostic: ([O II] (lambda)(lambda)3726, 3729 + [OIII] (lambda)(lambda)4959, 5007)/H(beta). Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10(exp 9.8) Stellar Mass to 12+log(O/H)= 8.2 at M = 10(exp 8.2) Stellar Mass. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M > or approx. 10(exp 9.5) Stellar Mass and z approx. 2.3. Within the statistical uncertainties, our MZ relation agrees with the z approx. 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M∗ relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.

Hgih Redshifts↗
NASA NTRS1994

Time scales of pattern evolution from cross-spectrum analysis of advanced very high resolution radiometer and coastal zone color scanner imagery

We have selected square subareas (110 km on a side) from coastal zone color scanner (CZCS) and advanced very high resolution radiometer (AVHRR) images for 1981 in the California Current region off northern California for which we could identify sequences of cloud-free data over periods of days to weeks. We applied a two-dimensional fast Fourier transformation to images after median filtering, (x, y) plane removal, and cosine tapering. We formed autospectra and coherence spectra as functions of a scalar wavenumber. Coherence estimates between pairs of images were plotted against time separation between images for several wide wavenumber bands to provide a temporal lagged coherence function. The temporal rate of loss of correlation (decorrelation time scale) in surface patterns provides a measure of the rate of pattern change or evolution as a function of spatial dimension. We found that patterns evolved (or lost correlation) approximately twice as rapidly in upwelling jets as in the 'quieter' regions between jets. The rapid evolution of pigment patterns (lifetime of about 1 week or less for scales of 50-100 km) ought to hinder biomass transfer to zooplankton predators compared with phytoplankton patches that persist for longer times. We found no significant differences between the statistics of CZCS and AVHRR images (spectral shape or rate of decorrelation). In addition, in two of the three areas studied, the peak correlation between AVHRR and CZCS images from the same area occurred at zero lag, indicating that the patterns evolved simutaneously. In the third area, maximum coherence between thermal and pigment patterns occurred when pigment images lagged thermal images by 1-2 days, mirroring the expected lag of high pigment behind low temperatures (and high nutrients) in recently upwelled water. We conclude that in dynamic areas such as coastal upwelling systems, the phytoplankton cells (identified by pigment color patterns) behave largely as passive scalars at the mesoscale and that growth, death, and sinking of phytoplankton collectively play at most a mariginal role in determining the spectral statistics of the pigment patterns.

Denman, Kenneth L.↗