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Results for “Roughness Formation”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Cross Flow Effects on Glaze Ice Roughness Formation

The present study examines the impact of large-scale cross flow on the creation of ice roughness elements on the leading edge of a swept wing under glaze icing conditions. A three-dimensional triple-deck structure is developed to describe the local interaction of a 3 D air boundary layer with ice sheets and liquid films. A linear stability analysis is presented here. It is found that, as the sweep angle increases, the local icing instabilities enhance and the most linearly unstable modes are strictly three dimensional.

Tsao, Jen-Ching↗
NASA NTRS1991

The adverse aerodynamic impact of very small leading-edge ice (roughness) buildups on wings and tails

Systematic experimental studies were performed to establish the aerodynamic impact of very small leading-edge simulated ice (roughness) formations on lifting surfaces. The geometries studied include single element configurations (airfoil and 3-D tail) as well as multi-element high-lift airfoil geometries. Emphasis in these studies was placed on obtaining results at high Reynolds numbers to insure the applicability of the findings to full-scale situations. It was found that the well-known Brumby correlation for the adverse lift impact of discrete roughness elements at the leading edge is not appropriate for cases representative of initial ice build up (i.e., distributed roughness). It was also found that allowing initial ice formations of a size required for removal by presently proposed deicing systems could lead to maximum lift losses of approximately 40 percent for single-element airfoils. Losses in angle-of-attack margin to stall are equally substantial - as high as 6 degrees. Percentage losses for multi-element airfoils are not as severe as for single-element configurations, but degradations of the angle-of-attack-to-stall margin are the same for both.

Lynch, Frank T.↗
NASA NTRS1991

Recent star formation in the interacting galaxy system NGC 520

New optical spectroscopy, near-infrared spectroscopy, and mid-infrared imaging of the interacting system NGC 520 are presented. The data show that the heavily obscured primary nucleus has a current star-forming rate about 35 times the typical rate for a late-type galaxy nucleus, which may account for most of the large far-infrared luminosity of NGC 520. The secondary nucleus has little current star formation but has recently undergone a mild starburst. Optical colors and absorption line equivalent widths suggest that the extranuclear regions in both galaxies have experienced enhanced star formation roughly at the same time as the secondary nucleus, though at a lesser intensity. The extent of the extranuclear burst is large; at least half of the projected surface area of the two disks took part to varying degrees in the episode. Determining the exact age and strength of the recent star-formation episode in NGC 520 is uncertain. The best estimate for the initiation time of about few x 10 exp 8 yrs ago is consistent with the system-wide starburst being caused by the galaxy collision.

Stanford, S. A.↗
NASA NTRS2013

Assessment of Ice Shape Roughness Using a Self-Orgainizing Map Approach

Self-organizing maps are neural-network techniques for representing noisy, multidimensional data aligned along a lower-dimensional and nonlinear manifold. For a large set of noisy data, each element of a finite set of codebook vectors is iteratively moved in the direction of the data closest to the winner codebook vector. Through successive iterations, the codebook vectors begin to align with the trends of the higher-dimensional data. Prior investigations of ice shapes have focused on using self-organizing maps to characterize mean ice forms. The Icing Research Branch has recently acquired a high resolution three dimensional scanner system capable of resolving ice shape surface roughness. A method is presented for the evaluation of surface roughness variations using high-resolution surface scans based on a self-organizing map representation of the mean ice shape. The new method is demonstrated for 1) an 18-in. NACA 23012 airfoil 2 AOA just after the initial ice coverage of the leading 5 of the suction surface of the airfoil, 2) a 21-in. NACA 0012 at 0AOA following coverage of the leading 10 of the airfoil surface, and 3) a cold-soaked 21-in.NACA 0012 airfoil without ice. The SOM method resulted in descriptions of the statistical coverage limits and a quantitative representation of early stages of ice roughness formation on the airfoils. Limitations of the SOM method are explored, and the uncertainty limits of the method are investigated using the non-iced NACA 0012 airfoil measurements.

Icing↗
NASA NTRS2020

Magnetospheric Multiscale Observations of Earth’s Oblique Bow Shock Reformation by Foreshock Ultra-Low Frequency Waves

Collisionless shocks can be nonstationary with periodic reformation shown in many simulation results, but direct observations are still tenuous and difficult to conclusively interpret. In this study, using Magnetospheric Multiscale (MMS) observations, we report direct observational evidence of Earth’s oblique bow shock reformation driven by the foreshock ultra-low frequency (ULF)waves. When the four MMS spacecraft were in a string-of-pearls formation roughly along the bow shock normal, they observed that when each period of foreshock ULF waves encountered the bow shock, a new shock ramp formed. Meanwhile, in the magnetosheath, the old bow shock’s remnants were observed periodically convecting downstream. We propose that the reformation mechanism of the oblique bow shock is the variation of the upstream conditions by the periodic ULF waves as they encounter the bow shock. We also examine the nature of reflected ions during the reformation process.

Terry Z Liu↗
NASA NTRS2016

Characterization of Ice Roughness Variations in Scaled Glaze Icing Conditions

Because of the significant influence of surface tension in governing the stability and breakdown of the liquid film in flooded stagnation regions of airfoils exposed to glaze icing conditions, the Weber number is expected to be a significant parameter governing the formation and evolution of ice roughness. To investigate the influence of the Weber number on roughness formation, 53.3-cm (21-in.) and 182.9-cm (72-in.) NACA 0012 airfoils were exposed to flow conditions with essentially the same Weber number and varying stagnation collection efficiency to illuminate similarities of the ice roughness created on the different airfoils. The airfoils were exposed to icing conditions in the Icing Research Tunnel (IRT) at the NASA Glenn Research Center. Following exposure to the icing event, the airfoils were then scanned using a ROMER Absolute Arm scanning system. The resulting point clouds were then analyzed using the self-organizing map approach of McClain and Kreeger (2013) to determine the spatial roughness variations along the surfaces of the iced airfoils. The roughness characteristics on each airfoil were then compared using the relative geometries of the airfoil. The results indicate that features of the ice shape and roughness such as glaze-ice plateau limits and maximum airfoil roughness were captured well by Weber number and collection efficiency scaling of glaze icing conditions. However, secondary ice roughness features relating the instability and waviness of the liquid film on the glaze-ice plateau surface are scaled based on physics that were not captured by the local collection efficiency variations.

Roughness Formation↗
NASA NTRS1989

Molecular gas, the interstellar medium, and star formation in S0 and Sa galaxies

The results are presented of a survey for CO J = 1 - 0 emission from S0 and S0/a galaxies. The results show that molecular gas is abundant within some early-type disk galaxies, and that the range in the ratio of molecular gas to atomic gas mass is similar to those in other disk galaxies. In the S0 and S0/a galaxies studied, estimated rates of star formation are substantially smaller than, but efficiencies of star formation are roughly the same as, those in Sb or Sc galaxies. Although the rate of cooling of the hot, X-ray emitting gas may be close to the estimated stellar mass return rate in the sample, the star formation rate probably exceeds both by a significant factor.

Thronson, Harley A., Jr.↗
NASA NTRS2005

Experimental Investigation of Ice Accretion Effects on a Swept Wing

An experimental investigation was conducted to study the effects of 2-, 5-, 10-, and 22.5-min ice accretions on the aerodynamic performance of a swept finite wing. The ice shapes tested included castings of ice accretions obtained from icing tests at the NASA Glenn Icing Research Tunnel (IRT) and simulated ice shapes obtained with the LEWICE 2.0 ice accretion code. The conditions used for the icing tests were selected to provide five glaze ice shapes with complete and incomplete scallop features and a small rime ice shape. The LEWICE ice shapes were defined for the same conditions as those used in the icing tests. All aerodynamic performance tests were conducted in the 7- x 10-ft Low-Speed Wind Tunnel Facility at Wichita State University. Six component force and moment measurements, aileron hinge moments, and surface pressures were obtained for a Reynolds number of 1.8 million based on mean aerodynamic chord and aileron deflections in the range of -15o to 20o. Tests were performed with the clean wing, six IRT ice shape castings, seven smooth LEWICE ice shapes, and seven rough LEWICE ice shapes. Roughness for the LEWICE ice shapes was simulated with 36-size grit. The experiments conducted showed that the glaze ice castings reduced the maximum lift coefficient of the clean wing by 11.5% to 93.6%, while the 5-min rime ice casting increased maximum lift by 3.4%. Minimum iced wing drag was 133% to 3533% greater with respect to the clean case. The drag of the iced wing near the clean wing stall angle of attack was 17% to 104% higher than that of the clean case. In general, the aileron remained effective in changing the lift of the clean and iced wings for all angles of attack and aileron deflections tested. Aileron hinge moments for the iced wing cases remained within the maximum and minimum limits defined by the clean wing hinge moments. Tests conducted with the LEWICE ice shapes showed that in general the trends in aerodynamic performance degradation of the wing with the simulated ice shapes were similar to those obtained with the IRT ice shape castings. However, in most cases, the ice castings resulted in greater aerodynamic performance losses than those obtained with the LEWICE ice shapes. For the majority of the LEWICE ice shapes, the addition of 36-size grit roughness to the smooth ice shapes increased aerodynamic performance losses.

Ice shape↗
NASA NTRS2011

Crack Growth Behavior in the Threshold Region for High Cyclic Loading

The present studies show that fanning in the threshold regime is likely caused by other factors than a plastic wake developed during load shedding. The cause of fanning at low R-values is a result of localized roughness, mainly formation of a faceted crack surface morphology , plus crack bifurcations which alters the crack closure at low R-values. The crack growth behavior in the threshold regime involves both crack closure theory and the dislocation theory of metals. Research will continue in studying numerous other metal alloys and performing more extensive analysis, such as the variation in dislocation properties (e.g., stacking fault energy) and its effects in different materials.

Forman, R.↗
NASA NTRS2016

Convection from Hemispherical and Conical Model Ice Roughness Elements in Stagnation Region Flows

To improve ice accretion prediction codes, more data regarding ice roughness and its effects on convective heat transfer are required. The Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research was used to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. In the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with multiple surfaces or sets of roughness panels, each with a different representation of ice roughness. The sets of roughness panels were constructed using two element distribution patterns that were created based on a laser scan of an iced airfoil acquired in the Icing Research Tunnel at NASA Glenn. For both roughness patterns, surfaces were constructed using plastic hemispherical elements, plastic conical elements, and aluminum conical elements. Infrared surface thermometry data from tests run in the VIST were used to calculate area averaged heat transfer coefficient values. The values from the roughness surfaces were compared to the smooth control surface, showing convective enhancement as high as 400% in some cases. The data gathered during this study will ultimately be used to improve the physical modeling in LEWICE or other ice accretion codes and produce predictions of in-flight ice accretion on aircraft surfaces with greater confidence.

Icing Physics↗
NASA NTRS1984

A possibility of avoiding surface roughness due to insects

Discussion of a method for eliminating turbulence caused by the formation of insect roughness upon the leading edges and fuselage, particularly in aircraft using BLC. The proposed technique foresees the use of elastic surfaces on which insect roughness cannot form. The operational characteristics of highly elastic rubber surface fastened to the wing leading edges and fuselage edges are examined. Some preliminary test results are presented. The technique is seen to be advantageous primarily for short-haul operations.

Wortmann, F. X.↗
NASA NTRS2017

Ice Roughness and Thickness Evolution on a Swept NACA 0012 Airfoil

Several recent studies have been performed in the Icing Research Tunnel (IRT) at NASA Glenn Research Center focusing on the evolution, spatial variations, and proper scaling of ice roughness on airfoils without sweep exposed to icing conditions employed in classical roughness studies. For this study, experiments were performed in the IRT to investigate the ice roughness and thickness evolution on a 91.44-cm (36-in.) chord NACA 0012 airfoil, swept at 30-deg with 0deg angle of attack, and exposed to both Appendix C and Appendix O (SLD) icing conditions. The ice accretion event times used in the study were less than the time required to form substantially three-dimensional structures, such as scallops, on the airfoil surface. Following each ice accretion event, the iced airfoils were scanned using a ROMER Absolute Arm laser-scanning system. The resulting point clouds were then analyzed using the self-organizing map approach of McClain and Kreeger to determine the spatial roughness variations along the surfaces of the iced airfoils. The resulting measurements demonstrate linearly increasing roughness and thickness parameters with ice accretion time. Further, when compared to dimensionless or scaled results from unswept airfoil investigations, the results of this investigation indicate that the mechanisms for early stage roughness and thickness formation on swept wings are similar to those for unswept wings.

glaze icing↗
NASA NTRS1976

On vegetation mapping in Alaska using LANDSAT imagery with primary concerns for method and purpose in satellite image-based vegetation and land-use mapping and the visual interpretation of imagery in photographic format

The author has identified the following significant results. A simulated color infrared LANDSAT image covering the western Seward Peninsula was used for identifying and mapping vegetation by direct visual examination. The 1:1,083,400 scale print used was prepared by a color additive process using positive transparencies from MSS bands 4, 5, and 7. Seven color classes were recognized. A vegetation map of 3200 sq km area just west of Fairbanks, Alaska was made. Five colors were recognized on the image and identified to vegetation types roughly equivalent to formations in the UNESCO classification: orange - broadleaf deciduous forest; gray - needleleaf evergreen forest; light violet - subarctic alpine tundra vegetation; violet - broadleaf deciduous shrub thicket; and dull violet - bog vegetation.

Anderson, J. H.↗
NASA NTRS1992

Near-infrared observations of young stellar objects in the Rho Ophiuchi dark cloud

We have conducted an imaging survey of 1.4 sq pc of the Rho Ophiuchi dark cloud in the J, H, and K near-infrared photometric bands. Approximately 337 of our 481 detected sources are associated with the cloud, and we estimate that 48 percent of these have near-infrared excesses, indicative of disks or circumstellar material surrounding these young stellar objects (YSOs). The K-band luminosity function is significantly different in different regions of our survey area, suggesting that YSOs in these regions have different ages or mass functions. We estimate that the entire survey area has a high star-formation efficiency, at roughly 23 percent. Finally, our many newly detected sources provide a relatively large, uniformly sensitive sample of objects for study at longer wavelengths to better determine true source luminosities and evolutionary lifetimes.

Greene, Thomas P.↗
NASA NTRSDate not supplied

Collecting Samples from the Máaz Formation of Jezero Crater with the Mars 2020 Perseverance Rover

Collection of samples that could be returned to Earth from the floor of Jezero,a Noachian crater characterized by a delta–lake system with high potential for habitability, is a major goal of the Mars 2020 mission. The Mars 2020 Perseverancerover iscurrently exploringthe Máaz and Séítahformationsto the southeastof the delta. Here wefocus on thecrater-retainingMáaz formation, a widespread, rough and fractured terrain with lobatemarginsmapped in orbital images, e.g.[1]. Outcrop morphology and texture, as well as the appearance, composition and mineralogy of abraded rock surfaces observed by Perseverance suggest that theMáazformation consists of asequence of maficigneous units, likely lavas flows. These rocks have experienced variable interaction with aqueous fluids. Type localities of the lower Roubion and the more resistant Rochette members of the Máazformation have been targeted and their abraded surfaces characterized prior to sample collection. In thispresentation we will summarize these sampling activities and potential future sampling of theheavily crateredupperCh’ałmember that is indicative of the Máazformationfrom orbit.

Justin Ibrahim Simon↗
NASA NTRS1987

Plume formation in the D-double prime-layer and the roughness of the core-mantle boundary

A series of very-high-resolution finite element calculations of plume formation in the D-double prime-layer has been performed for several plausible rheologies and boundary conditions in order to study both the early and later stages of boundary layer development. The results show that plumes are initiated by coalescence of small-scale convective instabilities within the low-viscosity region immediately above the core-mantle boundary (CMB). These instabilities support topographic roughness on the CMB having horizontal scales of 20-50 km and provide a source for scattered P-waves seen as precursors to the phases PKIKP and PKKP. The calculated structure of fully developed plumes emerging from the D-double prime-layer consists of 5-50 cm/yr flow confined to 50-100 km thick vertical conduits. With strongly temperature-dependent viscosity, plumes exhibit time-dependent behavior, including upward propagating solitary conduit waves, which may contribute to episodicity in hotspot volcanism.

Olson, Peter↗