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1

SHARP REFRACTORY COMPOSITE LEADING EDGES ON HYPERSONIC VEHICLES  

Microsoft Academic Search

On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the

Sandra P. Walker; Brian J. Sullivan

2003-01-01

2

Sharp Refractory Composite Leading Edges on Hypersonic Vehicles  

NASA Technical Reports Server (NTRS)

On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the technology along with the use of advanced fiber architectures to improve the thermal-structural response is explored in the current work. Thermal and structural finite element analyses are conducted for several advanced fiber architectures of interest. A tailored thermal shock parameter for sharp orthotropic leading edges is identified for evaluating composite material systems. The use of the tailored thermal shock parameter has the potential to eliminate the need for detailed thermal-structural finite element analyses for initial screening of material systems being considered for a leading edge component.

Walker, Sandra P.; Sullivan, Brian J.

2003-01-01

3

A Thermostructural Analysis of a Diboride Composite Leading Edge  

NASA Technical Reports Server (NTRS)

In an effort to support the design of zirconium diboride composite leading edges for hypersonic vehicles, a finite element model (FEM) of a prototype leading edge was created and finite element analysis (FEA) was employed to assess its thermal and structural response to aerothermal boundary conditions. Unidirectional material properties for the structural components of the leading edge, a continuous fiber reinforced diboride composite, were computed with COSTAR. These properties agree well with those experimentally measured. To verify the analytical approach taken with COSMOS/M, an independent FEA of one of the leading edge assembly components was also done with COSTAR. Good agreement was obtained between the two codes. Both showed that a unidirectional lay-up had the best margin of safety for a simple loading case. Both located the maximum stress in the same region and ply. The magnitudes agreed within 4 percent. Trajectory based aerothermal heating was then applied to the leading edge assembly FEM created with COSMOS/M to determine steady state temperature response, displacement, stresses, and contact forces due to thermal expansion and thermal strains. Results show that the leading edge stagnation line temperature reached 4700 F. The maximum computed failure index for the laminated composite components peaks at 4.2, and is located at the bolt flange in layer 2 of the side bracket. The temperature gradient in the tip causes a compressive stress of 279 ksi along its width and substantial tensile stresses within its depth.

Kowalski, Tom; Buesking, Kent; Kolodziej, Paul; Bull, Jeff

1996-01-01

4

Bird strike simulation on a novel composite leading edge design  

Microsoft Academic Search

A methodology for the numerical simulation of bird strike on a novel leading edge (LE) structure of a horizontal tail plane is presented. The innovative LE design is based on the ‘tensor skin’ concept, comprising one or more folded composite sub-laminates that unfold during the bird impact, thus providing high-energy absorption characteristics. The simulation technique is based on a non-linear

Th Kermanidis; G. Labeas; M. Sunaric; A. F. Johnson; M. Holzapfel

2006-01-01

5

Development and Validation of a Novel Bird Strike Resistant Composite Leading Edge Structure  

Microsoft Academic Search

A novel design of a fibre-reinforced composite Leading Edge (LE) of a Horizontal Tail Plain (HTP) is proposed. The development and validation approach of the innovative composite LE structure are described. The main design goal is the satisfactory impact resistance of the novel composite LE in the case of bird strike. The design concept is based on the absorption of

Th. Kermanidis; G. Labeas; M. Sunaric; L. Ubels

2005-01-01

6

Advanced leading edge thermal-structure concept. Direct bond reusable surface insulation to a composite structure  

NASA Technical Reports Server (NTRS)

An advanced leading-edge concept was analyzed using the space shuttle leading edge system as a reference model. The comparison indicates that a direct-bond system utilizing a high temperature (2700 F) fibrous refractory composite insulation tile bonded to a high temperature (PI/graphite) composite structure can result in a weight savings of up to 800 lb. The concern that tile damage or loss during ascent would result in adverse entry aerodynamics if a leading edge tile system were used is addressed. It was found from experiment that missing tiles (as many as 22) on the leading edge would not significantly affect the basic force-and-moment aerodynamic coefficients. Additionally, this concept affords a degree of redundancy to a thermal protection system in that the base structure (being a composite material) ablates and neither melts nor burns through when subjected to entry heating in the event tiles are actually lost or damaged during ascent.

Riccitiello, S. R.; Figueroa, H.; Coe, C. F.; Kuo, C. P.

1984-01-01

7

Ultra-high Temperature Ceramic Composites for Leading Edges, 2004  

NASA Technical Reports Server (NTRS)

Ultrahigh temperature ceramics (UHTC) have performed unreliably due to material flaws and attachment design. These deficiencies are brought to the fore by the low fracture toughness and thermal shock resistance of the UHTC. If these deficiencies are overcome, we are still faced with poor oxidation resistance as a limitation on UHTC applicability to reusable launch vehicles. We have been addressing the deficiencies of UHTC for the past two years via a small task at GRC that is in the Airframe part of the Next Generation Launch Technology Program. Our focus is on composite constructions and functional grading to address the mechanical issues and on composition modification to address the oxidation issue. The progress on approaches to improving oxidation resistance by alloying and functional grading will be reported.

Levine, Stanley R.; Opila, Elizabeth J.; Lorincz, Jonathan A.; Singh, Mrityunjay; Robinson, Raymond C.; Ellerby, Donald T.; Gasch, Matthew J.

2004-01-01

8

Mechanical Properties and Microstructural Characterization of Particulate Reinforced Diboride Composites for High Temperature Leading Edge Applications  

NASA Technical Reports Server (NTRS)

Previous work on refractory diboride composites has shown that these systems have the potential for use in high temperature leading edge applications for reusable reentry vehicles. Experiments in reentry environments have shown that these materials have multiple use temperatures greater than 1900 C. The work to be discussed focuses on three compositions: HfB2/SiC, ZrB2/SiC, and ZrB2/C/SiC. These composites have been hot pressed and their mechanical properties measured at room and elevated temperatures. Extensive microstructural characterization has been conducted on polished cross sections and the fracture surfaces have been examined to determine their failure origins.

Ellerby, Donald T.; Bull, J. D.; Johnson, S. M.; Stackpoole, M. M.; Gusman, M.; Stuffle, K.; Cull, A. D.; Causey, S. J.; Arnold, Jim (Technical Monitor)

2001-01-01

9

Arc Jet Results on Candidate High Temperature Coatings for NASA's NGLT Refractory Composite Leading Edge Task  

NASA Technical Reports Server (NTRS)

In 2000, arc jet testing was conducted on thirteen material systems for possible use on the nose leading edge of the Hyper-X program s X-43A Mach 10 vehicle. Six material systems survived 3, 130- second cycles. To support NASA s Next Generation Launch Technology Programs (NGLT) need for passive refractory composite leading edges with multiple reuse capability at temperatures up to 3600 F, these six materials were subjected to an expanded arc jet test program. This expanded arc jet test program included three phases. The purpose of the first phase was to generate emissivity data as a function of temperature. The purpose of the second phase was to determine if the material systems had any thermal cycling durability, and the third phase was to determine whether the materials could survive an arc jet test of one hour duration. Some of the coating systems were found to have very low emissivities, suggesting that they would not be good candidates for leading edges coating. Other coating systems survived both the second and third phases of the test program and showed potential for use as an oxidation protection coating for leading edges. This presentation summarizes the test program results.

Ohlhorst, C. W.; Vaughn, W. L.; Lewis, R. K.; Milhoan, J. D.

2004-01-01

10

Space environmental effects on LDEF composites: Leading graphite/epoxy panel, selected trailing edge specimens  

NASA Technical Reports Server (NTRS)

The composite electronics-module cover for the leading edge (row D9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a multi-oriented layup. This panel contained thermal control coatings in three of the four quadrants with the fourth quadrant left uncoated as a control. The composite experienced different thermal cycling extremes in each quadrant due to the differing optical properties of the coatings. Results will be presented on microcracking and other Low Earth Orbital (LEO) effects on the coated panel substrate.

Dursch, Harry; George, Pete; Hill, Sylvester

1992-01-01

11

Supersonic Leading Edge Receptivity  

NASA Technical Reports Server (NTRS)

This paper describes experimental studies of leading edge boundary layer receptivity for imposed stream disturbances. Studies were conducted in the supersonic T-325 facility at ITAM and include data for both sharp and blunt leading edges. The data are in agreement with existing theory and should provide guidance for the development of more complete theories and numerical computations of this phenomena.

Maslov, Anatoly A.

1998-01-01

12

Space environmental effects on LDEF composites: A leading edge coated graphite epoxy panel  

NASA Technical Reports Server (NTRS)

The electronics module cover for the leading edge (Row D 9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a (O(sub 2), +/- 45, O(sub 2), +/- 45, 90, 0)(sub s) layup. This 11.75 in x 16.75 in panel was covered with thermal control coatings in three of the four quadrants with the fourth quadrant uncoated. The composite panel experienced different thermal cycling extremes in each quadrant due to the different optical properties of the coatings and bare composite. The panel also experienced ultraviolet (UV) and atomic oxygen (AO) attack as well as micrometeoroid and space debris impacts. An AO reactivity of 0.99 x 10(exp -24) cm(sup 3)/atom was calculated for the bare composite based on thickness loss. The white urethane thermal control coatings (A276 and BMS 1060) prevented AO attack of the composite substrate. However, the black urethane thermal control coating (Z306) was severely eroded by AO, allowing some AO attack of the composite substrate. An interesting banding pattern on the AO eroded bare composite surface was investigated and found to match the dimensions of the graphite fiber tow widths as prepregged. Also, erosion depths were greater in the darker bands. Five micrometeoroid/space debris impacts were cross sectioned to investigate possible structural damage as well as impact/AO interactions. Local crushing and delaminations were found to some extent in all of the impacts. No signs of coating undercutting were observed despite the extensive AO erosion patterns seen in the exposed composite material at the impact sites. An extensive microcrack study was performed on the panel along with modeling of the thermal environment to estimate temperature extremes and thermal shock. The white coated composite substrate displayed almost no microcracking while the black coated and bare composite showed extensive microcracking. Significant AO erosion was seen in many of the cracks in the bare composite.

George, Pete E.; Dursch, Harry W.; Hill, Sylvester G.

1993-01-01

13

Development and Validation of a Novel Bird Strike Resistant Composite Leading Edge Structure  

NASA Astrophysics Data System (ADS)

A novel design of a fibre-reinforced composite Leading Edge (LE) of a Horizontal Tail Plain (HTP) is proposed. The development and validation approach of the innovative composite LE structure are described. The main design goal is the satisfactory impact resistance of the novel composite LE in the case of bird strike. The design concept is based on the absorption of the major portion of the bird kinetic energy by the composite skins, in order to protect the ribs and the inner LE structure from damaging, thus preserving the tail plane functionality for safe landing. To this purpose, the LE skin is fabricated from specially designed composite panels, so called ‘tensor skin’ panels, comprising folded layers, which unfold under the impact load and increase the energy absorption capability of the LE. A numerical model simulating the bird strike process is developed and bird strike experimental testing is performed, in order to validate the proposed layout and prove the capability of the structure to successfully withstand the impact loading. The numerical modelling issues and the critical parameters of the simulation are discussed. The present work is part of the European Aeronautics Research Project, ‘Crashworthiness of aircraft for high velocity impact CRAHVI’ [1].

Kermanidis, Th.; Labeas, G.; Sunaric, M.; Ubels, L.

2005-11-01

14

Leading Edge `Fore Brain  

E-print Network

. (2010) follow the latter approach and identify a brain region of the seg- mented worm Platynereis patterns from multiple worms onto a standard brain template. This allows the simultaneous mappingLeading Edge Previews `Fore Brain: A Hint of the Ancestral Cortex Lora B. Sweeney1,2,3 and Liqun

Luo, Liqun

15

Wing Leading Edge Debris Analysis  

NASA Technical Reports Server (NTRS)

This is a slide presentation showing the Left Wing Leading Edge (WLE) heat damage observations: Heavy "slag" deposits on select RCC panels. Eroded and knife-edged RCC rib sections. Excessive overheating and slumping of carrier panel tiles. Missing or molten attachment bolts but intact bushing. Deposit mainly on "inside" RCC panel. Deposit on some fractured RCC surface

Shah, Sandeep; Jerman, Gregory

2004-01-01

16

Advanced X-Ray Inspection of Reinforced Carbon Composite Materials on the Orbiter Leading Edge Structural Subsystem (LESS)  

NASA Technical Reports Server (NTRS)

The post return-to-flight (RTF) inspection methodology for the Orbiter Leading Edge Structural Subsystem (LESS) is currently being defined. Numerous NDT modalities and techniques are being explored to perform the flight-to-flight inspections of the reinforced carbon/carbon (RCC) composite material for impact damage, general loss of mass in the bulk layers, or other anomalous conditions that would pose risk to safe return upon re-entry. It is possible to have an impact upon ascent that is not visually observable on the surface, yet causes internal damage. Radiographic testing may be a useful NDT technique for such occurrences. The authors have performed radiographic tests on full-sized mock samples of LESS hardware with embedded image quality phantoms. Digitized radiographic film, computed radiography and flat panel digital real-time radiography was acquired using a GE Eresco 200 x-ray tube, and Se-75 and Yb-169 radioisotopes.

Hernandez, Jose M.; Berry, Robert F.; Osborn, Robin; Bueno, Clifford; Osterlitz, Mark; Mills, Richard; Morris, Philip; Phalen, Robert; McNab, Jim; Thibodeaux, Tahanie; Thompson, Kyle

2004-01-01

17

Aerothermal/FEM Analysis of Hypersonic Sharp Leading Edges  

NASA Technical Reports Server (NTRS)

Advanced hypersonic vehicles, like wave riders, will have sharp leading edges to minimize drag. These designs require accurate finite element modeling (FEM) of the thermal-structural behavior of a diboride ceramic matrix composite sharp leading edge. By coupling the FEM solver to an engineering model of the aerothermodynamic heating environment the impact of non catalytic surfaces, rarefied flow effects, and multidimensional conduction on the performance envelopes of sharp leading edges can be examined.

Kolodziej, Paul; Bull, Jeffrey D.; Kowalski, Thomas R.; Rasky, Daniel J. (Technical Monitor)

1995-01-01

18

Leading Edge Bacterial Genomics and Pathogen Evolution  

E-print Network

Leading Edge Review Bacterial Genomics and Pathogen Evolution David M. Raskin,1 Rekha Seshadri,2 Medical School, Boston, MA 02115, USA 2 The Institute for Genomic Research, 9712 Medical Center Drive.02.002 The availability of hundreds of bacterial genome sequences has altered the study of bacte- rial pathogenesis

Mekalanos, John

19

INTERNATIONAL WATER ASSOCIATION LEADING EDGE CONFERENCE  

E-print Network

INTERNATIONAL WATER ASSOCIATION 4th LEADING EDGE CONFERENCE ON STRATEGIC ASSET MANAGEMENT SEPTEMBER in the notification of acceptance 002 Paper Title: Using a break prediction model for drinking water networks asset-00655812,version1-2Jan2012 Author manuscript, published in "International water association, 4 th keadubg

Paris-Sud XI, Université de

20

Leading Edge Democracy Derived? New Trajectories  

E-print Network

Leading Edge Commentary Democracy Derived? New Trajectories in Pluripotent Stem Cell Research of stem cell research? Here, coauthorship networks of stem cell research articles and analysis of cell lines used in stem cell research indicate that hiPSCs are not replacing human embryonic stem cells

21

SPH – Lagrangian study of bird impact on leading edge wing  

Microsoft Academic Search

Experimental bird-strike tests were conducted using a dead chicken of 8lb with a speed of 250kts that hit on leading edge bay in composite material made with aluminium alloy 2024-T3, core panel of honeycomb and GLARE cover plates. A validated simulation methodology has been developed in order to use a reference in further bird test certification procedure on the fin

M. Guida; F. Marulo; M. Meo; A. Grimaldi; G. Olivares

2011-01-01

22

Investigation of a Laminar Flow Leading Edge  

NASA Technical Reports Server (NTRS)

The recent resurgence of interest in utilizing laminar flow on aircraft surfaces for reduction in skin friction drag has generated a considerable amount of research in natural laminar flow (NLF) and hybrid laminar flow control (HLFC) on transonic aircraft wings. This research has focused primarily on airfoil design and understanding transition behavior with little concern for the surface imperfections and manufacturing variations inherent to most production aircraft. In order for laminar flow to find wide-spread use on production aircraft, techniques for constructing the wings must be found such that the large surface imperfections present in the leading edge region of current aircraft do not occur. Toward this end, a modification to existing leading edge construction techniques was devised such that the resulting surface did not contain large gaps and steps as are common on current production aircraft of this class. A lowspeed experiment was first conducted on a simulation of the surface that would result from this construction technique. Preston tube measurements of the boundary layer downstream of the simulated joint and flow visualization using sublimation chemicals validated the literature on the effects of steps on a laminar boundary layer. These results also indicated that the construction technique was indeed compatible with laminar flow. In order to fully validate the compatibility of this construction technique with laminar flow, thus proving that it is possible to build wings that are smooth enough to be used on business jets and light transports in a manner compatible with laminar flow, a flight experiment is being conducted. In this experiment Mach number and Reynolds number will be matched in a real flight environment. The experiment is being conducted using the NASA Dryden F-104 Flight Test Fixture (FTF). The FTF is a low aspect ratio ventral fin mounted beneath an F-104G research aircraft. A new nose shape was designed and constructed for this experiment. This nose shape provides an accelerating pressure gradient in the leading edge region. By flying the aircraft at appropriate Mach numbers and altitudes, this nose shape simulates the leading edge region of a laminar flow wing for a business jet or light transport. Manufactured into the nose shape is a spanwise slot located approximately four inches downstream of the leading edge. The slot, which is an inch wide and one-eighth of an inch deep allows the simulation of surface imperfections, such as gaps and steps at skin joints, which will occur on aircraft using this new construction technique. By placing strips of aluminum of various sizes and shapes in the slot, the effect on the boundary layer of different sizes and shapes of steps and gaps will be examined. It is planned to use five different configurations, differing primarily in the size and number of gaps. Downstream of the slot, the state of the boundary layer is determined using hot film gages and Stanton gages. Agreement between these two very different techniques of measuring boundary layer properties is considered important to being able to state with confidence the effects on the boundary layer of the simulated manufacturing imperfections. To date, the aircraft has not flown. First flights of the aircraft are on schedule to begin October 4, 1993. Low-speed, preliminary experiments at matching Reynolds numbers have been completed.

Drake, Aaron; Kennelly, Robert A., Jr.; Koga, Dennis J.; Westphal, Russell V.; Zuniga, Fanny

1994-01-01

23

Wing Leading Edge Joint Laminar Flow Tests  

NASA Technical Reports Server (NTRS)

An F-104G aircraft at NASA's Dryden Flight Research Center has been equipped with a specially designed and instrumented test fixture to simulate surface imperfections of the type likely to be present near the leading edge on the wings of some laminar flow aircraft. The simulated imperfections consisted of five combinations of spanwise steps and gaps of various sizes. The unswept fixture yielded a pressure distribution similar to that of some laminar flow airfoils. The experiment was conducted at cruise conditions typical for business-jets and light transports: Mach numbers were in the range 0.5-0.8, and unit Reynolds numbers were 1.5-2.5 million per foot. Skin friction measurements indicated that laminar flow was often maintained for some distance downstream of the surface imperfections. Further work is needed to more precisely define transition location and to extend the experiments to swept-wing conditions and a broader range of imperfection geometries.

Drake, Aaron; Westphal, Russell V.; Zuniga, Fanny A.; Kennelly, Robert A., Jr.; Koga, Dennis J.

1996-01-01

24

Experimental investigation of leading-edge thrust at supersonic speeds  

NASA Technical Reports Server (NTRS)

Wings, designed for leading edge thrust at supersonic speeds, were investigated in the Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.80, 2.00, 2.16, and 2.36. Experimental data were obtained on a uncambered wing which had three interchangeable leading edges that varied from sharp to blunt. The leading edge thrust concept was evaluated. Results from the investigation showed that leading edge flow separation characteristics of all wings tested agree well with theoretical predictions. The experimental data showed that significant changes in wing leading edge bluntness did not affect the zero lift drag of the uncambered wings.

Wood, R. M.; Miller, D. S.

1983-01-01

25

Composite laminate free edge reinforcement concepts  

NASA Technical Reports Server (NTRS)

The presence of a free edge in a laminated composite structure can result in delamination of the composite under certain loading conditions. Linear finite element analysis predicts large or even singular interlaminar stresses near the free edge. Edge reinforcements which will reduce these interlaminar stresses, prevent or delay the onset of delaminations, and thereby increase the strength and life of the structure were studied. Finite element models are used to analyze reinforced laminates which were subsequently fabricated and loaded to failure in order to verify the analysis results.

Howard, W. E.; Gossard, T., Jr.; Jones, R. M.

1985-01-01

26

Laminar Flow Control Leading Edge Systems in Simulated Airline Service  

NASA Technical Reports Server (NTRS)

Achieving laminar flow on the wings of a commercial transport involves difficult problems associated with the wing leading edge. The NASA Leading Edge Flight Test Program has made major progress toward the solution of these problems. The effectiveness and practicality of candidate laminar flow leading edge systems were proven under representative airline service conditions. This was accomplished in a series of simulated airline service flights by modifying a JetStar aircraft with laminar flow leading edge systems and operating it out of three commercial airports in the United States. The aircraft was operated as an airliner would under actual air traffic conditions, in bad weather, and in insect infested environments.

Wagner, R. D.; Maddalon, D. V.; Fisher, D. F.

1988-01-01

27

Measurements of leading edge vortices in a supersonic stream  

Microsoft Academic Search

An experimental investigation of the leading edge vortices from a 75° sweptback, sharp edge delta wing has been carried out in a Mach 2.49 stream. Five-hole conical probe traverses were conducted vertically and horizontally through the primary vortices at the trailing edge and at one half chord downstream station for 7° and 12° angles of attack. The main objective was

Ivana Milija Milanovic

1999-01-01

28

Leading-edge singularities in thin-airfoil theory  

NASA Technical Reports Server (NTRS)

If the thin airfoil theory is applied to an airfoil having a rounded leading edge, a certain error will arise in the determination of the pressure distribution around the nose. It is shown that the evaluation of the drag of such a blunt nosed airfoil by the thin airfoil theory requires the addition of a leading edge force, analogous to the leading edge thrust of the lifting airfoil. The method of calculation is illustrated by application to: (1) The Joukowski airfoil in subsonic flow; and (2) the thin elliptic cone in supersonic flow. A general formula for the edge force is provided which is applicable to a variety of wing forms.

Jones, R. T.

1976-01-01

29

Heat-Pipe-Cooled Leading Edges for Hypersonic Vehicles  

NASA Technical Reports Server (NTRS)

Heat pipes can be used to effectively cool wing leading edges of hypersonic vehicles. . Heat-pipe leading edge development. Design validation heat pipe testing confirmed design. Three heat pipes embedded and tested in C/C. Single J-tube heat pipe fabricated and testing initiated. HPCLE work is currently underway at several locations.

Glass, David E.

2006-01-01

30

Observations on the leading edge in lifted flame stabilization  

Microsoft Academic Search

The objective of this paper is to report some of the first experimental evidence for the “leading edge” flame as the stabilization mechanism in lifted jet diffusion flames [1–5]. CH fluorescence has been used to indicate the flame front location (i.e., region of chemical reaction) and thereby characterize features of the stabilization region [5, 6]. The “leading edge” flame phenomenon

K. A. Watson; K. M. Lyons; J. M. Donbar; C. D. Carter

1999-01-01

31

Timing discriminator using leading-edge extrapolation  

DOEpatents

A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting is described. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

Gottschalk, B.

1981-07-30

32

Timing discriminator using leading-edge extrapolation  

DOEpatents

A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

Gottschalk, Bernard (Palo Alto, CA)

1983-01-01

33

Leading-Edge Learning: Two Views.  

ERIC Educational Resources Information Center

Peter Senge and Jack Welch share thoughts about what it means to learn and lead into the next century. Senge urges leaders to be aware of the economic and the natural environment. Welch asserts that an organization's ability to learn and translate learning into action is the ultimate competitive advantage. (JOW)

Abernathy, Donna J.

1999-01-01

34

Leading Edge Uncovering a Tumor Suppressor  

E-print Network

of the protein tyrosine phosphatase PTPN12 is lost in a large percentage of this breast cancer subtype, offering. The molecular characterization of breast cancer subtypes has lead to significant progress in treating this common disease. Tumors that express the estrogen recep- tor (ER) or progesterone receptor (PR) respond

Albeck, John

35

Leading Edge Spinning the Web of Cell Fate  

E-print Network

Leading Edge Minireview Spinning the Web of Cell Fate Kevin Van Bortle1 and Victor G. Corces1,* 1 involved in spinning the web of cell fate. Chromatin at the Nuclear Lamina The nuclear lamina is a thin

Corces, Victor G.

36

Shock Interaction Control for Scramjet Cowl Leading Edges  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to qualitatively determine the effectiveness of stagnation-region gas injection in protecting a scramjet cowl leading edge from the intense heating produced by Type III and Type IV shock interactions. The model consisted of a two-dimensional leading edge, representative of that of a scramjet cowl. Tests were conducted at a nominal freestream Mach number of 6. Gaseous nitrogen was supersonically injected through the leading-edge nozzles at various mass flux ratios and with the model pitched at angles of 0deg and -20deg relative to the freestream flow. Qualitative data, in the form of focusing and conventional schlieren images, were obtained of the shock interaction patterns. Results indicate that large shock displacements can be achieved and both the Type III and IV interactions can be altered such that the interaction does not impinge on the leading edge surface.

Albertson, Cindy W.; Venkat, Venki, S.

2005-01-01

37

Design and Analysis of UHTC Leading Edge Attachment  

NASA Technical Reports Server (NTRS)

NASA Glenn Research Center was contacted to provide technical support to NASA Ames Research Center in the design and analysis of an ultra high temperature ceramic (UHTC) leading edge. UHTC materials are being considered for reusable launch vehicles because their high temperature capability may allow for un-cooled sharp leading edge designs. While ceramic materials have the design benefit of allowing subcomponents to run hot, they also provide a design challenge in that they invariably must be in contact with cooler subcomponents elsewhere in the structure. NASA Glenn Research Center proposed a modification to an existing attachment design. Thermal and structural analyses of the leading edge assembly were carried out using ABAQUS finite element software. Final results showed that the proposed modifications aided in thermally isolating hot and cold subcomponents and reducing bearing stresses at the attachment location.

Thomas, David J.; Nemeth, Noel N. (Technical Monitor)

2002-01-01

38

Wake of forced flow around elliptical leading edge plates  

NASA Astrophysics Data System (ADS)

Previous investigations have shown that flows around rectangular plates with transverse forcing involve interactions between vortices shed from the leading and trailing edges and vortex merging in the wakes. The Strouhal number of vortex shedding at which peak base drag occurs varies with chord-to-thickness ratio in a stepwise fashion, similar to the self-sustained oscillations at low Reynolds number for unforced flows. In the present study, the leading edge flow separation and vortex shedding is eliminated by using plates with elliptical leading edges, and the trailing edge flow is examined through particle image velocimetry. In particular, the response of the trailing-edge vortex shedding and the base pressure coefficient to applied transverse oscillations of different Strouhal number and amplitude is measured. Substantial variation in the base pressure coefficient is found, with peaks appearing at the natural shedding frequency and at a harmonic. The effect of the forcing on the wake dimension and the strength of the wake vortices is quantified using particle image velocimetry. Three-dimensional structures in addition to the two-dimensional Kármán vortices in the wake are also visualized.

Mills, R.; Sheridan, J.; Hourigan, K.

2005-02-01

39

Low Reynolds Number Low Aspect Ratio Leading Edge Separation Dynamics  

NASA Astrophysics Data System (ADS)

The low Reynolds number flow conditions for a low aspect ratio wing are investigated using time resolved PIV with specific emphasis on the leading edge vortex generation at high angles of attack. The flow is highly three dimensional and the flow visualization shows very strong tip vortices which extend over a major portion of the wing. The separation bubble consists of a triangular shaped region extending back to about one third of the chord length. Three component velocity data are obtained at the centerline, one half span and at the wing tip. The time variation of the leading edge vortex shedding is studied in each of these regions using a swirl detection algorithm. The frequency of shedding is shown to be an order of magnitude higher than the dominant frequency within the recirculation region. The tip vortex flow dominate near the edge of the wing.

Morse, Daniel; Liburdy, James

2008-11-01

40

Leading Edge Studying Circuits with Therapy in Mind  

E-print Network

Leading Edge Voices Studying Circuits with Therapy in Mind Prostheses: Hopes and Hurdles Krishna V of therapy. Progress will continue to depend on deeper scientific under- standing of the underlying neural imaging (PET, EEG, DTI, MRI). Such approaches provide critical foundation for explicit reverse

Shenoy, Krishna V.

41

AIRFOIL NOSE SHAPES DELAYING LEADING-EDGE SEPARATION  

E-print Network

AIRFOIL NOSE SHAPES DELAYING LEADING-EDGE SEPARATION E. O. Tuck and A. Dostovalova ABSTRACT We show on the upper sur- face of an airfoil. Symmetric modifications, of the nature sharpening the nose allow assumptions of the thin-airfoil theory and was motivated by the work carried out in Van Dyke, M.D. (1954

Stokes, Yvonne

42

The Columbia River--on the Leading Edge  

Microsoft Academic Search

On the leading edge of the North American plate, the Columbia River is the largest of the world's 40 or so rivers with drainage areas greater than 500,000 square kilometers to drain toward a convergent plate boundary. This unique setting results in a unique continental river basin; marked by episodic and cataclysmic geologic disturbance, but also famously fecund with perhaps

J. E. O'Connor

2005-01-01

43

Leading Edge Wnt/b-Catenin Signaling and Disease  

E-print Network

activated by integration of mouse mammary tumor virus proviral DNA in virally induced breast tumors (NusseLeading Edge Review Wnt/b-Catenin Signaling and Disease Hans Clevers1,* and Roel Nusse2 1Hubrecht various components contribute to disease, and pose outstanding questions to be addressed in the future

Bejerano, Gill

44

Thermal Management at Hypersonic Leading Edges A Dissertation  

E-print Network

the leading edge, thereby eliminating local hot spots. It makes use of high thermal conductance heat pipes of elevated vapor pressure inside the pipe. The latent heat is transported down the resulting pressure for a wedge-shaped heat pipe is presented which uses a coupled flow-wall temperature model to construct design

Wadley, Haydn

45

Rotational accelerations stabilize leading edge vortices on revolving fly wings  

Microsoft Academic Search

The aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed

D. Lentink; M. H. Dickinson

2009-01-01

46

Detail view of the leading and top edge of the ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail view of the leading and top edge of the vertical stabilizer of the Orbiter Discovery showing the thermal protection system components with the white Advanced Flexible Reusable Surface Insulation (AFRSI) blanket and the black High-temperature Reusable Surface Insulation (HRSI) tiles along the outer edges. The marks seen on the HRSI tiles are injection point marks and holes for the application of waterproofing material. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

47

Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe  

NASA Technical Reports Server (NTRS)

The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a 'D-shaped' cross section and was fabricated from arc cast Mo-4lRe. An artery was included in the wick. Several issues were resolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuum chamber at Los Alamos National Laboratory using induction heating and was started up from the frozen state several times. However, design temperatures and heat fluxes were not obtained due to premature failure of the heat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Though a testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe was demonstrated.

Glass, David E.; Merrigan, Michael A.; Sena, J. Tom; Reid, Robert S.

1998-01-01

48

Turbine Airfoil With CMC Leading-Edge Concept Tested Under Simulated Gas Turbine Conditions  

NASA Technical Reports Server (NTRS)

Silicon-based ceramics have been proposed as component materials for gas turbine engine hot-sections. When the Navy s Harrier fighter experienced engine (Pegasus F402) failure because of leading-edge durability problems on the second-stage high-pressure turbine vane, the Office of Naval Research came to the NASA Glenn Research Center at Lewis Field for test support in evaluating a concept for eliminating the vane-edge degradation. The High Pressure Burner Rig (HPBR) was selected for testing since it could provide temperature, pressure, velocity, and combustion gas compositions that closely simulate the engine environment. The study focused on equipping the stationary metal airfoil (Pegasus F402) with a ceramic matrix composite (CMC) leading-edge insert and evaluating the feasibility and benefits of such a configuration. The test exposed the component, with and without the CMC insert, to the harsh engine environment in an unloaded condition, with cooling to provide temperature relief to the metal blade underneath. The insert was made using an AlliedSignal Composites, Inc., enhanced HiNicalon (Nippon Carbon Co. LTD., Yokohama, Japan) fiber-reinforced silicon carbide composite (SiC/SiC CMC) material fabricated via chemical vapor infiltration. This insert was 45-mils thick and occupied a recessed area in the leading edge and shroud of the vane. It was designed to be free floating with an end cap design. The HPBR tests provided a comparative evaluation of the temperature response and leading-edge durability and included cycling the airfoils between simulated idle, lift, and cruise flight conditions. In addition, the airfoils were aircooled, uniquely instrumented, and exposed to the exact set of internal and external conditions, which included gas temperatures in excess of 1370 C (2500 F). In addition to documenting the temperature response of the metal vane for comparison with the CMC, a demonstration of improved leading-edge durability was a primary goal. First, the metal vane was tested for a total of 150 cycles. Both the leading edge and trailing edge of the blade exhibited fatigue cracking and burn-through similar to the failures experienced in service by the F402 engine. Next, an airfoil, fitted with the ceramic leading edge insert, was exposed for 200 cycles. The temperature response of those HPBR cycles indicated a reduced internal metal temperature, by as much as 600 F at the midspan location for the same surface temperature (2100 F). After testing, the composite insert appeared intact, with no signs of failure on either the vane s leading or trailing edge. Only a slight oxide scale, as would be expected, was noted on the insert. Overall, the CMC insert performed similarly to a thick thermal barrier coating. With a small air gap between the metal and the SiC/SiC leading edge, heat transfer from the CMC to the metal alloy was low, effectively lowering the temperatures. The insert's performance has proven that an uncooled CMC can be engineered and designed to withstand the thermal up-shock experienced during the severe lift conditions in the Pegasus engine. The design of the leading-edge insert, which minimized thermal stresses in the SiC/SiC CMC, showed that the CMC/metal assembly can be engineered to be a functioning component.

Robinson, R. Craig; Hatton, Kenneth S.

2000-01-01

49

Probabilistic Structural Health Monitoring of the Orbiter Wing Leading Edge  

NASA Technical Reports Server (NTRS)

A structural health monitoring (SHM) system can contribute to the risk management of a structure operating under hazardous conditions. An example is the Wing Leading Edge Impact Detection System (WLEIDS) that monitors the debris hazards to the Space Shuttle Orbiter s Reinforced Carbon-Carbon (RCC) panels. Since Return-to-Flight (RTF) after the Columbia accident, WLEIDS was developed and subsequently deployed on board the Orbiter to detect ascent and on-orbit debris impacts, so as to support the assessment of wing leading edge structural integrity prior to Orbiter re-entry. As SHM is inherently an inverse problem, the analyses involved, including those performed for WLEIDS, tend to be associated with significant uncertainty. The use of probabilistic approaches to handle the uncertainty has resulted in the successful implementation of many development and application milestones.

Yap, Keng C.; Macias, Jesus; Kaouk, Mohamed; Gafka, Tammy L.; Kerr, Justin H.

2011-01-01

50

Heat pipes for wing leading edges of hypersonic vehicles  

NASA Technical Reports Server (NTRS)

Wing leading edge heat pipes were conceptually designed for three types of vehicle: an entry research vehicle, aero-space plane, and advanced shuttle. A full scale, internally instrumented sodium/Hastelloy X heat pipe was successfully designed and fabricated for the advanced shuttle application. The 69.4 inch long heat pipe reduces peak leading edge temperatures from 3500 F to 1800 F. It is internally instrumented with thermocouples and pressure transducers to measure sodium vapor qualities. Large thermal gradients and consequently large thermal stresses, which have the potential of limiting heat pipe life, were predicted to occur during startup. A test stand and test plan were developed for subsequent testing of this heat pipe. Heat pipe manufacturing technology was advanced during this program, including the development of an innovative technique for wick installation.

Boman, B. L.; Citrin, K. M.; Garner, E. C.; Stone, J. E.

1990-01-01

51

An Aeroacoustic Study of a Leading Edge Slat Configuration  

NASA Technical Reports Server (NTRS)

Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper describes detailed flow and acoustic measurements that have been made in order to better understand the noise generated from airflow over a wing leading edge slat configuration, and to possibly predict and reduce this noise source. The acoustic database is obtained by a moveable Small Aperture Directional Array of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.

Mendoza, J. M.; Brooks, T. F.; Humphreys, W. M., Jr.

2002-01-01

52

Method Improvements in Thermal Analysis of Mach 10 Leading Edges  

NASA Technical Reports Server (NTRS)

Several improvements have recently been made in the thermal analysis methods for leading edges of a hypersonic vehicle. The leading edges of this vehicle undergo exceptionally high heat loads that incorporate extreme spatial gradients as well as severe transients. Due to the varying flight conditions, complex geometry, and need for thermal loads at many points along the trajectory, full computational fluid dynamics (CFD) analysis of the aeroheating; loads is not feasible. Thus, engineering methods must be used to determine the aeroheating on the vehicle surfaces, and that must be utilized in the thermal analysis. Over the last year, the thermal analysis of a hypersonic vehicle has been enhanced in several ways. Two different engineering codes are used to predict aeroheating loads: one over the curve near the stagnation point, and the other on flat surfaces downstream of the leading edge. These two are matched together at the intersection point using a method that allows closer approximation of CFD results. User-developed FORTRAN, which is part of the thermal solver PATRAN Thermal, is used to accomplish this. The customizable FORTRAN code also allows use of many different time- and space-dependent factors, interpolation of the heat load in time and space, and inclusion of both highly swept and unswept grid structures. This FORTRAN is available to other PATRAN users who may want to accomplish a similar objective in analysis. Flux, rather than convective coefficient, is used to define heat loads, which allows more accurate analysis as well as better application of margins. Improvements have also been made in more efficient utilization of imported CAD geometry, by creating faces on solids to facilitate load application.

Amundsen, Ruth M.

2001-01-01

53

Laminar flow control leading edge systems in simulated airline service  

NASA Technical Reports Server (NTRS)

The feasibility of two candidate leading-edge flow laminarization systems applicable to airline service was tested using representative airline operational conditions with respect to air traffic, weather, and airport insect infestation. One of the systems involved a perforated Ti alloy suction surface with about 1 million 0.0025-in. diameter holes drilled by electron beam, as well as a Krueger-type flap that offered protective shielding against insect impingement; the other supplied surface suction through a slotted Ti alloy skin with 27 spanwise slots on the upper and lower surface.

Wagner, R. D.; Maddalon, D. V.; Fisher, D. F.

1988-01-01

54

Measurements of leading edge vortices in a supersonic stream  

NASA Astrophysics Data System (ADS)

An experimental investigation of the leading edge vortices from a 75° sweptback, sharp edge delta wing has been carried out in a Mach 2.49 stream. Five-hole conical probe traverses were conducted vertically and horizontally through the primary vortices at the trailing edge and at one half chord downstream station for 7° and 12° angles of attack. The main objective was to determine the Mach number and pressure distributions in the primary vortex and to present comparisons of flow properties at different survey stations. In response to the continued interest in efficient supersonic flight vehicles, particularly in the missile arena, the motivation for this research has been to provide the quantitative details of supersonic leading edge vortices, the understanding of which up to now has been largely based on flow visualizations and presumed similarity to low speed flows. As a prerequisite to the measurement campaign, the employed five-hole conical probe was numerically calibrated using a three-dimensional Thin Layer Navier-Stokes solver in order to circumvent the traditional experimental approach vastly demanding on resources. The pressure readings at the probe orifices were computed for a range of Mach numbers and pitch angles, and subsequently verified in wind tunnel tests. The calibration phase also demonstrated the profound influence of the probe bluntness on the nearby static pressure ports, its relevance to the ultimate modeling strategy and the resulting calibration charts. Flow diagnostics of the leading edge vortices included both qualitative flow visualizations, as well as quantitative measurements. Shadowgraphs provided information regarding the trajectory and relative size of the generated vortices while assuring that no probe-induced vortex breakdown occurred. Surface oil patterns revealed the general spanwise locations of leeward vortices, and confirmed topological similarity to their low speed counterparts. The probe measurements revealed substantial Pitot, total and static pressure deficits in the vortex core. The magnitude of these deficits increase with increasing angle of attack for the same measurement plane and decrease with downstream distance from the model. Pressure deficits in the same survey station also grow spatially with the higher incidence angle. Very large swirl Mach numbers, at times reaching low supersonic values, were recorded and their distribution resembles that of the classical low speed Lamb-Oseen vortex. At the core edges, the presence of substantial radial flow directed towards the vortex center indicates the entrainment of the surrounding fluid. A decrease in the radial Mach number component confirms the change in vortex trajectory from a strong downward flow over the planform to a gradual return towards the free stream in the near-wake. The axial profiles follow the general trend exhibited in the total Mach number distribution thereby confirming the dominance of the streamwise flow. The axial Mach number profiles also demonstrated that the initially conical convection over the wing does not proceed in the wake as a uniform translation of the profiles found at the trailing edge. Most remarkably, contrary to its transonic and low speed counterparts, the axial Mach number profiles exhibit a strong wake-like behavior. Consistent with the shadowgraphs and other existing flow visualizations, measurements illustrated vortex shape adjustment in the near-wake. In the absence of the constraint from the wing surface, the primary vortices stretch in the vertical direction while convecting downstream where a more round shape is ultimately developed.

Milanovic, Ivana Milija

55

Thermostructural applications of heat pipes for cooling leading edges of high-speed aerospace vehicles  

NASA Technical Reports Server (NTRS)

Heat pipes have been considered for use on wing leading edge for over 20 years. Early concepts envisioned metal heat pipes cooling a metallic leading edge. Several superalloy/sodium heat pipes were fabricated and successfully tested for wing leading edge cooling. Results of radiant heat and aerothermal testing indicate the feasibility of using heat pipes to cool the stagnation region of shuttle-type space transportation systems. The test model withstood a total seven radiant heating tests, eight aerothermal tests, and twenty-seven supplemental radiant heating tests. Cold-wall heating rates ranged from 21 to 57 Btu/sq ft-s and maximum operating temperatures ranged from 1090 to 1520 F. Follow-on studies investigated the application of heat pipes to cool the stagnation regions of single-stage-to-orbit and advanced shuttle vehicles. Results of those studies indicate that a 'D-shaped' structural design can reduce the mass of the heat-pipe concept by over 44 percent compared to a circular heat-pipe geometry. Simple analytical models for heat-pipe startup from the frozen state (working fluid initially frozen) were adequate to approximate transient, startup, and steady-state heat-pipe performance. Improvement in analysis methods has resulted in the development of a finite-element analysis technique to predict heat-pipe startup from the frozen state. However, current requirements of light-weight design and reliability suggest that metallic heat pipes embedded in a refractory composite material should be used. This concept is the concept presently being evaluated for NASP. A refractory-composite/heat-pipe-cooled wing leading edge is currently being considered for the National Aero-Space Plane (NASP). This concept uses high-temperature refractory-metal/lithium heat pipes embedded within a refractory-composite structure and is significantly lighter than an actively cooled wing leading edge because it eliminates the need for active cooling during ascent and descent. Since the NASP vehicle uses cryogenic hydrogen to cool structural components and then burns this fuel in the combustor, hydrogen necessary for descent cooling only, when the vehicle is unpowered, is considered to be a weight penalty. Details of the design of the refractory-composite/heat-pipe-cooled wing leading edge are currently being investigated. Issues such as thermal contact resistance and thermal stress are also being investigated.

Camarda, Charles J.; Glass, David E.

1992-01-01

56

Leading Edge Vortex Detection Using On-Body Pressure Sensing  

NASA Astrophysics Data System (ADS)

Ongoing experiments within the Center for Environmental Sensing and Modeling (CENSAM) have shown that the low pressure region characteristic of a vortex allows for their detection and tracking using pressure sensors alone. While early experiments were conducted with wall mounted pressure sensors and externally generated vortices, a new series of experiments has succeeded in detecting separated flow generated by the sensing body. A combined pressure sensing and particle image velocimetry (PIV) approach was used to detect the leading edge vortex shed from a hydrofoil accelerated at a fixed angle of attack. A NACA 0018 foil was instrumented with four pressure sensors at discrete locations along the foil in the chord-wise direction. When accelerated from rest, the traces from each of the four pressure sensors displayed a distinctive, transient drop, consistent with results observed in previous experiments. From the pressure sensor results, it was theorized that a leading edge vortex was being created, and subsequently shed and convected along the foil chord. Two-dimensional PIV techniques were used to image the flow near the foil surface, allowing the anticipated vortex formation and shedding to be verified.

Dusek, Jeff; Dahl, Jason; Triantafyllou, Michael

2010-11-01

57

Feasibility of Metallic Structural Heat Pipes as Sharp Leading Edges for Hypersonic Vehicles  

Microsoft Academic Search

Hypersonic flight with hydrocarbon-fueled airbreathing pr opulsion requires sharp leading edges. This generates high temperatures at the leading edge surface which cannot be sustained by most materials. By integrating a planar heat pipe into the structure of the leading edge, the heat can be conducted to large flat surfaces from which it can b e radiated out to the environ-

Craig A. Steeves; Ming Y. He; Scott D. Kasen; Lorenzo Valdevit; Haydn N. G. Wadley; Anthony G. Evans

2009-01-01

58

Edge delamination in angle-ply composite laminates, part 5  

NASA Technical Reports Server (NTRS)

A theoretical method was developed for describing the edge delamination stress intensity characteristics in angle-ply composite laminates. The method is based on the theory of anisotropic elasticity. The edge delamination problem is formulated using Lekhnitskii's complex-variable stress potentials and an especially developed eigenfunction expansion method. The method predicts exact orders of the three-dimensional stress singularity in a delamination crack tip region. With the aid of boundary collocation, the method predicts the complete stress and displacement fields in a finite-dimensional, delaminated composite. Fracture mechanics parameters such as the mixed-mode stress intensity factors and associated energy release rates for edge delamination can be calculated explicity. Solutions are obtained for edge delaminated (theta/-theta theta/-theta) angle-ply composites under uniform axial extension. Effects of delamination lengths, fiber orientations, lamination and geometric variables are studied.

Wang, S. S.

1981-01-01

59

An embedded mesh procedure for leading-edge vortex flows  

NASA Technical Reports Server (NTRS)

A cell-vertex scheme is outlined for solving the flow about a delta wing with M (sub infinity) is greater than 1. Embedded regions of mesh refinement allow solutions to be obtained which have much higher resolution than those achieved to date. Effects of mesh refinement and artificial viscosity on the solutions are studied, to determine at what point leading-edge vortex solutions are grid-converged. A macroscale and a microscale for the size of the vortex are defined, and it is shown that the macroscale (which includes the wing surface properties) is converged on a moderately refined grid, while the microscale is very sensitive to grid spacing. The level of numerical diffusion in the core of the vortex is found to be substantial. Comparisons with the experiment are made for two cases which have transonic cross-flow velocities.

Powell, Kenneth G.; Murman, Earll M.

1989-01-01

60

Managed aquifer recharge: rediscovering nature as a leading edge technology.  

PubMed

Use of Managed Aquifer Recharge (MAR) has rapidly increased in Australia, USA, and Europe in recent years as an efficient means of recycling stormwater or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas. Yet aquifers have been relied on knowingly for water storage and unwittingly for water treatment for millennia. Hence if 'leading edge' is defined as 'the foremost part of a trend; a vanguard', it would be misleading to claim managed aquifer recharge as a leading edge technology. However it has taken a significant investment in scientific research in recent years to demonstrate the effectiveness of aquifers as sustainable treatment systems to enable managed aquifer recharge to be recognised along side engineered treatment systems in water recycling. It is a 'cross-over' technology that is applicable to water and wastewater treatment and makes use of passive low energy processes to spectacularly reduce the energy requirements for water supply. It is robust within limits, has low cost, is suitable from village to city scale supplies, and offers as yet almost untapped opportunities for producing safe drinking water supplies where they do not yet exist. It will have an increasingly valued role in securing water supplies to sustain cities affected by climate change and population growth. However it is not a universal panacea and relies on the presence of suitable aquifers and sources of water together with effective governance to ensure human health and environment protection and water resources planning and management. This paper describes managed aquifer recharge, illustrates its use in Australia, outlining economics, guidelines and policies, and presents some of the knowledge about aquifer treatment processes that are revealing the latent value of aquifers as urban water infrastructure and provide a driver to improving our understanding of urban hydrogeology. PMID:21076220

Dillon, P; Toze, S; Page, D; Vanderzalm, J; Bekele, E; Sidhu, J; Rinck-Pfeiffer, S

2010-01-01

61

Studies on Effects of Periodic Wake Passing upon a Blade Leading Edge Separation Bubble: Experimental Investigation using a Simple Leading Edge Model  

Microsoft Academic Search

This paper describes experimental investigation on aerodynamic interaction between incoming periodic wakes and leading edge sepa- ration bubble on a compressor or turbine blade, using a scaled leading edge model. The studies aims at expanding the range of the test condi- tions from that of the previous study (Funazaki and Kato(15)) in order to deepen the knowledge on how and

K. Funazaki; K. Yamada; Y. Kato

62

Rotational accelerations stabilize leading edge vortices on revolving fly wings.  

PubMed

The aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed the Navier-Stokes equations in a rotating frame of reference attached to the wing's surface. Using these equations we show that LEV dynamics on flapping wings are governed by three terms: angular, centripetal and Coriolis acceleration. Our analysis for hovering conditions shows that angular acceleration is proportional to the inverse of dimensionless stroke amplitude, whereas Coriolis and centripetal acceleration are proportional to the inverse of the Rossby number. Using a dynamically scaled robot model of a flapping fruit fly wing to systematically vary these dimensionless numbers, we determined which of the three accelerations mediate LEV stability. Our force measurements and flow visualizations indicate that the LEV is stabilized by the ;quasi-steady' centripetal and Coriolis accelerations that are present at low Rossby number and result from the propeller-like sweep of the wing. In contrast, the unsteady angular acceleration that results from the back and forth motion of a flapping wing does not appear to play a role in the stable attachment of the LEV. Angular acceleration is, however, critical for LEV integrity as we found it can mediate LEV spiral bursting, a high Reynolds number effect. Our analysis and experiments further suggest that the mechanism responsible for LEV stability is not dependent on Reynolds number, at least over the range most relevant for insect flight (100leading edge) vortices could represent a convergent solution for the generation of high fluid forces over a quite large range in size. PMID:19648415

Lentink, David; Dickinson, Michael H

2009-08-01

63

Leading edge vortex in a slow-flying passerine  

PubMed Central

Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for the nearly inactive upstroke by generating stronger LEVs. Contrary to other animals, the LEV strength in the flycatcher is lowest near the wing tip, instead of highest. This is correlated with a spanwise reduction of the wing's angle-of-attack, partly owing to upward bending of primary feathers. We suggest that this helps to delay bursting and shedding of the particularly strong LEV in passerines. PMID:22417792

Muijres, Florian T.; Johansson, L. Christoffer; Hedenstrom, Anders

2012-01-01

64

Boundary element simulation of oscillating foil with leading-edge separation  

E-print Network

In this thesis, we develop a numerical model to account for the leading-edge separation for the boundary element simulation of the oscillating foil with potential flow assumption. Similar to the trailing-edge separation, ...

Dong, Xiaoxia, S.M. Massachusetts Institute of Technology

2007-01-01

65

Nondestructive Evaluation Tests Performed on Space Shuttle Leading- Edge Materials Subjected to Impact  

NASA Technical Reports Server (NTRS)

In support of the space shuttle Return To Flight efforts at the NASA Glenn Research Center, a series of nondestructive evaluation (NDE) tests were performed on reinforced carbon/carbon (RCC) composite panels subjected to ballistic foam impact. The impact tests were conducted to refine and verify analytical models of an external tank foam strike on the space shuttle leading edge. The NDE tests were conducted to quantify the size and location of the resulting damage zone as well as to identify hidden damage.

Roth, Don J.; Martin, Richard E.; Bodis, James R.

2005-01-01

66

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 1: Material Modelling  

Microsoft Academic Search

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts from objects such as runway debris or birds. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed,

M. A. McCarthy; J. R. Xiao; N. Petrinic; A. Kamoulakos; V. Melito

2004-01-01

67

The Columbia River--on the Leading Edge  

NASA Astrophysics Data System (ADS)

On the leading edge of the North American plate, the Columbia River is the largest of the world's 40 or so rivers with drainage areas greater than 500,000 square kilometers to drain toward a convergent plate boundary. This unique setting results in a unique continental river basin; marked by episodic and cataclysmic geologic disturbance, but also famously fecund with perhaps 10 to 16 million salmon historically spawning in its waters each year. Now transformed by dams, transportation infrastructure, dikes and diversions, the Columbia River presents an expensive conundrum for management of its many values. Inclusion of river ecology and geomorphology in discussions of river management is generally limited to observations of the last 200 years-a time period of little natural disturbance and low sediment transport. However, consideration of longer timescales provides additional perspective of historical ecologic and geomorphic conditions. Only 230 km from its mouth, the Columbia River bisects the volcanic arc of the Cascade Range, forming the Columbia River Gorge. Cenozoic lava flows have blocked the river, forcing diversions and new canyon cutting. Holocene eruptions of Mount Mazama (Crater Lake), Mount Hood, Mount St. Helens, and Mount Rainier have shed immense quantities of sediment into the lower Columbia River, forming a large percentage of the Holocene sediment transported through the lower river. Quaternary landslides, perhaps triggered by great earthquakes, have descended from the 1000-m-high gorge walls, also blocking and diverting the river, one as recently as 550 years ago. These geologic disturbances, mostly outside the realm of historical observation and operating at timescales of 100s to 1000s of years in the gorge and elsewhere, have clearly affected basin geomorphology, riverine ecology, and past and present cultural utilization of river resources. The historic productivity of the river, however, hints at extraordinary resilience (and perhaps dependence) of the Columbia River system to such disturbances, many of which are similar to engineered disturbances of the last 200 years.

O'Connor, J. E.

2005-05-01

68

Edge effects in angle-ply composite laminates  

NASA Technical Reports Server (NTRS)

This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation techniques and a limiting free body approach. The general solution for edge effects in laminates of arbitrary angle ply is applied to the special case of a (+ or - 45)s graphite/epoxy laminate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio and compared to finite difference results. The solution predicts stable, continuous stress distributions, determines finite maximum tensile interlaminar normal stress and provides mathematical evidence for singular interlaminar shear stresses in (+ or - 45) graphite/epoxy laminates.

Hsu, P. W.; Herakovich, C. T.

1977-01-01

69

High current composite superconductor electrical power lead  

NASA Astrophysics Data System (ADS)

We have developed and tested a nominal 100A lead to conduct electrical current between room and helium temperatures. The lead affords considerable savings in refrigeration costs by incorporating elements made of high transition temperature superconductors (HTSC). The lead was designed to operate both in the conduction mode and in the vapor cooled mode. Several leads have been combined to make a high current composite electrical conductor which carries currents of up to 1200A.

Zimmerman, G. O.; Negm, Y. Z.; Tahar, M. Z.; Buczkowski, S.; Powers, R. E.; McConeghy, R.

1993-04-01

70

Characteristic length scales for vortex detachment on plunging profiles with varying leading-edge geometry  

NASA Astrophysics Data System (ADS)

Experiments on leading-edge vortex (LEV) growth and detachment from a plunging profile have been conducted in a free-surface water tunnel. Direct-force and velocity-field measurements have been performed at a Reynolds number of Re = 10,000, a reduced frequency of k = 0.25, and a Strouhal number of St = 0.16, for three varying leading-edge geometries. The leading-edge shape is shown to influence the shear layer feeding the LEV, and thus to some extent the development of the LEV and associated flow topology. This effect in turn influences the arrival time of the rear (LEV) stagnation point at the trailing edge, which, once breached, constitutes a detachment of the LEV. It is found that despite minor phase changes in LEV detachment through leading-edge shape, the position of the trailing edge (chord length) should be chosen as the characteristic length scale for the vortex separation process.

Rival, David E.; Kriegseis, Jochen; Schaub, Pascal; Widmann, Alexander; Tropea, Cameron

2014-01-01

71

A simplified method for thermal analysis of a cowl leading edge subject to intense local shock-wave-interference heating  

NASA Technical Reports Server (NTRS)

Type IV shock wave interference heating on a blunt body causes extremely intense heating over a very localized region of the body. An analytical solution is presented to a heat transfer problem that approximates the shock wave interference heating of an engine cowl leading edge of the National Aero-Space Plane. The problem uses a simplified geometry to represent the leading edge. An analytical solution is developed that provides a means for approximating maximum temperature differences between the outer and inner surface temperatures of the leading edge. The solution is computationally efficient and, as a result, is well suited for conceptual and preliminary design or trade studies. Transient and steady state analyses are conducted, and results obtained from the analytical solution are compared with results of 2-D thermal finite element analyses over a wide range of design parameters. Isotropic materials as well as laminated composite materials are studied. Results of parametric studies are presented to indicate the effects of the thickness of the cowl leading edge and the width of the region heated by the shock wave interference on the thermal response of the leading edge.

Mcgowan, David M.; Camarda, Charles J.; Scotti, Stephen J.

1992-01-01

72

Effects of leading-edge camber on low-speed characteristics of slender delta wings  

NASA Technical Reports Server (NTRS)

Wind-tunnel studies have been conducted to determine the effects of leading-edge camber on the low-speed aerodynamic characteristics of a thin, sharp-edge 74 deg delta wing. The results include force and moment measurements, pressure distributions, and flow visualization patterns determined from oil flow, tuft and water vapor observations. The study indicated that leading-edge camber near the apex is effective in controlling the pitch-up tendency of slender delta wings.

Wentz, W. H., Jr.

1972-01-01

73

Conjugate Calculation of Gas Turbine Vanes Cooled with Leading Edge Films  

Microsoft Academic Search

Conjugate calculation methodology is used to simulate the C3X gas turbine vanes cooled with leading edge films of “shower-head” type. By comparing calculated results of different turbulence models with the measured data, it is clear that calculation with the transition model can better simulate the flow and heat transfer in the boundary layers with leading edge film cooling. In the

Ping Dong; Qiang Wang; Zhaoyuan Guo; Hongyan Huang; Guotai Feng

2009-01-01

74

Experimental investigation of boundary layer transition on a flat plate with C4 leading edge  

Microsoft Academic Search

This paper considers the effects of freestream turbulence intensity on the boundary layer transition over a range of Reynolds numbers. Bypass mode of transition has been considered using a flat plate with a C4 leading edge, designed to avoid laminar separation. This configuration provides the opportunity to study the effect of a realistic turbomachinery leading edge shape on transition. Hot

A. I. Kalfas; R. L. Elder

1993-01-01

75

Low Reynolds Number Flow Dynamics of a Thin Airfoil with an Actuated Leading Edge  

E-print Network

Low Reynolds Number Flow Dynamics of a Thin Airfoil with an Actuated Leading Edge Kevin J. Drost of a thin, flat, rigid airfoil, as a poten- tial mechanism for control or improved performance of a micro at low Reynolds numbers. The leading edge of the airfoil is hinged at 30% of the chord length allowing

Apte, Sourabh V.

76

Low Reynolds Number Aerodynamics of Leading Edge Flaps A. R. Jones  

E-print Network

that the leading edge ap functions as a boundary layer trip rather than as a conventional high-lift device and wire trips are ineective at high angles of attack, leading edge aps and wires can greatly improve lift maneuvers requiring high lift coecients at low ight speeds and high angles of attack. Laminar separation

Alonso, Juan J.

77

Preparation and Support of a Tap Test on the Leading Edge Surfaces of the Space Shuttle  

NASA Technical Reports Server (NTRS)

This slide presentation reports on a Tap test for the leading edge surfaces of the Space Shuttle. A description of the Wing Leading Edge Impact Detection System (WLEIDS) flight system is given, and the rationale and approach for improving the WLEIDS system. The three phases of the strategy of the test project amd the results of the tests are reviewed.

Bohr, Jerry

2009-01-01

78

Leading-edge deflection optimization for a highly swept arrow wing configuration  

NASA Technical Reports Server (NTRS)

Tests were also conducted to determine the sensitivity of the lateral stability derivative C sub l sub beta to geometric anhedral. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to the spanwise variation of upwash, the resulting optimized leading edge was a smooth, continuously warped surface. For the particular configuration studied, levels of leading edge suction on the order of 90 percent were achieved with the smooth, continuously warped leading edge contour. The results of tests conducted to determine the sensitivity of C sub l sub beta to geometric anhedral indicate values of delta C sub l sub beta/delta T which are in reasonable agreement with estimates provided by simple vortex lattice theories.

Coe, P. L., Jr.; Huffman, J. K.; Fenbert, J. W.

1980-01-01

79

High-performance wings with significant leading-edge thrust at supersonic speeds  

NASA Technical Reports Server (NTRS)

A new class of curved-leading-edge wings with which significant levels of leading-edge thrust may be achieved at moderate supersonic speeds is suggested. A recent analysis of the factors limiting such leading-edge thrust has led to a new method for the prediction of attainable leading-edge thrust from subsonic through supersonic speeds for wings of arbitrary planform. Recent supersonic tests of a new wing shape, which largely meets design criteria given by the new prediction method, give evidence of significant levels of leading-edge thrust. The consequent unusually high levels of aerodynamic performance should renew interest in supersonic-cruise vehicle design in general and in cruise-speed selection in particular.

Robins, A. W.; Carlson, H. W.

1979-01-01

80

Static and dynamic analysis of a typical wing section with leading edge-trailing edge control surface configuration  

NASA Astrophysics Data System (ADS)

Aeroelastic phenomena have been studied for many years and their effects on flexible structures are well documented. These phenomena are investigated in the following research in a two-fold investigation. The first investigation examines the static characteristics of a wing section with a full span, leading edge-trailing edge control surface configuration. A linear configuration is used in the investigation of control surface reversal and the prevention thereof, with reversal behavior described in terms of roll performance as well as lift effectiveness. Using leading edge control, it is possible to delay reversal, and is accomplished by an appropriate choice of control surface deflections, given in terms of a deflection ratio or gearing ratio. The second investigation examines nonlinear behavior, namely, the occurrence of limit cycle oscillations, in which the nonlinearities occur in the pitch motion. It has been recognized that a multiple control surface configuration provides guarantees on the control capabilities of the aeroelastic system. The use of the multiple control surface configurations, namely, the leading edge-trailing edge control surface configuration, is used herein to suppress limit cycle oscillations. Adaptive control strategies are developed and implemented in wind tunnel experiments.

Platanitis, George

81

A method for computing the leading-edge suction in a higher-order panel method  

NASA Technical Reports Server (NTRS)

Experimental data show that the phenomenon of a separation induced leading edge vortex is influenced by the wing thickness and the shape of the leading edge. Both thickness and leading edge shape (rounded rather than point) delay the formation of a vortex. Existing computer programs used to predict the effect of a leading edge vortex do not include a procedure for determining whether or not a vortex actually exists. Studies under NASA Contract NAS1-15678 have shown that the vortex development can be predicted by using the relationship between the leading edge suction coefficient and the parabolic nose drag. The linear theory FLEXSTAB was used to calculate the leading edge suction coefficient. This report describes the development of a method for calculating leading edge suction using the capabilities of the higher order panel methods (exact boundary conditions). For a two dimensional case, numerical methods were developed using the double strength and downwash distribution along the chord. A Gaussian quadrature formula that directly incorporates the logarithmic singularity in the downwash distribution, at all panel edges, was found to be the best method.

Ehlers, F. E.; Manro, M. E.

1984-01-01

82

Analysis of edge impact stresses in composite plates  

NASA Technical Reports Server (NTRS)

The in-plane edge impact of composite plates, with or without a protection strip, is investigated. A computational analysis based on the Fast Fourier Transform technique is presented. The particular application of the present method is in the understanding of the foreign object damage problem of composite fan blades. The method is completely general and may be applied to the study of other stress wave propagation problems in a half space. Results indicate that for the protective strip to be effective in reducing impact stresses in the composite the thickness must be equal or greater than the impact contact dimension. Large interface shear stresses at the strip - composite boundary can be induced under impact.

Moon, F. C.; Kang, C. K.

1974-01-01

83

Study of supersonic wings employing the attainable leading-edge thrust concept  

NASA Technical Reports Server (NTRS)

A theoretical study was made of supersonic wing geometries at Mach 1.8, using the attainable leading-edge thrust concept. The attainable thrust method offers a powerful means to improve overall aerodynamic efficiency by identifying wing leading-edge geometries that promote attached flow and by defining a local angle-of-attack range over which attached flow may be obtained. The concept applies to flat and to cambered wings, which leads to the consideration of drooped-wing leading edges for attached flow at high lift coefficients.

Middleton, W. D.

1982-01-01

84

Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels using LS-DYNA  

NASA Technical Reports Server (NTRS)

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using 'physics-based- codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which issued because of its thermal properties to protect the shuttle during re-entry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of individual foam cylinders impacting 6-in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Fasanella, Edwin; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2008-01-01

85

Dynamics Impact Tolerance of Shuttle RCC Leading Edge Panels Using LS-DYNA  

NASA Technical Reports Server (NTRS)

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using physics-based codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which is used because of its thermal properties to protect the shuttle during reentry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of foam cylinders impacting 6- in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2005-01-01

86

Simulated airline service experience with laminar-flow control leading-edge systems  

NASA Technical Reports Server (NTRS)

The first JetStar leading edge flight test was made November 30, 1983. The JetStar was flown for more than 3 years. The titanium leading edge test articles today remain in virtually the same condition as they were in on that first flight. No degradation of laminar flow performance has occurred as a result of service. The JetStar simulated airline service flights have demonstrated that effective, practical leading edge systems are available for future commercial transports. Specific conclusions based on the results of the simulated airline service test program are summarized.

Maddalon, Dal V.; Fisher, David F.; Jennett, Lisa A.; Fischer, Michael C.

1987-01-01

87

Experimental evaluation of joint designs for a space-shuttle orbiter ablative leading edge  

NASA Technical Reports Server (NTRS)

The thermal performance of two types of ablative leading-edge joints for a space-shuttle orbiter were tested and evaluated. Chordwise joints between ablative leading-edge segments, and spanwise joints between ablative leading-edge segments and reusable surface insulation tiles were exposed to simulated shuttle heating environments. The data show that the thermal performance of models with chordwise joints to be as good as jointless models in simulated ascent-heating and orbital cold-soak environments. The suggestion is made for additional work on the joint seals, and, in particular, on the effects of heat-induced seal-material surface irregularities on the local flow.

Tompkins, S. S.; Kabana, W. P.

1975-01-01

88

Effect of leading-edge load constraints on the design and performance of supersonic wings  

NASA Technical Reports Server (NTRS)

A theoretical and experimental investigation was conducted to assess the effect of leading-edge load constraints on supersonic wing design and performance. In the effort to delay flow separation and the formation of leading-edge vortices, two constrained, linear-theory optimization approaches were used to limit the loadings on the leading edge of a variable-sweep planform design. Experimental force and moment tests were made on two constrained camber wings, a flat uncambered wing, and an optimum design with no constraints. Results indicate that vortex strength and separation regions were mildest on the severely and moderately constrained wings.

Darden, C. M.

1985-01-01

89

Edge crack growth of thermally aged graphite/polyimide composites  

NASA Technical Reports Server (NTRS)

Laminates of Celion 6000/LARC-160 and Celion 6000/PMR-15 graphite/polyimide composite materials were aged in air at temperatures of 202, 232, 260 and 288 C for various times up to 15,000 hours. Three unidirectional specimen types were studied: short beam shear (SBS), flexure, and 153 mm square panels. The interior region of the square panels exhibited little or no property degradation, whereas both laminate materials degraded and cracked preferentially at the specimen edge perpendicular to the fibers. Using a dye penetrant, the specimens were X-rayed and the crack depth measured as a function of time and temperature. A time temperature superposition of the crack data was successfully performed using an Arrhenius form for the shift factor. A direct correlation was found for edge crack depth and SBS strength for the LARC-160 laminates but the correlation for PMR-15 laminates was more complex.

Nelson, J. B.

1984-01-01

90

Influence of flow injection angle on a leading-edge horseshoe vortex Alan A. Thrift  

E-print Network

-edge obstruction as in the case of a pin fin within a channel or a nozzle guide vane in a gas turbine engine channel, an increase in heat transfer for a gas turbine airfoil can be detrimental to the component life placed upstream of a vane leading-edge with four injection angles of 90°, 65°, 45°, and 30°. Results

Thole, Karen A.

91

Spanwise visualization of the flow around a three-dimensional foil with leading edge protuberances  

NASA Astrophysics Data System (ADS)

Studies of model humpback whale fins have shown that leading edge protuberances, or tubercles, can lead to delayed stall and increased lift at higher angles of attack, compared to foils with geometrically smooth leading edges. Such enhanced performance characteristics could prove highly useful in underwater vehicles such as gliders or long range AUVs (autonomous underwater vehicles). In this work, Particle Imaging Velocimetry (PIV) is performed on two static wings in a water tunnel over a range of angles of attack. These three- dimensional, finite-aspect ratio wings are modeled after a humpback whale flipper and are identical in shape, tapered from root to tip, except for the leading edge. In one of the foils the leading edge is smooth, whereas in the other, regularly spaced leading edge bumps are machined to simulate the whale’s fin tubercles. Results from these PIV tests reveal distinct cells where coherent flow structures are destroyed as a result of the leading edge perturbations. Tests are performed at Reynolds numbers Re ˜ O(10^5), based on chordlength, in a recirculating water tunnel. An inline six-axis load cell is mounted to measure the forces on the foil over a range of static pitch angles. It is hypothesized that this spanwise breakup of coherent vortical structures is responsible for the delayed angle of stall. These quantitative experiments complement exiting qualitative studies with two dimensional foils.

Stanway, M. J.; Techet, A. H.

2006-11-01

92

Effect of leading edge roundness on a delta wing in wing-rock motion  

NASA Technical Reports Server (NTRS)

The effect of wing leading-edge roundness on wing rock was investigated using flow visualization in a water tunnel. Eighty degree delta wing models were tested on free-to-roll and forced oscillation rigs. The onset of wing rock was delayed by increasing the roundness of the leading edges. The wing rock amplitude and frequency results suggested that damping was increased at lower angles of attack but reduced at higher angles of attack. Vortex lift-off and vortex breakdown, especially during dynamic situations, were strongly affected by the leading edge roundness. Different forms of wing rock motion could be sustained by combinations of vortex breakdown and vortex lift-off. Behaviors of the wing and vortex motions were explained by the influence of leading edge roundness on the separation location, vortex trajectory, and vortex breakdown.

Ng, T. Terry; Malcolm, Gerald N.

1990-01-01

93

Hydrodynamic effects of leading-edge tubercles on control surfaces and in flapping foil propulsion  

E-print Network

This thesis investigates the hydrodynamic effects of biologically-inspired leading-edge tubercles. Two complementary studies examine the performance of three-dimensional hydrofoils based on the pectoral flippers of the ...

Stanway, Michael Jordan

2008-01-01

94

User's manual for interfacing a leading edge, vortex rollup program with two linear panel methods  

NASA Technical Reports Server (NTRS)

Sufficient instructions are provided for interfacing the Mangler-Smith, leading edge vortex rollup program with a vortex lattice (POTFAN) method and an advanced higher order, singularity linear analysis for computing the vortex effects for simple canard wing combinations.

Desilva, B. M. E.; Medan, R. T.

1979-01-01

95

Manipulation of upstream rotor leading edge vortex and its effects on counter rotating propeller noise  

NASA Technical Reports Server (NTRS)

The leading edge vortex of a counter rotating propeller (CRP) model was altered by using shrouds and by turning the upstream rotors to a forward sweep configuration. Performance, flow, and acoustic data were used to determine the effect of vortex impingement on the noise signature of the CRP system. Forward sweep was found to eliminate the leading edge vortex of the upstream blades. Removal of the vortex had little effect on the tone noise at the forward and rear blade passing frequencies (BPF's) but significantly altered both the sound pressure level and directivity of the interaction tone which occurs at the sum of the two BPF's. A separate manipulation of the leading edge vortex performed by installing shrouds of various inlet length on the CRP verified that diverting the vortex path increases the noise level of the interaction tone. An unexpected link has been established between the interaction tone and the leading edge vortex-blade interaction phenomenon.

Squires, Becky

1993-01-01

96

Heat transfer characteristics of hypersonic waveriders with an emphasis on the leading edge effects. M.S. Thesis, 1991  

NASA Technical Reports Server (NTRS)

The heat transfer characteristics in surface radiative equilibrium and the aerodynamic performance of blunted hypersonic waveriders are studied along two constant dynamic pressure trajectories for four different Mach numbers. The inviscid leading edge drag was found to be a small (4 to 8 percent) but not negligible fraction of the inviscid drag of the vehicle. Although the viscous drag at the leading edge can be neglected, the presence of the leading edge will influence the transition pattern of the upper and the lower surfaces and therefore affect the viscous drag of the entire vehicle. For an application similar to the National Aerospace Plane (NASP), the present study demonstrates that the waverider remains a valuable concept at high Mach numbers if a state-of-the-art active cooling device is used along the leading edge. At low Mach number (less than 5), the study shows the surface radiative cooling might be sufficient. In all cases, radiative cooling is sufficient for the upper and lower surfaces of the vehicle if ceramic composites are used as thermal protection.

Vanmol, Denis O.; Anderson, John D., Jr.

1992-01-01

97

Small Leading-Edge Flap for Flow Control on a 45Deg Delta Wing  

Microsoft Academic Search

The characteristics of rolling moment in a 45-deg delta wing with a leading-edge flap were studied to examine its effects in pre- and post-stall regimes, where conventional control surfaces are ineffective. A small flap with a height of 2mm was employed to control the flow, which was placed on the round leading-edge of the delta wing from 10 to 75%

Takashi Matsuno; Shigeru Yokouchi; Yoshiaki Nakamura

2004-01-01

98

Leading Edge Aerothermal Inverse Design of Hyersonic Vehicle Based on Homotopy Optimization Method  

NASA Astrophysics Data System (ADS)

Blunt leading edge with profiles of circular or power law shape is often used to decrease the aerodynamic heating of a vehicle when it flights into hypersonic regime. In order to further reduce the peak of heat flux of the leading edge, an inverse shape design method is presented in this paper. The leading edge is parameterized by using B-spline curve method. The hypersonic flow field and the heat flux distribution around the leading edge is evaluated by computational fluid dynamics. A homotopy method is developed as the optimizer. The computational heat flux distribution is driven by the optimizer to meet the objective . In order to verify the validity of the method, the inverse aerothermal design of a 2D leading edge with the thickness of 5 mm was carried out in the design condition Mach number is 6.5. The initial profile of the leading edge approximates to a circular arc. An H-type structured grid was used to discrete the computational domain. A 2D thin-layer Reynolds-averaged Navier-Stokes equations in strong conservation law form was employed as the solver. The results have shown that the peak value of the heat flux decreases about 4.6%.

Cui, K.; Hu, S. C.; Gao, T. Y.; Wang, X. P.; Yang, G. W.

2011-09-01

99

Hypersonic Engine Leading Edge Experiments in a High Heat Flux, Supersonic Flow Environment  

NASA Technical Reports Server (NTRS)

A major concern in advancing the state-of-the-art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of withstanding the sustained high thermal loads expected during hypersonic flight. Three aerothermal load related concerns are the boundary layer transition from laminar to turbulent flow, articulating panel seals in high temperature environments, and strut (or cowl) leading edges with shock-on-shock interactions. A multidisciplinary approach is required to address these technical concerns. A hydrogen/oxygen rocket engine heat source has been developed at the NASA Lewis Research Center as one element in a series of facilities at national laboratories designed to experimentally evaluate the heat transfer and structural response of the strut (or cowl) leading edge. A recent experimental program conducted in this facility is discussed and related to cooling technology capability. The specific objective of the experiment discussed is to evaluate the erosion and oxidation characteristics of a coating on a cowl leading edge (or strut leading edge) in a supersonic, high heat flux environment. Heat transfer analyses of a similar leading edge concept cooled with gaseous hydrogen is included to demonstrate the complexity of the problem resulting from plastic deformation of the structures. Macro-photographic data from a coated leading edge model show progressive degradation over several thermal cycles at aerothermal conditions representative of high Mach number flight.

Gladden, Herbert J.; Melis, Matthew E.

1994-01-01

100

Boundary layer receptivity to free-stream sound on elliptic leading edges of flat plates  

NASA Astrophysics Data System (ADS)

The leading-edge receptivity to acoustic waves of two-dimensional bodies is investigated using a spatial solution of the Navier Stokes equations in vorticity/stream function form in general curvilinear coordinates. The free stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke (1998), in which the solution for the basic flow and the linearized perturbation flow are solved separately. The initial motivation for the work comes from past physical experiments for flat plates with elliptic leading edges, which indicated narrow frequency bands of higher neutral-curve Branch I receptivity. We investigate the same conditions in our simulations, as well as on a parabolic leading edge. The results document the importance of the leading edge, junction between the ellipse and flat plate, and pressure gradient to the receptivity coefficient at Branch I. Comparisons to the past experiments and other numerical simulations showed the influence of the elliptic leading-edge/flat-plate joint as an additional site of receptivity which, along with the leading edge, provides a wavelength selection mechanism which favours certain frequencies through linear superposition.

Wanderley, Juan B. V.; Corke, Thomas C.

2001-02-01

101

STUDIES ON EFFECTS OF PERIODIC WAKE PASSING UPON A BLADE LEADING EDGE SEPARATION BUBBLE : TRANSITIONAL BEHAVIORS OF SEPARATED BOUNDARY LAYER  

Microsoft Academic Search

This paper describes an experimental investigation on aerody- namic interaction between incoming periodic wakes and leading edge separation bubble on a compressor or turbine blade, using a scaled leading edge model that consists of a semi-circular leading edge and two flat-plates. Cylindrical bars of the wake generator produce the periodic wakes in front of the test model. The study aims

K. Funazaki; K. Yamada; Y. Kato

2003-01-01

102

Numerical prediction of vortex cores of the leading and trailing edges of delta wings  

NASA Technical Reports Server (NTRS)

The purpose of the present paper is to predict the roll-up of the vortex sheets emanating from the leading- and trailing-edges of delta wings with emphasis on the interaction of vortex cores beyond the trailing edge. The motivation behind the present work is the recent experimental data published by Hummel. The Nonlinear Discrete-Vortex method (NDV-method) is modified and extended to predict the leading- and trailing-vortex cores beyond the trailing edge. The present model alleviates the problems previously encountered in predicting satisfactory pressure distributions. This is accomplished by lumping the free-vortex lines during the iteration procedure. The leading- and trailing-edge cores and their feeding sheets are obtained as parts of the solution. The numerical results show that the NDV-method is successful in confirming the formation of a trailing-edge core with opposite circulation and opposite roll-up to those of the leading-edge core. This work is a breakthrough in the high angle of attack aerodynamics and moreover, it is the first numerical prediction done on this problem

Kandil, O. A.

1980-01-01

103

Evaluation of cloud detection instruments and performance of laminar-flow leading-edge test articles during NASA Leading-Edge Flight-Test Program  

NASA Technical Reports Server (NTRS)

Summary evaluations of the performance of laminar-flow control (LFC) leading edge test articles on a NASA JetStar aircraft are presented. Statistics, presented for the test articles' performance in haze and cloud situations, as well as in clear air, show a significant effect of cloud particle concentrations on the extent of laminar flow. The cloud particle environment was monitored by two instruments, a cloud particle spectrometer (Knollenberg probe) and a charging patch. Both instruments are evaluated as diagnostic aids for avoiding laminar-flow detrimental particle concentrations in future LFC aircraft operations. The data base covers 19 flights in the simulated airline service phase of the NASA Leading-Edge Flight-Test (LEFT) Program.

Davis, Richard E.; Maddalon, Dal V.; Wagner, Richard D.; Fisher, David F.; Young, Ronald

1989-01-01

104

A three-dimensional solution of flows over wings with leading-edge vortex separation  

NASA Technical Reports Server (NTRS)

The application of a new, general, potential flow computational technique to the solution of the subsonic, three-dimensional flow over wings with leading-edge vortex separation is presented. The present method is capable of predicting forces, moments, and detailed surface pressures on thin, sharp-edged wings of rather arbitrary planform. The wing geometry is arbitrary in the sense that leading and trailing edges may be curved or kinked and the wing may have arbitrary camber and twist. The method employs an inviscid flow model in which the wing, the rolled-up vortex sheets, and the wake are represented by piecewise continuous quadratic doublet sheet distributions. The Kutta condition is imposed along all wing edges. Strengths of the doublet distributions as well as shape and position of the free fortex sheet spirals are computed in iterative fashion starting with an assumed initial sheet geometry. The method is verified by numerous computed results.

Weber, J. A.; Brune, G. W.; Johnson, F. T.; Lu, P.; Rubbert, P. E.

1975-01-01

105

Subsonic balance and pressure investigation of a 60 deg delta wing with leading edge devices  

NASA Technical Reports Server (NTRS)

Low supersonic wave drag makes the thin highly swept delta wing the logical choice for use on aircraft designed for supersonic cruise. However, the high-lift maneuver capability of the aircraft is limited by severe induced-drag penalties attributed to loss of potential flow leading-edge suction. This drag increase may be alleviated through leading-edge flow control to recover lost aerodynamic thrust through either retention of attached leading-edge flow to higher angles of attack or exploitation of the increased suction potential of separation-induced vortex flow. A low-speed wind-tunnel investigation was undertaken to examine the high-lift devices such as fences, chordwise slots, pylon vortex generators, leading-edge vortex flaps, and sharp leading-edge extensions. The devices were tested individually and in combinations in an attempt to improve high-alpha drag performance with a minimum of low-alpha drag penalty. This report presents an analysis of the force, moment, and static pressure data obtained in angles of attack up to 23 deg, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter, respectively. The results indicate that all the devices produced drag and longitudinal/lateral stability improvements at high lift with, in most cases, minor drag penalties at low angles of attack.

Tingas, S. A.; Rao, D. M.

1982-01-01

106

Transonic flight test of a laminar flow leading edge with surface excrescences  

NASA Technical Reports Server (NTRS)

A flight experiment, conducted at NASA Dryden Flight Research Center, investigated the effects of surface excrescences, specifically gaps and steps, on boundary-layer transition in the vicinity of a leading edge at transonic flight conditions. A natural laminar flow leading-edge model was designed for this experiment with a spanwise slot manufactured into the leading-edge model to simulate gaps and steps like those present at skin joints of small transonic aircraft wings. The leading-edge model was flown with the flight test fixture, a low-aspect ratio fin mounted beneath an F-104G aircraft. Test points were obtained over a unit Reynolds number range of 1.5 to 2.5 million/ft and a Mach number range of 0.5 to 0.8. Results for a smooth surface showed that laminar flow extended to approximately 12 in. behind the leading edge at Mach number 0.7 over a unit Reynolds number range of 1.5 to 2.0 million/ft. The maximum size of the gap-and-step configuration over which laminar flow was maintained consisted of two 0.06-in. gaps with a 0.02-in. step at a unit Reynolds number of 1.5 million/ft.

Zuniga, Fanny A.; Drake, Aaron; Kennelly, Robert A., Jr.; Koga, Dennis J.; Westphal, Russell V.

1994-01-01

107

Multiple laminar-turbulent transition cycles around a swept leading edge  

NASA Astrophysics Data System (ADS)

Certain interesting flow features involving multiple transition/relaminarization cycles on the leading edge of a swept wing at low speeds are reported here. The wing geometry tested had a circular nose and a leading edge sweep of 60°. Tests were made at a chord Reynolds number of 1.3 × 106 with model incidence ? varied in the range of 3°-18° in discrete steps. Measurements made included wing chord-wise surface pressure distributions and wall shear stress fluctuations (using hot-film gages) within about 10 % of the chord in the leading edge zone. Results at ? = 16° and 18° showed that several (often incomplete) transition cycles between laminar-like and turbulent-like flows occurred. These rather surprising results are attributable chiefly to the fact that the Launder acceleration parameter K (appropriately modified for swept wings) can exceed a critical range more than once along the contour of the airfoil in the leading edge region. Each such crossing results in a relaminarization followed by direct retransition to turbulence as K drops to sufficiently low values. It is further shown that the extent of each observed transition zone (of either type) is consistent with earlier data acquired in more detailed studies of direct transition and relaminarization. Swept leading edge boundary layers therefore pose strong challenges to numerical modelling.

Mukund, R.; Narasimha, R.; Viswanath, P. R.; Crouch, J. D.

2012-12-01

108

Modeling Creep-Induced Stress Relaxation at the Leading Edge of SiC/SiC Airfoils  

NASA Technical Reports Server (NTRS)

Anticipating the implementation of advanced SiC/SiC composites into internally cooled airfoil components within the turbine section of future aero-propulsion engines, the primary objective of this study was to develop physics-based analytical and finite-element modeling tools to predict the effects of composite creep and stress relaxation at the airfoil leading edges, which will generally experience large thermal gradients at high temperatures. A second objective was to examine how some advanced NASA-developed SiC/SiC systems coated with typical EBC materials would behave as leading edge materials in terms of long-term steady-state operating temperatures. Because of the complexities introduced by mechanical stresses inherent in internally cooled airfoils, a simple cylindrical thin-walled tube model subjected to thermal stresses only is employed for the leading edge, thereby obtaining a best-case scenario for the material behavior. In addition, the SiC/SiC composite materials are assumed to behave as isotropic materials with temperature-dependent viscoelastic creep behavior as measured in-plane on thin-walled panels. Key findings include: (1) without mechanical stresses and for typical airfoil geometries, as heat flux is increased through the leading edge, life-limiting tensile crack formation will occur first in the hoop direction on the inside wall of the leading edge; (2) thermal gradients through all current SiC/SiC systems should be kept below approx.300 F at high temperatures to avoid this cracking; (3) at temperatures near the maximum operating temperatures of advanced SiC/SiC systems, thermal stresses induced by the thermal gradients will beneficially relax with time due to creep; (4) although stress relaxation occurs, the maximum gradient should still not exceed 300oF because of residual tensile stress buildup on the airfoil outer wall during cool-down; and (5) without film cooling and mechanical stresses, the NASA-developed N26 SiC/SiC system with thru-thickness Sylramic-iBN fiber reinforcement and a typical EBC coating has the potential of offering a maximum long-term steady-state operating temperature of approx.3100 F at the surface of the EBC.

Lang, Jerry; DiCarlo, James A.

2007-01-01

109

Wind-tunnel investigation of leading-edge thrust on arrow wings in supersonic flow  

NASA Technical Reports Server (NTRS)

Six wing models were tested in the Langley Unitary Plan Wind Tunnel to identify and study leading-edge thrust at supersonic speeds. The tests were conducted at Mach numbers of 1.6, 1.8, 2.0, and 2.16, at a stagnation temperature of 125.0 F, and at Reynolds numbers per foot of 2.0 x 10 to the 6th power and 5.0 x 10 the 6th power. Test results showed that significant benefits from leading-edge thrust and nonlinear thickness effects can be obtained with very little airfoil bluntness, that these benefits were lost when the airfoil was severely blunted, and that such benefits seem to be found on wings with supersonic as well as subsonic leading edges.

Mack, R. J.

1983-01-01

110

Effect of leading-edge porosity on blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

The effect of the porous leading-edge of an airfoil on the blade-vortex interaction noise, which dominates far-field acoustic spectrum of the helicopter, is investigated. The thin-layer Navier-Stokes equations are solved with a high-order upwind-biased scheme and a multizonal grid system. The Baldwin-Lomax turbulence model is modified for considering transpiration on the surface. The amplitudes of the propagating acoustic wave in the near-field are calculated directly from the computation. The porosity effect on the surface is modeled. Results show leading-edge transpiration can suppress pressure fluctuations at the leading-edge during BVI, and consequently reduce the amplitude of propagating noise by 30 percent at maximum in the near-field. The effect of porosity factor on the noise level is also investigated.

Lee, Soogab

1993-01-01

111

A feasibility study of heat-pipe-cooled leading edges for hypersonic cruise aircraft  

NASA Technical Reports Server (NTRS)

A theoretical study of the use of heat pipe structures for cooling the leading edges of hypersonic cruise aircraft was carried out over a Mach number range of 6 to 12. Preliminary design studies showed that a heat pipe cooling structure with a 33-in. chordwise length could maintain the maximum temperature of a 65 deg sweepback wing with a 0.5-in. leading edge radius below 1600 F during cruise at Mach 8. A few relatively minor changes in the steady-state design of the structure were found necessary to insure satisfactory cooling during the climb to cruise speed and altitude. It was concluded that heat pipe cooling is an attractive, feasible technique for limiting leading edge temperatures of hypersonic cruise aircraft.

Silverstein, C. C.

1971-01-01

112

Low Reynolds Number Flow Dynamics of a Thin, Flat Airfoil with Elastically Mounted Leading Edge Actuator  

NASA Astrophysics Data System (ADS)

Direct numerical simulations are performed to investigate the effect of an elastically mounted leading edge actuator on the unsteady flow at high angles of attack over a flat, thin airfoil at Reynolds number of 14700 based on the chord length. The leading edge actuator is mounted with a torsion spring at one-third the chord length allowing dynamic variations in the effective angle of attack through flow-induced oscillations. The goal is to investigate potential benefits of flow induced flapping motion of the leading edge actuator to the lift and drag characteristics of thin airfoils. The structural model for the rigid actuator is based on a torsional spring-mounted compound pendulum. A fictitious-domain based finite volume approach [(Apte et al. (JCP 2009)] is used to compute this fluid-structure interaction problem on a fixed background mesh. It is shown that a lock-in region leading to limit cycle oscillations of the leading edge actuator can be achieved for certain spring parameters leading to improvements in mean lift-to-drag ratio.

Apte, Sourabh

2011-11-01

113

Summary of past experience in natural laminar flow and experimental program for resilient leading edge  

NASA Technical Reports Server (NTRS)

The potential of natural laminar flow for significant drag reduction and improved efficiency for aircraft is assessed. Past experience with natural laminar flow as reported in published and unpublished data and personal observations of various researchers is summarized. Aspects discussed include surface contour, waviness, and smoothness requirements; noise and vibration effects on boundary layer transition, boundary layer stability criteria; flight experience with natural laminar flow and suction stabilized boundary layers; and propeller slipstream, rain, frost, ice and insect contamination effects on boundary layer transition. The resilient leading edge appears to be a very promising method to prevent leading edge insect contamination.

Carmichael, B. H.

1979-01-01

114

The influence of leading-edge thrust on twisted and cambered wing design for supersonic cruise  

NASA Technical Reports Server (NTRS)

A study of leading-edge thrust phenomena at supersonic speeds has shown that although these forces are not large, they can be a significant factor in the design of wings for supersonic cruise. It is seen that the rather severe twisted and cambered wing surfaces resulting from the application of present design methods, which ignore leading-edge thrust, can be replaced by more moderate surfaces with little or no loss in aerodynamic efficiency if realistic possibilities for the attainment of some fraction of the theoretical thrust are taken into account.

Carlson, H. W.; Miller, D. S.

1981-01-01

115

The effects of a jet on vortex breakdown over a sharp leading-edge delta wing  

E-print Network

THE EFFECTS OF A JET ON VORTEX BREAKDOWN OVER A SHARP LEADING-EDGE DELTA WING A Thesis Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1985... Major Subject: Aerospace Engineering THE EFFECTS OF A JET ON VORTEX BREAKDOWN OVER A SHARP LEADING-EDGE DELTA WING A Thesis by IAN KENNETH MAYNARD Approved as to style and content by: Cyrus Ostowar (Chairman of Committee) Stan J Miley (M er...

Maynard, Ian Kenneth

2012-06-07

116

A leading edge heating array and a flat surface heating array - operation, maintenance and repair manual  

NASA Technical Reports Server (NTRS)

A general description of the leading edge/flat surface heating array is presented along with its components, assembly instructions, installation instructions, operation procedures, maintenance instructions, repair procedures, schematics, spare parts lists, engineering drawings of the array, and functional acceptance test log sheets. The proper replacement of components, correct torque values, step-by-step maintenance instructions, and pretest checkouts are described.

1975-01-01

117

Leading Edge 184 Cell 142, July 23, 2010 2010 Elsevier Inc.  

E-print Network

Leading Edge Essay 184 Cell 142, July 23, 2010 ©2010 Elsevier Inc. Perception, action, and cognition in higher vertebrates all depend crucially on the neocortex. Reflecting these many roles, for example, can respond preferentially to a specific face, to a specific auditory tone, or to taps

Moore, Christopher

118

CARMIL leading edge localization depends on a non-canonical PH domain and dimerization  

PubMed Central

CARMIL is a ~1370 amino acid cytoskeletal scaffold that plays crucial roles in cell motility and tissue development through interactions with cytoskeletal effectors and regulation of capping protein at the leading edge. However, the mechanism of CARMIL leading edge localization is unknown. Here we show that CARMIL interacts directly with the plasma membrane through its N-terminal region. The crystal structure of CARMIL1-668 reveals that this region harbors a non-canonical pleckstrin homology (PH) domain connected to a 16 leucine-rich repeat domain. Lipid binding is mediated by the PH domain, but is further enhanced by a central helical domain. Small angle x-ray scattering reveals that the helical domain mediates antiparallel dimerization, properly positioning the PH domains for simultaneous membrane interaction. In cells, deletion of the PH domain impairs leading edge localization. The results support a direct membrane binding mechanism for CARMIL localization at the leading edge, where it regulates cytoskeletal effectors and motility. PMID:24071777

Zwolak, Adam; Yang, Changsong; Feeser, Elizabeth A.; Ostap, E. Michael; Svitkina, Tatyana; Dominguez, Roberto

2013-01-01

119

Effects of Fin Leading Edge Sweep on Shock-Shock Interaction at Mach 6  

NASA Technical Reports Server (NTRS)

The effects of fin leading edge sweep on peak heating rates due to shock-shock interaction have been experimentally examined in the Langley 20-Inch Mach 6 Tunnel. The shock interaction was produced by the intersection of a planar incident shock (16.8 deg shock angle relative to the freestream, generated by a 9 deg wedge) with the bow shock formed around a O.5-inch diameter cylindrical leading edge fin. Heating distributions along the leading edge stagnation line have been obtained using densely spaced thin film resistive-type sensors. Schlieren images were obtained to illustrate the very complex shock-shock interactions. The fin leading edge sweep angle was varied from 15-degrees swept back to 45-degrees swept forward for a freestream unit Reynolds number of 2 x 10(exp 6)/ft. Two models were utilized during the study, one with 0.025-inch spacing between gage centers, and the other 0.015-inch spacing. Gage spatial resolution on the order of 0.015-in appeared to accurately capture the narrow spike in heating. Peak heating due to shock interaction was maximized when the fin was swept forward 15 deg and 25 deg, both promoting augmentations about 7 times the baseline value. The schlieren images for these cases revealed Type 4 and Type 3 interactions, respectively.

Berry, Scott A.; Nowak, Robert J.

1996-01-01

120

The Leading Edge: Competencies for Community College Leadership in the New Millennium.  

ERIC Educational Resources Information Center

Published in collaboration with the National Institute for Leadership Development (NILD), this monograph reports on a study of leading-edge community college presidents. The authors cluster the 22 competencies identified through the study into four categories. Each category is presented as a chapter which identifies and provides examples of the…

Desjardins, Carolyn

121

Control of Leading-Edge Separation by Periodic Forcing Yuli Lifshitz*, David Degani  

E-print Network

of incompressible laminar flow with periodic perturbations. This model is based on the decomposition of flow the excitation is inserted in the flow on the possibility of the separation control is analyzed in the presentControl of Leading-Edge Separation by Periodic Forcing Yuli Lifshitz*, David Degani Technion

Kaplan, Alexander

122

Direct numerical simulations of leading-edge receptivity for freestream sound  

NASA Technical Reports Server (NTRS)

The objective of this paper is to review our efforts in spatial direct numerical simulations for modeling leading-edge receptivity to freestream sound and vorticity. These results begin to provide the link between the freestream and the initial boundary-layer response and can provide the upstream conditions for further simulations marching through the transition process toward turbulence.

Fuciarelli, David A.; Reed, Helen L.

1994-01-01

123

Tests on a sodium/Hastelloy X wing leading edge heat pipe for hypersonic vehicles  

NASA Technical Reports Server (NTRS)

A full-scale, internally instrumented, sodium/Hastelloy X heat pipe was designed and fabricated for the wing leading edge of an advanced reentry vehicle. A computer model was developed to predict the heat pipe startup. The heat pipe was tested, and the results were used to validate the startup methodologies. In addition, valuable fabrication and test procedure lessons were learned.

Boman, B. L.; Elias, T. I.

1990-01-01

124

Evaluation of a sodium/Hastelloy-X heat pipe for wing leading edge cooling  

SciTech Connect

This report covers assembly of a sodium heat pipe, testing to verify performance during start-up and under steady-state conditions with stagnation point heat loads to about 80 W/cm{sup 2}, performance analysis and evaluation. Evaluation of this leading edge cooling concept is offered and recommendations for further research discussed.

Merrigan, M.A.; Sena, J.T. [Los Alamos National Lab., NM (United States); Glass, D.E. [Analytical Services and Materials, Hampton, VA (United States)

1996-12-31

125

Leading Edge Cell 128, February 9, 2007 2007 Elsevier Inc. 441  

E-print Network

Leading Edge Minireview Cell 128, February 9, 2007 ©2007 Elsevier Inc. 441 Current thinking about residues. These changes depend on subtle details of the folding energy landscape of the protein, and thus protein-coupled receptor on a haploid yeast cell. This causes the release of a G dimer from a trimeric G

126

Leading Edge Cell 126, September 22, 2006 2006 Elsevier Inc. 1017  

E-print Network

to the manip- ulation of stem cells and attempts at tissue regeneration. These biomedi- cal merits clearly or aging, how- ever. It was found as a solution to one of the most basic problems in cell biologyLeading Edge Essay Cell 126, September 22, 2006 ©2006 Elsevier Inc. 1017 On September 29, the 2006

de Lange, Titia

127

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 2: Modelling of Impact with SPH Bird Model  

Microsoft Academic Search

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts such as runway debris or bird strikes. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built,

M. A. McCarthy; J. R. Xiao; C. T. McCarthy; A. Kamoulakos; J. Ramos; J. P. Gallard; V. Melito

2004-01-01

128

Power law shapes for leading-edge blunting with minimal standoff distance in low-density hypersonic flow  

NASA Astrophysics Data System (ADS)

The steady-state aerodynamic characteristics of power law shaped leading edges immersed in high-speed rarefied air flow are examined by using a Direct Simulation Monte Carlo method. The work is motivated by interest in investigating power-law shaped leading edges as possible candidates for blunting geometries of hypersonic configurations. The aerodynamic performance of power law shapes is compared to a corresponding round leading edge shape based on equivalent shock standoff distance. For the flow conditions considered, the analysis shows that round leading edges provide smaller stagnation point heating and smaller drag than power law shapes for equivalent shock standoff distance.

Santos, W. F. N.

129

Effects of leading and trailing edge flaps on the aerodynamics of airfoil/vortex interactions  

NASA Technical Reports Server (NTRS)

A numerical procedure has been developed for predicting the two-dimensional parallel interaction between a free convecting vortex and a NACA 0012 airfoil having leading and trailing edge integral-type flaps. Special emphasis is placed on the unsteady flap motion effects which result in alleviating the interaction at subcritical and supercritical onset flows. The numerical procedure described here is based on the implicit finite-difference solutions to the unsteady two-dimensional full potential equation. Vortex-induced effects are computed using the Biot-Savart Law with allowance for a finite core radius. The vortex-induced velocities at the surface of the airfoil are incorporated into the potential flow model via the use of the velocity transpiration approach. Flap motion effects are also modeled using the transpiration approach. For subcritical interactions, our results indicate that trailing edge flaps can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, our results demonstrate the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time-dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented

Hassan, Ahmed A.; Sankar, L. N.; Tadghighi, H.

1994-01-01

130

Boundary Layer Resolved Measurements of Unsteady Leading Edge Separation on a Pitching Airfoil  

NASA Astrophysics Data System (ADS)

When an airfoil pitches rapidly to high angles of attack, the flow can remain attached well beyond the static stall angle. The flow will eventually separate from the leading edge culminating in the formation of the dynamic stall vortex. While this flow has been the subject of numerous studies, the details of the flow within the boundary layer at the onset of separation have not been captured experimentally to date. Using Molecular Tagging Velocimetry (MTV), we have obtained the first boundary layer resolved measurements of flow separation near the leading edge of a pitching airfoil. The data provide a detailed picture of the evolution of the velocity and spanwise vorticity for an airfoil executing a ramp motion trajectory. Results are compared with 2-D Navier-Stokes computations for flow conditions similar to our experiments. The experimental data suggest that the process of boundary layer separation occurs over a shorter time scale, and is more eruptive, than that captured by the computations.

Gendrich, Charles P.; Koochesfahani, Manoochehr

1998-11-01

131

Integrated production overlay field-by-field control for leading edge technology nodes  

NASA Astrophysics Data System (ADS)

As photolithography will continue with 193nm immersion multiple patterning technologies for the leading edge HVM process node, the production overlay requirement for critical layers in logic devices has almost reached the scanner hardware performance limit. To meet the extreme overlay requirements in HVM production environment, this study investigates a new integrated overlay control concept for leading edge technology nodes that combines the run-to-run (R2R) linear or high order control loop, the periodic field-by-field or correction per exposure (CPE) wafer process signature control loop, and the scanner baseline control loop into a single integrated overlay control path through the fab host APC system. The goal is to meet the fab requirements for overlay performance, lower the cost of ownership, and provide freedom of control methodology. In this paper, a detailed implementation of this concept will be discussed, along with some preliminary results.

Chung, Woong Jae; Tristan, John; Gutjahr, Karsten; Subramany, Lokesh; Li, Chen; Sun, Yulei; Yelverton, Mark; Kim, Young Ki; Kim, Jeong Soo; Huang, Chin-Chou Kevin; Pierson, William; Karur-Shanmugam, Ramkumar; Riggs, Brent; Jug, Sven; Robinson, John C.; Yap, Lipkong; Ramanathan, Vidya

2014-04-01

132

Test and Analysis of a Hyper-X Carbon-Carbon Leading Edge Chine  

NASA Technical Reports Server (NTRS)

During parts production for the X43A Mach 10 hypersonic vehicle nondestructive evaluation (NDE) of a leading edge chine detected on imbedded delamination near the lower surface of the part. An ultimate proof test was conducted to verify the ultimate strength of this leading edge chine part. The ultimate proof test setup used a pressure bladder design to impose a uniform distributed pressure field over the bi-planar surface of the chine test article. A detailed description of the chine test article and experimental test setup is presented. Analysis results from a linear status model of the test article are also presented and discussed. Post-test inspection of the specimen revealed no visible failures or areas of delamination.

Smith, Russell W.; Sikora, Joseph G.; Lindell, Michael C.

2005-01-01

133

Heat pipes for wing leading edges of hypersonic vehicles. Final report  

SciTech Connect

Wing leading edge heat pipes were conceptually designed for three types of vehicle: an entry research vehicle, aero-space plane, and advanced shuttle. A full scale, internally instrumented sodium/Hastelloy X heat pipe was successfully designed and fabricated for the advanced shuttle application. The 69.4 inch long heat pipe reduces peak leading edge temperatures from 3500 F to 1800 F. It is internally instrumented with thermocouples and pressure transducers to measure sodium vapor qualities. Large thermal gradients and consequently large thermal stresses, which have the potential of limiting heat pipe life, were predicted to occur during startup. A test stand and test plan were developed for subsequent testing of this heat pipe. Heat pipe manufacturing technology was advanced during this program, including the development of an innovative technique for wick installation.

Boman, B.L.; Citrin, K.M.; Garner, E.C.; Stone, J.E.

1990-01-01

134

Leading-edge receptivity of a hypersonic boundary layer on a flat plate  

Microsoft Academic Search

Experimental investigations of the boundary layer receptivity, on the sharp leading edge of a at plate, to acoustic waves induced by two-dimensional and three- dimensional perturbers, have been performed for a free-stream Mach number M[infty infinity] = 5.92. The fields of controlled free-stream disturbances were studied. It was shown that two-dimensional and three-dimensional perturbers radiate acoustic waves and that these

A. A. Maslov; A. N. Shiplyuk; A. A. Sidorenko; D. Arnal

2001-01-01

135

Simulation of orbital debris impact on the Space Shuttle wing leading edge  

Microsoft Academic Search

A series of three dimensional hypervelocity impact simulations has been performed to study the effects of orbital debris impact on the Space Shuttle wing leading edge. The simulations employed an improved hybrid particle-finite element method and an orthotropic elastic-plastic material model recently developed for reinforced carbon–carbon. The simulation results are consistent with the available experimental data, and suggest the use

Eric P. Fahrenthold; Roque J. Hernandez

2006-01-01

136

The lift of sharp-leading-edged delta wings with blowing  

NASA Technical Reports Server (NTRS)

An analysis of the lift augmentation due to a thin jet of air issuing from a slot along the leading edge of a delta wing is presented. The problem is treated with an extension of the method of Brown and Michael, representing the separated flow on the lee side of the wing by a pair of concentrated vortices and corresponding feeding sheets. It is assumed that the jet is not affected by Coanda forces. The analysis produces qualitative agreement with experiments.

Tavella, D. A.

1985-01-01

137

THERMOVISCOPLASTIC RESPONSE OF HYPERSONIC LEADING EDGE STRUCTURES SUBJECTED TO INTENSE LOCAL HEATING  

Microsoft Academic Search

A hypersonic leading edge structure subjected to intense localized transient heating is modeled using the finite element method and a three-dimensional assembly of CST-DKT plate elements in the shape of a half cylinder and incorporates the large deflection uon Kármán assumptions. The thermoviscoplastic material behavior is characterized by the Bodner-Partom constitutive model. This article compares the results of a dynamic

Ted G. Byrom; David H. Allen

1994-01-01

138

Towards Active Control of Leading Edge Stall by Means of Pneumatic Actuators  

Microsoft Academic Search

This contribution summarizes the flow control research results obtained at TU Braunschweig and their implication for control\\u000a on high-lift devices. The superordinate aim of the examination is the control of leading-edge stall on a two-element airfoil\\u000a by means of dynamic 3D actuators. This is of great practical interest in order to increase the maximum angle of attack and\\/or\\u000a the lift

C. J. Kahler; P. Scholz; J. Ortmanns; R. Radespiel

139

Effect of leading-edge vortex flaps on aerodynamic performance of delta wings  

NASA Technical Reports Server (NTRS)

The effect of leading-edge vortex flaps on the aerodynamic characteristics of highly swept-back wings is analytically investigated, using the free vortex sheet method. The method, based on a three-dimensional inviscid flow model, is an advanced panel type employing quadratic doublet distributions to represent the wing surface, rolled-up vortex sheet and wake and is capable of computing forces, moments and surface pressures.

Reddy, C. S.

1981-01-01

140

Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading-Edge Panels  

NASA Technical Reports Server (NTRS)

The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.

Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.

2011-01-01

141

Visualization of leading edge vortices on a series of flat plate delta wings  

NASA Technical Reports Server (NTRS)

A summary of flow visualization data obtained as part of NASA Grant NAG2-258 is presented. During the course of this study, many still and high speed motion pictures were taken of the leading edge vortices on a series of flat plate delta wings at varying angles of attack. The purpose is to present a systematic collection of photographs showing the state of vortices as a function of the angle of attack for the four models tested.

Payne, Francis M.; Ng, T. Terry; Nelson, Robert C.

1991-01-01

142

The isotopic composition of lead in Easter Island rhyolite  

Microsoft Academic Search

A sample of Cerro Ourito obsidian, a rhyolite from the Mount Ourito flow ; on Easter Island, was analyzed for its lead isotope composition. The isotopic ; compositions of the leads were found to be identical to the compositions found in ; a dredge sample of K-feldspar, which was collected about 1000 miles apart from ; the rhyolite on the

C. Patterson; B. Duffield

1963-01-01

143

LFC leading edge glove flight: Aircraft modification design, test article development and systems integration  

NASA Technical Reports Server (NTRS)

Reduction of skin friction drag by suction of boundary layer air to maintain laminar flow has been known since Prandtl's published work in 1904. The dramatic increases in fuel costs and the potential for periods of limited fuel availability provided the impetus to explore technologies to reduce transport aircraft fuel consumption. NASA sponsored the Aircraft Energy Efficiency (ACEE) program in 1976 to develop technologies to improve fuel efficiency. This report documents the Lockheed-Georgia Company accomplishments in designing and fabricating a leading-edge flight test article incorporating boundary layer suction slots to be flown by NASA on their modified JetStar aircraft. Lockheed-Georgia Company performed as the integration contractor to design the JetStar aircraft modification to accept both a Lockheed and a McDonnell Douglas flight test article. McDonnell Douglas uses a porous skin concept. The report describes aerodynamic analyses, fabrication techniques, JetStar modifications, instrumentation requirements, and structural analyses and testing for the Lockheed test article. NASA will flight test the two LFC leading-edge test articles in a simulated commercial environment over a 6 to 8 month period in 1984. The objective of the flight test program is to evaluate the effectiveness of LFC leading-edge systems in reducing skin friction drag and consequently improving fuel efficiency.

Etchberger, F. R.

1983-01-01

144

Simulation of Flow Through Breach in Leading Edge at Mach 24  

NASA Technical Reports Server (NTRS)

A baseline solution for CFD Point 1 (Mach 24) in the STS-107 accident investigation was modified to include effects of holes through the leading edge into a vented cavity. The simulations were generated relatively quickly and early in the investigation by making simplifications to the leading edge cavity geometry. These simplifications in the breach simulations enabled: 1) A very quick grid generation procedure; 2) High fidelity corroboration of jet physics with internal surface impingements ensuing from a breach through the leading edge, fully coupled to the external shock layer flow at flight conditions. These simulations provided early evidence that the flow through a 2 inch diameter (or larger) breach enters the cavity with significant retention of external flow directionality. A normal jet directed into the cavity was not an appropriate model for these conditions at CFD Point 1 (Mach 24). The breach diameters were of the same order or larger than the local, external boundary-layer thickness. High impingement heating and pressures on the downstream lip of the breach were computed. It is likely that hole shape would evolve as a slot cut in the direction of the external streamlines. In the case of the 6 inch diameter breach the boundary layer is fully ingested.

Gnoffo, Peter A.; Alter, Stephen J.

2004-01-01

145

Controlled vortical flow on delta wings through unsteady leading edge blowing  

NASA Technical Reports Server (NTRS)

The vortical flow over a delta wing contributes an important part of the lift - the so called nonlinear lift. Controlling this vortical flow with its favorable influence would enhance aircraft maneuverability at high angle of attack. Several previous studies have shown that control of the vortical flow field is possible through the use of blowing jets. The present experimental research studies vortical flow control by applying a new blowing scheme to the rounded leading edge of a delta wing; this blowing scheme is called Tangential Leading Edge Blowing (TLEB). Vortical flow response both to steady blowing and to unsteady blowing is investigated. It is found that TLEB can redevelop stable, strong vortices even in the post-stall angle of attack regime. Analysis of the steady data shows that the effect of leading edge blowing can be interpreted as an effective change in angle of attack. The examination of the fundamental time scales for vortical flow re-organization after the application of blowing for different initial states of the flow field is studied. Different time scales for flow re-organization are shown to depend upon the effective angle of attack. A faster response time can be achieved at angles of attack beyond stall by a suitable choice of the initial blowing momentum strength. Consequently, TLEB shows the potential of controlling the vortical flow over a wide range of angles of attack; i.e., in both for pre-stall and post-stall conditions.

Lee, K. T.; Roberts, Leonard

1990-01-01

146

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation  

Microsoft Academic Search

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density

Kelly Carney; Matthew Melis; Edwin L. Fasanella; Karen H. Lyle; Jonathan Gabrys

147

Case Studies of Leading Edge Small Urban High Schools. Core Academic Strategic Designs: 2. Noble Street Charter High School  

ERIC Educational Resources Information Center

This report is one of nine detailed case studies of small urban high schools that served as the foundation for the Education Resource Strategies (ERS) report "Strategic Designs: Lessons from Leading Edge Small Urban High Schools." These nine schools were dubbed "Leading Edge Schools" because they stand apart from other high schools across the…

Shields, Regis Anne; Ireland, Nicole; City, Elizabeth; Derderian, Julie; Miles, Karen Hawley

2008-01-01

148

Case Studies of Leading Edge Small Urban High Schools. Personalization Strategic Designs: 9. MetWest High School  

ERIC Educational Resources Information Center

This report is one of nine detailed case studies of small urban high schools that served as the foundation for the Education Resource Strategies (ERS) report "Strategic Designs: Lessons from Leading Edge Small Urban High Schools." These nine schools were dubbed "Leading Edge Schools" because they stand apart from other high schools across the…

Shields, Regis Anne; Ireland, Nicole; City, Elizabeth; Derderian, Julie; Miles, Karen Hawley

2008-01-01

149

Case Studies of Leading Edge Small Urban High Schools. Relevance Strategic Designs: 8. High Tech High School  

ERIC Educational Resources Information Center

This report is one of nine detailed case studies of small urban high schools that served as the foundation for the Education Resource Strategies (ERS) report "Strategic Designs: Lessons from Leading Edge Small Urban High Schools." These nine schools were dubbed "Leading Edge Schools" because they stand apart from other high schools across the…

Shields, Regis Anne; Ireland, Nicole; City, Elizabeth; Derderian, Julie; Miles, Karen Hawley

2008-01-01

150

Lead isotopic compositions of ash sourced from Australian bushfires.  

PubMed

This study identifies natural and industrial lead remobilized in ash deposits from three bushfires in relatively pristine areas of Australia in 2011 using lead isotopic compositions ((208)Pb/(207)Pb; (206)Pb/(207)Pb). Lead concentrations in the ash ranged from 1 to 36 mg/kg, bracketing the range of lead (4-23 mg/kg) in surface soils (0-2 cm), subsurface (40-50 cm) soils and rocks. The lead isotopic compositions of ash and surface soil samples were compared to subsurface soils and local bedrock samples. The data show that many of the ash and surface soil lead isotopic compositions were a mixture of natural lead and legacy industrial lead depositions (such as leaded petrol combustion). However, some of the ash samples at each of the sites had lead isotopic compositions that did not fit a simple two end-member mixing model, indicating other, unidentified sources. PMID:24763391

Kristensen, Louise J; Taylor, Mark Patrick; Odigie, Kingsley O; Hibdon, Sharon A; Flegal, A Russell

2014-07-01

151

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation  

NASA Technical Reports Server (NTRS)

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density polyurethane foam, BX-250. Challenges in modeling the RCC include its extreme brittleness, the differing behavior in compression and tension, and the anisotropic fabric layup. These effects were successfully included in LS-DYNA Material Model 58, *MAT_LAMINATED_ COMPOSITE_ FABRIC. The differing compression and tension behavior was modeled using the available damage parameters. Each fabric layer was given an integration point in the shell element, and was allowed to fail independently. Comparisons were made to static test data and coupon ballistic impact tests before being utilized in the full scale analysis. The foam's properties were typical of elastic automotive foams; and LS-DYNA Material Model 83, *MAT_FU_CHANG_FOAM, was successfully used to model its behavior. Material parameters defined included strain rate dependent stress-strain curves for both loading and un-loading, and for both compression and tension. This model was formulated with static test data and strain rate dependent test data, and was compared to ballistic impact tests on load-cell instrumented aluminum plates. These models were subsequently utilized in analysis of the Shuttle leading edge full scale ballistic impact tests, and are currently being used in the Return to Flight Space Shuttle re-certification effort.

Carney, Kelly; Melis, Matthew; Fasanella, Edwin L.; Lyle, Karen H.; Gabrys, Jonathan

2004-01-01

152

Composite polymer-glass edge cladding for laser disks  

DOEpatents

Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation.

Powell, Howard T. (Livermore, CA); Riley, Michael O. (San Ramon, CA); Wolfe, Charles R. (Palo Alto, CA); Lyon, Richard E. (Livermore, CA); Campbell, John H. (Livermore, CA); Jessop, Edward S. (Tracy, CA); Murray, James E. (Livermore, CA)

1989-01-01

153

Thermal Edge-Effects Model for Automated Tape Placement of Thermoplastic Composites.  

National Technical Information Service (NTIS)

Two-dimensional thermal models for automated tape placement (ATP) of thermoplastic composites neglect the diffusive heat transport that occurs between the newly placed tape and the cool substrate beside it. Such lateral transport can cool the tape edges p...

R. C. Costen

2000-01-01

154

The effects of leading-edge serrations on reducing flow unsteadiness about airfoils.  

NASA Technical Reports Server (NTRS)

High frequency surface pressure measurements were obtained from wind-tunnel tests over the Reynolds number range 1.2 x 1,000,000 to 6.2 x 1,000,000 on a rectangular wing of NACA 63-009 airfoil section. A wide selection of leading-edge serrations were also added to the basic airfoil. Under a two-dimensional laminar bubble very close to the leading edge of the basic airfoil there is a large peak in rms pressure, which is interpreted as an oscillation in size and position of the bubble. The serrations divide the bubble into segments and reduce the peak rms pressures. A low Reynolds number flow visualization test on a hydrofoil in water was also conducted. A von Karman vortex street was found trailing from the rear of the foil. Its frequency is at a much lower Strouhal number than in the high Reynolds number experiment, and is related mathematically to the airfoil trailing-edge and boundary-layer thicknesses.

Schwind, R. G.; Allen, H. J.

1973-01-01

155

Hypersonic aerospace vehicle leading-edge cooling using heat-pipe, transpiration and film-cooling techniques  

SciTech Connect

The feasibility of cooling hypersonic-vehicle leading-edge structures exposed to severe aerodynamic surface heat fluxes was studied, using a combination of liquid-metal heat pipes and surface-mass-transfer cooling techniques. A generalized, transient, finite-difference-based hypersonic leading-edge cooling model was developed that incorporated these effects and was demonstrated on an assumed aerospace plane-type wing leading edge section and a SCRAMJET engine inlet leading-edge section. The hypersonic leading-edge cooling model was developed using an existing, experimentally verified heat-pipe model. Then the existing heat-pipe model was modified by adding both transpiration and film-cooling options as new surface boundary conditions. The models used to predict the leading-edge surface heat-transfer reduction effects of the transpiration and film cooling were modifications of more-generalized, empirically based models obtained from the literature. It is concluded that cooling leading-edge structures exposed to severe hypersonic-flight environments using a combination of liquid-metal heat pipe, surface transpiration, and film cooling methods appears feasible.

Modlin, J.M.

1991-01-01

156

Increased heat transfer to elliptical leading edges due to spanwise variations in the freestream momentum: Numerical and experimental results  

NASA Technical Reports Server (NTRS)

A study of the effect of spanwise variation in momentum on leading edge heat transfer is discussed. Numerical and experimental results are presented for both a circular leading edge and a 3:1 elliptical leading edge. Reynolds numbers in the range of 10,000 to 240,000 based on leading edge diameter are investigated. The surface of the body is held at a constant uniform temperature. Numerical and experimental results with and without spanwise variations are presented. Direct comparison of the two-dimensional results, that is, with no spanwise variations, to the analytical results of Frossling is very good. The numerical calculation, which uses the PARC3D code, solves the three-dimensional Navier-Stokes equations, assuming steady laminar flow on the leading edge region. Experimentally, increases in the spanwise-averaged heat transfer coefficient as high as 50 percent above the two-dimensional value were observed. Numerically, the heat transfer coefficient was seen to increase by as much as 25 percent. In general, under the same flow conditions, the circular leading edge produced a higher heat transfer rate than the elliptical leading edge. As a percentage of the respective two-dimensional values, the circular and elliptical leading edges showed similar sensitivity to span wise variations in momentum. By equating the root mean square of the amplitude of the spanwise variation in momentum to the turbulence intensity, a qualitative comparison between the present work and turbulent results was possible. It is shown that increases in leading edge heat transfer due to spanwise variations in freestream momentum are comparable to those due to freestream turbulence.

Rigby, D. L.; Vanfossen, G. J.

1992-01-01

157

Flexible Metallic Overwrap Concept Developed for On-Orbit Repair of Space Shuttle Orbiter Leading Edges  

NASA Technical Reports Server (NTRS)

The Columbia accident has focused attention on the critical need for on-orbit repair concepts for leading edges in the event that damage is incurred during space shuttle orbiter flight. Damage that is considered as potentially catastrophic for orbiter leading edges ranges from simple cracks to holes as large as 16 in. in diameter. NASA is particularly interested in examining potential solutions for areas of larger damage since such a problem was identified as the cause for the Columbia disaster. One possible idea for the on-orbit repair of the reinforced carbon/carbon (RCC) leading edges is an overwrap concept that would use a metallic sheet flexible enough to conform to the contours of the orbiter and robust enough to protect any problem area from catastrophic failure during reentry. The simplified view of the application of a refractory metal sheet over a mockup of shuttle orbiter panel 9, which experiences the highest temperatures on the shuttle during reentry is shown. The metallic overwrap concept is attractive because of its versatility as well as the ease with which it can be included in an onboard repair kit. Reentry of the orbiter into Earth's atmosphere imposes extreme requirements on repair materials. Temperatures can exceed 1650 C for up to 15 min in the presence of an extremely oxidizing plasma environment. Several other factors are critical, including catalysity, emissivity, and vibrational and aerodynamic loads. Materials chosen for this application will need to be evaluated with respect to high-temperature capability, resistance to oxidation, strength, coefficient of thermal expansion, and thermal conductivity. The temperature profile across panel 9 during reentry as well as a schematic of the overwrap concept itself is shown.

Ritzert, Frank J.; Nesbitt, James A.

2005-01-01

158

Structure of unsteady flows at leading- and trailing-edges: Flow visualization and its interpretation  

NASA Technical Reports Server (NTRS)

Unsteady two- and three-dimensional flow structure at leading and trailing edges of bodies can be characterized effectively using recently developed techniques for acquisition and interpretation of flow visualization. The techniques addressed here include: flow image/surface pressure correlations; 3-D reconstruction of flow structure from flow images; and interactive interpretation of flow images with theoretical simulations. These techniques can be employed in conjunction with: visual correlation and ensemble-averaging, both within a given image and between images; recognition of patterns from images; and estimates of velocity eigenfunctions from images.

Rockwell, D.; Atta, R.; Kramer, L.; Lawson, R.; Lusseyran, D.; Magness, C.; Sohn, D.; Staubli, T.

1987-01-01

159

Initial development of an ablative leading edge for the space shuttle orbiter  

NASA Technical Reports Server (NTRS)

A state-of-the-art preliminary design for typical wing areas is developed. Seven medium-density ablators (with/without honeycomb, flown on Apollo, Prime, X15A2) are evaluated. The screening tests include: (1) leading-edge models sequentially subjected to ascent heating, cold soak, entry heating, post-entry pressure fluctuations, and touchdown shock, and (2) virgin/charred models subjected to bondline strains. Two honeycomb reinforced 30 pcf elastomeric ablators were selected. Roughness/recession degradation of low speed aerodynamics appears acceptable. The design, including attachments, substructure and joints, is presented.

Daforno, G.; Rose, L.; Graham, J.; Roy, P.

1974-01-01

160

Turbine vane leading edge gas film cooling with spanwise angled coolant holes  

NASA Technical Reports Server (NTRS)

An experimental film cooling study was conducted on a 3x size model turbine vane. Injection at the leading edge was from a single row of holes angled in a spanwise direction for two configurations of holes at 18 or 35 deg to the surface. The reduction in the local Stanton number for injection at a coolant-to-mainstream density ratio of 2.18 was calculated from heat flux measurements downstream of injection. Results indicate that optimum cooling occurs near a coolant-to-mainstream velocity ratio of 0.5. Shallow injection angles appear to be most beneficial when injecting into a highly accelerated mainstream.

Hanus, G. J.; Lecuyer, M. R.

1976-01-01

161

Measurement of Leading Edge Vortices from a Delta Wing Using a Three Component Laser Velocimeter  

NASA Technical Reports Server (NTRS)

A demonstration of the capabilities of a three component laser velocimeter to provide a detailed experimental database of a complex flow field i s presented. The orthogonal three component laser velocimeter was used to measure the leading edge vortex flow field above a 75 degrees delta wing at angles-of-attack of 20.5 degrees and 40.0 degrees. The resulting mean velocity and turbulence intensity measurements are presented. The laser velocimeter is described in detail including a description of the data processing algorithm. A full error analysis was conducted and the results presented.

Meyers, James F.; Hepner, Timothy E.

1988-01-01

162

Initial development of an ablative leading edge for the Space Shuttle orbiter.  

NASA Technical Reports Server (NTRS)

A state-of-the-art preliminary design for typical wing areas is developed. Seven medium-density ablators (with/without honeycomb, flown on Apollo, Prime, X15A2) are evaluated. The screening tests include (1) leading-edge models sequentially subjected to ascent heating, cold soak, entry heating, post-entry pressure fluctuations, and touchdown shock, and (2) virgin/charred models subjected to bondline strains. Four materials (none molded) are found acceptable. The ESA 3560 HF and MOD 7 Hc (an AVCO 30 pcf elastomer) are selected. Roughness/recession degradation of low speed aerodynamics appears acceptable. The design, including attachments, substructure and joints, is presented.

Daforno, G.; Graham, J.; Tompkins, S.

1973-01-01

163

Estimating Blade Section Airloads from Blade Leading-Edge Pressure Measurements  

NASA Technical Reports Server (NTRS)

The Tilt-Rotor Aeroacoustic Model (TRAM) test in the Duitse-Nederlandse Wind (DNW) Tunnel acquired blade pressure data for forward flight test conditions of a tiltrotor in helicopter mode. Chordwise pressure data at seven radial locations were integrated to obtain the blade section normal force. The present investigation evaluates the use of linear regression analysis and of neural networks in estimating the blade section normal force coefficient from a limited number of blade leading-edge pressure measurements and representative operating conditions. These network models are subsequently used to estimate the airloads at intermediate radial locations where only blade pressure measurements at the 3.5% chordwise stations are available.

vanAken, Johannes M.

2003-01-01

164

Spanwise pressure distribution on delta wing with leading-edge vortex flap  

NASA Technical Reports Server (NTRS)

The aerodynamic characteristics of a highly swept planar delta wing employing conical leading edge flaps are numerically investigated, using a free vortex sheet method that is based on an advanced, three-dimensional inviscid flow panel method employing quadratic doublet distributions to represent the wing surface and the rolled-up vortex sheet and wake. Upward flap deflection shifts the negative pressure peak inboard of the basic wing and develops a significant suction pressure on the flap that then produces thrust component in the direction of flight; overall drag is thereby reduced.

Reddy, C. S.

1987-01-01

165

Predicted Static Aeroelastic Effects on Wings with Supersonic Leading Edges and Streamwise Tips  

NASA Technical Reports Server (NTRS)

A method is presented for calculation of static aeroelastic effects on wings with supersonic leading edges and streamwise tips. Both chord-wise and spanwise deflections are taken into account. Aerodynamic and structural forces are introduced in influence coefficient form; the former are developed from linearized supersonic wing theory and the latter are assumed to be known from load-deflection tests or theory. The predicted effects of flexibility on lateral-control effectiveness, damping in roll, and lift-curve slope are shown for a low-aspect-ratio wing at Mach numbers of 1.25 and 2.60. The control effectiveness is shown for a trailing-edge aileron, a tip aileron, and a slot-deflector spoiler located along the 0.70 chord line. The calculations indicate that the tip aileron is particularly attractive from an aeroelastic standpoint, because the changes in effectiveness with dynamic pressure are small compared to the changes in effectiveness of the trailing-edge aileron and slot-deflector spoiler. The effects of making several simplifying assumptions in the example calculations are shown. The use of a modified strip theory to determine the aerodynamic influence coefficients gave adequate results only for the high Mach number case. Elimination of chordwise bending in the structural influence coefficients exaggerated the aeroelastic effects on rolling-moment and lift coefficients for both Mach numbers.

Brown, Stuart C.

1959-01-01

166

COMMUNICATIONS Composition dependence of the ultraviolet absorption edge  

E-print Network

the composition of the samples with an absolute accuracy of 0.05 mol %. This absolute determination a congruently melting composition which does not coincide with the sto- ichiometric one, but shows a Li spectral features and, from an application point of view even more importantly makes the material less sus

Osnabrück, Universität

167

Zinc halogen battery electrolyte composition with lead additive  

DOEpatents

This disclosure relates to a zinc halogen battery electrolyte composition containing an additive providing improved zinc-on-zinc recyclability. The improved electrolyte composition involves the use of a lead additive to inhibit undesirable irregular plating and reduce nodular or dendritic growth on the electrode surface. The lead-containing electrolyte composition of the present invention appears to influence not only the morphology of the base plate zinc, but also the morphology of the zinc-on-zinc replate. In addition, such lead-containing electrolyte compositions appear to reduce hydrogen formation.

Henriksen, Gary L. (Troy, MI)

1981-01-01

168

Bird-strike simulation for certification of the Boeing 787 composite moveable trailing edge  

Microsoft Academic Search

A validated simulation methodology has been developed to support the bird-strike certification of the carbon fibre epoxy composite, moveable trailing edge (MTE) of the Boeing 787 Dreamliner. The explicit finite element software PAM-CRASH™ was selected to perform the simulations utilising the advanced composite material, fastener and smooth particle hydrodynamic bird models available in the code. The modelling procedures were validated

Steve Georgiadis; Andrew J. Gunnion; Rodney S. Thomson; Bruce K. Cartwright

2008-01-01

169

Composition of White Lead and Paints.  

E-print Network

we shall see in the following pages, "white lead" sometimes consists en- tirely of barytes. This is a fraud, pure and simple. Linseed Oil flubstitutes.-Linseed oil, as we have stated, is the best oil for use in mixing paints. Resin oils and other... must be considered as highly adulterated. It appears that in the majority of cases consumers of white lead, mixed paints, ancl other pint materials, have no mcans of knowing anything about the quality of the materials which they use. The r of the v...

Fraps, G. S. (George Stronach)

1908-01-01

170

Dynamic Stall Measurements and Computations for a VR-12 Airfoil with a Variable Droop Leading Edge  

NASA Technical Reports Server (NTRS)

High density-altitude operations of helicopters with advanced performance and maneuver capabilities have lead to fundamental research on active high-lift system concepts for rotor blades. The requirement for this type of system was to improve the sectional lift-to-drag ratio by alleviating dynamic stall on the retreating blade while simultaneously reducing the transonic drag rise of the advancing blade. Both measured and computational results showed that a Variable Droop Leading Edge (VDLE) airfoil is a viable concept for application to a rotor high-lift system. Results are presented for a series of 2D compressible dynamic stall wind tunnel tests with supporting CFD results for selected test cases. These measurements and computations show a dramatic decrease in the drag and pitching moment associated with severe dynamic stall when the VDLE concept is applied to the Boeing VR-12 airfoil. Test results also show an elimination of the negative pitch damping observed in the baseline moment hysteresis curves.

Martin, P. B.; McAlister, K. W.; Chandrasekhara, M. S.; Geissler, W.

2003-01-01

171

Coronin 1B coordinates Arp2/3 complex and Cofilin activities at the leading edge  

PubMed Central

Summary Actin filament nucleation and turnover are interdependent processes in migrating cells, but the mechanisms coordinating these events are unknown. Coronin 1B influences motility, lamellipodial dynamics and actin filament architecture at the leading edge of Rat2 cells in a manner consistent with a role in coordinating filament formation and turnover. Coronin 1B interacts simultaneously with both Arp2/3 complex and Slingshot (SSH1L) phosphatase, two regulators of actin filament formation and turnover, respectively. Coronin 1B inhibits filament nucleation by Arp2/3 complex and this inhibition is attenuated by phosphorylation of Coronin 1B on Serine 2, a site targeted by SSH1L. Coronin 1B directs SSH1L to lamellipodia where it likely regulates Cofilin. Accordingly, depleting Coronin 1B increases phospho-Cofilin levels and expressing activated Cofilin partially suppresses the effects on lamellipodia dynamics of Coronin 1B depletion. Thus, Coronin 1B coordinates filament nucleation via Arp2/3 complex and turnover by Cofilin at the leading edge of migrating cells. PMID:17350576

Cai, Liang; Marshall, Thomas W.; Uetrecht, Andrea C.; Schafer, Dorothy A.; Bear, James E.

2008-01-01

172

Experimental investigation of the transonic flow around the leading edge of an eroded fan airfoil  

NASA Astrophysics Data System (ADS)

The influence of leading edge modification on the time-averaged and instantaneous flow around a fan airfoil is investigated by particle image velocimetry (PIV), schlieren imaging and high-speed shock shadowgraphs in a transonic cascade windtunnel. In addition to a global characterization of the time-averaged flow using PIV, the instantaneous passage shock position was extracted from single-shot PIV measurements by matching the tracer velocity across the normal shock with an exponential fit. The instantaneous shock positions are assigned to a probability density distribution in order to obtain the average position and the range of fluctuations of the eroded and reference leading edge. The profiles are used to estimate the response time of the particles to the normal shock which was found to be in the sub-microsecond range. Averaged PIV measurements and the probability density of shock position from both geometries are obtained at near stall and choked conditions. In order to extract the frequency range of the shock motion, the shadow of the shock wave was tracked using high-speed shadowgraphy. The paper also provides details on the experimental implementation such as a specifically designed light-sheet probe.

Klinner, Joachim; Hergt, Alexander; Willert, Christian

2014-09-01

173

High Mach Number Leading-edge Flow Separation Control using AC DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to quantify the effectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy efficient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the effect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted for a range of Mach numbers between 0.1 and 0.4. corresponding to a Reynolds number range of 560,000 through 2,260,000. Lift, drag, quarter chord moment, and suction side pressures were measured near stall for baseline, steady actuation, and a scan of nondimensional duty cycle frequencies. The results show that the plasma actuators were effective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coefficient and stall angle (as much as 2.5 degrees). The experiment also showed that lift was increased the most when the plasma actuator was operated unsteady with a nondimensional frequency of unity.

Kelley, Christopher; Bowles, Patrick; Cooney, John; He, Chuan; Corke, Thomas; Osborne, Bradley; Silkey, Joseph; Zehnle, Joseph

2011-11-01

174

Tethered cube stabilization by means of leading-edge DBD plasma actuation  

NASA Astrophysics Data System (ADS)

An experimental investigation was carried out to assess the effectiveness of active flow control as a means for suppressing oscillations of a tethered cube. Two experimental configurations were considered: a static configuration involving surface pressure and particle image velocimetry (PIV) flow field measurements and a dynamic, tethered, configuration. Corner-mounted, dielectric barrier discharge plasma actuators were employed at the leading-edges and were pulsed at reduced frequencies of order one and at varying duty cycles. On the static configuration, actuation changed the direction of the side-forces and virtually eliminated yawing-moment excursions. Surface pressure and flow field measurements showed that control of separation bubbles on the surfaces, as well as control of the separated shear layer, were responsible for these effects. Phase-averaged PIV measurements elucidated the mechanism whereby actuation severs the leading-edge vortex that subsequently sheds downstream. For the tethered cube, actuation dramatically reduced the yawing motions, particularly when the momentum coefficient exceeded 0.3 %. Drag reduction, based on the deflection of the cube, was estimated to be approximately 12 %, consistent with the static data. Reduced frequency and duty cycle had a marked effect on control effectiveness.

Goyta, Snir; Mueller-Vahl, Hanns; Greenblatt, David

2013-01-01

175

Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading Edge Panels  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter wing comprises of 22 leading edge panels on each side of the wing. These panels are part of the thermal protection system that protects the Orbiter wings from extreme heating that take place on the reentry in to the earth atmosphere. On some panels that experience extreme heating, liberation of silicon carbon (SiC) coating was observed on the slip side regions of the panels. Global structural and local fracture mechanics analyses were performed on these panels as a part of the root cause investigation of this coating liberation anomaly. The wing-leading-edge reinforced carbon-carbon (RCC) panels, Panel 9, T-seal 10, and Panel 10, are shown in Figure 1 and the progression of the stress analysis models is presented in Figure 2. The global structural analyses showed minimal interaction between adjacent panels and the T-seal that bridges the gap between the panels. A bounding uniform temperature is applied to a representative panel and the resulting stress distribution is examined. For this loading condition, the interlaminar normal stresses showed negligible variation in the chord direction and increased values in the vicinity of the slip-side joggle shoulder. As such, a representative span wise slice on the panel can be taken and the cross section can be analyzed using plane strain analysis.

Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.

2010-01-01

176

Low-speed cascade investigation of loaded leading-edge compressor blades  

NASA Technical Reports Server (NTRS)

Six percent thick NACA 63-series compressor-blade sections having a loaded leading-edge A4K6 mean line have been investigated systematically in a two-dimensional porous-wall cascade over a range of Reynolds numbers from 160,000 to 385,000. Blades cambered to have isolated-airfoil lift coefficients of 0.6, 1.2, 1.8, and 2.4 were tested over the usable angle-of-attack range at inlet-air angles of 30 degrees, 45 degrees, and 60 degrees and solidities of 1.0 and 1.5. A comparison with data of NACA RM L51G31, shows that the angle-of-attack operating range is 2 degrees to 4 degrees less than the range for the uniformly loaded section; however, the wake losses near design angle of attack are slightly lower than those for the uniformly loaded section. Except for highly cambered blades at high inlet angles, the 63-(C s oA4K6)06 compressor-blade sections are capable of more efficient operation for moderate-speed subsonic compressors at design angle of attack than are the 65-(C s oa10)10 or the 65-(c s oA2I8b)10 compressor-blade sections. In contrast to the other sections, the loaded leading-edge sections are capable of operating efficiently at the lower Reynolds numbers.

Emery, James C

1956-01-01

177

The effects of leading edge and downstream film cooling on turbine vane heat transfer  

NASA Technical Reports Server (NTRS)

The progress under contract NAS3-24619 toward the goal of establishing a relevant data base for use in improving the predictive design capabilities for external heat transfer to turbine vanes, including the effect of downstream film cooling with and without leading edge showerhead film cooling. Experimental measurements were made in a two-dimensional cascade previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils under contract NAS3-22761 and leading edge showerhead film cooled airfoils under contract NAS3-23695. The principal independent parameters (Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio) were maintained over ranges consistent with actual engine conditions and the test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. Data provide a data base for downstream film cooled turbine vanes and extends the data bases generated in the two previous studies. The vane external heat transfer obtained indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The data obtained and presented illustrate the interaction of the variables and should provide the airfoil designer and computational analyst the information required to improve heat transfer design capabilities for film cooled turbine airfoils.

Hylton, L. D.; Nirmalan, V.; Sultanian, B. K.; Kaufman, R. M.

1988-01-01

178

Measurements in a leading-edge separation bubble due to a simulated airfoil ice accretion  

NASA Technical Reports Server (NTRS)

The separation bubble formed on an airfoil at low Reynolds number behind a simulated leading-edge glaze ice accretion is studied experimentally. Surface pressure and split hot-film measurements as well as flow visualization studies of the bubble reattachment point are reported. The simulated ice generates an adverse pressure gradient that causes a laminar separation bubble of the long bubble type to form. The boundary layer separates at a location on the ice accretion that is independent of angle of attack and reattaches at a downstream location 5-40 percent chord behind the leading edge, depending on the angle of attack. Velocity profiles show a large region of reverse flow that extends up from the airfoil surface as much as 2.5 percent chord. After reattachment, a thick distorted turbulent boundary layer exists. The separation bubble growth and reattachment are clearly seen in the plots of boundary-layer momentum thickness vs surface distance. Local minima and maxima in the boundary-layer momentum thickness development compare well with the shear layer transition point as indicated by the surface pressures and the reattachment point as measured from surface oil flow, respectively.

Bragg, M. B.; Khodadoust, A.; Spring, S. A.

1992-01-01

179

The effect of undulating leading-edge modifications on NACA 0021 airfoil characteristics  

NASA Astrophysics Data System (ADS)

In spite of its mammoth physical size, the humpback whale's manoeuvrability in hunting has captured the attention of biologists as well as fluid mechanists. It has now been established that the protrusions on the leading-edges of the humpback's pectoral flippers, known as tubercles, account for this species' agility and manoeuvrability. In the present work, Prandtl's nonlinear lifting-line theory was employed to propose a hypothesis that the favourable traits observed in the performance of tubercled lifting bodies are not exclusive to this form of leading-edge configuration. Accordingly, a novel alternative to tubercles was introduced and incorporated into the design of four airfoils that underwent wind tunnel force and pressure measurement tests in the transitional flow regime. In addition, a Computation Fluid Dynamics study was performed using the Shear Stress Transport transitional model in the context of unsteady Reynolds-Averaged Navier-Stokes at several attack angles. The results from the numerical investigation are in reasonable agreement with those of the experiments, and suggest the presence of features that are also observed in flows over tubercled foils, most notably a distinct pair of streamwise vortices for each wavelength of the tubercle-like feature.

Rostamzadeh, N.; Kelso, R. M.; Dally, B. B.; Hansen, K. L.

2013-11-01

180

Analytical observations on the aerodynamics of a delta wing with leading edge flaps  

NASA Technical Reports Server (NTRS)

The effect of a leading edge flap on the aerodynamics of a low aspect ratio delta wing is studied analytically. The separated flow field about the wing is represented by a simple vortex model composed of a conical straight vortex sheet and a concentrated vortex. The analysis is carried out in the cross flow plane by mapping the wing trace, by means of the Schwarz-Christoffel transformation into the real axis of the transformed plane. Particular attention is given to the influence of the angle of attack and flap deflection angle on lift and drag forces. Both lift and drag decrease with flap deflection, while the lift-to-drag ratioe increases. A simple coordinate transformation is used to obtain a closed form expression for the lift-to-drag ratio as a function of flap deflection. The main effect of leading edge flap deflection is a partial suppression of the separated flow on the leeside of the wing. Qualitative comparison with experiments is presented, showing agreement in the general trends.

Oh, S.; Tavella, D.

1986-01-01

181

Efficient mitigation of founder effects during the establishment of a leading-edge oak population  

PubMed Central

Numerous plant species are shifting their range polewards in response to ongoing climate change. Range shifts typically involve the repeated establishment and growth of leading-edge populations well ahead of the main species range. How these populations recover from founder events and associated diversity loss remains poorly understood. To help fill this gap, we exhaustively investigated a newly established population of holm oak (Quercus ilex) growing more than 30 km ahead of the nearest larger stands. Pedigree reconstructions showed that plants belong to two non-overlapping generations and that the whole population originates from only two founder trees. The four first-generation trees that have reached maturity showed disparate mating patterns despite being full-sibs. Long-distance pollen immigration was notable despite the strong isolation of the stand: 6 per cent gene flow events in acorns collected on the trees (n = 255), and as much as 27 per cent among their established offspring (n = 33). Our results show that isolated leading-edge populations of wind-pollinated forest trees can rapidly restore their genetic diversity through the interacting effects of efficient long-distance pollen flow and purging of inbred individuals during recruitment. They imply that range expansions of these species are primarily constrained by initial propagule arrival rather than by subsequent gene flow. PMID:23782887

Hampe, Arndt; Pemonge, Marie-Helene; Petit, Remy J.

2013-01-01

182

Influence of Large Positive Dihedral on Heat Transfer to Leading Edges of Highly Swept Wings at Very High Mach Numbers  

NASA Technical Reports Server (NTRS)

A geometric study has been made of some of the effects of dihedral on the heat transfer to swept delta wings. The results of this study show that the incorporation of large positive dihedral on highly swept wings can shift, even at moderately low angles of attack, the stagnation-line heat-transfer problem from the leading edges to the axis of symmetry (ridge line). An order-of-magnitude analysis (assuming laminar flow) indicates conditions for which it may be possible to reduce the heating at the ridge line (except in the vicinity of the wing apex) to a small fraction of the leading-edge heat transfer of a flat wing at the same lift. Furthermore, conditions are indicated where dihedral reduces the leading-edge heat transfer for angles of attack less than those required to shift the stagnation line from the leading edge to the ridge line.

Cooper, Morton; Stainback, P. Calvin

1959-01-01

183

Effects of increased leading-edge thickness on performance of a transonic rotor blade. [in single stage transonic compressor  

NASA Technical Reports Server (NTRS)

A single-stage transonic compressor was tested with two rotor blade leading-edge configurations to investigate the effect of increased leading-edge thickness on the performance of a transonic blade row. The original rotor blade configuration was modified by cutting back the leading edge sufficiently to double the blade leading-edge thickness and thus the blade gap blockage in the tip region. At design speed this modification resulted in a decrease in rotor overall peak efficiency of four points. The major portion of this decrement in rotor overall peak efficienty was attributed to the flow conditions in the outer 30 percent of the blade span. At 70 and 90 percent of design speed, the modification had very little effect on rotor overall performance.

Reid, L.; Urasek, D. C.

1972-01-01

184

Flight experience on the need and use of inflight leading edge washing for a laminar flow airfoil  

NASA Technical Reports Server (NTRS)

An investigation of leading-edge contamination by insects was conducted at the NASA Dryden Flight Research Center with a JetStar airplane instrumented to detect transition on the outboard leading-edge flap and equipped with a system to wash the leading edge in flight. The results of airline-type flights with the JetStar indicated that insects can contaminate the leading edge during take-off and climbout at large jet airports in the United States. The results also showed that the insects collected on the leading edges at 180 knots did not erode at cruise conditions for a laminar flow control airplane and caused premature transition of the laminar boundary layer. None of the superslick and hydrophobic surfaces tested showed any significant advantages in alleviating the insect contamination problem. While there may be other solutions to the insect contamination problem, the results of these tests with a washer system showed that a continuous water spray while encountering the insects is effective in preventing insect contamination of the leading edges.

Fisher, D. F.; Peterson, J. B., Jr.

1978-01-01

185

Aerodynamic Forces and Loadings on Symmetrical Circular-Arc Airfoils with Plain Leading-Edge and Plain Trailing-Edge Flaps  

NASA Technical Reports Server (NTRS)

An investigation has been made in the Langley two-dimensional low-turbulence tunnel and in the Langley two-dimensional low-pressure tunnel of 6- and 10-percent-thick symmetrical circular-arc airfoil sections at low Mach numbers and several Reynolds numbers. The airfoils were equipped with 0.15-chord plain leading-edge flaps and 0.20-chord plan trailing-edge flaps. The section lift and pitching-moment characteristics were determined for both airfoils with the flaps deflected individually and in combination. The section drag characteristics were obtained for the 6-percent-thick airfoil with the flaps partly deflected as low-drag-control flaps and for airfoils with the flaps neutral. Surface pressures were measured on the 6-percent-thick airfoil section with the flaps deflected either individually or in appropriate combination to furnish flap load and hinge-moment data applicable to the structural design of the airfoil. A generalized method is developed that permits the determination of the chordwise pressure distribution over sharp-edge airfoils with plain leading-edge flaps and plain trailing-edge flaps of arbitrary size and deflection.

Cahill, Jones F; Underwood, William J; Nuber, Robert J; Cheesman, Gail A

1953-01-01

186

Interlaminar stress singularities at a straight free edge in composite laminates  

NASA Technical Reports Server (NTRS)

A quasi-three-dimensional finite-element analysis was used to analyze the edge-stress problem in four-ply, composite laminates. The seven laminates that were considered belong to the laminate family where the outer ply angle is between 0 and 90 deg. Systematic convergence studies were made to explore the existence of stress singularities near the free edge. The present analysis appears to confirm the existence of stress singularities at the intersection of the interface and the free edge. The power of the stress singularity was the same for all seven laminates considered.

Raju, I. S.; Crews, J. H., Jr.

1981-01-01

187

ALES, the multi­mission Adaptive Leading Edge Sub­Waveform Retracker, design and validation  

NASA Astrophysics Data System (ADS)

Satellite altimetry has revolutionized our understanding of ocean dynamics thanks to high repetition rate and global coverage. Nevertheless, coastal data has been flagged as unreliable due to land and calm water interference in the altimeter and radiometer footprint and high frequency tidal and atmospheric forcing. Our study addresses the first issue, i.e. retracking, presenting ALES, the Adaptive Leading Edge Subwaveform Retracker. ALES is potentially applicable to all the pulse­limited altimetry altimetry missions and its aim is to retrack with the same precision both open ocean and coastal data with the same algorithm. ALES selects part of each returned echo and models it with a classic ‘open ocean’ Brown functional form, by means of least square estimation whose convergence is found through the Nelder­Mead nonlinear optimization technique. By avoiding echoes from bright targets along the trailing edge, it is capable of retrieving the majority of coastal waveform up to 2 to 3 Km from the coasts. By adapting the estimation window to the significant wave height, it aims at preserving the precision of the standard data both in open ocean and in the coastal strip. ALES is validated against tide gauges in the Adriatic Sea and in the Greater Agulhas System for three different missions: Envisat, Jason­1 and Jason­2. Considerations on noise and biases provide a further verification of the strategy.

Passaro, Marcello; Benveniste, Jérôme; Vignudelli, Stefano; Cipollini, Paolo; Quartly, Graham; Snaith, Helen

188

Effects of leading-edge roughness on fluid flow and heat transfer in the transitional boundary layer over a flat plate  

Microsoft Academic Search

An experimental study was undertaken to gain insight into the physical mechanisms that affect the laminar-turbulent transition process downstream of the leading-edge roughness condition. Sandpaper strips and small cylinders were attached to the leading edge of a heated test surface to simulate leading edge roughness typical of gas turbine blades. The roughness Reynolds numbers ranged from 2 to 2840. For

Mark W. Pinson; Ting Wang

1997-01-01

189

Measurements of heat transfer coefficients and friction factors in rib-roughened channels simulating leading-edge cavities of a modern turbine blade  

Microsoft Academic Search

Leading edge cooling cavities in modern gas turbine blades play an important role in maintaining the leading edge temperature at levels consistent with air foil design life. These cavities often have a complex cross-sectional shape to be compatible with the external contour of the blade at the leading edge. A survey of many existing geometries shows that, for analytical as

M. E. Taslim; T. Li; S. D. Spring

1997-01-01

190

The Cutting Edge of High-Temperature Composites  

NASA Technical Reports Server (NTRS)

NASA s Ultra-Efficient Engine Technology (UEET) program was formed in 1999 at Glenn Research Center to manage an important national propulsion program for the Space Agency. The UEET program s focus is on developing innovative technologies to enable intelligent, environmentally friendly, and clean-burning turbine engines capable of reducing harmful emissions while maintaining high performance and increasing reliability. Seven technology projects exist under the program, with each project working towards specific goals to provide new technology for propulsion. One of these projects, Materials and Structures for High Performance, is concentrating on developing and demonstrating advanced high-temperature materials to enable high-performance, high-efficiency, and environmentally compatible propulsion systems. Materials include ceramic matrix composite (CMC) combustor liners and turbine vanes, disk alloys, turbine airfoil material systems, high-temperature polymer matrix composites, and lightweight materials for static engine structures.

2006-01-01

191

Thermal Degradation of Lead Monoxide Filled Polymer Composite Radiation Shields  

SciTech Connect

Lead monoxide filled Isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the thermo gravimetric analysis of the composites done to understand their thermal properties especially the effect of filler concentration on the thermal stability and degradation rate of composites. Pristine polymer exhibits single stage degradation whereas filled composites exhibit two stage degradation processes. Further, the IDT values as well as degradation rates decrease with the increased filler content in the composite.

Harish, V. [Department of Physics, Government First Grade College, Shivamogga-577201 (India); Nagaiah, N. [Department of Physics, Bangalore University, Jnanabharati, Bangalore-560056 (India)

2011-07-15

192

An experimental study of turbine vane heat transfer with leading edge and downstream film cooling  

NASA Technical Reports Server (NTRS)

This paper presents the effects of downstream film cooling, with and without leading edge showerhead film cooling, on turbine-vane external heat transfer. Steady-state experimental measurements were made in a three-vane linear two-dimensional cascade. The principal independent parameters were maintained over ranges consistent with actual engine conditions. The test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. The data obtained indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The downstream film cooling process was shown to be a complex interaction of two competing mechanisms. The thermal dilution effect, associated with the injection of relatively cold fluid, results in a decrease in the heat transfer to the airfoil. Conversely, the turbulence augmentation, produced by the injection process, results in increased heat transfer to the airfoil.

Nirmalan, V.; Hylton, L. D.

1989-01-01

193

Airfoil leading-edge suction and energy conservation for compressible flow  

SciTech Connect

The leading-edge suction force produced when a flat-plate airfoil at zero angle of attack encounters a vertical gust was examined for compressible flow with a time-dependent gust. A simple derivation of the thrust force shows that the acoustic energy can be calculated using compact assumptions at low frequency, but that it must be calculated non-compactly at high frequency. For a general gust, the work done on the airfoil equals the energy taken from the fluid. For a sinusoidal gust the energy contained in the incident gust equals the sum of the energy remaining in the wake, the work done on the airfoil and the acoustic energy radiated away. Also, the relative proportions of the energy going to these three energy types depend on the gust frequency.

Amiet, R.K.

1995-04-01

194

Stagnation region gas film cooling for turbine blade leading edge applications  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to model the film-cooling performance for a turbine-vane leading edge using the stagnation region of a cylinder in cross flow. Experiments were conducted with a single row of spanwise-angled coolant holes for a range of the coolant blowing ratio with a freestream-to-wall temperature ratio of about 2.1 and a Reynolds number of 170,000, characteristic of the gas-turbine environment. Data from local heat-flux measurements are presented for coolant-hole injection angles of 25, 35, and 45 deg with the row of holes located at three positions relative to the stagnation line on the cylinder. Results show the spanwise (hole-to-hole) variation of heat-flux reduction due to film cooling and indicate conditions for the optimum film-cooling performance.

Luckey, D. W.; Winstanley, D. K.; Hanus, G. J.; Lecuyer, M. R.

1976-01-01

195

Application of superplastically formed and diffusion bonded aluminum to a laminar flow control leading edge  

NASA Technical Reports Server (NTRS)

NASA sponsored the Aircraft Energy Efficiency (ACEE) program in 1976 to develop technologies to improve fuel efficiency. Laminar flow control was one such technology. Two approaches for achieving laminar flow were designed and manufactured under NASA sponsored programs: the perforated skin concept used at McDonnell Douglas and the slotted design used at Lockheed-Georgia. Both achieved laminar flow, with the slotted design to a lesser degree (JetStar flight test program). The latter design had several fabrication problems concerning springback and adhesive flow clogging the air flow passages. The Lockheed-Georgia Company accomplishments is documented in designing and fabricating a small section of a leading edge article addressing a simpler fabrication method to overcome the previous program's manufacturing problems, i.e., design and fabrication using advanced technologies such as diffusion bonding of aluminum, which has not been used on aerospace structures to date, and the superplastic forming of aluminum.

Goodyear, M. D.

1987-01-01

196

An experimental study of pressures on 60 deg Delta wings with leading edge vortex flaps  

NASA Technical Reports Server (NTRS)

An experimental study was conducted in the Virginia Tech Stability Wind Tunnel to determine surface pressures over a 60 deg sweep delta wing with three vortex flap designs. Extensive pressure data was collected to provide a base data set for comparison with computational design codes and to allow a better understanding of the flow over vortex flaps. The results indicated that vortex flaps can be designed which will contain the leading edge vortex with no spillage onto the wing upper surface. However, the tests also showed that flaps designed without accounting for flap thickness will not be optimum and the result can be oversized flaps, early flap vortex reattachment and a second separation and vortex at the wing/flap hinge line.

Marchman, J. F., III; Terry, J. E.; Donatelli, D. A.

1983-01-01

197

Leading edge serrations which reduce the noise of low-speed rotors  

NASA Technical Reports Server (NTRS)

Acoustic effects of serrated brass strips attached near the leading edges of two different size rotors were investigated. The two bladed rotors were tested in hover. Rotor rotational speed, blade angle, serration shape, and serration position were varied. The serrations were more effective as noise suppressors at rotor tip speeds less than 135 m/sec (444 ft/sec) than at higher speeds. high frequency noise was reduced but the low frequency rotational noise was little affected. Noise reductions from 4 to 8 db overall sound pressure level and 3 to 17 db in the upper octave bands were achieved on the 1.52 m (5.0 ft) diameter rotor. Noise reductions up to 4 db overall sound pressure level were measured for the 2.59 m (8.5 ft) diameter rotor at some conditions.

Soderman, P. T.

1973-01-01

198

Vibration and sound of an elastic wing actuated at its leading edge  

NASA Astrophysics Data System (ADS)

The motion and sound of a thin elastic plate, subject to uniform low-Mach flow and actuated at its leading edge, is studied. The linearized response to arbitrary small-amplitude translation and rotation is analyzed using Fourier decomposition of the forcing signal. Both periodic (sinusoidal) and non-periodic ("step-jump") actuations are investigated. When the frequency spectrum of the forcing signal contains an eigenfrequency ?res of the unforced system, a resonance motion is excited and the plate oscillates at the corresponding eigenmode. The dynamical description is applied to formulate the acoustic problem, where the sources of sound include the plate velocity and fluid vorticity. Acoustic radiation of a dipole type is calculated and discussed in the limit where the plate is acoustically compact. In the case of sinusoidal excitation, plate elasticity has two opposite effects on sound radiation, depending on the forcing frequency: at frequencies close to ?res, the near-resonance motion results in the generation of high sound levels; however, at frequencies far from ?res, plate elasticity reduces the amplitude of plate deflection (compared to that of a rigid plate), leading to noise reduction. In the case of non-periodic actuation, the plate-fluid system amplifies those frequencies that are closest to ?res, which, in turn, dominate the acoustic signature. The results identify the trailing edge noise as the main source of sound, dominating the sound generated by direct plate motion. We suggest the present theory as a preliminary tool for examining the acoustic signature of flapping flight, common in insects and flapping micro-air-vehicles.

Manela, A.

2012-01-01

199

A mechanism for mitigation of blade-vortex interaction using leading edge blowing flow control  

NASA Astrophysics Data System (ADS)

The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI, the parallel blade-vortex interaction (BVI) is the most common, often encountered in helicopters and propulsors. In this work, we report on the implementation of leading edge blowing (LEB) active flow control for successfully minimizing the parallel BVI. Our results show reduction of the airfoil vibrations up to 38% based on the root-mean-square of the vibration velocity amplitude. This technique is based on displacing an incident vortex using a jet issued from the leading edge of a sharp airfoil effectively increasing the stand-off distance of the vortex from the body. The effectiveness of the method was experimentally analyzed using time-resolved digital particle image velocimetry (TRDPIV) recorded at an 800 Hz rate, which is sufficient to resolve the spatio-temporal dynamics of the flow field and it was combined with simultaneous accelerometer measurements of the airfoil, which was free to oscillate in a direction perpendicular to the freestream. Analysis of the flow field spectra and a Proper Orthogonal Decomposition (POD) of the TRDPIV data of the temporally resolved planar flow fields indicate that the LEB effectively modified the flow field surrounding the airfoil and increased the convecting vortices stand-off distance for over half of the airfoil chord length. It is shown that LEB also causes a redistribution of the flow field spectral energy over a larger range of frequencies.

Weiland, Chris; Vlachos, Pavlos P.

2009-09-01

200

Static and dynamic leading-edge-flap effects on the vortex lift of a delta wing  

NASA Astrophysics Data System (ADS)

Experiments were performed to determine the static and dynamic effects of leading edge flaps on the vortex lift of a delta wing. The flaps were linearly tapered, for a constant flap height to wing-span ratio of 0.33 or 0.22 and were able to pivot about the wing's leading edge. Experiments consisted mainly of pressure surveys, but also included flow visualizations and lift force measurements. Flap deflections, for most static flap cases and all the moving flap cases, were from folded on to the upper (suction) wing surface to normal to it. At low angles of attack, the static flaps created strong separated vortices and a flap-angle controlled lift increment. The flow structure of the main vortices were no different from those of plain delta wings. At high angles of attack the flaps caused a decrease of lift, unless they were unfolded beyond the wing, forming a new, nearly planar, delta wing of reduced sweep, Asymmetric deployment of a single flap failed to control the rolling moment monotonicly. Rapid opening of the flaps, in the order of one convective time length, increased the vortex lift further, above its quasi steady value. Transient vortex-lift increments were typically of the order of 40% of the static flap increments, at low angles of attack. Rapid closing of the flaps diminished the vortex lift below its quasi steady value. The power needed to operate the flaps at such speeds was enormous, comparable to the propulsive power required by the wing. The data following the completion of flap motion had to be discarded, because the abrupt arrest of flap motion caused both structural and data interference problems. A co-planar delta wing with dynamically variable sweep angle is proposed to overcome the deficiencies of the present arrangement.

Karagounis, Thales

201

Piezoelectric Properties of Polycrystalline Lead Titanate Zirconate Compositions  

Microsoft Academic Search

Detailed data are given for the piezoelectric, elastic, and dielectric properties of lead titanate zirconate ceramic compositions near the rhombohedral-tetragonal phase boundary. These compositions have markedly higher electromechanical coupling factors, remanent ferroelectric charge, and coercive field, than ceramic barium titanate. Another interesting feature is a pronounced change in the free permittivity ¿33T by the poling process; this change is in

D. A. Berlincourt; C. Cmolik; H. Jaffe

1960-01-01

202

Effect of leading- and trailing-edge flaps on clipped delta wings with and without wing camber at supersonic speeds  

NASA Technical Reports Server (NTRS)

An experimental investigation of the aerodynamic characteristics of thin, moderately swept fighter wings has been conducted to evaluate the effect of camber and twist on the effectiveness of leading- and trailing-edge flaps at supersonic speeds in the Langley Unitary Plan Wind Tunnel. The study geometry consisted of a generic fuselage with camber typical of advanced fighter designs without inlets, canopy, or vertical tail. The model was tested with two wing configurations an uncambered (flat) wing and a cambered and twisted wing. Each wing had an identical clipped delta planform with an inboard leading edge swept back 65 deg and an outboard leading edge swept back 50 deg. The trailing edge was swept forward 25 deg. The leading-edge flaps were deflected 4 deg to 15 deg, and the trailing-edge flaps were deflected from -30 deg to 10 deg. Longitudinal force and moment data were obtained at Mach numbers of 1.60, 1.80, 2.00, and 2.16 for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.16 x 10(exp 6) per foot and for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.0 x 10(exp 6) per foot. Vapor screen, tuft, and oil flow visualization data are also included.

Hernandez, Gloria; Wood, Richard M.; Covell, Peter F.

1994-01-01

203

A comparison of experimental and calculated thin-shell leading-edge buckling due to thermal stresses  

NASA Technical Reports Server (NTRS)

High-temperature thin-shell leading-edge buckling test data are analyzed using NASA structural analysis (NASTRAN) as a finite element tool for predicting thermal buckling characteristics. Buckling points are predicted for several combinations of edge boundary conditions. The problem of relating the appropriate plate area to the edge stress distribution and the stress gradient is addressed in terms of analysis assumptions. Local plasticity was found to occur on the specimen analyzed, and this tended to simplify the basic problem since it effectively equalized the stress gradient from loaded edge to loaded edge. The initial loading was found to be difficult to select for the buckling analysis because of the transient nature of thermal stress. Multiple initial model loadings are likely required for complicated thermal stress time histories before a pertinent finite element buckling analysis can be achieved. The basic mode shapes determined from experimentation were correctly identified from computation.

Jenkins, Jerald M.

1988-01-01

204

Aluminium foams as a filler for leading edges: Improvements in the mechanical behaviour under bird strike impact tests  

Microsoft Academic Search

The use of aluminium foams as filler materials in aeronautical leading edges is investigated. Particularly, the improvement of the mechanical behaviour of the filled structure respect to the hollow one is analysed by means of standard bird strike impact tests. For this purpose, a collection of AlSi10 foams were fabricated using the powder metallurgical route (PM), and introduced into leading

J. A. Reglero; M. A. Rodríguez-Pérez; E. Solórzano; J. A. de Saja

2011-01-01

205

Teachers on the Leading Edge: A Place-Based Professional Development Program for K-12 Earth Science Teachers  

Microsoft Academic Search

Teachers on the Leading Edge (TOTLE) is an Earth Science teacher professional development program featuring Pacific Northwest active continental margin geology. To engage middle-school teachers and students, TOTLE workshops: (1) invite novice learners to geophysical studies of tectonics, earthquakes, and volcanoes; (2) provide access to EarthScope research; and (3) explain geologic hazards as understandable aspects of living on the ``leading

Robert Butler

2010-01-01

206

A Three-Dimensional Solution of Flows over Wings with Leading-Edge Vortex Separation. Part 1: Engineering Document  

NASA Technical Reports Server (NTRS)

A method of predicting forces, moments, and detailed surface pressures on thin, sharp-edged wings with leading-edge vortex separation in incompressible flow is presented. The method employs an inviscid flow model in which the wing and the rolled-up vortex sheets are represented by piecewise, continuous quadratic doublet sheet distributions. The Kutta condition is imposed on all wing edges. Computed results are compared with experimental data and with the predictions of the leading-edge suction analogy for a selected number of wing planforms over a wide range of angle of attack. These comparisons show the method to be very promising, capable of producing not only force predictions, but also accurate predictions of detailed surface pressure distributions, loads, and moments.

Brune, G. W.; Weber, J. A.; Johnson, F. T.; Lu, P.; Rubbert, P. E.

1975-01-01

207

Pressure distributions from subsonic tests of an advanced laminar-flow-control wing with leading- and trailing-edge flaps  

NASA Technical Reports Server (NTRS)

An unswept, semispan wing model equipped with full-span leading- and trailing-edge flaps was tested in the Langley 14- by 22-Foot Subsonic Tunnel to determine the effect of high-lift components on the aerodynamics of an advanced laminar-flow-control (LFC) airfoil section. Chordwise pressure distributions near the midsemispan were measured for four configurations: cruise, trailing-edge flap only, and trailing-edge flap with a leading edge Kreuger flap of either 0.10 or 0.12 chord. Part 1 of this report presents a representative sample of the plotted pressure distribution data for each configuration tested. Part 2 (under separate cover) presents the entire set of plotted and tabulated pressure distribution data. The data are presented without analysis.

Applin, Zachary T.; Gentry, Garl L., Jr.

1988-01-01

208

Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads  

NASA Astrophysics Data System (ADS)

We theoretically investigate the spin-dependent transport for the system of an armchair-edge graphene nanoribbon (AGNR) between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the AGNR to induce an exchange splitting between spin-up and -down carriers. By using the standard nonequilibrium Green's function (NGF) technique, it is demonstrated that the spin-resolved transport property for the system depends sensitively on both the width of AGNR and the polarization strength of FM leads. The tunneling magnetoresistance (TMR) around zero bias voltage possesses a pronounced plateau structure for a system with semiconducting 7-AGNR or metallic 8-AGNR in the absence of exchange splitting, but this plateau structure for the 8-AGNR system is remarkably broader than that for the 7-AGNR one. Interestingly, an increase of the exchange splitting ? suppresses the amplitude of the structure for the 7-AGNR system. However, the TMR is much enhanced for the 8-AGNR system under a bias amplitude comparable to the splitting strength. Further, the current-induced spin-transfer torque (STT) for the 7-AGNR system is systematically larger than that for the 8-AGNR one. The findings here suggest the design of GNR-based spintronic devices by using a metallic AGNR, but it is more favorable to fabricate a current-controlled magnetic memory element by using a semiconducting AGNR.

Zhou, Benhu; Chen, Xiongwen; Zhou, Benliang; Ding, Kai-He; Zhou, Guanghui

2011-04-01

209

Growth Cone Collapse through Coincident Loss of Actin Bundles and Leading Edge Actin without Actin Depolymerization  

PubMed Central

Repulsive guidance cues can either collapse the whole growth cone to arrest neurite outgrowth or cause asymmetric collapse leading to growth cone turning. How signals from repulsive cues are translated by growth cones into this morphological change through rearranging the cytoskeleton is unclear. We examined three factors that are able to induce the collapse of extending Helisoma growth cones in conditioned medium, including serotonin, myosin light chain kinase inhibitor, and phorbol ester. To study the cytoskeletal events contributing to collapse, we cultured Helisoma growth cones on polylysine in which lamellipodial collapse was prevented by substrate adhesion. We found that all three factors that induced collapse of extending growth cones also caused actin bundle loss in polylysine-attached growth cones without loss of actin meshwork. In addition, actin bundle loss correlated with specific filamentous actin redistribution away from the leading edge that is characteristic of repulsive factors. Finally, we provide direct evidence using time-lapse studies of extending growth cones that actin bundle loss paralleled collapse. Taken together, these results suggest that actin bundles could be a common cytoskeletal target of various collapsing factors, which may use different signaling pathways that converge to induce growth cone collapse. PMID:11381091

Zhou, Feng-quan; Cohan, Christopher S.

2001-01-01

210

Anodic corrosion of fiber reinforced lead composites for use in large lead-acid batteries  

Microsoft Academic Search

The corrosion resistance of lightweight, high strength lead metal matrix composites under conditions that simulate their use as grid materials in large lead-acid batteries has been studied. Constant potential testing provides an effective means for holding constant the oxidizing power of a metal-electrolyte system. Data are presented on corrosion currents, effect of exposure time on corrosion rates, dependence of the

C. M. Dacres; S. M. Reamer; R. A. Sutula; I. A. Angres

1981-01-01

211

Theory and experiment for flutter of a rectangular plate with a fixed leading edge in three-dimensional axial flow  

NASA Astrophysics Data System (ADS)

This paper explores cantilevered beam flutter for both clamped and pinned leading edge boundary conditions. Specifically, a three-dimensional vortex lattice panel method is coupled with a classical Lagrangian one-dimensional beam structural model to predict the linear flutter boundary for finite size rectangular plates. The paper explores the change in flutter characteristics as a function of the fluid to structure mass ratio and the structural aspect ratio. The paper also presents an exploration of the non-monotonic transition in flutter velocity between the pinned-free and clamped-free boundary conditions which is modeled using a leading edge torsional spring. The theoretical results are compared to vibration and aeroelastic test results collected in the Duke University wind tunnel as well as previous theoretical and experimental results for the leading edge clamped configuration. The aeroelastic experiments confirmed the validity of the three-dimensional vortex lattice aerodynamic model over a subset of mass ratios.

Chad Gibbs, S.; Wang, Ivan; Dowell, Earl

2012-10-01

212

{alpha}-Crystallin localizes to the leading edges of migrating lens epithelial cells  

SciTech Connect

{alpha}-crystallin ({alpha}A and {alpha}B) is a major lens protein, which belongs to the small heat-shock family of proteins and binds to various cytoskeletal proteins including actin, vimentin and desmin. In this study, we investigated the cellular localization of {alpha}A and {alpha}B-crystallins in migrating epithelial cells isolated from porcine lens. Immunofluorescence localization and confocal imaging of {alpha}B-crystallin in confluent and in migrating subconfluent cell cultures revealed a distinct pattern of subcellular distribution. While {alpha}B-crystallin localization was predominantly cytoplasmic in confluent cultures, it was strongly localized to the leading edges of cell membrane or the lamellipodia in migrating cells. In accordance with this pattern, we found abundant levels of {alpha}B-crystallin in membrane fractions compared to cytosolic and nuclear fractions in migrating lens epithelial cells. {alpha}A-crystallin, which has 60% sequence identity to {alpha}B-crystallin, also exhibited a distribution profile localizing to the leading edge of the cell membrane in migrating lens epithelial cells. Localization of {alpha}B-crystallin to the lamellipodia appears to be dependent on phosphorylation of residue serine-59. An inhibitor of p38 MAP kinase (SB202190), but not the ERK kinase inhibitor PD98059, was found to diminish localization of {alpha}B-crystallin to the lamellipodia, and this effect was found to be associated with reduced levels of Serine-59 phosphorylated {alpha}B-crystallin in SB202190-treated migrating lens epithelial cells. {alpha}B-crystallin localization to the lamellipodia was also altered by the treatment with RGD (Arg-Ala-Asp) peptide, dominant negative N17 Rac1 GTPase, cytochalasin D and Src kinase inhibitor (PP2), but not by the Rho kinase inhibitor Y-27632 or the myosin II inhibitor, blebbistatin. Additionally, in migrating lens epithelial cells, {alpha}B-crystallin exhibited a clear co-localization with the actin meshwork, {beta}-catenin, WAVE-1, a promoter of actin nucleation, Abi-2, a component of WAVE-1 protein complex and Arp3, a protein of the actin nucleation complex, suggesting potential interactions between {alpha}B-crystallin and regulatory proteins involved in actin dynamics and cell adhesion. This is the first report demonstrating specific localization of {alpha}A and {alpha}B-crystallins to the lamellipodia in migrating lens epithelial cells and our findings indicate a potential role for {alpha}-crystallin in actin dynamics during cell migration.

Maddala, Rupalatha [Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710 (United States); Vasantha Rao, P. [Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710 (United States) and Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710 (United States)]. E-mail: rao00011@mc.duke.edu

2005-05-15

213

Leading edge boundary layer receptivitivy to oblique free stream acoustic waves on parabolic bodies  

NASA Astrophysics Data System (ADS)

In this study, the effect of the incidence angle of free strewn acoustic waves on the leading edge boundary layer receptivity of a two dimensional laminar incompressible flow over parabolic bodies is investigated. For this, the full Navier-Stokes equations in parabolic coordinates in streamfunction and vorticity variables were solved numerically. For the receptivity problem a spatial approach is used. With this approach, the free stream flow variables are composed of a uniform flow with a superimposed perturbation fluctuations of small amplitude. Using Normal Mode form and linearization assuming that the perturbations are small, the unsteady governing equations are converted into two systems of equations; the steady nonlinear basic flow equations and the steady linear complex perturbation flow equations. For the solution of nonlinear basic flow equations, a new numerical technique is developed which provides very accurate solutions. The perturbation equations are solved using a direct linear solver (LINPACK subroutines). In the numerical calculations, the numerical domain extends downstream of Branch II predicted by the linear theory for Blasius flow, for the frequency of the free stream oscillations used in the problem. The numerical codes for the solution of both the basic flow and the perturbation flow equations are first tested extensively to validate the solutions. In order to determine the receptivity coefficient, KLE, three steps are followed. First the basic flow equations are solved. Second, using the basic flow solution, the perturbation equations are solved. Third, the Stokes wave solution is obtained and subtracted from the perturbation solution. Using this final solution, the receptivity coefficient is extrapolated to the leading edge. The results obtained are compared with the past numerical results of Haddad [17], where they were found to be in excellent quantitative agreement. Quantitative comparisons with the analytical results of Hammerton and Kerschen [20] could not be made because of differences between the semi-infinite geometry used here and the finite geometry used by them. However, we observed excellent qualitative comparisons which indicate that the essential physics were represented by our numerical approach.

Erturk, Ercan

214

The influence of airfoil kinematics on the formation of leading-edge vortices in bio-inspired flight  

NASA Astrophysics Data System (ADS)

The formation process of leading-edge vortices has been investigated experimentally using Particle Image Velocimetry. Various airfoil kinematics have been tested, including asymmetric and peak-shifted plunging motions, and are evaluated for Re = 30,000 and a reduced frequency range of 0.2 ? k ? 0.33. By measuring the growth in the leading-edge vortex during the dynamic-stall process, the vortex pinch-off process is examined based on the concept of an optimal vortex formation time. The various kinematics are then evaluated with respect to their associated vortex strength, timing and convection into the wake.

Rival, David; Prangemeier, Tim; Tropea, Cameron

215

The influence of airfoil kinematics on the formation of leading-edge vortices in bio-inspired flight  

NASA Astrophysics Data System (ADS)

The formation process of leading-edge vortices has been investigated experimentally using Particle Image Velocimetry. Various airfoil kinematics have been tested, including asymmetric and peak-shifted plunging motions, and are evaluated for Re = 30,000 and a reduced frequency range of 0.2 ? k ? 0.33. By measuring the growth in the leading-edge vortex during the dynamic-stall process, the vortex pinch-off process is examined based on the concept of an optimal vortex formation time. The various kinematics are then evaluated with respect to their associated vortex strength, timing and convection into the wake.

Rival, David; Prangemeier, Tim; Tropea, Cameron

2009-05-01

216

Thermostructural Evaluation of Joggle Region on the Shuttle Orbiter's Wing Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation was initiated to determine the cause of coating spallation occurring on the Shuttle Orbiter's wing leading edge panels in the slip-side joggle region. The coating spallation events were observed, post flight, on differing panels on different missions. As part of the investigation, the high re-entry heating occurring on the joggles was considered here as a possible cause. Thus, a thermostructural evaluation was conducted to determine the detailed state-of-stress in the joggle region during re-entry and the feasibility of a laboratory test on a local joggle specimen to replicate this state-of-stress. A detailed three-dimensional finite element model of a panel slip-side joggle region was developed. Parametric and sensitivity studies revealed significant stresses occur in the joggle during peak heating. A critical interlaminar normal stress concentration was predicted in the substrate at the coating interface and was confined to the curved joggle region. Specifically, the high interlaminar normal stress is identified to be the cause for the occurrence of failure in the form of local subsurface material separation occurring in the slip-side joggle. The predicted critical stresses are coincident with material separations that had been observed with microscopy in joggle specimens obtained from flight panels.

Walker, Sandra P.; Warren, Jerry E.

2012-01-01

217

Fracture Mechanics Analyses of Reinforced Carbon-Carbon Wing-Leading-Edge Panels  

NASA Technical Reports Server (NTRS)

Fracture mechanics analyses of subsurface defects within the joggle regions of the Space Shuttle wing-leading-edge RCC panels are performed. A 2D plane strain idealized joggle finite element model is developed to study the fracture behavior of the panels for three distinct loading conditions - lift-off and ascent, on-orbit, and entry. For lift-off and ascent, an estimated bounding aerodynamic pressure load is used for the analyses, while for on-orbit and entry, thermo-mechanical analyses are performed using the extreme cold and hot temperatures experienced by the panels. In addition, a best estimate for the material stress-free temperature is used in the thermo-mechanical analyses. In the finite element models, the substrate and coating are modeled separately as two distinct materials. Subsurface defects are introduced at the coating-substrate interface and within the substrate. The objective of the fracture mechanics analyses is to evaluate the defect driving forces, which are characterized by the strain energy release rates, and determine if defects can become unstable for each of the loading conditions.

Raju, Ivatury S.; Phillips, Dawn R.; Knight, Norman F., Jr.; Song, Kyongchan

2010-01-01

218

A practical study of the aerodynamic impact of wind turbine blade leading edge erosion  

NASA Astrophysics Data System (ADS)

During operation wind turbine blades are exposed to a wide variety of atmospheric and environmental conditions; inspection reports for blades that have been operating for several years show varying degrees of leading edge erosion. It is important to be able to estimate the impact of different stages of erosion on wind turbine performance, but this is very difficult even with advanced CFD models. In this study, wind tunnel testing was used to evaluate a range of complex erosion stages. Erosion patterns were transferred to thin films that were applied to 18% thick commercial wind turbine aerofoils and full lift and drag polars were measured in a wind tunnel. Tests were conducted up to a Reynolds number of 2.20 × 106 scaling based on the local roughness Reynolds number was used in combination with different film thicknesses to simulate a variety of erosion depths. The results will be very useful for conducting cost/benefit analyses of different methods of blade protection and repair, as well as for defining the appropriate timescales for these processes.

Gaudern, N.

2014-06-01

219

Effect of Impact Location on the Response of Shuttle Wing Leading Edge Panel 9  

NASA Technical Reports Server (NTRS)

The objective of this paper is to compare the results of several simulations performed to determine the worst-case location for a foam impact on the Space Shuttle wing leading edge. The simulations were performed using the commercial non-linear transient dynamic finite element code, LS-DYNA. These simulations represent the first in a series of parametric studies performed to support the selection of the worst-case impact scenario. Panel 9 was selected for this study to enable comparisons with previous simulations performed during the Columbia Accident Investigation. The projectile for this study is a 5.5-in cube of typical external tank foam weighing 0.23 lb. Seven locations spanning the panel surface were impacted with the foam cube. For each of these cases, the foam was traveling at 1000 ft/s directly aft, along the orbiter X-axis. Results compared from the parametric studies included strains, contact forces, and material energies for various simulations. The results show that the worst case impact location was on the top surface, near the apex.

Lyle, Karen H.; Spellman, Regina L.; Hardy, Robin C.; Fasanella, Edwin L.; Jackson, Karen E.

2005-01-01

220

Wing Leading Edge RCC Rapid Response Damage Prediction Tool (IMPACT2)  

NASA Technical Reports Server (NTRS)

This rapid response computer program predicts Orbiter Wing Leading Edge (WLE) damage caused by ice or foam impact during a Space Shuttle launch (Program "IMPACT2"). The program was developed after the Columbia accident in order to assess quickly WLE damage due to ice, foam, or metal impact (if any) during a Shuttle launch. IMPACT2 simulates an impact event in a few minutes for foam impactors, and in seconds for ice and metal impactors. The damage criterion is derived from results obtained from one sophisticated commercial program, which requires hours to carry out simulations of the same impact events. The program was designed to run much faster than the commercial program with prediction of projectile threshold velocities within 10 to 15% of commercial-program values. The mathematical model involves coupling of Orbiter wing normal modes of vibration to nonlinear or linear springmass models. IMPACT2 solves nonlinear or linear impact problems using classical normal modes of vibration of a target, and nonlinear/ linear time-domain equations for the projectile. Impact loads and stresses developed in the target are computed as functions of time. This model is novel because of its speed of execution. A typical model of foam, or other projectile characterized by material nonlinearities, impacting an RCC panel is executed in minutes instead of hours needed by the commercial programs. Target damage due to impact can be assessed quickly, provided that target vibration modes and allowable stress are known.

Clark, Robert; Cottter, Paul; Michalopoulos, Constantine

2013-01-01

221

Numerical Predictions of Sonic Boom Signatures for a Straight Line Segmented Leading Edge Model  

NASA Technical Reports Server (NTRS)

A sonic boom wind tunnel test was conducted on a straight-line segmented leading edge (SLSLE) model in the NASA Langley 4- by 4- Foot Unitary Plan Wind Tunnel (UPWT). The purpose of the test was to determine whether accurate sonic boom measurements could be obtained while continuously moving the SLSLE model past a conical pressure probe. Sonic boom signatures were also obtained using the conventional move-pause data acquisition method for comparison. The continuous data acquisition approach allows for accurate signatures approximately 15 times faster than a move-pause technique. These successful results provide an incentive for future testing with greatly increased efficiency using the continuous model translation technique with the single probe to measure sonic boom signatures. Two widely used NASA codes, USM3D (Navier-Stokes) and CART3D-AERO (Euler, adjoint-based adaptive mesh), were used to compute off-body sonic boom pressure signatures of the SLSLE model at several different altitudes below the model at Mach 2.0. The computed pressure signatures compared well with wind tunnel data. The effect of the different altitude for signature extraction was evaluated by extrapolating the near field signatures to the ground and comparing pressure signatures and sonic boom loudness levels.

Elmiligui, Alaa A.; Wilcox, Floyd J.; Cliff, Susan; Thomas, Scott

2012-01-01

222

Stroke plane angle controls leading edge vortex in a bat-inspired flapper  

NASA Astrophysics Data System (ADS)

The present interest in micro air vehicles has given the research on bat flight a new impulse. With the use of high speed cameras and improved PIV techniques, the kinematics and aerodynamics of bats have been studied in great detail. A robotic flapper makes it possible to do measurements by systematically changing only one parameter at a time and investigate the parameter space outside the natural flight envelope of bats without risking animal safety. For this study, a robotic flapper (RoBat), inspired by Leptonycteris yerbabuenae was developed and tested over the speed range 1-7 m/s, with variable maximum angles of attacks ( AoA=55° and 15°, respectively) and constant AoA=55°. These measurements show the presence of a leading edge vortex (LEV) for low speeds and a fully attached flow for high speeds at low AoA, which is in line with natural bat flight. A LEV occurs for AoA=55° throughout the complete flight speed range, and throughout which the LEV circulation coefficient remains rather constant. This implies that bats and micro air vehicles could use LEVs for high load maneuvers also at relatively high flight speeds. However, at high flight speeds the LEV bursts, which causes increased drag, most likely due to a decrease in Strouhal number.

Koekkoek, Gide; Muijres, Florian T.; Johansson, L. Christoffer; Stuiver, Melanie; van Oudheusden, Bas W.; Hedenström, Anders

2012-01-01

223

Suppression of dynamic stall with a leading-edge slat on a VR-7 airfoil  

NASA Technical Reports Server (NTRS)

The VR-7 airfoil was experimentally studied with and without a leading-edge slat at fixed angles of attack from 0 deg to 30 deg at Re = 200,000 and for unsteady pitching motions described by alpha equals alpha(sub m) + 10 deg(sin(wt)). The models were two dimensional, and the test was performed in a water tunnel at Ames Research Center. The unsteady conditions ranged over Re equals 100,000 to 250,000, k equals 0.001 to 0.2, and alpha(sub m) = 10 deg to 20 deg. Unsteady lift, drag, and pitching-moment measurements were obtained along with fluorescent-dye flow visualizations. The addition of the slat was found to delay the static-drag and static-moment stall by about 5 degrees and to eliminate completely the development of a dynamic-stall vortex during unsteady motions that reached angles as high as 25 degrees. In all of the unsteady cases studied, the slat caused a significant reduction in the force and moment hysteresis amplitudes. The reduced frequency was found to have the greatest effect on the results, whereas the Reynolds number had little effect on the behavior of either the basic or the slatted airfoil. The slat caused a slight drag penalty at low angles of attack, but generally increased the lift/drag ratio when averaged over the full cycle of oscillation.

Mcalister, K. W.; Tung, C.

1993-01-01

224

Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil  

NASA Technical Reports Server (NTRS)

This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

2012-01-01

225

Augmentation of Fighter-Aircraft Performance by Spanwise Blowing over the Wing Leading Edge  

NASA Technical Reports Server (NTRS)

Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 to 60 deg, and yaw-angle sweeps from -8 to 36 deg at fixed angles of attack 0, 10, 20, 25, 30, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.

Seginer, A.; Salomon, M.

1983-01-01

226

Augmentation of fighter-aircraft performance by spanwise blowing over the wing leading edge  

NASA Technical Reports Server (NTRS)

Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter-airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 deg to 60 deg, and yaw-angle sweeps from -8 deg to 36 deg at fixed angles of attack 0 deg, 10 deg, 20 deg, 25 deg, 30 deg, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.

Seginer, A.; Salomon, M.

1983-01-01

227

Lithium tantalate\\/lead zirconate titanate composite ultrasonic transducers  

Microsoft Academic Search

Lithium tantalate (LiTaO3)\\/lead zirconate titanate (PZT) ceramic films of thickness about 50 mum have been deposited on stainless-steel substrates using a modified sol-gel process. LiTaO3 powders are dispersed in a PZT sol-gel matrix to form a 0-3 ceramic\\/ceramic composite. The dielectric, electric, and piezoelectric properties have been studied. Ultrasonic pulse-echo measurements using the composite films as piezoelectric ultrasonic transducers demonstrate

Y. Chen; M. Sayer; L. Zou; C.-K. Jen

1999-01-01

228

Prediction of unsteady aerodynamic loadings caused by leading edge and trailing edge control surface motions in subsonic compressible flow: Analysis and results  

NASA Technical Reports Server (NTRS)

A theoretical analysis and computer program was developed for the prediction of unsteady lifting surface loadings caused by motions of leading edge and trailing edge control surfaces having sealed gaps. The final form of the downwash integral equation was formulated by isolating the singularities from the nonsingular terms and using a preferred solution process to remove and evaluate the downwash discontinuities in a systematic manner. Comparisons of theoretical and experimental pressure data are made for several control surface configurations. The comparisons indicate that reasonably accurate theoretical pressure distributions and generalized forces may be obtained for a wide variety of control surface configurations. Spanwise symmetry or antisymmetry of motion, and up to six control surfaces on each half span can be accommodated.

Rowe, W. S.; Redman, M. C.; Ehlers, F. E.; Sebastian, J. D.

1975-01-01

229

Subsonic Investigation of a Leading-Edge Boundary Layer Control Suction System on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

A wind tunnel investigation of a leading edge boundary layer control system was conducted on a High Speed Civil Transport (HSCT) configuration in the Langley 14- by 22-Foot Subsonic Tunnel. Data were obtained over a Mach number range of 0.08 to 0.27, with corresponding chord Reynolds numbers of 1.79 x 10(exp 6) to 5.76 x 10(exp 6). Variations in the amount of suction, as well as the size and location of the suction area, were tested with outboard leading edge flaps deflected 0 and 30 deg and trailing-edge flaps deflected 0 and 20 deg. The longitudinal and lateral aerodynamic data are presented without analysis. A complete tabulated data listing is also presented herein.

Campbell, Bryan A.; Applin, Zachary T.; Kemmerly, Guy T.; Coe, Paul L., Jr.; Owens, D. Bruce; Gile, Brenda E.; Parikh, Pradip G.; Smith, Don

1999-01-01

230

Mixed-mode strain-energy-release rate effects on edge delamination of composites  

NASA Technical Reports Server (NTRS)

Unnotched graphite/epoxy laminates, designed to delaminate at the edges under static and cyclic tensile loads, were tested and analyzed. The specimen stacking sequences were chosen so that the total strain-energy-release rate, G, for edge delamination was identical for all three layups. However, each layup had different percentages of crack-opening and shear-mode strain-energy-release rates, G sub 1 and G sub 2, respectively. Results with composites made from T300 graphite fibers and 5208 epoxy, a brittle resin, indicated that only G sub 1 contributed to delamination onset under static loading. However, results with composites made from C6000 fibers and H205 epoxy, a tougher resin, indicated that the total F governed the onset of edge delaminations under cyclic loads. In addition, for both materials, the threshold level of G for delamination onset in fatigue was significantly less than the critical G sub c measured in static tests. Futhermore, although the C6000/H205 material had a much higher static G sub c than T300/5208, its fatigue resistance was only slightly better. A series of mixed-mode tests, like the ones in this study, may be needed to evaluate toughened-resin composites developed for highly strained composite structures subjected to cyclic loads.

Obrien, T. K.

1983-01-01

231

Free edge strain concentrations in real composite laminates: Experimental-theoretical correlation  

NASA Technical Reports Server (NTRS)

The magnitude of the maximum shear strain at the free edge of axially loaded theta (2)/-theta(2)(s) and (+ or - theta(2) (s) composite laminates was investigated experimentally and numerically to ascertain the actual value of strain concentration in resin matrix laminates and to determine the accuracy of finite element results. Experimental results using moire interferometry show large, but finite, shear strain concentrations at the free edge of graphite-epoxy and graphite-polyimide laminates. Comparison of the experimental results with those obtained using several different finite element representations showed that a four node isoparametric finite element provided the best and most trouble free numerical results. The results indicate that the ratio of maxium shear strain at the free edge to applied axial strain varies with fiber orientation and does not exceed nine for the most critical angle which is 15 deg.

Herakovich, C. T.; Post, D.; Buczek, M. B.; Czarnek, R.

1984-01-01

232

Effects of leading-edge devices on the low-speed aerodynamic characteristics of a highly-swept arrow-wing  

NASA Technical Reports Server (NTRS)

An investigation was conducted in the Texas A&M University 7 by 10 foot Low Speed Wind Tunnel to provide a direct comparison of the effect of several leading edge devices on the aerodynamic performance of a highly swept wing configuration. Analysis of the data indicates that for the configuration with undeflected leading edges, vortex separation first occurs on the outboard wing panel for angles of attack of approximately 2, and wing apex vorticies become apparent for alpha or = 4 deg. However, the occurrence of the leading edge vortex flow may be postponed with leading edge devices. Of the devices considered, the most promising were a simple leading edge deflection of 30 deg and a leading edge slat system. The trailing edge flap effectiveness was found to be essentially the same for the configuration employing either of these more promising leading edge devices. Analysis of the lateral directional data showed that for all of the concepts considered, deflecting leading edge downward in an attempt to postpone leading edge vortex flows, has the favorable effect of reducing the effective dihedral.

Scott, S. J.; Nicks, O. W.; Imbrie, P. K.

1985-01-01

233

Analysis of actin dynamics at the leading edge of crawling cells: implications for the shape of keratocyte lamellipodia  

E-print Network

ARTICLE Analysis of actin dynamics at the leading edge of crawling cells: implications of the critical events in the cell motility cycle and it is believed to be driven by the assembly of the actin network. The con- cept of dendritic nucleation of actin filaments provides a basis for understanding

Mogilner, Alex

234

Eliciting a human understandable model of ice adhesion strength for rotor blade leading edge materials from uncertain experimental data  

E-print Network

Eliciting a human understandable model of ice adhesion strength for rotor blade leading edge and imprecise information. Ã? 2012 Elsevier Ltd. All rights reserved. 1. Introduction Helicopter rotors are more susceptible to icing than fixed-wing vehicles. Rotors impact more super-cooled water particles per sec- ond

Granada, Universidad de

235

Turbulent Vortex-Flow Simulation Over a 65 deg Sharp and Blunt Leading-Edge Delta Wing at Subsonic Speeds  

NASA Technical Reports Server (NTRS)

Turbulent thin-layer, Reynolds-Averaged Navier-Stokes solutions, based on a multi-block structured grid, are presented for a 65 deg delta wing having either a sharp leading edge (SLE) or blunt leading edge (BLE) geometry. The primary objective of the study is to assess the prediction capability of the method for simulating the leading-edge flow separation and the ensuing vortex flow characteristics. Computational results are obtained for two angles of attack of approximately 13 and 20 deg, at free-stream Mach number of 0.40 and Reynolds number of 6 million based on the wing mean aerodynamic chord. The effects of two turbulence models of Baldwin-Lomax with Degani-Schiff (BL/DS) and the Spalart-Allmaras (SA) on the numerical results are also discussed. The computations also explore the effects of two numerical flux-splitting schemes, i.e., flux difference splitting (fds) and flux vector splitting (fvs), on the solution development and convergence characteristics. The resulting trends in solution sensitivity to grid resolution for the selected leading-edge geometries, angles of attack, turbulence models and flux splitting schemes are also presented. The validity of the numerical results is evaluated against a unique set of experimental wind-tunnel data that was obtained in the National Transonic Facility at the NASA Langley Research Center.

Ghaffari, Farhad

2005-01-01

236

Correlation of laminar-turbulent transition data over flat plates in supersonic\\/hypersonic flow including leading edge bluntness effects  

Microsoft Academic Search

The paper discusses flat plate boundary layer transition in supersonic\\/hypersonic flow conditions. Examination of experimental infrared thermography data illustrates the importance of the leading edge thickness and (non-) uniformity to the transition process. Such observations have triggered the collection of a wide range of experimental data on supersonic\\/hypersonic flat plate boundary layer transition, and a number of attempts to correlate

G. A. Simeonides; Rio Patras

2003-01-01

237

Preliminary thermal/structural analysis of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge  

NASA Technical Reports Server (NTRS)

This study presents preliminary thermal/structural analyses of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge concept designed for an air breathing single-stage-to-orbit hypersonic vehicle. The concept features chordwise (i.e., normal to the leading edge) and spanwise (i.e., parallel to the leading edge) refractory-metal heat pipes which are completely embedded within a carbon-carbon primary structure. Studies of the leading edge were performed using nonlinear thermal and linear structural three-dimensional finite element analyses. The concept was shown to be thermally feasible within the limits of the assumptions made in the analyses when internal radiative cooling is present during ascent, and a three-dimensional carbon-carbon architecture is used. In addition, internal radiative cooling was found not to be necessary during descent. The linear stress analysis indicated excessively large thermal stresses in the rafractory metal walls of the heat pipes even though a soft layer of carbon was included between the heat pipe and the carbon-carbon structure in an attempt to reduce the thermal stresses. A nonlinear structural analysis may be necessary to properly model the response of the refractory-metal heat pipes.

Glass, David E.; Camarda, Charles J.

1990-01-01

238

Thermal\\/structural analyses of several hydrogen-cooled leading-edge concepts for hypersonic flight vehicles  

Microsoft Academic Search

The aerodynamic heating at high flight Mach numbers, when shock interference heating is included, can be extremely high and can exceed the capability of most conventional metallic and potential ceramic materials available. Numerical analyses of the heat transfer and thermal stresses are performed on three actively cooled leading-edge geometries (models) made of three different materials to address the issue of

Herbert J. Gladden; Matthew E. Melis; Theodore T. Mockler; Mike Tong

1990-01-01

239

40 The Leading Edge January 2009 SPECIAL SECTION: R o c k p h y s i c s  

E-print Network

40 The Leading Edge January 2009 SPECIAL SECTION: R o c k p h y s i c s Cracks in porous rocks sandstones. Even shales, that are certainly the most complex sedimentary rocks, have also been well by water adsorption. Water adsorption decreases the surface and fracture energy, making cracking easier

Fortin, Jérôme

240

"Partners in Science": A Model Cooperative Program Introducing High School Teachers and Students to Leading-Edge Pharmaceutical Science  

ERIC Educational Resources Information Center

"Partners in Science" is a cooperative program between Boehringer Ingelheim Pharmaceuticals, Inc. and area high schools in the community surrounding our Connecticut campus. It is a two-phase program that introduces high school students and teachers to the world of drug discovery and leading-edge pharmaceutical research. Phase 1 involves a series…

Woska, Joseph R., Jr.; Collins, Danielle M.; Canney, Brian J.; Arcario, Erin L.; Reilly, Patricia L.

2005-01-01

241

Piezoelectric lead zirconate titanate ceramic fiber\\/polymer composites  

Microsoft Academic Search

This papers on piezoelectric lead zirconate titanate (PZT) ceramic fiber\\/polymer composite were fabricated by a novel technique referred to as relic processing. Basically, this involved impregnating a woven carbon-fiber template material with PZT precursor by soaking the template in a PZT stock solution. Careful heat treatment pyrolized the carbon, resulting in a PZT ceramic relic that retained the fibrous template

David J. Waller; P. Safari

1992-01-01

242

Characterization of multifunctional skin-material for morphing leading-edge applications  

NASA Astrophysics Data System (ADS)

Former research on morphing droop-nose applications revealed great economical and social ecological advantages in terms of providing gapless surfaces for long areas of laminar flow. Furthermore a droop-nose for laminar flow applications provides a low noise exposing high-lift system at the leading-edge. Various kinematic concepts for the active deployment of such devices are already published but the major challenge is still an open issue: a skin material which meets the compromise of needed stiffness and flexibility. Moreover additional functions have to be added to keep up with standard systems. As a result of several national and European projects the DLR developed a gapless 3D smart droop-nose concept, which was successfully analyzed in a low speed wind tunnel test under relevant loads to prove the functionality and efficiency. The main structure of this concept is made of commercial available glass fiber reinforced plastics (GRFP). This paper presents elementary tests to characterize material lay-ups and their integrity by applying different loads under extreme thermal conditions using aged specimens. On the one hand the presented work is focused on the integrity of material-interfaces and on the other hand the efficiency and feasibility of embedded functions. It can be concluded that different preparations, different adhesives and used materials have their significant influence to the interface stability and mechanical property of the whole lay-up. Especially the laminate design can be optimized due to the e. g. mechanical exploitation of the added systems beyond their main function in order to reduce structural mass.

Geier, Sebastian; Kintscher, Markus; Mahrholz, Thorsten; Wierach, Peter; Monner, Hans-Peter; Wiedemann, Martin

2013-04-01

243

A numerical and experimental study of the effects of dynamic roughness on laminar leading edge separation  

NASA Astrophysics Data System (ADS)

The aircraft industry, as a whole, has been deeply concerned with improving the aerodynamic efficiency of current and future flight vehicles, particularly in the commercial and military markets. However, of particular interest to the field of aerodynamics is the elusive concept of a workable flow control mechanism. Effective flow control is a concept which if properly applied can increase aerodynamic efficiency. Various concepts and ideas to obtain successful flow control have been studied in an attempt to reap these rewards. Some examples include boundary layer blowing (steady and periodic), suction, and compliant walls for laminar flow control. The overall goal of flow control is to increase performance by increasing lift, reducing drag, and delaying or eliminating leading edge separation. The specific objectives of flow control are to (1) delay or eliminate flow separation, (2) delay boundary layer transition, and (3) and reduce skin friction drag. The purpose of this research is to investigate dynamic roughness as a novel method of flow control technology for external boundary layer flows. As opposed to standard surface roughness, dynamic roughness incorporates small time dependent perturbations to the surface of the airfoil. These surface perturbations are actual humps and/or ridges on the surface of the airfoil that are on the scale of the laminar boundary, and oscillate with an unsteady motion. Research has shown that this can provide a means to modify the instantaneous and mean velocity profile near the wall and favorably control the existing state of the boundary layer. Several flow control parameters were studied including dynamic roughness frequency, amplitude, and geometry. The results of this study have shown, both numerically and experimentally, that dynamic roughness can provide an effective means for eliminating both a short and long laminar separation bubble and possibly prove a viable alternative in effective flow control, hence reaping some of the rewards of an effective flow control system.

Gall, Peter D.

244

Measuring forces at the leading edge: a force assay for cell motility.  

PubMed

Cancer cells become mobile by remodelling their cytoskeleton to form migratory structures. This transformation is dominated by actin assembly and disassembly (polymerisation and depolymerisation) in the cytoplasm. Synthesis of filamentous actin produces a force at the leading edge that pushes the plasma membrane forward. We describe an assay to measure the restoring force of the membrane in response to forces generated within the cytoplasm adjacent to the membrane. A laser trap is used to form a long membrane nanotube from a living cell and to measure the axial membrane force at the end of the tube. When the tube, resembling a filopodium, is formed and in a relaxed state the axial membrane force exhibits a positive stationary value. This value reflects the influence of the cytoskeleton that acts to pull the tube back to the cell. A dynamic sawtooth force that rides upon the stationary value is also observed. This force is sensitive to a toxin that affects actin assembly and disassembly, but not affected by agents that influence microtubules and myosin light chain kinase. We deduce from the magnitude and characteristics of dynamic force measurements that it originates from depolymerisation and polymerisation of F-actin. The on- and off-rates, the number of working filaments, and the force per filament (2.5 pN) are determined. We suggest the force-dependent transitions are thermodynamically uncoupled as both the on- and off-rates decrease exponentially with a compressive load. We propose kinetic schemes that require attachment of actin filaments to the membrane during depolymerisation. This demonstrates that actin kinetics can be monitored in a living cell by measuring force at the membrane, and used to probe the mobility of cells including cancer cells. PMID:23080534

Farrell, Brenda; Qian, Feng; Kolomeisky, Anatoly; Anvari, Bahman; Brownell, William E

2013-01-01

245

Anodic corrosion of fiber reinforced lead composites for use in large lead-acid batteries  

NASA Astrophysics Data System (ADS)

The corrosion resistance of lightweight, high strength lead metal matrix composites under conditions that simulate their use as grid materials in large lead-acid batteries has been studied. Constant potential testing provides an effective means for holding constant the oxidizing power of a metal-electrolyte system. Data are presented on corrosion currents, effect of exposure time on corrosion rates, dependence of the rate of corrosion on temperature, and the current flow that is proportional to the rate of corrosion.

Dacres, C. M.; Reamer, S. M.; Sutula, R. A.; Angres, I. A.

1981-10-01

246

Approximate free-edge stresses in an orthotropic laminated composite under uniaxial inplane loading  

SciTech Connect

The classic problem of determining the stresses in the free-edge boundary region of a composite laminate under uniaxial inplane loading is addressed. Laminated plate theory including transverse shear deformation is utilized in obtaining an approximation of the interlaminar stresses throughout the boundary region of an orthotropic composite subjected to uniaxial inplane loading. In the analysis a quarter section of the laminate is treated as a plate fastened to a rigid foundation. The resulting inplane normal stress transverse to the load is modified by adding additional terms which assure that the appropriate boundary conditions at the free-edge are satisfied ply-by-ply. Interlaminar stresses are determined throughout the plate by integrating the equations of equilibrium from classical theory of elasticity in conjunction with the modified inplane stresses. Numerical results are compared to another approximation involving a higher order laminated plate theory which includes transverse normal strain in addition to transverse shear deformation.

Whitney, J.M. [Univ. of Dayton, OH (United States)

1993-12-31

247

A general aerodynamic approach to the problem of decaying or growing vibrations of thin, flexible wings with supersonic leading and trailing edges and no side edges  

NASA Technical Reports Server (NTRS)

Indicial aerodynamic influence coefficients were evaluated from potential theory for a thin, flexible wing with supersonic leading and trailing edges only. The analysis is based on the use of small surface areas in which the downwash is assumed uniform. Within this limitation, the results are exact except for the restriction of linearized theory. The areas are not restricted either to square boxes or Mach boxes. A given area may be any rectangle or square which may or may not be cut by the Mach forecone, and any area can be used anywhere in the forecone without loss of accuracy.

Warner, R. W.

1975-01-01

248

Numerical investigations of free edge effects in integrally stiffened layered composite panels  

Microsoft Academic Search

A linear finite element analysis is conducted to examine the free edge stresses and the displacement behavior of an integrally stiffened layered composite panel loaded under uniform inplane tension. Symmetric (+Phi, -Phi, 0, -Phi, +Phi) graphite-epoxy laminates with various fiber orientations in the off-axis plies are considered. The quadratic stress criterion, the Tsai-Wu criterion and the Mises equivalent stresses are

I. Skrna-Jakl; F. G. Rammerstorfer

1993-01-01

249

Low Subsonic Pressure Distributions on Three Rigid Wings Simulating Paragliders with Varied Canopy Curvature and Leading-Edge Sweep  

NASA Technical Reports Server (NTRS)

An investigation has been made in the Langley 7- by 10-foot transonic tunnel to determine the subsonic pressure distribution of three paraglider models through an angle-of-attack range from 0 deg to 74 deg. Three rigid metal models simulated a 45 deg basic flat planform paraglider with leading-edge sweep angles of 61.6 deg, 52.5 deg, and 48.6 deg. These configurations resulted in one-half-circle, one-third-circle, and one-quarter-circle semispan trailing-edge curvature when viewed from downstream. The results of the investigation are presented as curves of chordwise pressure distributions at four spanwise locations.

Fournier, Paul G.; Bell, B. Ann

1961-01-01

250

Subsonic longitudinal aerodynamic characteristics of a vectored-engine-over-wing configuration having spanwise leading-edge vortex enhancement  

NASA Technical Reports Server (NTRS)

A configuration which integrates a close coupled canard wing combination, spanwise blowing for enhancement of the wing leading edge vortex, an engine-over-wing concept, and a wing trailing edge coanda-effect flap is studied. The data on the configuration are presented in tabular from without discussion. The investigation was conducted in the Langley 7- by 10-foot high speed tunnel at a Mach number of 0.166 through an angle-of-attack range from -2 to 22 deg. Rectangular main engine nozzles of aspect ratio 4, 6, and 8 were tested over a momentum coefficient range from 1.0 to 1.8.

Huffman, J. K.; Fox, C. H., Jr.

1977-01-01

251

Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane  

NASA Technical Reports Server (NTRS)

Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.

1979-01-01

252

Subscale, hydrogen-burning, airframe-integrated-scramjet: Experimental and theoretical evaluation of a water cooled strut airframe-integrated-scramjet: Experimental leading edge  

NASA Technical Reports Server (NTRS)

A water-cooled leading-edge design for an engine/airframe integrated scramjet model strut leading edge was evaluated. The cooling design employs a copper cooling tube brazed just downstream of the leading edge of a wedge-shaped strut which is constructed of oxygen-free copper. The survival of the strut leading edge during a series of tests at stagnation point heating rates confirms the practicality of the cooling design. A finite difference thermal model of the strut was also proven valid by the reasonable agreement of calculated and measured values of surface temperature and cooling-water heat transfer.

Pinckney, S. Z.; Guy, R. W.; Beach, H. L., Jr.; Rogers, R. C.

1975-01-01

253

Lithium tantalate/lead zirconate titanate composite ultrasonic transducers  

NASA Astrophysics Data System (ADS)

Lithium tantalate (LiTaO3)/lead zirconate titanate (PZT) ceramic films of thickness about 50 ?m have been deposited on stainless-steel substrates using a modified sol-gel process. LiTaO3 powders are dispersed in a PZT sol-gel matrix to form a 0-3 ceramic/ceramic composite. The dielectric, electric, and piezoelectric properties have been studied. Ultrasonic pulse-echo measurements using the composite films as piezoelectric ultrasonic transducers demonstrate a broadband frequency response and good signal-to-noise ratio up to a temperature of 368 °C.

Chen, Y.; Sayer, M.; Zou, L.; Jen, C.-K.

1999-04-01

254

The aerodynamics of Manduca sexta: digital particle image velocimetry analysis of the leading-edge vortex.  

PubMed

Here we present the first digital particle image velocimetry (DPIV) analysis of the flow field around the wings of an insect (the tobacco hawkmoth Manduca sexta, tethered to a 6-component force-moment balance in a wind tunnel). A leading-edge vortex (LEV) is present above the wings towards the end of the downstroke, as the net upward force peaks. Our DPIV analyses and smoke visualisations match the results of previous flow visualisation experiments at midwing, and we extend the experiments to provide the first analysis of the flow field above the thorax. Detailed DPIV measurements show that towards the end of the downstroke, the LEV structure is consistent with that recently reported in free-flying butterflies and dragonflies: the LEV is continuous across the thorax and runs along each wing to the wingtip, where it inflects to form the wingtip trailing vortices. The LEV core is 2-3 mm in diameter (approximately 10% of local wing chord) both at the midwing position and over the centreline at 1.2 m s(-1) and at 3.5 m s(-1) flight speeds. At 1.2 m s(-1) the measured LEV circulation is 0.012+/-0.001 m(2) s(-1) (mean +/-S.D.) at the centreline and 0.011+/-0.001 m(2) s(-1) halfway along the wing. At 3.5 m s(-1) LEV circulation is 0.011+/-0.001 m(2) s(-1) at the centreline and 0.020+/-0.004 m(2) s(-1) at midwing. The DPIV measurements suggest that if there is any spanwise flow in the LEV towards the end of the downstroke its velocity is less than 1 m s(-1). Estimates of force production show that the LEV contributes significantly to supporting body weight during bouts of flight at both speeds (more than 10% of body weight at 1.2 m s(-1) and 35-65% of body weight at 3.5 m s(-1)). PMID:15767309

Bomphrey, Richard J; Lawson, Nicholas J; Harding, Nicholas J; Taylor, Graham K; Thomas, Adrian L R

2005-03-01

255

Reinforcement of composite laminate free edges with U-shaped caps  

NASA Technical Reports Server (NTRS)

Generalized plane strain finite element analysis is used to predict reduction of interlaminar normal stresses when a U-shaped cap is bonded to the edge of a laminate. Three-dimensional composite material failure criteria are used in a progressive laminate failure analysis to predict failure loads of laminates with different edge cap designs. In an experimental program, symmetric 11-layer graphite-epoxy laminates with a one-layer cap of Kevlar-epoxy cloth are shown to be 130 to 140 percent stronger than uncapped laminates under static tensile and tension-tension fatigue loading. In addition, the coefficient of variation of the static tensile failure load decreases from 24 to 8 percent when edge caps are added. The predicted failure load calculated with the finite element results is 10 percent lower than the actual failure load. For both capped and uncapped laminates, actual failure loads are much lower than those predicted using classical lamination theory stresses and a two-dimensional failure criterion. Possible applications of the free edge reinforcement concept are described, and future research is suggested.

Howard, W. E.; Gossard, T., Jr.; Jones, R. M.

1986-01-01

256

Calculation of the 3-D viscous flow at the endwall leading edge region of an axial annular turbine cascade  

NASA Technical Reports Server (NTRS)

A three-dimensional viscous computer code (VANS/MD) was employed to calculate the turbulent flow field at the end wall leading edge region of a 20 inch axial annular turbine cascade. The initial boundary layer roll-up and formation of the end wall vortices were computed at the vane leading edge. The calculated flow field was found to be periodic with a frequency of approximately 1600 Hz. The calculated size of the separation region for the hub endwall vortex compared favorably with measured endwall oil traces. In an effort to determine the effects of the turbulence model on the calculated unsteadiness, a laminar calculation was made. The periodic nature of the calculated flow field persisted with the frequency essentially unchanged.

Walitt, L.

1984-01-01

257

Alignment of leading-edge and peak-picking time of arrival methods to obtain accurate source locations  

SciTech Connect

The location of a radiating source can be determined by time-tagging the arrival of the radiated signal at a network of spatially distributed sensors. The accuracy of this approach depends strongly on the particular time-tagging algorithm employed at each of the sensors. If different techniques are used across the network, then the time tags must be referenced to a common fiducial for maximum location accuracy. In this report we derive the time corrections needed to temporally align leading-edge, time-tagging techniques with peak-picking algorithms. We focus on broadband radio frequency (RF) sources, an ionospheric propagation channel, and narrowband receivers, but the final results can be generalized to apply to any source, propagation environment, and sensor. Our analytic results are checked against numerical simulations for a number of representative cases and agree with the specific leading-edge algorithm studied independently by Kim and Eng (1995) and Pongratz (2005 and 2007).

Roussel-Dupre, R.; Symbalisty, E.; Fox, C.; and Vanderlinde, O.

2009-08-01

258

A new look at numerical analyses of free-edge stresses in composite laminates  

NASA Technical Reports Server (NTRS)

The edge stress problem for a + or - 45 deg graphite/epoxy laminate was examined. The reliability of the displacement formulated finite element method in analyzing the edge stress problem was investigated. Analyses of two well known elasticity problems, one involving a stress discontinuity and one a singularity, showed that the finite element analysis yields accurate stress distributions everywhere except in two elements closest to the stress discontinuity of singularity. Stress distributions for a + or - 45 deg laminate showed the same behavior near the singularity found in the well known problems with exact solutions. The displacement formulated finite element method appears to be a highly accurate technique for calculating interlaminar stress in composite laminates. The disagreement among the numerical methods was attributed to the unsymmetric stress tensor at the singularity.

Raju, I. S.; Whitcomb, J. D.; Goree, J. G.

1980-01-01

259

A Unit-Problem Investigation of Blunt Leading-Edge Separation Motivated by AVT-161 SACCON Research  

NASA Technical Reports Server (NTRS)

A research effort has been initiated to examine in more detail some of the challenging flow fields discovered from analysis of the SACCON configuration aerodynamics. This particular effort is oriented toward a diamond wing investigation specifically designed to isolate blunt leading-edge separation phenomena relevant to the SACCON investigations of the present workshop. The approach taken to design this new effort is reviewed along with the current status of the program.

Luckring, James M.; Boelens, Okko J.

2011-01-01

260

Influence of the radius of the leading edge of worm vanes on the critical cavitation allowance of a pump  

SciTech Connect

This paper theoretically and experimentally investigates the influence of the cylindrical (curved) leading edge of the worm vanes on the cavitation characteristics of the pump. Considers the disruptive flow around the worm wheel with a constant screw spacing (pitch) of an ideal liquid flow. The proposed equations, verified on pumps with worms of different types and sizes with a wide range of attack angles, can be used for the calculation of the sucking capacity of high-speed worm centrifugal pumps.

Shcherbatenko, I.V.; Khankin, V.P.

1982-11-01

261

Investigation of Porous Gas-Heated Leading-Edge Section for Icing Protection of a Delta Wing  

NASA Technical Reports Server (NTRS)

A tip section of a delta wing having an NACA 0004-65 airfoil section and a 600 leading-edge sweepback was equipped with a porous leading-edge section through which hot gas was 'bled for anti-icing. Heating rates for anti-icing were determined for a wide range of icing conditions. The effects of gas flow through the porous leading-edge section on airfoil pressure distribution and drag in dry air were investigated. The drag increase caused by an ice formation on the unheated airfoil was measured for several icing conditions. Experimental porous surface- to free-stream convective heat-transfer coefficients were obtained in dry air and compared with theory. Adequate icing protection was obtained at all icing conditions investigated. Savings in total gas-flow rate up to 42 percent may be obtained with no loss in anti-icing effectiveness by sealing half the upper-surface porous area. Gas flow through the leading-edge section had no appreciable effect on airfoil pressure distribution. The airfoil section drag increased slightly (5-percent average) with gas flow through the porous surface. A heavy glaze-ice formation produced after 10 minutes of icing caused an increase in section drag coefficient of 240 percent. Experimental convective heat-transfer coefficients obtained with hot-gas flow through the porous area in dry air and turbulent flow were 20 to 30 percent lower than the theoretical values for a solid surface under similar conditions. The transition region from laminar to turbulent flow moved forward as the ratio of gas velocity through the porous surface to air-stream velocity was increased.

Bowden, Dean T.

1955-01-01

262

Influence of leading-edge lateral injection angles on the film cooling effectiveness of a gas turbine blade  

Microsoft Academic Search

Typical film-cooling configuration of a symmetrical turbine blade leading edge is investigated using a three-dimensional finite volume method and a multi-block technique. The computational domain includes the curved blade surface as well as the coolant regions and the plenum. The turbulence is approximated by a two layer k–? model. The computations have been performed using the TLV two-layer and the

Abbès Azzi; Bassam Ali Jubran

2004-01-01

263

HTS current lead using a composite heat pipe  

NASA Astrophysics Data System (ADS)

The design and fabrication of HTS current leads being built by Los Alamos to supply power to a demonstration HTS coil which will operate in a vacuum cooled by a cryocooler is discussed. Because vapor cooling is not an option for this application, the leads must be entirely conductively cooled. In the design of HTS current leads for this type of application, it is desirable to intercept part of the heat load at an intermediate temperature. This thermal intercept or connection must be electrically insulating but thermally conductive, two mutually exclusive properties of most candidate solid materials. To achieve this end we incorporate a composite nitrogen heat pipe, constructed of conducting and non-conducting materials, to provide efficient thermal communication and simultaneously, electrical isolation between the lead and the intermediate temperature heat sink. Another important feature of the current lead design is the use of high Jc thick film superconductors deposited on a non-conducting substrate to reduce the conductive heat leak through the lower portion of the lead. Two flexible electrical conductors are incorporated to accommodate handling, assembly and the dissimilar expansion coefficients of the various materials.

Daugherty, M. A.; Prenger, F. C.; Hill, D. D.; Daney, D. E.; Woloshun, K. A.

264

HTS current lead using a composite heat pipe  

SciTech Connect

This paper discusses the design and fabrication of HTS current leads being built by Los Alamos to supply power to a demonstration HTS coil which will operate in a vacuum cooled by a cryocooler. Because vapor cooling is not an option for this application the leads must be entirely conductively cooled. In the design of HTS current leads for this type of application, it is desirable to intercept part of the heat load at an intermediate temperature. This thermal intercept or connection must be electrically insulating but thermally conductive, two mutually exclusive properties of most candidate solid materials. To achieve this end we incorporate a composite nitrogen heat pipe, constructed of conducting and non-conducting materials, to provide efficient thermal communication and simultaneously, electrical isolation between the lead and the intermediate temperature heat sink. Another important feature of the current lead design is the use of high Jc thick film superconductors deposited on a non-conducting substrate to reduce the conductive heat leak through the lower portion of the lead. Two flexible electrical conductors are incorporated to accommodate handling, assembly and the dissimilar expansion coefficients of the various materials.

Daugherty, M.A.; Prenger, F.C.; Hill, D.D.; Daney, D.E.; Woloshun, K.A.

1995-12-31

265

Flight test operations using an F-106B research airplane modified with a wing leading-edge vortex flap  

NASA Technical Reports Server (NTRS)

Flight tests of an F-106B aircraft equipped with a leading-edge vortex flap, which represented the culmination of a research effort to examine the effectiveness of the flap, were conducted at the NASA Langley Research Center. The purpose of the flight tests was to establish a data base on the use of a wing leading-edge vortex flap as a means to validate the design and analysis methods associated with the development of such a vortical flow-control concept. The overall experiment included: refinements of the design codes for vortex flaps; numerous wind tunnel entries to aid in verifying design codes and determining basic aerodynamic characteristics; design and fabrication of the flaps, structural modifications to the wing tip and leading edges of the test aircraft; development and installation of an aircraft research instrumentation system, including wing and flap surface pressure measurements and selected structural loads measurements; ground-based simulation to assess flying qualities; and finally, flight testing. This paper reviews the operational aspects associated with the flight experiment, which includes a description of modifications to the research airplane, the overall flight test procedures, and problems encountered. Selected research results are also presented to illustrate the accomplishments of the research effort.

Dicarlo, Daniel J.; Brown, Philip W.; Hallissy, James B.

1992-01-01

266

Low-Speed Aerodynamic Data for an 0.18-Scale Model of an F-16XL with Various Leading-Edge Modifications  

NASA Technical Reports Server (NTRS)

Using the F-16XL as a test-bed, two strategies for improving the low-speed flying characteristics that had minimal impact on high-speed performance were evaluated. In addition to the basic F-16XL configuration several modifications to the baseline configuration were tested in the Langley 30- X 60-Foot Tunnel: 1) the notched area at the wing leading edge and fuselage juncture was removed resulting in a continuous 70 deg leading-edge sweep on the inboard portion of the wing; 2) an integral attached-flow leading-edge flap concept was added to the continuous leading edge; and 3) a deployable vortex flap concept was added to the continuous leading edge. The purpose of this report is simply to document the test configurations, test conditions, and data obtained in this investigation for future reference and analysis. No analysis is presented herein and the data only appear in tabulated format.

Hahne, Daniel E.

1999-01-01

267

Boundary-layer effects in composite laminates: Free-edge stress singularities, part 6  

NASA Technical Reports Server (NTRS)

A rigorous mathematical model was obtained for the boundary-layer free-edge stress singularity in angleplied and crossplied fiber composite laminates. The solution was obtained using a method consisting of complex-variable stress function potentials and eigenfunction expansions. The required order of the boundary-layer stress singularity is determined by solving the transcendental characteristic equation obtained from the homogeneous solution of the partial differential equations. Numerical results obtained show that the boundary-layer stress singularity depends only upon material elastic constants and fiber orientation of the adjacent plies. For angleplied and crossplied laminates the order of the singularity is weak in general.

Wanag, S. S.; Choi, I.

1981-01-01

268

The effects of leading-edge serrations on reducing flow unsteadiness about airfoils, an experimental and analytical investigation  

NASA Technical Reports Server (NTRS)

High frequency surface pressure measurements were obtained from wind-tunnel tests over the Reynolds number range 1.2 times one million to 6.2 times one million on a rectangular wing of NACA 63-009 airfoil section. Measurements were also obtained with a wide selection of leading-edge serrations added to the basic airfoil. Under a two-dimensional laminar bubble very close to the leading edge of the basic airfoil there is a large apatial peak in rms pressure. Frequency analysis of the pressure signals in this region show a large, high-frequency energy peak which is interpreted as an oscillation in size and position of the bubble. The serrations divide the bubble into segments and reduce the peak rms pressures. A low Reynolds number flow visualization test on a hydrofoil in water was also conducted. A von Karman vortex street was found trailing from the rear of the foil. Its frequency is at a much lower Strouhal number than in the high Reynolds number experiment, and is related to the trailing-edge and boundary-layer thicknesses.

Schwind, R. G.; Allen, H. J.

1973-01-01

269

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

NASA Technical Reports Server (NTRS)

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.; Valarezo, Walter O.; Mcghee, Robert J.

1991-01-01

270

How much information can be obtained from tracking the position of the leading edge in a scratch assay?  

PubMed

Moving cell fronts are an essential feature of wound healing, development and disease. The rate at which a cell front moves is driven, in part, by the cell motility, quantified in terms of the cell diffusivity D, and the cell proliferation rate ?. Scratch assays are a commonly reported procedure used to investigate the motion of cell fronts where an initial cell monolayer is scratched, and the motion of the front is monitored over a short period of time, often less than 24 h. The simplest way of quantifying a scratch assay is to monitor the progression of the leading edge. Use of leading edge data is very convenient because, unlike other methods, it is non-destructive and does not require labelling, tracking or counting individual cells among the population. In this work, we study short-time leading edge data in a scratch assay using a discrete mathematical model and automated image analysis with the aim of investigating whether such data allow us to reliably identify D and ?. Using a naive calibration approach where we simply scan the relevant region of the (D, ?) parameter space, we show that there are many choices of D and ? for which our model produces indistinguishable short-time leading edge data. Therefore, without due care, it is impossible to estimate D and ? from this kind of data. To address this, we present a modified approach accounting for the fact that cell motility occurs over a much shorter time scale than proliferation. Using this information, we divide the duration of the experiment into two periods, and we estimate D using data from the first period, whereas we estimate ? using data from the second period. We confirm the accuracy of our approach using in silico data and a new set of in vitro data, which shows that our method recovers estimates of D and ? that are consistent with previously reported values except that that our approach is fast, inexpensive, non-destructive and avoids the need for cell labelling and cell counting. PMID:24850906

Johnston, Stuart T; Simpson, Matthew J; McElwain, D L Sean

2014-08-01

271

How much information can be obtained from tracking the position of the leading edge in a scratch assay?  

PubMed Central

Moving cell fronts are an essential feature of wound healing, development and disease. The rate at which a cell front moves is driven, in part, by the cell motility, quantified in terms of the cell diffusivity D, and the cell proliferation rate ?. Scratch assays are a commonly reported procedure used to investigate the motion of cell fronts where an initial cell monolayer is scratched, and the motion of the front is monitored over a short period of time, often less than 24 h. The simplest way of quantifying a scratch assay is to monitor the progression of the leading edge. Use of leading edge data is very convenient because, unlike other methods, it is non-destructive and does not require labelling, tracking or counting individual cells among the population. In this work, we study short-time leading edge data in a scratch assay using a discrete mathematical model and automated image analysis with the aim of investigating whether such data allow us to reliably identify D and ?. Using a naive calibration approach where we simply scan the relevant region of the (D, ?) parameter space, we show that there are many choices of D and ? for which our model produces indistinguishable short-time leading edge data. Therefore, without due care, it is impossible to estimate D and ? from this kind of data. To address this, we present a modified approach accounting for the fact that cell motility occurs over a much shorter time scale than proliferation. Using this information, we divide the duration of the experiment into two periods, and we estimate D using data from the first period, whereas we estimate ? using data from the second period. We confirm the accuracy of our approach using in silico data and a new set of in vitro data, which shows that our method recovers estimates of D and ? that are consistent with previously reported values except that that our approach is fast, inexpensive, non-destructive and avoids the need for cell labelling and cell counting. PMID:24850906

Johnston, Stuart T.; Simpson, Matthew J.; McElwain, D. L. Sean

2014-01-01

272

DETECTION OF CURRENT SHEETS AND MAGNETIC RECONNECTIONS AT THE TURBULENT LEADING EDGE OF AN INTERPLANETARY CORONAL MASS EJECTION  

SciTech Connect

The relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection detected by four Cluster spacecraft on 2005 January 21 is studied. We report the observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer with the following characteristics: (1) a Kolmogorov power spectrum in the inertial subrange of the magnetic turbulence, (2) the scaling exponent of structure functions of magnetic fluctuations exhibiting multi-fractal scaling predicted by the She-Leveque magnetohydrodynamic model, and (3) bifurcated current sheets with the current density computed by both single-spacecraft and multi-spacecraft techniques.

Chian, Abraham C.-L. [California Institute of Technology, Pasadena, CA 91125 (United States); Munoz, Pablo R., E-mail: abraham.chian@gmail.com, E-mail: pablocus@gmail.com [National Institute for Space Research (INPE) and World Institute for Space Environment Research (WISER), P.O. Box 515, Sao Jose dos Campos SP 12227-010 (Brazil)

2011-06-01

273

An efficient way to more power 344 metres of leading edge  

E-print Network

, while the arrangement of tower and nacelle components has been optimised to facilitate service VMP-Top controller with converter Service crane OptiSpeed® generator Composite disc coupling Yaw gears pitch cylinders. Tower Hub height: 80 m, 105 m Operational data Cut-in wind speed: 4 m/s Nominal wind

Firestone, Jeremy

274

Unsteady Flow and Noise Production Mechanisms in the Leading Edge Slat Region of a Multi-Element Airfoil  

NASA Astrophysics Data System (ADS)

Motivated by airframe noise reduction, the present study experimentally investigates the unsteady flow and noise production mechanisms associated with the leading edge slat region of a multi-element airfoil system. Flow visualization in the slat cove has documented unsteady separated and reattaching flow. Multi-point hot-wire and single microphone measurements were acquired for acoustically active and inactive cases of slat orientation. Fourier and wavelet decomposition applied to trailing edge vorticity estimates and microphone signals acquired simultaneously over a large range of freestream velocities reveal two different acoustic mechanisms: (1) a resonant feedback condition and (2) trailing edge noise. Pseudo-flow visualization (PFV) in the slat near-wake indicates periodic velocity fluctuations for both types of radiated acoustics but with a large diversity in scale and fundamental organization. To better understand the hydrodynamic source of unsteadiness, a flush-mounted hot-film array is mounted in the slat cove to document characteristics of the quasi-2D separation region.

Olson, S.; Thomas, F. O.; Nelson, R. C.

1999-11-01

275

Temperate forest fragments maintain aboveground carbon stocks out to the forest edge despite changes in community composition.  

PubMed

Edge effects are among the primary mechanisms by which forest fragmentation can influence the link between biodiversity and ecosystem processes, but relatively few studies have quantified these mechanisms in temperate regions. Carbon storage is an important ecosystem function altered by edge effects, with implications for climate change mitigation. Two opposing hypotheses suggest that aboveground carbon (AGC) stocks at the forest edge will (a) decrease due to increased tree mortality and compositional shifts towards smaller, lower wood density species (e.g., as seen in tropical systems) or, less often, (b) increase due to light/temperature-induced increases in diversity and productivity. We used field-based measurements, allometry, and mixed models to investigate the effects of proximity to the forest edge on AGC stocks, species richness, and community composition in 24 forest fragments in southern Quebec. We also asked whether fragment size or connectivity with surrounding forests altered these edge effects. AGC stocks remained constant across a 100 m edge-to-interior gradient in all fragment types, despite changes in tree community composition and stem density consistent with expectations of forest edge effects. We attribute this constancy primarily to compensatory effects of small trees at the forest edge; however, it is due in some cases to the retention of large trees at forest edges, likely a result of forest management. Our results suggest important differences between temperate and tropical fragments with respect to mechanisms linking biodiversity and AGC dynamics. Small temperate forest fragments may be valuable in conservation efforts based on maintaining biodiversity and multiple ecosystem services. PMID:25185776

Ziter, Carly; Bennett, Elena M; Gonzalez, Andrew

2014-11-01

276

KNN-NTK composite lead-free piezoelectric ceramic  

NASA Astrophysics Data System (ADS)

A (K,Na)NbO3-based lead-free piezoelectric ceramic was successfully densified. It exhibited an enhanced electromechanical coupling factor of kp = 0.52, a piezoelectric constant d33 = 252 pC/N, and a frequency constant Np = 3170 Hz m because of the incorporation of an elaborate secondary phase composed primarily of KTiNbO5. The ceramic's nominal composition was 0.92K0.42Na0.44Ca0.04Li0.02Nb0.85O3-0.047K0.85Ti0.85Nb1.15O5-0.023BaZrO3-0.0017Co3O4-0.002Fe2O3-0.005ZnO, abbreviated herein as KNN-NTK composite. The KNN-NTK ceramic exhibited a dense microstructure with few microvoids which significantly degraded its piezoelectric properties. Elemental maps recorded using transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS) revealed regions of high concentrations of Co and Zn inside the NTK phase. In addition, X-ray diffraction patterns confirmed that a small portion of the NTK phase was converted into K2(Ti,Nb,Co,Zn)6O13 or CoZnTiO4 by a possible reaction between Co and Zn solutes and the NTK phase during a programmed sintering schedule. TEM studies also clarified a distortion around the KNN/NTK interfaces. Such an NTK phase filled voids between KNN particles, resulting in an improved chemical stability of the KNN ceramic. The manufacturing process was subsequently scaled to 100 kg per batch for granulated ceramic powder using a spray-drying technique. The properties of the KNN-NTK composite ceramic produced using the scaled-up method were confirmed to be identical to those of the ceramic prepared by conventional solid-state reaction sintering. Consequently, slight changes in the NTK phase composition and the distortion around the KNN/NTK interfaces affected the KNN-NTK composite ceramic's piezoelectric characteristics.

Matsuoka, T.; Kozuka, H.; Kitamura, K.; Yamada, H.; Kurahashi, T.; Yamazaki, M.; Ohbayashi, K.

2014-10-01

277

Young Children of Immigrants: The Leading Edge of America's Future. Brief No. 3  

ERIC Educational Resources Information Center

Children of immigrants have nearly doubled as a share of pre-K to 3rd grade students since 1990. The share of children under age 8 with immigrant parents stood at 24 percent in 2008, up from 13 percent in 1990. Young children of immigrants account for more than 30 percent of children in seven states, with California leading the nation at 50…

Fortuny, Karina; Hernandez, Donald J.; Chaudry, Ajay

2010-01-01

278

Leading Edge 234 Cell 139, October 16, 2009 2009 Elsevier Inc.  

E-print Network

relevant and harm- ful compounds in food and trigger innate behaviors leading to acceptance or rejection of potential food sources. Taste is therefore a powerful system in which to ask the question, how is sensory (Lindemann, 2001; Chandrashekar et al., 2006). The tastes of sweet, bitter, sour, and salty are familiar

Zuker, Charles

279

Fact Sheet: Facilities UC San Diego Health Sciences facilities house leading-edge technologies, investigational therapies,  

E-print Network

March 2014 Fact Sheet: Facilities UC San Diego Health Sciences facilities house leading procedures within its walls. UC San Diego Medical Center Opened: 1966 | Size: 490,000 GSF 200 West Arbor Drive San Diego, CA 92103 Facility Highlights >> 392 beds >> UC San Diego Stroke Center >> The area

Squire, Larry R.

280

A leading edge heating array and a flat surface heating array: Final design. [for testing the thermal protection system of the space shuttle  

NASA Technical Reports Server (NTRS)

A heating array is described for testing full-scale sections of the leading edge and lower fuselage surfaces of the shuttle. The heating array was designed to provide a tool for development and acceptance testing of leading edge segments and large flat sections of the main body thermal protection system. The array was designed using a variable length module concept to meet test requirements using interchangeable components from one test configuration in another configuration. Heat generating modules and heat absorbing modules were employed to achieve the thermal gradient around the leading edge. A support was developed to hold the modules to form an envelope around a variety of leading edges; to supply coolant to each module; the support structure and to hold the modules in the flat surface heater configuration. An optical pyrometer system mounted within the array was designed to monitor specimen surface temperatures without altering the test article's surface.

1975-01-01

281

Development of composite materials for non-leaded glove for use in radiological hand protection  

NASA Astrophysics Data System (ADS)

Lead is a hazardous material and US congress has mandated the rapid reduction of all hazardous waste generation as a matter of national policy. With the large amount of plutonium handling in numerous projects including the development of MOX fuel, power source etc., hand glove protection for the emitted alpha-beta- and low energy photons is an important issue. Leaded gloves are the prime shields used for radiological hand protection. US Department of Energy laboratories require a substitute material for the lead oxide in the gloves, as a way to reduced mixed waste. To solve this problem, a new blend of non-hazardous materials that have the same radiological properties, approximately the same cost of production, and lastly not potentially fall under the Resource Conservation and Recovery Act (RCRA) regulation, to replace the lead oxide currently used in the gloves had been investigated. The investigations have produced alternative materials using calculations (deterministic and Monte Carlo, MCNP) and experiments. The selection of the constituent compounds for the new composite materials, were based on the k-absorption edge energy of the main constituent element(s) in the compound. The formulations of these composites were fashioned on the principle of blending neoprene rubber formulation with several constituent compounds. Calculations based on the Lambert-Beer attenuation law together with the mass attenuation coefficient values from the XCOM cross section database program were used to determine the transmission fractions of these proposed composite materials. Selected composite materials that compared favorably with the leaded-neoprene were fabricated. These fabricated composite materials were tested with attenuation experiments and the results were in excellent agreement with the calculations using the Lambert-Beer law. For the purpose of benchmarking the result of the calculations, Monte Carlo calculations were also made. The success of this research would mean that this new composite material could also replace the lead aprons currently in use, as shields against radiation like x-ray in most hospitals. Based on computational and experimental results, the recommended compositions of the composite materials for the glove are: (i) Erbium III Oxide (Er2O3)---40% and 40 Tungsten Boride (WB) blend with 20% Neoprene formulation, or with the reduced Er2O3, (ii) Erbium III Oxide (Er2O 3)---5% and 75% Tungsten Boride (WB) blend with 20% Neoprene formulation. (iii) Tungsten III Oxide (WO3)---80% blended with 20% Neoprene formulation. Toxicity Characteristic Leaching Procedure (TCLP) results show that, several heavy metals used in these new materials that would leach out were below the US EPA limit or are not on the list of regulated heavy metals. However, on the original gloves Lead leached out at a concentration of 5.2 mL/L, slightly above the regulatory limit.

Dodoo-Amoo, David Nii Amoo

282

Boundary-layer effects in composite laminates. I - Free-edge stress singularities. II - Free-edge stress solutions and basic characteristics  

NASA Technical Reports Server (NTRS)

The fundamental nature of the boundary-layer effect in fiber-reinforced composite laminates is formulated in terms of the theory of anisotropic elasticity. The basic structure of the boundary-layer field solution is obtained by using Lekhnitskii's stress potentials (1963). The boundary-layer stress field is found to be singular at composite laminate edges, and the exact order or strength of the boundary layer stress singularity is determined using an eigenfunction expansion method. A complete solution to the boundary-layer problem is then derived, and the convergence and accuracy of the solution are analyzed, comparing results with existing approximate numerical solutions. The solution method is demonstrated for a symmetric graphite-epoxy composite.

Wang, S. S.; Choi, I.

1982-01-01

283

Asian anthropogenic lead contamination in the North Pacific Ocean as evidenced by stable lead isotopic compositions  

NASA Astrophysics Data System (ADS)

This dissertation work determined the changing scope of lead (Pb) contamination in the North Pacific Ocean since the phase-out of leaded gasoline in most of the world. Chapters 1 and 2 consisted of validating our method for determining Pb concentrations and isotopic compositions in seawater. Chapter 3 established a baseline of Pb isotopic compositions (PbICs) in the western and central North Pacific in 2002. This was an ideal time to establish such a baseline because China had recently (mid-2000) ceased their use of leaded gasoline and simultaneously began consuming increasingly large amounts of coal, known to have relatively high Pb concentrations. We found subsurface waters were contaminated with Asian industrial Pb, predominantly Chinese coal emissions. In contrast, the abyssal waters were a mix of Asian industrial Pb and background (i.e., natural) Pb. Chapter 4 revisited the western and central North Pacific in 2009 -- 2011 to determine what, if any, changes had occurred in this short time period. We found that Pb in subsurface and abyssal waters of the western North Pacific were similar to Chinese aerosols. Such a large change in the PbICs of abyssal water in 9 years was unanticipated and attributed to the relatively large flux of particle-bound Pb from the euphotic zone to the deep ocean, which was in isotopic equilibrium with the reservoir of dissolved Pb. In contrast, the central North Pacific abyssal water PbICs were similar to values previously reported because of the relatively lower particulate export. Based on comparisons to baseline PbIC data, we determined that abyssal waters in the western and central North Pacific would be isotopically indistinguishable from surface waters in the next three decades. Sources of Pb to coastal California waters were reevaluated in Chapter 5. Prior studies had found that surface waters of the California Current System (CCS) were isotopically consistent with both Asian industrial Pb and US leaded gasoline, still in use at that point in time. In 2010 and 2011, we found that surface and subsurface waters of the CCS were isotopically similar to Asian industrial emissions. However, remobilized US gasoline Pb from sediments in the San Francisco Bay, California, were accumulating in the "mud belt" on the continental shelf and changing the isotopic composition of overlying waters. During periods of intense upwelling, this historic Pb was brought to the surface of the water. However, the much larger quantity of Pb from Asian industrial emissions made the isotopic composition of Pb from historic US gasoline unidentifiable in off-shore waters. A secondary research focus of this dissertation was to improve my own teaching abilities. Chapter 6 explored the intersection of system thinking and aquatic toxicology in undergraduate education. Among a wealth of information, I found that group concept mapping was no more useful to student learning than the same activity done individually. This was due to poor implementation of team learning strategies by me and inadequate time for students to adjust to non-traditional instruction methodologies.

Zurbrick, Cheryl M.

284

General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra  

SciTech Connect

Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

2012-10-31

285

Effects of wing-leading-edge modifications on a full-scale, low-wing general aviation airplane: Wind-tunnel investigation of high-angle-of-attack aerodynamic characteristics. [conducted in Langley 30- by 60-foot tunnel  

NASA Technical Reports Server (NTRS)

Wing-leading-edge modifications included leading-edge droop and slat configurations having full-span, partial-span, or segmented arrangements. Other devices included wing-chord extensions, fences, and leading-edge stall strips. Good correlation was apparent between the results of wind-tunnel data and the results of flight tests, on the basis of autorotational stability criterion, for a wide range of wing-leading-edge modifications.

Newsom, W. A., Jr.; Satran, D. R.; Johnson, J. L., Jr.

1982-01-01

286

Basic science research in pediatric radiology - how to empower the leading edge of our field.  

PubMed

Basic science research aims to explore, understand and predict phenomena in the natural world. It spurs the discovery of fundamentally new principles and leads to new knowledge and new concepts. By comparison, applied research employs basic science knowledge toward practical applications. In the clinical realm, basic science research and applied research should be closely connected. Basic science discoveries can build the foundation for a broad range of practical applications and thereby bring major benefits to human health, education, environment and economy. This article explains how basic science research impacts our field, it describes examples of new research directions in pediatric imaging and it outlines current challenges that we need to overcome in order to enable the next groundbreaking discovery. PMID:25060618

Daldrup-Link, Heike E

2014-08-01

287

X-ray absorption near edge structure spectrometry study of nickel and lead speciation in coals and coal combustion products  

SciTech Connect

The fate and environmental impacts of trace elements from coal fired power stations are a significant concern because of the large quantities of coal used as an energy source. The ultimate environmental fate and health impact of some of these trace elements is dependent on their various forms and oxidation states. Nickel and lead are two of the trace elements classified as 'priority pollutants' by the National Pollutant Inventory (NPI) in Australia. This study attempts to understand speciation of nickel and lead in coal and coal combustion products from five coal fired power stations in Australia where bituminous rank coals are utilized. Non-destructive X-ray Absorption Near Edge Structure Spectrometry (XANES) was used to determine speciation of these metals. Semiquantitative speciation of nickel and lead was calculated using a linear combination fit of XANES spectra obtained for selected pure reference compounds. In all fly ash samples, 28-80% of nickel was present as nickel in NiSO{sub 4} form, which is a more toxic and more bioavailable form of nickel. Less toxic NiO was detected in fly ash samples in the range of 0-15%. Speciation of lead revealed that 65-70% is present as PbS in the feed coals. In all fly ash samples analyzed, lead comprised different proportions of PbCl{sub 2}, PbO, and PbSO{sub 4}. PbCl{sub 2} and PbSO{sub 4} contents varied between 30-70% and 30-60%, respectively. Chemical reactions resulting in nickel and lead transformation that are likely to have occurred in the post-combustion environment are discussed. 22 refs., 7 figs., 7 tabs.

Pushan Shah; Vladimir Strezov; Peter F. Nelson [Macquarie University, Sydney, NSW (Australia). CRC for Coal in Sustainable Development

2009-03-15

288

An improved panel method for the solution of three-dimensional leading-edge vortex flows. Volume 1: Theory document  

NASA Technical Reports Server (NTRS)

An improved panel method for the solution of three dimensional flow and wing and wing-body combinations with leading edge vortex separation is presented. The method employs a three dimensional inviscid flow model in which the configuration, the rolled-up vortex sheets, and the wake are represented by quadratic doublet distributions. The strength of the singularity distribution as well as shape and position of the vortex spirals are computed in an iterative fashion starting with an assumed initial sheet geometry. The method calculates forces and moments as well as detail surface pressure distributions. Improvements include the implementation of improved panel numerics for the purpose of elimination the highly nonlinear effects of ring vortices around double panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A complete description of the method is included. A variety of cases generated by the computer program implementing the method are presented which verify the mathematical assumptions of the method and which compare computed results with experimental data to verify the underlying physical assumptions made by the method.

Johnson, F. T.; Lu, P.; Tinoco, E. N.

1980-01-01

289

The formation mechanism and impact of streamwise vortices on NACA 0021 airfoil's performance with undulating leading edge modification  

NASA Astrophysics Data System (ADS)

Wings with tubercles have been shown to display advantageous loading behavior at high attack angles compared to their unmodified counterparts. In an earlier study by the authors, it was shown that an undulating leading-edge configuration, including but not limited to a tubercled model, induces a cyclic variation in circulation along the span that gives rise to the formation of counter-rotating streamwise vortices. While the aerodynamic benefits of full-span tubercled wings have been associated with the presence of such vortices, their formation mechanism and influence on wing performance are still in question. In the present work, experimental and numerical tests were conducted to further investigate the effect of tubercles on the flow structure over full-span modified wings based on the NACA 0021 profile, in the transitional flow regime. It is found that a skew-induced mechanism accounts for the formation of streamwise vortices whose development is accompanied by flow separation in delta-shaped regions near the trailing edge. The presence of vortices is detrimental to the performance of full-span wings pre-stall, however renders benefits post-stall as demonstrated by wind tunnel pressure measurement tests. Finally, primary and secondary vortices are identified post-stall that produce an enhanced momentum transfer effect that reduces flow separation, thus increasing the generated amount of lift.

Rostamzadeh, N.; Hansen, K. L.; Kelso, R. M.; Dally, B. B.

2014-10-01

290

The endosomal adaptor protein APPL1 impairs the turnover of leading edge adhesions to regulate cell migration.  

PubMed

Cell migration is a complex process that requires the integration of signaling events that occur in distinct locations within the cell. Adaptor proteins, which can localize to different subcellular compartments, where they bring together key signaling proteins, are emerging as attractive candidates for controlling spatially coordinated processes. However, their function in regulating cell migration is not well understood. In this study, we demonstrate a novel role for the adaptor protein containing a pleckstrin-homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif 1 (APPL1) in regulating cell migration. APPL1 impairs migration by hindering the turnover of adhesions at the leading edge of cells. The mechanism by which APPL1 regulates migration and adhesion dynamics is by inhibiting the activity of the serine/threonine kinase Akt at the cell edge and within adhesions. In addition, APPL1 significantly decreases the tyrosine phosphorylation of Akt by the nonreceptor tyrosine kinase Src, which is critical for Akt-mediated cell migration. Thus, our results demonstrate an important new function for APPL1 in regulating cell migration and adhesion turnover through a mechanism that depends on Src and Akt. Moreover, our data further underscore the importance of adaptor proteins in modulating the flow of information through signaling pathways. PMID:22379109

Broussard, Joshua A; Lin, Wan-hsin; Majumdar, Devi; Anderson, Bridget; Eason, Brady; Brown, Claire M; Webb, Donna J

2012-04-01

291

The endosomal adaptor protein APPL1 impairs the turnover of leading edge adhesions to regulate cell migration  

PubMed Central

Cell migration is a complex process that requires the integration of signaling events that occur in distinct locations within the cell. Adaptor proteins, which can localize to different subcellular compartments, where they bring together key signaling proteins, are emerging as attractive candidates for controlling spatially coordinated processes. However, their function in regulating cell migration is not well understood. In this study, we demonstrate a novel role for the adaptor protein containing a pleckstrin-homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif 1 (APPL1) in regulating cell migration. APPL1 impairs migration by hindering the turnover of adhesions at the leading edge of cells. The mechanism by which APPL1 regulates migration and adhesion dynamics is by inhibiting the activity of the serine/threonine kinase Akt at the cell edge and within adhesions. In addition, APPL1 significantly decreases the tyrosine phosphorylation of Akt by the nonreceptor tyrosine kinase Src, which is critical for Akt-mediated cell migration. Thus, our results demonstrate an important new function for APPL1 in regulating cell migration and adhesion turnover through a mechanism that depends on Src and Akt. Moreover, our data further underscore the importance of adaptor proteins in modulating the flow of information through signaling pathways. PMID:22379109

Broussard, Joshua A.; Lin, Wan-hsin; Majumdar, Devi; Anderson, Bridget; Eason, Brady; Brown, Claire M.; Webb, Donna J.

2012-01-01

292

Composite laminate free-edge reinforcement with U-shaped caps. I - Stress analysis. II - Theoretical-experimental correlation  

NASA Technical Reports Server (NTRS)

The present generalized plane-strain FEM analysis for the prediction of interlaminar normal stress reduction when a U-shaped cap is bonded to the edge of a composite laminate gives attention to the highly variable transverse stresses near the free edge, cap length and thickness, and a gap under the cap due to the manufacturing process. The load-transfer mechanism between cap and laminate is found to be strain-compatibility, rather than shear lag. In the second part of this work, the three-dimensional composite material failure criteria are used in a progressive laminate failure analysis to predict failure loads of laminates with different edge-cap designs; symmetric 11-layer graphite-epoxy laminates with a one-layer cap of kevlar-epoxy are shown to carry 130-140 percent greater loading than uncapped laminates, under static tensile and tension-tension fatigue loading.

Howard, W. E.; Gossard, Terry, Jr.; Jones, Robert M.

1989-01-01

293

Sensitivity of F-106B Leading-Edge-Vortex Images to Flight and Vapor-Screen Parameters  

NASA Technical Reports Server (NTRS)

A flight test was undertaken at NASA Langley Research Center with vapor-screen and image-enhancement techniques to obtain qualitative and quantitative information about near-field vortex flows above the wings of fighter aircraft. In particular, the effects of Reynolds and Mach numbers on the vortex system over an angle-of-attack range were sought. The relevance of these flows stems from their present and future use at many points in the flight envelope, especially during transonic maneuvers. The aircraft used in this flight program was the F-106B because it was available and had sufficient wing sweep (60 deg) to generate a significant leading-edge vortex system. The sensitivity of the visual results to vapor screen hardware and to onset flow changes is discussed.

Lamar, John E.; Johnson, Thomas D., Jr.

1988-01-01

294

CFD Analysis of the Aerodynamics of a Business-Jet Airfoil with Leading-Edge Ice Accretion  

NASA Technical Reports Server (NTRS)

For rime ice - where the ice buildup has only rough and jagged surfaces but no protruding horns - this study shows two dimensional CFD analysis based on the one-equation Spalart-Almaras (S-A) turbulence model to predict accurately the lift, drag, and pressure coefficients up to near the stall angle. For glaze ice - where the ice buildup has two or more protruding horns near the airfoil's leading edge - CFD predictions were much less satisfactory because of the large separated region produced by the horns even at zero angle of attack. This CFD study, based on the WIND and the Fluent codes, assesses the following turbulence models by comparing predictions with available experimental data: S-A, standard k-epsilon, shear-stress transport, v(exp 2)-f, and differential Reynolds stress.

Chi, X.; Zhu, B.; Shih, T. I.-P.; Addy, H. E.; Choo, Y. K.

2004-01-01

295

Turbine vane gas film cooling with injection in the leading edge region from a single row of spanwise angled holes  

NASA Technical Reports Server (NTRS)

An experimental study of gas film cooling was conducted on a 3X size model turbine vane. Injection in the leading edge region was from a single row of holes angled in a spanwise direction. Measurements of the local heat flux downstream from the row of coolant holes, both with and without film coolant flow, were used to determine the film cooling performance presented in terms of the Stanton number ratio. Results for a range of coolant blowing ratio, M = 0 to 2.0, indicate a reduction in heat flux of up to 15 to 30 percent at a point 10 to 11 hole diameters downstream from injection. An optimum coolant blowing ratio corresponds to a coolant-to-freestream velocity ratio in the range of 0.5. The shallow injection angle resulted in superior cooling performance for injection closest to stagnation, while the effect of injection angle was insignificant for injection further from stagnation.

Lecuyer, M. R.; Hanus, G. J.

1976-01-01

296

An Experimental Investigation of NACA Submerged Inlets at High Subsonic Speeds I: Inlets Forward of the Wing Leading Edge  

NASA Technical Reports Server (NTRS)

This report covers the first part of an experimental investigation of NACA submerged inlets at four locations on the fuselage of a fighter airplane model for Mach numbers from 0.30 to 0.875. Data are presented showing the characteristics of the model without inlets and with inlets 16.7 percent of the root chord forward of the wing-root leading edge and equipped with small boundary-layer deflectors. The data show that variations in the mass of air entering the inlet had a large effect on the ram-recovery ratio. Representative values of ram-recovery ratio were 0.50 with zero flow, 0.90 with 0.6 mass-flow coefficient, and 0.95 with 1.00 mass-flow coefficient. Variations in Mach number and angle of attack, in general, caused less than a 0.03 variation in the ram-recovery ratio.

Hall, Charles F; Barclay, F Dorn

1948-01-01

297

Test-Analysis Correlation for Space Shuttle External Tank Foam Impacting RCC Wing Leading Edge Component Panels  

NASA Technical Reports Server (NTRS)

The Space Shuttle Columbia Accident Investigation Board recommended that NASA develop, validate, and maintain a modeling tool capable of predicting the damage threshold for debris impacts on the Space Shuttle Reinforced Carbon-Carbon (RCC) wing leading edge and nosecap assembly. The results presented in this paper are one part of a multi-level approach that supported the development of the predictive tool used to recertify the shuttle for flight following the Columbia Accident. The assessment of predictive capability was largely based on test analysis comparisons for simpler component structures. This paper provides comparisons of finite element simulations with test data for external tank foam debris impacts onto 6-in. square RCC flat panels. Both quantitative displacement and qualitative damage assessment correlations are provided. The comparisons show good agreement and provided the Space Shuttle Program with confidence in the predictive tool.

Lyle, Karen H.

2008-01-01

298

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade With Supersonic Leading-Edge Locus  

NASA Technical Reports Server (NTRS)

An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.

Ramsey, John K.; Erwin, Dan

2004-01-01

299

Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.  

PubMed

The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff. PMID:23851351

Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

2013-09-01

300

Rate and topography of peptidoglycan synthesis during cell division in Escherichia coli: concept of a leading edge.  

PubMed Central

The rate at which the peptidoglycan of Escherichia coli is synthesized during the division cycle was studied with two methods. One method involved synchronization of E. coli MC4100 lysA cultures by centrifugal elutriation and subsequent pulse-labeling of the synchronously growing cultures with [meso-3H]diaminopimelic acid ([3H]Dap). The second method was autoradiography of cells pulse-labeled with [3H]Dap. It was found that the peptidoglycan is synthesized at a more or less exponentially increasing rate during the division cycle with a slight acceleration in this rate as the cells start to constrict. Apparently, polar cap formation requires synthesis of extra surface components, presumably to accommodate for a change in the surface-to-volume ratio. Furthermore, it was found that the pool size of Dap was constant during the division cycle. Close analysis of the topography of [3H]Dap incorporation at the constriction site revealed that constriction proceeded by synthesis of peptidoglycan at the leading edge of the invaginating cell envelope. During constriction, no reallocation of incorporation occurred, i.e., the incorporation at the leading edge remained high throughout the process of constriction. Impairment of penicillin-binding protein 3 by mutation or by the specific beta-lactam antibiotic furazlocillin did not affect [3H]Dap incorporation during initiation of constriction. However, the incorporation at the constriction site was inhibited in later stages of the constriction process. It is concluded that during division at least two peptidoglycan-synthesizing systems are operating sequentially. Images PMID:2656655

Wientjes, F B; Nanninga, N

1989-01-01

301

An experimental analysis of critical factors involved in the breakdown process of leading edge vortex flows. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Experimental crosswire measurements of the flowfield above a 70 and 75 degree flat plate delta wing were performed at a Reynolds number of 250,000. Survey grids were taken normal to the platform at a series of chordwise locations for angles of attack of 20 and 30 degrees. Axial and azimuthal vorticity distributions were derived from the velocity fields. The dependence of circulation on distance from the vortex core as well as on chordwise location was examined. The effects of nondimensionalization in comparison with other experimental data was made. The circulation distribution scales with the local semispan and grows approximately linearly in the chordwise direction. For regions of the flow outside of the vortex subcore, the circulation at any chordwise station was observed to vary logarithmically with distance from the vortex axis. The circulation was also found to increase linearly with angle of incidence at a given chordwise station. A reduction in the local circulation about the vortex axis occurred at breakdown. The spanwise distribution of axial vorticity was severely altered through the breakdown region and the spanwise distribution of axial vorticity present appeared to reach a maximum immediately preceding breakdown. The local concentration of axial vorticity about the vortex axis was reduced while the magnitude of the azimuthal vorticity decreased throughout the breakdown zone. The axial vorticity components with a negative sense, found in the secondary vortex, remained unaffected by changes in wing sweep or angle of attack, in direct contrast to the positive components. The inclusion of the local wing geometry into a previously derived correlation parameter indicated that the circulation of growing leading edge vortex flows were similar at corresponding radii from the vortex axis. It was concluded that the flow over a delta wing, upstream of the breakdown regions and away from the apex and trailing edge regions, is conical. In addition, the dominating factors leading to the onset of breakdown are felt to be the local circulation of the vortex and the accompanying pressure field.

Visser, Kenneth D.

1991-01-01

302

Particle Image Velocimetry Near the Leading Edge of a Sikorsky SSC-A09 Wing During Dynamic Stall  

E-print Network

edge region and the first indications of separation are observed at 18 degree angle of attack. The edge of the boundary layer has been characterized for alpha = 18 degrees. The roles of the Reynolds stresses and vorticity are examined....

Vannelli, Rachel Renee

2012-02-14

303

Planform curvature effects on flutter characteristics of a wing with 56 deg leading-edge sweep and panel aspect ratio of 1.14  

NASA Technical Reports Server (NTRS)

An experimental and analytical investigation was initiated to determine the effects of planform curvature (curving the leading and trailing edges of a wing in the X-Y plane) on the transonic flutter characteristics of a series of three moderately swept wing models. Experimental flutter results were obtained in the Langley Transonic Dynamics Tunnel for Mach numbers from 0.60-1.00, with air as the test medium. The models were semispan cantilevered wings with a 3 percent biconvex airfoil and a panel aspect ratio of 1.14. The baseline model had straight leading and trailing edges (i.e., no planform curvature). The radii of curvature of the leading edges for these two models were 200 and 80 inches. The radii of curvature of the leading edges of the other two models were determined so that the root and tip chords were identical for all three models. Experimental results showed that flutter-speed index and flutter frequency ratio increased as planform curvature increase (radius of curvature of the leading edge was decreased) over the test range of Mach numbers. Analytical flutter results were calculated with a subsonic flutter-prediction program, and they agreed well with the experimental results.

Keller, Donald F.; Sandford, Maynard C.; Pinkerton, Theresa L.

1991-01-01

304

Leading Edge Book Review  

E-print Network

production is triggered by the nervous system in response to the perceived environment, are the effectors are required for the completion of differentiation. The same applies to the development of the immune system devel- opment. Teratogens, such as thalido- mide, and endocrine disruptors, such as the pesticide DDT

Monteiro, Antónia

305

Leading Edge Book Review  

E-print Network

19th and early 20th century, Haeckel's name has been relegated to the shadows of modern thought-Darwinism, and--in the worst of cases--racism. So, what brought about this change in the standing of the man

Alvarado, Alejandro Sánchez

306

First results from core-edge parallel composition in the FACETS project  

SciTech Connect

FACETS (Framework Application for Core-Edge Transport Simulations), now in its second year, has achieved its first coupled core-edge transport simulations. In the process, a number of accompanying accomplishments were achieved. These include a new parallel core component, a new wall component, improvements in edge and source components, and the framework for coupling all of this together. These accomplishments were a result of an interdisciplinary collaboration among computational physics, computer scientists, and applied mathematicians on the team.

Cary, John R. [Tech-X Corporation; Candy, Jeff [General Atomics; Cohen, Ronald H. [Lawrence Livermore National Laboratory (LLNL); Krasheninnikov, Sergei [University of California, San Diego; McCune, Douglas [Princeton Plasma Physics Laboratory (PPPL); Estep, Donald J [Colorado State University, Fort Collins; Larson, Jay [Argonne National Laboratory (ANL); Malony, Allen [University of Oregon; Pankin, A. [Lehigh University, Bethlehem, PA; Worley, Patrick H [ORNL; Carlsson, Johann [Tech-X Corporation; Hakim, A H [Tech-X Corporation; Hamill, P [Tech-X Corporation; Kruger, Scott [Tech-X Corporation; Miah, Mahmood [Tech-X Corporation; Muzsala, S [Tech-X Corporation; Pletzer, Alexander [Tech-X Corporation; Shasharina, Svetlana [Tech-X Corporation; Wade-Stein, D [Tech-X Corporation; Wang, N [Tech-X Corporation; Balay, Satish [Argonne National Laboratory (ANL); McInnes, Lois [Argonne National Laboratory (ANL); Zhang, Hong [Argonne National Laboratory (ANL); Casper, T. A. [Lawrence Livermore National Laboratory (LLNL); Diachin, Lori [Lawrence Livermore National Laboratory (LLNL); Epperly, Thomas [Lawrence Livermore National Laboratory (LLNL); Rognlien, T. D. [Lawrence Livermore National Laboratory (LLNL); Fahey, Mark R [ORNL; Cobb, John W [ORNL; Morris, A [University of Oregon; Shende, Sameer [University of Oregon; Hammett, Greg [Princeton Plasma Physics Laboratory (PPPL); Indireshkumar, K [Tech-X Corporation; Stotler, D. [Princeton Plasma Physics Laboratory (PPPL); Pigarov, A [University of California, San Diego

2008-01-01

307

First results from core-edge parallel composition in the FACETS project.  

SciTech Connect

FACETS (Framework Application for Core-Edge Transport Simulations), now in its second year, has achieved its first coupled core-edge transport simulations. In the process, a number of accompanying accomplishments were achieved. These include a new parallel core component, a new wall component, improvements in edge and source components, and the framework for coupling all of this together. These accomplishments were a result of an interdisciplinary collaboration among computational physics, computer scientists, and applied mathematicians on the team.

Cary, J. R.; Candy, J.; Cohen, R. H.; Krasheninnikov, S.; McCune, D. C.; Estep, D. J.; Larson, J.; Malony, A. D.; Pankin, A.; Worley, P. H.; Carlsson, J. A.; Hakim, A. H.; Hamill, P.; Kruger, S.; Miah, M.; Muzsala, S.; Pletzer, A.; Shasharina, S.; Wade-Stein, D.; Wang, N.; Balay, S.; McInnes, L.; Zhang, H.; Casper, T.; Diachin, L. (Mathematics and Computer Science); (Tech-X Corp.); (General Atomics); (LLNL); (Univ. of California at San Diego); (Princeton Plasma Physics Lab.); (Colorado State Univ.); (ParaTools Inc.); (Lehigh Univ.); (ORNL)

2008-01-01

308

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Vol. 3: Medium-radius leading edge  

NASA Technical Reports Server (NTRS)

An experimental wind tunnel test of a 65 deg delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 120 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at Reynolds numbers of 6 x 10(exp 6), 60 x 10(exp 6), and 120 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

309

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Volume 2; Small-Radius Leading Edge  

NASA Technical Reports Server (NTRS)

An experimental wind tunnel test of a 65 deg. delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 84 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at Reynolds numbers of 6 x 10(exp 6) and 60 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

310

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Vol. 4: Large-radius leading edge  

NASA Technical Reports Server (NTRS)

An experimental wind tunnel test of a 65 deg delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 120 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at Reynolds numbers of 6 x 10(exp 6) and 60 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

311

Subsonic Investigation of Leading-Edge Flaps Designed for Vortex- and Attached-Flow on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

A wind tunnel investigation of two separate leading-edge flaps, designed for vortex and attached-flow, respectively, were conducted on a High Speed Civil Transport (HSCT) configuration in the Langley 14- by 22-Foot Subsonic Tunnel. Data were obtained over a Mach number range of 0.12 to 0.27, with corresponding chord Reynolds numbers of 2.50 x 10 (sup 6) to 5.50 x 10 (sup 6). Variations of the leading-edge flap deflection angle were tested with outboard leading-edge flaps deflected 0 deg. and 26.4 deg. Trailing-edge flaps were deflected 0 deg., 10 deg., 12.9 deg., and 20 deg. The longitudinal and lateral aerodynamic data are presented without analysis. A complete tabulated data listing is also presented herein. The data associated with each deflected leading-edge flap indicate L/D improvements over the undeflected configuration. These improvements may be instrumental in providing the necessary lift augmentation required by an actual HSCT during the climb-out and landing phases of the flight envelope. However, further tests will have to be done to assess their full potential.

Campbell, Bryan A.; Kemmerly, Guy T.; Kjerstad, Kevin J.; Lessard, Victor R.

1999-01-01

312

Three-dimensional thermal-structural analysis of a swept cowl leading edge subjected to skewed shock-shock interference heating  

NASA Technical Reports Server (NTRS)

A three-dimensional flux-based thermal analysis method has been developed and its capability is demonstrated by predicting the transient nonlinear temperature response of a swept cowl leading edge subjected to intense three-dimensional aerodynamic heating. The predicted temperature response from the transient thermal analysis is used in a linear elastic structural analysis to determine thermal stresses. Predicted thermal stresses are compared with those obtained from a two-dimensional analysis which represents conditions along the chord where maximum heating occurs. Results indicate a need for a three-dimensional analysis to predict accurately the leading edge thermal stress response.

Polesky, Sandra P.; Dechaumphai, Pramote; Glass, Christopher E.; Pandey, Ajay K.

1990-01-01

313

Aeroelastic loads prediction for an arrow wing. Task 3: Evaluation of the Boeing three-dimensional leading-edge vortex code  

NASA Technical Reports Server (NTRS)

Two separated flow computer programs and a semiempirical method for incorporating the experimentally measured separated flow effects into a linear aeroelastic analysis were evaluated. The three dimensional leading edge vortex (LEV) code is evaluated. This code is an improved panel method for three dimensional inviscid flow over a wing with leading edge vortex separation. The governing equations are the linear flow differential equation with nonlinear boundary conditions. The solution is iterative; the position as well as the strength of the vortex is determined. Cases for both full and partial span vortices were executed. The predicted pressures are good and adequately reflect changes in configuration.

Manro, M. E.

1983-01-01

314

Turbine Vane External Heat Transfer. Volume 1: Analytical and Experimental Evaluation of Surface Heat Transfer Distributions with Leading Edge Showerhead Film Cooling  

NASA Technical Reports Server (NTRS)

Progress in predictive design capabilities for external heat transfer to turbine vanes was summarized. A two dimensional linear cascade (previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils) was used to examine the effect of leading edge shower head film cooling on downstream heat transfer. The data were used to develop and evaluate analytical models. Modifications to the two dimensional boundary layer model are described. The results were used to formulate and test an effective viscosity model capable of predicting heat transfer phenomena downstream of the leading edge film cooling array on both the suction and pressure surfaces, with and without mass injection.

Turner, E. R.; Wilson, M. D.; Hylton, L. D.; Kaufman, R. M.

1985-01-01

315

Simulator study of the stall departure characteristics of a light general aviation airplane with and without a wing-leading-edge modification  

NASA Technical Reports Server (NTRS)

A six-degree-of-freedom nonlinear simulation was developed for a two-place, single-engine, low-wing general aviation airplane for the stall and initial departure regions of flight. Two configurations, one with and one without an outboard wing-leading-edge modification, were modeled. The math models developed are presented simulation predictions and flight-test data for validation purposes and simulation results for the two configurations for various maneuvers and power settings are compared to show the beneficial influence of adding the wing-leading-edge modification.

Riley, D. R.

1985-01-01

316

The Vercors and Chartreuse Massifs at the leading edge of the alpine thrust belt: Tetonic history and petroleum assessment  

SciTech Connect

The Vercors and Chartreuse Massifs are located at the leading edge of the Western Alps Thrust Belt. They developed in late Miocene-Pliocene times above a major decollement hosted in late Triassic evaporites and/or Liassic marls. The uplift of both massifs led to the oblique and partial inversion of the previous Mesozoic margin of the Southeastern Basin, the thickest onshore sedimentary basin in France. Both massifs are unexplored. The regional geology of eastern France and the results of ten wells located in the near foreland suggest that source rocks are present in late Paleozoic and late Liassic strata, and that fractured sandstones and/or limestones of Triassic/Jurassic age could act as reservoirs. A nonexclusive seismic survey has been shot in 1991 by CGG allowing the first well constrained balanced sections to be drawn across both massifs. They have been used inturn to model the forward kinematics of thrust propagation, and the source rock maturation history, using the {open_quotes}Thrustpack{close_quotes} software developed by IFP and partners.

Deville, E.; Mascle, A.; Philippe, Y. [Institut Francais du Petrole, Rueil-Malmaison (France)] [and others

1995-08-01

317

Leading edge vortices in lesser long-nosed bats occurring at slow but not fast flight speeds.  

PubMed

Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but that they avoid doing so, probably to increase flight efficiency. In addition, at slow flight speeds we find LEVs of opposite spin at the inner and outer wing during the upstroke, potentially providing a control challenge to the animal. We also note that the LEV stays attached to the wing throughout the downstoke and does not show the complex structures found in insects. This suggests that bats are able to control the development of the LEV and potential control mechanisms are discussed. PMID:24855067

Muijres, Florian T; Christoffer Johansson, L; Winter, York; Hedenström, Anders

2014-06-01

318

Goertler vortices in growing boundary layers: The leading edge receptivity problem, linear growth and the nonlinear breakdown stage  

NASA Technical Reports Server (NTRS)

Goertler vortices are thought to be the cause of transition in many fluid flows of practical importance. A review of the different stages of vortex growth is given. In the linear regime, nonparallel effects completely govern this growth, and parallel flow theories do not capture the essential features of the development of the vortices. A detailed comparison between the parallel and nonparallel theories is given and it is shown that at small vortex wavelengths, the parallel flow theories have some validity; otherwise nonparallel effects are dominant. New results for the receptivity problem for Goertler vortices are given; in particular vortices induced by free stream perturbations impinging on the leading edge of the walls are considered. It is found that the most dangerous mode of this type can be isolated and it's neutral curve is determined. This curve agrees very closely with the available experimental data. A discussion of the different regimes of growth of nonlinear vortices is also given. Again it is shown that, unless the vortex wavelength is small, nonparallel effects are dominant. Some new results for nonlinear vortices of 0(1) wavelengths are given and compared to experimental observations.

Hall, Philip

1989-01-01

319

Determining the optical absorption edge in organic semiconductor composites with a bulk heterojunction by the constant photocurrent method  

NASA Astrophysics Data System (ADS)

Spectral dependences of photoconductivity in thin layers of polyconjugated polymers (PCDTBT, PTB7) and their composites with a fullerene derivative (PC70BM), which are promising for the development of organic solar cells, have been studied. It was found that the photoconductivity in the polymeric composite exceeds that in the polymer in the whole spectral range under study and the edge of the photoconductivity spectrum is shifted to the long-wavelength part of the spectrum. Use of the constant photocurrent method made it possible to obtain spectral dependences of the absorption coefficients and determine the optical gap width of the materials studied.

Malov, V. V.; Kazanskii, A. G.; Khenkin, M. V.; Tameev, A. R.

2014-09-01

320

AERO2S - SUBSONIC AERODYNAMIC ANALYSIS OF WINGS WITH LEADING- AND TRAILING-EDGE FLAPS IN COMBINATION WITH CANARD OR HORIZONTAL TAIL SURFACES (IBM PC VERSION)  

NASA Technical Reports Server (NTRS)

This code was developed to aid design engineers in the selection and evaluation of aerodynamically efficient wing-canard and wing-horizontal-tail configurations that may employ simple hinged-flap systems. Rapid estimates of the longitudinal aerodynamic characteristics of conceptual airplane lifting surface arrangements are provided. The method is particularly well suited to configurations which, because of high speed flight requirements, must employ thin wings with highly swept leading edges. The code is applicable to wings with either sharp or rounded leading edges. The code provides theoretical pressure distributions over the wing, the canard or horizontal tail, and the deflected flap surfaces as well as estimates of the wing lift, drag, and pitching moments which account for attainable leading edge thrust and leading edge separation vortex forces. The wing planform information is specified by a series of leading edge and trailing edge breakpoints for a right hand wing panel. Up to 21 pairs of coordinates may be used to describe both the leading edge and the trailing edge. The code has been written to accommodate 2000 right hand panel elements, but can easily be modified to accommodate a larger or smaller number of elements depending on the capacity of the target computer platform. The code provides solutions for wing surfaces composed of all possible combinations of leading edge and trailing edge flap settings provided by the original deflection multipliers and by the flap deflection multipliers. Up to 25 pairs of leading edge and trailing edge flap deflection schedules may thus be treated simultaneously. The code also provides for an improved accounting of hinge-line singularities in determination of wing forces and moments. To determine lifting surface perturbation velocity distributions, the code provides for a maximum of 70 iterations. The program is constructed so that successive runs may be made with a given code entry. To make additional runs, it is necessary only to add an identification record and the namelist data that are to be changed from the previous run. This code was originally developed in 1989 in FORTRAN V on a CDC 6000 computer system, and was later ported to an MS-DOS environment. Both versions are available from COSMIC. There are only a few differences between the PC version (LAR-14458) and CDC version (LAR-14178) of AERO2S distributed by COSMIC. The CDC version has one main source code file while the PC version has two files which are easier to edit and compile on a PC. The PC version does not require a FORTRAN compiler which supports NAMELIST because a special INPUT subroutine has been added. The CDC version includes two MODIFY decks which can be used to improve the code and prevent the possibility of some infrequently occurring errors while PC-version users will have to make these code changes manually. The PC version includes an executable which was generated with the Ryan McFarland/FORTRAN compiler and requires 253K RAM and an 80x87 math co-processor. Using this executable, the sample case requires about four hours to execute on an 8MHz AT-class microcomputer with a co-processor. The source code conforms to the FORTRAN 77 standard except that it uses variables longer than six characters. With two minor modifications, the PC version should be portable to any computer with a FORTRAN compiler and sufficient memory. The CDC version of AERO2S is available in CDC NOS Internal format on a 9-track 1600 BPI magnetic tape. The PC version is available on a set of two 5.25 inch 360K MS-DOS format diskettes. IBM AT is a registered trademark of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation. CDC is a registered trademark of Control Data Corporation. NOS is a trademark of Control Data Corporation.

Carlson, H. W.

1994-01-01

321

AERO2S - SUBSONIC AERODYNAMIC ANALYSIS OF WINGS WITH LEADING- AND TRAILING-EDGE FLAPS IN COMBINATION WITH CANARD OR HORIZONTAL TAIL SURFACES (CDC VERSION)  

NASA Technical Reports Server (NTRS)

This code was developed to aid design engineers in the selection and evaluation of aerodynamically efficient wing-canard and wing-horizontal-tail configurations that may employ simple hinged-flap systems. Rapid estimates of the longitudinal aerodynamic characteristics of conceptual airplane lifting surface arrangements are provided. The method is particularly well suited to configurations which, because of high speed flight requirements, must employ thin wings with highly swept leading edges. The code is applicable to wings with either sharp or rounded leading edges. The code provides theoretical pressure distributions over the wing, the canard or horizontal tail, and the deflected flap surfaces as well as estimates of the wing lift, drag, and pitching moments which account for attainable leading edge thrust and leading edge separation vortex forces. The wing planform information is specified by a series of leading edge and trailing edge breakpoints for a right hand wing panel. Up to 21 pairs of coordinates may be used to describe both the leading edge and the trailing edge. The code has been written to accommodate 2000 right hand panel elements, but can easily be modified to accommodate a larger or smaller number of elements depending on the capacity of the target computer platform. The code provides solutions for wing surfaces composed of all possible combinations of leading edge and trailing edge flap settings provided by the original deflection multipliers and by the flap deflection multipliers. Up to 25 pairs of leading edge and trailing edge flap deflection schedules may thus be treated simultaneously. The code also provides for an improved accounting of hinge-line singularities in determination of wing forces and moments. To determine lifting surface perturbation velocity distributions, the code provides for a maximum of 70 iterations. The program is constructed so that successive runs may be made with a given code entry. To make additional runs, it is necessary only to add an identification record and the namelist data that are to be changed from the previous run. This code was originally developed in 1989 in FORTRAN V on a CDC 6000 computer system, and was later ported to an MS-DOS environment. Both versions are available from COSMIC. There are only a few differences between the PC version (LAR-14458) and CDC version (LAR-14178) of AERO2S distributed by COSMIC. The CDC version has one main source code file while the PC version has two files which are easier to edit and compile on a PC. The PC version does not require a FORTRAN compiler which supports NAMELIST because a special INPUT subroutine has been added. The CDC version includes two MODIFY decks which can be used to improve the code and prevent the possibility of some infrequently occurring errors while PC-version users will have to make these code changes manually. The PC version includes an executable which was generated with the Ryan McFarland/FORTRAN compiler and requires 253K RAM and an 80x87 math co-processor. Using this executable, the sample case requires about four hours to execute on an 8MHz AT-class microcomputer with a co-processor. The source code conforms to the FORTRAN 77 standard except that it uses variables longer than six characters. With two minor modifications, the PC version should be portable to any computer with a FORTRAN compiler and sufficient memory. The CDC version of AERO2S is available in CDC NOS Internal format on a 9-track 1600 BPI magnetic tape. The PC version is available on a set of two 5.25 inch 360K MS-DOS format diskettes. IBM AT is a registered trademark of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation. CDC is a registered trademark of Control Data Corporation. NOS is a trademark of Control Data Corporation.

Darden, C. M.

1994-01-01

322

Experimental study of pressure and heating rate on a swept cylindrical leading edge resulting from swept shock wave interference. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The effects of cylindrical leading edge sweep on surface pressure and heat transfer rate for swept shock wave interference were investigated. Experimental tests were conducted in the Calspan 48-inch Hypersonic Shock Tunnel at a nominal Mach number of 8, nominal unit Reynolds number of 1.5 x 10 to the 6th power per foot, leading edge and incident shock generator sweep angles of 0, 15, and 30 deg, and incident shock generator angle-of-attack fixed at 12.5 deg. Detailed surface pressure and heat transfer rate on the cylindircal leading edge of a swept shock wave interference model were measured at the region of the maximum surface pressure and heat transfer rate. Results show that pressure and heat transfer rate on the cylindrical leading edge of the shock wave interference model were reduced as the sweep was increased over the range of tested parameters. Peak surface pressure and heat transfer rate on the cylinder were about 10 and 30 times the undisturbed flow stagnation point value, respectively, for the 0 deg sweep test. A comparison of the 15 and 30 deg swept results with the 0 deg swept results showed that peak pressure was reduced about 13 percent and 44 percent, respectively, and peak heat transfer rate was reduced about 7 percent and 27 percent, respectively.

Glass, Christopher E.

1989-01-01

323

The importance of leading edge vortices under simplified flapping flight conditions at the size scale of birds.  

PubMed

Over the last decade, interest in animal flight has grown, in part due to the possible use of flapping propulsion for micro air vehicles. The importance of unsteady lift-enhancing mechanisms in insect flight has been recognized, but unsteady effects were generally thought to be absent for the flapping flight of larger animals. Only recently has the existence of LEVs (leading edge vortices) in small vertebrates such as swifts, small bats and hummingbirds been confirmed. To study the relevance of unsteady effects at the scale of large birds [reduced frequency k between 0.05 and 0.3, k=(pifc)/U(infinity); f is wingbeat frequency, U(infinity) is free-stream velocity, and c is the average wing chord], and the consequences of the lack of kinematic and morphological refinements, we have designed a simplified goose-sized flapping model for wind tunnel testing. The 2-D flow patterns along the wing span were quantitatively visualized using particle image velocimetry (PIV), and a three-component balance was used to measure the forces generated by the wings. The flow visualization on the wing showed the appearance of LEVs, which is typically associated with a delayed stall effect, and the transition into flow separation. Also, the influence of the delayed stall and flow separation was clearly visible in measurements of instantaneous net force over the wingbeat cycle. Here, we show that, even at reduced frequencies as low as those of large bird flight, unsteady effects are present and non-negligible and have to be addressed by kinematic and morphological adaptations. PMID:20472780

Hubel, Tatjana Y; Tropea, Cameron

2010-06-01

324

Lead content and isotopic composition in submound and recent soils of the Volga Upland  

NASA Astrophysics Data System (ADS)

Literature data on the historical reconstructions of the atmospheric lead deposition in Europe and the isotopic composition of the ores that are potential sources of the anthropogenic lead in the atmospheric deposition in the lower Volga steppes during different time periods have been compiled. The effect of the increasing anthropogenic lead deposition recorded since the Bronze Age on the level of soil contamination has been investigated. For the first time paleosol buried under a burial mound of the Bronze Age has been used as a reference point to assess of the current contamination level. The contents and isotopic compositions of the mobile and total lead have been determined in submound paleosols of different ages and their recent remote and roadside analogues. An increase in the content and fraction of the mobile lead and a shift of its isotopic composition toward less radiogenic values (typical for lead from the recent anthropogenic sources) has been revealed when going from a Bronze-Age paleosol to a recent soil. In the Bronze-Age soil, the isotopic composition of the mobile lead is inherited from the parent rock to a greater extent than in the modern soils, where the lead is enriched with the less radiogenic component. The effect of the anthropogenic component is traced in the analysis of the mobile lead, but it is barely visible for the total lead. An exception is provided by the recent roadside soils characterized by increased contents and the significantly less radiogenic isotopic composition of the mobile and total lead.

Pampura, T. V.; Probst, A.; Ladonin, D. V.; Demkin, V. A.

2013-11-01

325

Automated Screening of Microtubule Growth Dynamics Identifies MARK2 as a Regulator of Leading Edge Microtubules Downstream of Rac1 in Migrating Cells  

PubMed Central

Polarized microtubule (MT) growth in the leading edge is critical to directed cell migration, and is mediated by Rac1 GTPase. To find downstream targets of Rac1 that affect MT assembly dynamics, we performed an RNAi screen of 23 MT binding and regulatory factors and identified RNAi treatments that suppressed changes in MT dynamics induced by constitutively activated Rac1. By analyzing fluorescent EB3 dynamics with automated tracking, we found that RNAi treatments targeting p150glued, APC2, spastin, EB1, Op18, or MARK2 blocked Rac1-mediated MT growth in lamellipodia. MARK2 was the only protein whose RNAi targeting additionally suppressed Rac1 effects on MT orientation in lamellipodia, and thus became the focus of further study. We show that GFP-MARK2 rescued effects of MARK2 depletion on MT growth lifetime and orientation, and GFP-MARK2 localized in lamellipodia in a Rac1-activity-dependent manner. In a wound-edge motility assay, MARK2-depleted cells failed to polarize their centrosomes or exhibit oriented MT growth in the leading edge, and displayed defects in directional cell migration. Thus, automated image analysis of MT assembly dynamics identified MARK2 as a target regulated downstream of Rac1 that promotes oriented MT growth in the leading edge to mediate directed cell migration. PMID:22848487

Nishimura, Yukako; Applegate, Kathryn; Davidson, Michael W.; Danuser, Gaudenz; Waterman, Clare M.

2012-01-01

326

Nonlinear fracture mechanics of mode-I and mixed-mode free edge delamination in carbon-epoxy composites  

SciTech Connect

A geometrically and physically nonlinear finite element approach is presented for the analysis of free edge delamination in composite laminates which properly accounts for the effects of initial thermal and hygroscopic stresses. A constitutive model based on nonlinear fracture mechanics is used to describe delamination. An orthotropic plasticity model is used to determine the initiation and propagation of delamination. Although the orthotropic yield surface is based on stresses, it is proven, that in combination with a softening type of post-failure response, the resulting computational strategy converges to a unique and physically realistic solution upon mesh refinement. The results from the nonlinear finite element computations -- including predictive analyses -- are compared with model and mixed-mode free edge delamination experiments. This comparison shows that the numerical predictions are within 10% of the experimental data.

Schellekens, J.C.J.; Borst, R. de [Delft Univ. of Technology (Netherlands)

1993-12-31

327

Magnetoelectric effect in lead-free BNKLBT ceramic/terfenol-D continue fiber composite laminates  

SciTech Connect

A magnetostrictive-piezoelectric laminated composite has been developed by sandwiching a lead-free BNKLBT ceramic plate polarized in the thickness direction between two terfenol-D continuous fiber composite plates. This lead-free magnetoelectric (ME) laminated composite has a large ME voltage sensitivity of 2.5 V/Oe at the resonance frequency of 130.9 kHz under a low magnetic bias field (H{sub Bias}) of 0.6 kOe. This work shows the potential of BNKLBT lead-free ceramics in ME sensing application.

Lo, C. Y.; Choy, S. H.; Or, S. W.; Chan, H. L. W. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom (Hong Kong)

2010-05-15

328

Numerical and experimental study on the ability of dynamic roughness to alter the development of a leading edge vortex  

NASA Astrophysics Data System (ADS)

Dynamic stall is an unsteady aerodynamic phenomenon garnering much research interest because it occurs in a variety of applications. For example, dynamic stall is known to occur on helicopter rotor blades, wind turbines, high maneuvering military aircraft, and flapping wings. Dynamic stall occurs when an aerodynamic lifting device, such as an airfoil, wing, or turbomachine blade, undergoes a rapid pitching motion. It also occurs on lifting devices that are impulsively started at high angles of attack. Dynamic stall can "delay" aerodynamic stall to angles of attack that are significantly beyond the static stall angle of attack. During dynamic stall a large leading edge vortex (LEV) is formed, which creates greater fluid acceleration over the wing or airfoil, thus sustaining lift. As this vortex is shed downstream stall eventually occurs and there is an abrupt increase in drag and a large shift in pitching moment. Research has been performed to better understand the mechanisms occurring during dynamic stall in an effort to find ways to best take advantage of the increased lift associated with dynamic stall, but avoid the downfalls that occur once stall is initiated. Few attempts have been made to alter the LEV, and these attempts have used methods associated with laminar boundary layer separation control. Although these methods have shown promise, they suffer from the drawback that they exhaust more energy than is gained by flow control, while also only being effective at certain flight regimes. The research described herein documents the first study on the ability of dynamic roughness to alter the LEV encountered on a rapidly pitching airfoil. Both numerical and experimental studies were performed, including two-dimensional and three-dimensional computational fluid dynamics (CFD) simulations as well as stereo and planar particle image velocimetry (PIV) experiments. Evidence for the ability of small scale dynamic roughness to alter the development of the LEV was found in both the computational simulations and experiments. This research is the first of its kind to show both computationally and experimentally that dynamic roughness is a viable flow control method for both steady and unsteady aerodynamics.

Griffin, Christopher D.

329

Influence of blade leading edge geometry and upstream blowing on the heat/mass transfer in a turbine cascade  

NASA Astrophysics Data System (ADS)

The effect of secondary flows on mass transfer from a simulated gas turbine blade and hubwall is investigated. Measurements performed using naphthalene sublimation provide non-dimensional mass transfer coefficients, in the form of Sherwood numbers, that can be converted to heat transfer coefficients through the use of an analogy. Tests are conducted in a linear cascade composed of five blades having the profile of a first stage rotor blade of a high-pressure turbine aircraft engine. Detailed mass transfer maps on the airfoil and endwall surfaces allow the identification of significant flow features that are in good agreement with existing secondary flow models. These results are well-suited for validation of numerical codes, as they are obtained with an accurate technique that does not suffer from conduction or radiation errors and allows the imposition of precise boundary conditions. The performance of a RANS (Reynolds Averaged Navier-Stokes) numerical code that simulates the flow and heat/mass transfer in the cascade using the SST (Shear Stress Transport) k-o model is evaluated through a comparison with the experimental results. Tests performed with a modified blade leading edge show that the introduction of a fillet at the junction with the endwall reduces the effects of the horseshoe vortex in the first part of the passage, while no measurable changes in mass transfer are observed further downstream. Air injected through a slot located upstream of the cascade simulates the engine wheelspace coolant injection between the stator and the rotor. Local mass transfer data obtained injecting naphthalene-free and naphthalene-saturated air are reduced to derive maps of cooling effectiveness on the blade and endwall. Oil dot tests show the surface flow on the endwall. The surface downstream of the gap is coplanar to the upstream surface in the baseline configuration and is shifted to form a forward and backward facing step to investigate the effects of component misalignments. Sufficiently high injection rates alter the structure of the secondary flows and significantly improve the cooling performance.

Papa, Marco

330

Suppression of Chemotaxis by SSeCKS via Scaffolding of Phosphoinositol Phosphates and the Recruitment of the Cdc42 GEF, Frabin, to the Leading Edge  

PubMed Central

Chemotaxis is controlled by interactions between receptors, Rho-family GTPases, phosphatidylinositol 3-kinases, and cytoskeleton remodeling proteins. We investigated how the metastasis suppressor, SSeCKS, attenuates chemotaxis. Chemotaxis activity inversely correlated with SSeCKS levels in mouse embryo fibroblasts (MEF), DU145 and MDA-MB-231 cancer cells. SSeCKS loss induced chemotactic velocity and linear directionality, correlating with replacement of leading edge lamellipodia with fascin-enriched filopodia-like extensions, the formation of thickened longitudinal F-actin stress fibers reaching to filopodial tips, relative enrichments at the leading edge of phosphatidylinositol (3,4,5)P3 (PIP3), Akt, PKC-?, Cdc42-GTP and active Src (SrcpoY416), and a loss of Rac1. Leading edge lamellipodia and chemotaxis inhibition in SSeCKS-null MEF could be restored by full-length SSeCKS or SSeCKS deleted of its Src-binding domain (?Src), but not by SSeCKS deleted of its three MARCKS (myristylated alanine-rich C kinase substrate) polybasic domains (?PBD), which bind PIP2 and PIP3. The enrichment of activated Cdc42 in SSeCKS-null leading edge filopodia correlated with recruitment of the Cdc42-specific guanine nucleotide exchange factor, Frabin, likely recruited via multiple PIP2/3-binding domains. Frabin knockdown in SSeCKS-null MEF restores leading edge lamellipodia and chemotaxis inhibition. However, SSeCKS failed to co-immunoprecipitate with Rac1, Cdc42 or Frabin. Consistent with the notion that chemotaxis is controlled by SSeCKS-PIP (vs. -Src) scaffolding activity, constitutively-active phosphatidylinositol 3-kinase could override the ability of the Src inhibitor, SKI-606, to suppress chemotaxis and filopodial enrichment of Frabin in SSeCKS-null MEF. Our data suggest a role for SSeCKS in controlling Rac1 vs. Cdc42-induced cellular dynamics at the leading chemotactic edge through the scaffolding of phospholipids and signal mediators, and through the reorganization of the actin cytoskeleton controlling directional movement. PMID:25356636

Ko, Hyun-Kyung; Guo, Li-wu; Su, Bing; Gao, Lingqiu; Gelman, Irwin H.

2014-01-01

331

An instability at the edge of a tissue of collectively migrating cells can lead to finger formation during wound healing  

NASA Astrophysics Data System (ADS)

In wound healing assays, a monolayer of epithelial cells is allowed to migrate onto empty surface area. When the motile cells close the artificial wound, the edge of the tissue does usually not move uniformly but characteristic fingerlike protrusions are observed. We model the collectively moving cells as a system of self-propelled particles using the Toner-Tu equations for an active fluid. A linear stability analysis of perturbations at the tissue edge reveals an instability in the disordered nonmoving state. The instability is purely due to spontaneous motility and velocity alignment between cells. It can account for finger formation in wound healing experiments.

Zimmermann, J.; Basan, M.; Levine, H.

2014-06-01

332

Effects of discontinuous drooped wing leading-edge modifications on the spinning characteristics of a low-wing general aviation airplane  

NASA Technical Reports Server (NTRS)

Wind tunnel and flight tests were conducted to determine the effects of several discontinuous drooped wing leading-edge configurations on the spinning characteristics of a light, single-engine, low-wing research airplane. Particular emphasis was placed on the identification of modifications which would improve the spinning characteristics. The spanwise length of a discontinuous outboard droop was varied and several additional inboard segments were added to determine the influence of such leading-edge configurations on the spin behavior. Results of the study indicated that the use of only the discontinuous outboard droop, over a specific spanwise area, was most effective towards improving spin and spin recovery characteristics, whereas the segmented configurations having both inboard and outboard droop exhibited a tendency to enter a flat spin.

Dicarlo, D. J.; Stough, H. P., III; Patton, J. M., Jr.

1980-01-01

333

Experimental investigation of the self-induction theory of vortex breakdown and new observations in the transient development of a delta wing leading edge vortex  

NASA Astrophysics Data System (ADS)

The transient development of the leading edge vortex of a 65-deg sweep delta wing is investigated in water tunnel experiments using flow visualization and particle image velocimetry (PIV) measurements. The experiments were conducted at root chord Reynolds numbers from 0 to 3x10 4. The transient results provide experimental evidence supporting the self-induction theory of vortex breakdown. A core radius based circulation overshoot is discovered and attributed to transient development of the vortex core. The transient leading edge vortex core development indicates an initial conical vortex core along the axial direction that transitions to a cylindrical axial core. A passive device that asymmetrically extends the vortex breakdown location is discovered and the mechanisms describing the extension are proposed.

Thompson, Brad R.

334

Reef structure drives parrotfish species composition on shelf edge reefs in La Parguera, Puerto Rico  

NASA Astrophysics Data System (ADS)

Shelf edge reefs that exist in coral reef ecosystems provide essential habitats for a large variety of fish and other marine organisms. Marine herbivores act as differential algal grazers that advocate coral reef colonization. In the Caribbean basin parrotfishes make up a large contingency of such herbivores and act as important ecological ichthyofauna. By investigating parrotfish relationship with habitat, this study aims to aid in future predictive mapping techniques that will outline parrotfish distributions via benthic quantification. Parrotfish communities were evaluated on the shelf edge reef off of La Parguera, Puerto Rico. Parrotfish abundances were found to positively correlate with high values of overall reef structure. High values of coral cover and of rugosity were strong indicators of most parrotfish species. The lone exception, Scarus taeniopterus, negatively correlated with these factors and positively correlated with algal cover. Indications exist that Scarus taeniopterus and Scarus iseri are sympatric species and can be found in abundance at opposite locations.

Tzadik, Orian E.; Appeldoorn, Richard S.

2013-02-01

335

Compression-Loaded Composite Panels With Elastic Edge Restraints and Initial Prestress  

NASA Technical Reports Server (NTRS)

A parametric study of the effects of test-fixture-induced initial prestress and elastic edge restraints on the prebuckling and buckling responses of a compression-loaded, quasi-isotropic curved panel is presented. The numerical results were obtained by using a geometrically nonlinear finite element analysis code with high-fidelity models. The results presented show that a wide range of prebuckling and buckling behavior can be obtained by varying parameters that represent circumferential loaded-edge restraint and rotational unloaded-edge restraint provided by a test fixture and that represent the mismatch in specimen and test-fixture radii of curvature. For a certain range of parameters, the panels exhibit substantial nonlinear prebuckling deformations that yield buckling loads nearly twice the corresponding buckling load predicted by a traditional linear bifurcation buckling analysis for shallow curved panels. In contrast, the results show another range of parameters exist for which the nonlinear prebuckling deformations either do not exist or are relatively benign, and the panels exhibit buckling loads that are nearly equal to the corresponding linear bifurcation buckling load. Overall, the results should be of particular interest to scientists, engineers, and designers involved in simulating flight-hardware boundary conditions in structural verification and certification tests, involved in validating structural analysis tools, and interested in tailoring buckling performance.

Hilburger, Mark W.; Nemeth, Michael P.; Riddick, Jaret C.; Thornburgh, Robert P.

2005-01-01

336

Mesoscale Structures of Air Flow in a Meiyu Front Leading Edge Observed by Aircraft off the East Coast of Taiwan during TAMEX IOP 9  

Microsoft Academic Search

In order to investigate the mesoscale structures and appropriate mechanisms for their maintenance in the Mei-yu front leading edge during the TAMEX (Taiwan Area Mesoscale EXperiment) IOP 9 (15 June 1987) off the east coast of Taiwan, we measured the fine-scale in-situ data by different sensors and sensed radar data by two airborne radars mounted on the NOAA P-3 research

Tai-Hwa Hor; Mou-Hsiang CHANG; Ben Jong-Dao Jou

1998-01-01

337

Receptivity of the boundary layer on a flat plate with a blunted leading edge to steady nonuniformity of the free stream  

Microsoft Academic Search

The flow past a flat plate with a blunted leading edge by a flow of a viscous incompressible fluid with a small spanwise-periodic,\\u000a steady nonuniformity of the velocity profile is considered. Such a flow simulates the interaction of one type of vortex disturbances\\u000a of a turbulent external flow with the boundary layer. The solution obtained predicts generation of strong disturbances

M. V. Ustinov

2000-01-01

338

Effects of wing leading-edge deflection on low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration. [wind tunnel tests  

NASA Technical Reports Server (NTRS)

Static force tests were conducted in the Langley V/STOL tunnel at a Reynolds number (based on the mean aerodynamic chord) of about 2.0 x 10 to the 6th power for an angle-of-attack range from about - 10 deg to 17 deg and angles of sideslip of 0 and + or - 5 deg. Limited flow visualization studies were also conducted in order to provide a qualitative assessment of leading-edge upwash characteristics.

Coe, P. L., Jr.; Weston, R. P.

1979-01-01

339

Integrated ablative and radiative heat shield panels and leading edges for high l\\/d reentry vehicles. Final technical report Jun 70Aug 73  

Microsoft Academic Search

This program analytically and experimentally investigates the design and thermostructural performance of integrated ablative\\/radiative thermal protection systems in two phases: CONCEPT DEVELOPMENT AND FULL-SCALE PANEL DEVELOPMENT. In Phase I, the program includes the investigation, analysis, and test of sub-scale specimens and various design concepts to determine design values for the full-scale panels and leading edges. Phase II covers the design

Kiger

1973-01-01

340

Effect of rotation on leading edge region film cooling of a gas turbine blade with three rows of film cooling holes  

Microsoft Academic Search

Effect of rotation on detailed film cooling effectiveness distributions in the leading edge region of a gas turbine blade with three showerhead rows of radial-angle holes were measured using the Pressure Sensitive Paint (PSP) technique. Tests were conducted on the first-stage rotor blade of a three-stage axial turbine at three rotational speeds. The effect of the blowing ratio was also

Jaeyong Ahn; M. T. Schobeiri; Je-Chin Han; Hee-Koo Moon

2007-01-01

341

Heat-requirements for Ice Protection of a Cyclically Gas-heated, 36 Degree Swept Airfoil with Partial-span Leading-edge Slat  

NASA Technical Reports Server (NTRS)

Heating requirements for satisfactory cyclic de-icing over a wide range of icing and operating conditions have been determined for a gas-heated, 36deg swept airfoil of 6.9-foot chord with a partial-span leading-edge slat. Comparisons of heating requirements and effectiveness were made between the slatted and unslatted portions of the airfoil. Studies were also made comparing cyclic de-icing with continuous anti-icing, and cycll.cde-icing systems with and without leading-edge ice-free parting strips. De-icing heat requirements were approximately the same with either heated or unheated parting strips because of the aerodynamic effects of the 36deg sweep angle and the spanwise saw-tooth profile of leading-edge glaze-ice deposits. Cyclic de-icing heat-source requirements were found to be one-fourth or less of the heat requirements for complete anti-icing. The primary factors that affected the performance of the cyclic de-icing heating system were ambient air temperature, heat distribution, and thermal lag.

Gray, Vernon H; vonGlahn, Uwe H

1956-01-01

342

Transonic Investigation of Aerodynamic Characteristics of a Swept-Wing Fighter-Airplane Model with Leading-Edge Droop in Combination with Outboard Chord-Extensions and Notches  

NASA Technical Reports Server (NTRS)

An investigation of the effects of several wing leading-edge modifications on the aerodynamic characteristics of a 45 degree swept-wing fighter-airplane model has been conducted in the Langley 16-foot transonic tunnel at low and high lifting conditions at Mach numbers from 0.85 to 1.03. The investigation included the determination of the effect on longitudinal stability and performance characteristics of wing leading-edge and chord-extension droops of 60 and 20 degrees chord-extension overhangs of 0.075c and 0.15c (where c inboard end of the 0.075c chord-extension to depths of 0.075c and 0.l25c, and indention of the model fuselage to conform partially to the supersonic area rule for a Mach number of 1.20. Lift, drag, and pitching-moment data were obtained for configurations with the tail on and off. Comparisons of data obtained from the present model with data from a configuration with leading-edge slats are included. Generally, the model wing modifications provided only slight improvements of the airplane longitudinal stability characteristics, but did substantially reduce the airplane drag coefficients at moderate and high lifting conditions.

Whitcomb, Charles F.; Norton, Harry T., Jr.

1961-01-01

343

Lead-free precussion primer mixes based on metastable interstitial composite (MIC) technology  

DOEpatents

A lead-free percussion primer composition and a percussion cup containing e composition. The lead-free percussion primer composition is comprised of a mixture of about 45 wt % aluminum powder having an outer coating of aluminum oxide and molybdenum trioxide powder or a mixture of about 50 wt % aluminum powder having an outer coating of aluminum oxide and polytetrafluoroethylene powder. The aluminum powder, molybdenum trioxide powder and polytetrafluoroethylene powder has a particle size of 0.1 .mu.m or less, more preferably a particle size of from about 200-500 angstroms.

Dixon, George P. (Alexandria, VA); Martin, Joe A. (Espanola, NM); Thompson, Don (Ridgecrest, CA)

1998-01-01

344

Influence of optimized leading-edge deflection and geometric anhedral on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration. [langley 7 by 10 foot tunnel  

NASA Technical Reports Server (NTRS)

An investigation conducted in the Langley 7 by 10 foot tunnel to determine the influence of an optimized leading-edge deflection on the low speed aerodynamic performance of a configuration with a low aspect ratio, highly swept wing. The sensitivity of the lateral stability derivative to geometric anhedral was also studied. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to spanwise variation of unwash, the resulting optimized leading edge was a smooth, continuously warped surface for which the deflection varied from 16 deg at the side of body to 50 deg at the wing tip. For the particular configuration studied, levels of leading-edge suction on the order of 90 percent were achieved. The results of tests conducted to determine the sensitivity of the lateral stability derivative to geometric anhedral indicate values which are in reasonable agreement with estimates provided by simple vortex-lattice theories.

Coe, P. L., Jr.; Huffman, J. K.

1979-01-01

345

Compatibility of SiC and SiC Composites with Molten Lead  

SciTech Connect

The choice of structural material candidates to contain Lead at 1000 C are limited in number. Silicon carbide composites comprise one choice of possible containment materials. Short term screening studies (120 hours) were undertaken to study the behavior of Silicon Carbide, Silicon Nitride, elemental Silicon and various Silicon Carbide fiber composites focusing mainly on melt infiltrated composites. Isothermal experiments at 1000 C utilized graphite fixtures to contain the Lead and material specimens under a low oxygen partial pressure environment. The corrosion weight loss values (grams/cm{sup 2} Hr) obtained for each of the pure materials showed SiC (monolithic CVD or Hexoloy) to have the best materials compatibility with Lead at this temperature. Increased weight loss values were observed for pure Silicon Nitride and elemental Silicon. For the SiC fiber composite samples those prepared using a SiC matrix material performed better than Si{sub 3}N{sub 4} as a matrix material. Composites prepared using a silicon melt infiltration process showed larger corrosion weight loss values due to the solubility of silicon in lead at these temperatures. When excess silicon was removed from these composite samples the corrosion performance for these material improved. These screening studies were used to guide future long term exposure (both isothermal and non-isothermal) experiments and Silicon Carbide composite fabrication work.

H Tunison

2006-03-07

346

The International Polar Year (IPY) Circumpolar Flaw Lead (CFL) system study: a focus on fast ice edge systems  

Microsoft Academic Search

The Circumpolar Flaw Lead (CFL) system study supported a large multidisciplinary overwintering in the Banks Island (NT) flaw lead over the period September 2007 to August 2008 as part of the International Polar Year (IPY). The CFL system is formed when the central pack ice (which is mobile) moves away from coastal fast ice, opening a flaw lead. The CFL

D. G. Barber; C. J. Mundy; T. N. Papakyriakou; R. W. MacDonald; Y. Gratton; L. Fortier; M. Gosselin; J. Hanesiak; J. Tremblay; S. Ferguson; G. Stern; S. Meakin; J. W. Deming; D. Leitch

2009-01-01

347

Unsteady modes in the flowfield about an airfoil with a leading-edge horn-ice shape  

NASA Astrophysics Data System (ADS)

An analysis of unsteady modes present in the flowfield of an airfoil with a leading-edge horn-ice shape was performed in the current study. An NACA 0012 airfoil was tested in a subsonic wind tunnel at Re = 1.8 x 106. In addition to the clean configuration, the airfoil model was also tested with a set of boundary-layer trips, a two-dimensional extrusion of a horn-ice shape casting, and an array of simulated icing configurations created using simple geometries. Time-averaged and unsteady static pressure measurements were acquired about the airfoil surface, along with unsteady wake velocity and surface hot-film array measurements. Additionally, surface and off-body flow visualization techniques were used to visualize the airfoil flowfield. A technique was also developed to determine the unsteady shear-layer reattachment location of the ice-induced laminar separation bubble downstream of the horn-ice shape using the surface hot-film array measurements. The maximum amount of unsteadiness in the iced-airfoil flowfield was observed to increase with increasing angle of attack. For a fixed angle of attack prior to stall, a change in the feature height of the simulated ice shape led to a change in the distribution of flowfield unsteadiness, but did not change the maximum levels of unsteadiness present in the flowfield. The iced-airfoil flowfield unsteadiness was primarily associated with three different frequencies. The first was represented by an increase in spectral energy across a broad-band frequency range, and was observed just upstream of shear-layer reattachment as well as downstream of shear-layer reattachment. This increase in spectral energy was caused by the regular mode of unsteadiness due to vortical motion in the separated shear layer and vortex shedding from the separation bubble. The average Strouhal number of this regular mode corresponded to StL = 0.60, and the average vortex convection velocity was observed to be 0.45Uinfinity. These values were highly consistent with those reported elsewhere in the literature. The other two frequencies were much lower and were observed as narrow-band peaks in the spectral content of the acquired measurements that were primarily present in the region covered by the ice-induced separation bubble. The first was attributed to the shear-layer flapping phenomenon and was particularly dominant in the upstream portion of the separation bubble. The Strouhal number associated with this shear-layer flapping mode corresponded to St h = 0.0185, which was consistent with those reported in studies of separation bubbles about canonical geometries. The second frequency was lower than that of shear-layer flapping and was associated with a low-frequency mode of unsteadiness that can occur prior to static stall for airfoils of thin-airfoil stall type. This low-frequency mode was characterized by a low-frequency oscillation of the airfoil circulation, and it was clearly identified in the spectral content of the iced-airfoil lift coefficient. The resulting values of Strouhal number exhibited a dependence on the airfoil angle of attack and corresponded to a range that was consistent with the Strouhal number values reported in prior studies of the low-frequency mode in the literature. Using the method for determining the unsteady shear-layer reattachment location, the average time-dependent relationship between the reattachment location and the lift coefficient was calculated. It was discovered that at the low-frequency mode, the lift coefficient leads the shear-layer reattachment location by a phase of pi/2. This phase relationship occurred due to a feedback between the airfoil circulation and the separation bubble length. This improved understanding of the low-frequency mode in the iced-airfoil flowfield was utilized in a practical example to improve the predictive qualities of a hinge-moment-based stall prediction system. This improvement in the predictive qualities was performed by identifying the intermittent signature of the low-frequency mode in the wavelet transform of the hinge moment coeffic

Ansell, Phillip J.

348

Influence of restorative technique, Bevelling and aging on composite bonding to sectioned incisal edges: A comparative in vitro study  

PubMed Central

Aim: To evaluate the effect of direct and indirect technique, bevel placement, and aging on the fracture resistance of composite restorations bonded to sectioned incisal edges. Materials and Methods: Incisal thirds of 80 human maxillary incisors were sectioned. Four treatment groups of 20 teeth each were formed as follows: Direct composite with bevel and without bevel (Adper single bond 2/Filtek Z350); indirect composite with bevel and without bevel (prepolymerized Filtek Z350 cemented with Adper single bond 2/Relay × ARC). Ten teeth from each group were stored in distilled water for 24 h. The remaining ten teeth were stored in distilled water for 180 days with two thermocycling treatments. The specimens were subjected to shear testing using universal testing machine. Fractured specimens were examined with a stereomicroscope at ×10 magnification to evaluate the failure patterns. The obtained data were statistically analyzed by using ANOVA, Bonferroni test, and Student's t-test. Results: Beveled restorations exhibited higher fracture resistance values than nonbeveled restorations. Long-term water storage decreased the fracture resistance. Conclusion: The use of bevels resulted in improved fracture resistance of composite restorations and reduced the impact of aging. PMID:23349572

Poojary, Pradeep K; Bhandary, Shreetha; Srinivasan, Raghu; Nasreen, Farhat; Pramod, J; Mahesh, MC

2013-01-01

349

An improved method for the prediction of completely three-dimensional aerodynamic load distributions of configurations with leading edge vortex separation  

NASA Technical Reports Server (NTRS)

The application of a higher-order subsonic potential flow panel method to the solution of three-dimensional flow about wing and wing-body combinations with leading-edge vortex separation is presented. The governing equations are the linear flow differential equation and nonlinear boundary conditions which require that the flow be parallel to the wing and body surfaces and that the free vortex sheet, springing from the leading and trailing edges, be aligned with the local flow and support no pressure jump. The vortex core is modeled as a simple line vortex which receives vorticity from the free sheet through a connecting sheet. The Kutta condition is imposed on all appropriate edges of the wing. This set of nonlinear equations is solved by an iterative procedure. The Goethert rule accounts for compressibility. The method has been programmed for the CDC 6600. Delta wings, gothic wings, arrow wings, cambered wings, and wing with body have been analyzed. Initial studies involving variations of panel density, vortex sheet sizing, Jacobian update, and initial geometry demonstrate that the present method generally exhibits good convergence characteristics.

Rubbert, p. E.; Lu, P.; Brune, G. W.; Weber, J. A.

1976-01-01

350

Wind tunnel investigation of effects of variations in Reynolds number and leading-edge treatment on the aerodynamic characteristics of an externally blown jet-flap configuration  

NASA Technical Reports Server (NTRS)

An investigation has been conducted in a full-scale tunnel to determine the effects of variations in Reynolds number and leading-edge treatment on the aerodynamic characteristics of an externally blown jet-flap transport configuration. The model had a double-slotted trailing-edge flap and was powered by four high-bypass-ratio turbofan engines. Tests were performed by using each of three leading-edge devices (a 30-percent-chord flap and 15- and 25-percent-chord slats) at Reynolds numbers from 0.47 x one million to 1.36 x one million thrust coefficients up to 3.5. The use of a 25-percent-chord slat was found to be more effective than a 15-percent-chord slat or a 30-percent-chord flap in extending the stall angle of attack and in minimizing the loss of lift after the stall. The large slat was also effective in reducing the rolling moments that occurred when the engine-out wing stalled first.

Parlett, L. P.; Smith, C. C., Jr.; Megrail, J. L.

1973-01-01

351

Compositional development of a plutonium surrogate glass without listed RCRA elements (lead and barium)  

SciTech Connect

A lanthanide borosilicate (LaBS) glass composition, being evaluated by Savannah River Technology Center (SRTC) or plutonium disposition as part of the U.S. Department of Energy`s (DOE) Office of the Fissile Materials Disposition (OFMD) program , has been processed with greater than 15 elemental weight percent thorium (a plutonium surrogate) without the presence of lead oxide in the glass. The glass composition is a result of several efforts to remove the lead by replacing it with strontium and sodium. The initial melts that included sodium and considerably lower aluminum resulted in visible phase separation. Two homogeneous lead free melts have been processed. The first one replaced one-fifth of the total lead with Sr on a mole percent basis. Other changes included slightly less aluminum with increases in boron and silica. The second glass composition was exactly the same as the first with an additional 1:1 replacement of barium with strontium on a mole percent basis. This last composition contains no elements considered to be hazardous as defined by the Resource and Conservation Recovery Act (RCRA elements). The Product Consistency Test (PCT) results of these two homogeneous glass composition show them to be slightly more durable than the original lanthanide borosilicate glasses (with lead) loaded with thorium

Meaker, T.F.

1996-09-24

352

A low speed wind tunnel investigation of Reynolds number effects on a 60-deg swept wing configuration with leading and trailing edge flaps  

NASA Technical Reports Server (NTRS)

A low-speed wind tunnel test was performed to investigate Reynolds number effects on the aerodynamic characteristics of a supersonic cruise wing concept model with a 60-deg swept wing incorporating leading-edge and trailing-edge flap deflections. The Reynolds number ranged from 0.3 to 1.6 x 10 to the 6th, and corresponding Mach numbers from .05 to 0.3. The objective was to define a threshold Reynolds number above which the flap aerodynamics basically remained unchanged, and also to generate a data base useful for validating theoretical predictions for the Reynolds number effects on flap performance. This report documents the test procedures used and the basic data acquired in the investigation.

Rao, Dhanvada M.; Hoffler, Keith D.

1988-01-01

353

Lead  

MedlinePLUS

... Childhood Lead Poisoning Data, Statistics, and Surveillance Partners Policy Resources Prevention Tips Publications Tools and Training Calendar of Events Ten Great Public Health Achievements 2001--2010 Â Lead in Drinking Water Healthy Homes A Healthy Homes approach is a ...

354

[Effects of highway on the vegetation species composition along a distance gradient from road edge in southeastern margin of Tengeer Desert].  

PubMed

Aimed to examine the effects of highway on the vegetation species composition in arid desert area, forty-eight transects perpendicular to the provincial highway 201 from Shapotou to Jing-tai in the southeastern margin of Tengger Desert were installed, with the vegetation species distribution along a distance gradient from the road edge investigated. The results showed that with increasing distance from the road edge, the species number, coverage, biomass, and alpha-diversity of herbaceous plants declined, but had no significant differences with the control beyond 5 m. Within 0-6 m to the road edge, the herbaceous plant height was greater than that of the control, but their density had less change. Within 0-2 m to the road edge, the species turnover rate of herbaceous plants was lower; at 2-5m, this rate was the highest; while beyond 10 m, the species composition of herbaceous plants was similar to that of the control. The herbaceous plant community at the road edge was dominated by gramineous plants, with the disturbance-tolerant species Pennisetum centrasiaticum, Chloris virgata, and Agropyron cristatum accounting for 68.6% of the total. C. virgata beyond 1 m to the road edge had a rapid decrease in its individual number and presence frequency, P. centrasiaticum and A. cristatum beyond 2 m also showed a similar trend, while the composite plants Artemisia capillaris and A. frigida beyond 2 m from the road edge had a rapid increase in its individual number, accounting for 70% of the herbaceous plants. At the road edge, the coverage and density of shrubs were significantly lower than those of the control, but the species composition had no significant difference. PMID:21812282

Feng, Li; Li, Xin-Rong; Guo, Qun; Zhang, Jing-Guang; Zhang, Zhi-Shan

2011-05-01

355

Evolution Of The Band Gaps And Band Edges Of Quaternary Ga1-yInyAsxSb1-x\\/InAs Alloys As A Function of Composition  

Microsoft Academic Search

Using atomistic pseudopotential calculations we study the evolution of: (i) the conduction band edge Ec; (ii) the valence band edge Ev , and (iii) the fundamental band gap of the quaternary Ga1-yInyAsxSb1-x alloy lattice-matched to InAs as a function of the composition (x, y). We find a negative bowing parameter for Ec of the quaternary alloy with respect to the

Rita Magri; Alex Zunger; H. Kroemer

2005-01-01

356

300 W continuous-wave operation of a diode edge-pumped, hybrid composite Yb:YAG microchip laser.  

PubMed

300 W continuous-wave operation of a diode edge-pumped, hybrid (single-crystal/ceramic) composite,Yb3+:YAG microchip laser with a 5 mm diameter and 300 microm thickness single-crystal core uniformly bonded to a water-cooled heat sink by a new Au-Sn soldering system has been demonstrated. The beam quality factor M2 follows the mode mismatch between the core and the fundamental mode and was improved to 17 with a maximum output power of 230 W. A thermally induced convex mirror with a spherical radius of curvature ranging from -2.5 to -1.5 m was observed; the radius of curvature decreases through thermal deformation of the microchip as the pump power increases. PMID:16770413

Tsunekane, Masaki; Taira, Takunori

2006-07-01

357

Effect of dielectrophoretic structuring on piezoelectric and pyroelectric properties of lead titanate-epoxy composites  

NASA Astrophysics Data System (ADS)

Functional granular composites of lead titanate particles in an epoxy matrix prepared by dielectrophoresis show enhanced dielectric, piezoelectric and pyroelectric properties compared to 0–3 composites for different ceramic volume content from 10% to 50%. Two structuring parameters, the interparticle distance and the percentage of 1–3 connectivity are used based on the Bowen model and the mixed connectivity model respectively. The degree of structuring calculated according to both models correlate well with the increase in piezoelectric and pyroelectric sensitivities of the composites. Higher sensitivity of the electroactive properties are observed at higher ceramic volume fractions. The effect of electrical conductivity of the matrix on the pyroelectric responsivity of the composites has been demonstrated to be a key parameter in governing the pyroelectric properties of the composites.

Khanbareh, H.; van der Zwaag, S.; Groen, W. A.

2014-10-01

358

High-attitude low-speed static aerodynamic characteristics of an F-4D fighter airplane model with leading edge slats  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effects of two-position leading edge slats on the low speed aerodynamic characteristics of a swept wing twin-jet supersonic fighter airplane model at high angle of attack and various Reynolds numbers. The investigation was performed at a Mach number of 0.20 over a range of angle of attack from 19 deg to 90 deg and angles of slideslip from -10 deg to 30 deg and Reynolds numbers from 1.97 to 13.12 million per meter.

Monfort, J. C.; Whitcomb, W. M.

1975-01-01

359

Theoretical Calculations of the Pressures, Forces, and Moments Due to Various Lateral Motions Acting on Tapered Sweptback Vertical Tails with Supersonic Leading and Trailing Edges  

NASA Technical Reports Server (NTRS)

Based on expressions for the linearized velocity potentials and pressure distributions given in NACA Technical Report 1268, formulas for the span load distribution, forces, and moments are derived for families of thin isolated vertical tails with arbitrary aspect ratio, taper ratio, and sweepback performing the motions constant sideslip, steady rolling, steady yawing, and constant lateral acceleration. The range of Mach number considered corresponds, in general, to the condition that the tail leading and trailing edges are supersonic. To supplement the analytical results, design-type charts are presented which enable rapid estimation of the forces and moments (expressed as stability derivatives) for given combinations of geometry parameters and Mach number.

Margolis, Kenneth; Elliott, Miriam H.

1960-01-01

360

Isotopic composition of phanerozoic ore leads from the Swedish segment of the Fennoscandian Shield  

Microsoft Academic Search

95 analyses of ore lead isotope ratios from 23 Phanerozoic ore deposits from the Swedish segment of the Fennoscandian Shield form a marked linear trend on a 207Pb\\/204Pb versus 206Pb\\/204Pb diagram. The line may be interpreted in a two-stage model, the lead being derived from 1.8±0.15 Ga old Svecokarelian basement and mineralization occurring at 0.4±0.15 Ga. The initial composition of

Åke Johansson; David Rickard

1984-01-01

361

Surface-Pressure and Flow-Visualization Data at Mach Number of 1.60 for Three 65 deg Delta Wings Varying in Leading-Edge Radius and Camber  

NASA Technical Reports Server (NTRS)

An experimental investigation of the effect of leading-edge radius, camber, Reynolds number, and boundary-layer state on the incipient separation of a delta wing at supersonic speeds was conducted at the Langley Unitary Plan Wind Tunnel at Mach number of 1.60 over a free-stream Reynolds number range of 1 x 106 to 5 x 106 ft-1. The three delta wing models examined had a 65 deg swept leading edge and varied in cross-sectional shape: a sharp wedge, a 20:1 ellipse, and a 20:1 ellipse with a -9.750 circular camber imposed across the span. The wings were tested with and without transition grit applied. Surface-pressure coefficient data and flow-visualization data indicated that by rounding the wing leading edge or cambering the wing in the spanwise direction, the onset of leading-edge separation on a delta wing can be raised to a higher angle of attack than that observed on a sharp-edged delta wing. The data also showed that the onset of leading-edge separation can be raised to a higher angle of attack by forcing boundary-layer transition to occur closer to the wing leading edge by the application of grit or the increase in free-stream Reynolds number.

McMillin, S. Naomi; Bryd, James E.; Parmar, Devendra S.; Bezos-OConnor, Gaudy M.; Forrest, Dana K.; Bowen, Susan

1996-01-01

362

Design, fabrication, testing, and delivery of shuttle heat pipe leading edge test modules. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

Development in the design of leading heat pipes for the space shuttle are reported. The analysis, design, and integration of the heat pipes into the module structure are described along with the recommended tests. Results indicate the design goals were meet.

1973-01-01

363

Lead effects on body composition and organ size of wintering canvasbacks Aythya valisineria in Louisiana  

USGS Publications Warehouse

We tested whether lead exposure, as evidenced by liver lead concentration, affected body composition and organ sizes of canvasback ducks Aythya valisineria in Louisiana during winter 1987-88. After adjusting for body size, sex, age, and site and month of collection, we found decreases in ingesta-free body mass; breast, leg, and body protein; body fat; intestine length; and liver and gizzard masses associated with increased liver lead concentrations. There were no apparent associations between liver lead concentrations and testes and body ash masses, or caecal length. We used the concentration of 26.7 ppm of liver lead on a dry matter (dm) basis as indicative of lead toxicosis. We predicted that a canvasback with 26.7 ppm dm liver lead would weigh 209 g less and have 105 g less fat than an unexposed individual. Whereas many lead exposed canvasbacks may survive through winter, their subsequent survival, ability to reproduce and perform other annual cycle events may be compromised. We recommend management to make lead unavailable to waterfowl at major concentration areas and periodic monitoring of lead contamination in waterfowl populations.

Pace, R.M.; Hohman, W.L.; Custer, T.W.

1999-01-01

364

Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites  

NASA Technical Reports Server (NTRS)

The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. An ECT specimen is a rectangular laminate, containing an edge delamination at the laminate mid-plane. Torsion load is applied to the specimens, resulting in relative transverse shear sliding of the delaminated faces. The test data reduction schemes are intended to yield initiation values of critical mode III strain energy release rate, G(sub IIIc), that are constant with delamination length. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design as a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and specimens made from S2/8552 tape laminates. Several specimens, each with different delamination lengths are tested. Detailed, three-dimensional finite element analyses of the specimens were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode III-dominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of G(sub IIIc) exhibited significant dependence on delamination length. Furthermore, there was a large amount of scatter in the data. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

Ratcliffe, James G.

2004-01-01

365

Piezo, pyro-, ferro-, and dielectric properties of ceramic\\/polymer composites obtained from two modifications of lead titanate  

Microsoft Academic Search

Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer\\/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate\\/polyetherketoneketone (PTCa\\/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate\\/polyetherketoneketone (PSTM\\/PEKK) composite. Also, a lower dielectric permittivity and remanent

A. Peláiz-Barranco; P. Marin-Franch

2005-01-01

366

Piezo-, pyro-, ferro-, and dielectric properties of ceramic/polymer composites obtained from two modifications of lead titanate  

NASA Astrophysics Data System (ADS)

Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate/polyetherketoneketone (PTCa/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate/polyetherketoneketone (PSTM/PEKK) composite. Also, a lower dielectric permittivity and remanent polarization values with a higher coercive field are obtained. The results are discussed considering the modifications made in the ceramic phases of each composite. The presented properties for both composites are still substantially lower than those in bulk ceramics.

Peláiz-Barranco, A.; Marin-Franch, P.

2005-02-01

367

Current—voltage characteristics of lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composites  

NASA Astrophysics Data System (ADS)

Current-voltage measurements obtained from lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composite showed that a sinusoidal current applied to the copper coil wrapped around the hollow cylinder circumference induces voltage across the lead zirconate titanate layer thickness. The current-voltage coefficient and the maximum induced voltage in lead zirconate titanate at 1 kHz and resonance (60.1 kHz) frequencies increased linearly with the number of the coil turns and the applied current. The resonance frequency corresponds to the electromechanical resonance frequency. The current-voltage coefficient can be significantly improved by optimizing the magnetoelectric structure geometry and/or increasing the number of coil turns. Hollow cylindrical lead zirconate titanate/nickel structures can be potentially used as current sensors.

Pan, De-An; Zhang, Shen-Gen; Tian, Jian-Jun; Sun, Jun-Sai; Alex, Volinsky A.; Qiao, Li-Jie

2010-02-01

368

Lead Isotopic Composition of Fly Ash and Flue Gas Residues from Municipal Solid Waste Combustors in France: Implications for Atmospheric Lead Source Tracing.  

E-print Network

1 Lead Isotopic Composition of Fly Ash and Flue Gas Residues from Municipal Solid Waste Combustors@crpg.cnrs-nancy.fr _______________________________________________________________________________________ Fly ash and flue gas residues from eight municipal solid waste combusters (MSWC) in France (1992-93 and 1998-2002) were analysed for their Pb isotopic composition. Fly ashes are more representative of solid

Paris-Sud XI, Université de

369

Great Earthquakes and Tsunami Day for Teachers on the Leading Edge: Geologic Hazards and Links to EarthScope in a Field-Based Program  

NASA Astrophysics Data System (ADS)

Inviting K-12 science teachers into the field to observe the work of professional geologists and engage in learning that is scientifically important and socially relevant deepens their geologic understanding while instilling enthusiasm for inquiry-based instruction. "Teachers on the Leading Edge" (TOTLE) is a field-based and place-based teacher development program that features active continental margin geology of the Pacific Northwest. Program themes include: (1) Geophysics as fundamental to understanding plate tectonics and essential to deciphering Pacific Northwest geology that underlies a tree-covered landscape; and (2) Geologic Hazards as understandable and inevitable consequences of living on the leading edge of our continent. The two-week TOTLE 2005 field workshop traversed the active continental margin of Oregon from the Pacific Coast through the Cascade Range to accreted terranes along the Snake River. "Great Earthquakes and Tsunami Day" featured introductions to earthquake seismology and paleoseismology. Presentations on earthquake seismology with examples from the December 2004 Sumatra - Andaman earthquake and Indian Ocean tsunami provided context and background. During a morning low tide near Fort Clatsop south of Astoria, paleoseismologist Brian Atwater (USGS, Seattle) helped teachers observe and interpret drowned forests and tsunami deposits that mark four great Cascadia earthquakes of the past 2000 years. That afternoon, Darci Connor, former Tsunami Outreach Coordinator for the City of Seaside, helped teachers understand their critical role in educating K-12 students about natural hazard preparedness. In the evening, TOTLE teachers crafted their new understanding of great earthquakes and tsunami into interactive learning activities for Science Campers at Camp Kiwanilong operated by the Oregon Museum of Science and Industry. These experiences make frontier geophysical research, like GPS observations of slow earthquakes and seismic tomography of the subducting Juan de Fuca Plate, accessible to K-12 teachers and useful in their teaching of plate tectonics and earthquake seismology. Teachers on the Leading Edge is preparing K-12 teachers to convey the importance and discoveries of EarthScope's USArray and Plate Boundary Observatory experiments to their students.

Butler, R.; Bishop, E. M.; Ault, C.; Magura, B.; Hedeen, C.; Connor, D.; Southworth-Neumeyer, T.; Conrey, R.

2005-12-01

370

Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites  

NASA Technical Reports Server (NTRS)

The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and S2/8552 tape laminates. Three-dimensional finite element analyses were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode IIIdominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of GIIIc exhibited significant dependence on delamination length. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

Ratcliffe, James G.

2004-01-01

371

Low-Speed Investigation of Upper-Surface Leading-Edge Blowing on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

The paper identifies speed, agility, human interface, generation of sensitivity information, task decomposition, and data transmission (including storage) as important attributes for a computer environment to have in order to support engineering design effectively. It is argued that when examined in terms of these attributes the presently available environment can be shown to be inadequate. A radical improvement is needed, and it may be achieved by combining new methods that have recently emerged from multidisciplinary design optimisation (MDO) with massively parallel processing computer technology. The caveat is that, for successful use of that technology in engineering computing, new paradigms for computing will have to be developed - specifically, innovative algorithms that are intrinsically parallel so that their performance scales up linearly with the number of processors. It may be speculated that the idea of simulating a complex behaviour by interaction of a large number of very simple models may be an inspiration for the above algorithms; the cellular automata are an example. Because of the long lead time needed to develop and mature new paradigms, development should begin now, even though the widespread availability of massively parallel processing is still a few years away.

Banks, Daniel W.; Laflin, Brenda E. Gile; Kemmerly, Guy T.; Campbell, Bryan A.

1999-01-01

372

Quasi-Static 3-Point Reinforced Carbon-Carbon Bend Test and Analysis for Shuttle Orbiter Wing Leading Edge Impact Damage Thresholds  

NASA Technical Reports Server (NTRS)

Static 3-point bend tests of Reinforced Carbon-Carbon (RCC) were conducted to failure to provide data for additional validation of an LS-DYNA RCC model suitable for predicting the threshold of impact damage to shuttle orbiter wing leading edges. LS-DYNA predictions correlated well with the average RCC failure load, and were good in matching the load vs. deflection. However, correlating the detectable damage using NDE methods with the cumulative damage parameter in LS-DYNA material model 58 was not readily achievable. The difficulty of finding internal RCC damage with NDE and the high sensitivity of the mat58 damage parameter to the load near failure made the task very challenging. In addition, damage mechanisms for RCC due to dynamic impact of debris such as foam and ice and damage mechanisms due to a static loading were, as expected, not equivalent.

Fasanella, Edwin L.; Sotiris, Kellas

2006-01-01

373

Basanite-nephelinite suite from early Kilauea: Carbonated melts of phlogopite-garnet peridotite at Hawaii's leading magmatic edge  

USGS Publications Warehouse

A basanite-nephelinite glass suite from early submarine Kilauea defines a continuous compositional array marked by increasing concentrations of incompatible components with decreasing SiO2, MgO, and Al2O3. Like peripheral and post-shield strongly alkalic Hawaiian localities (Clague et al. in J Volcanol Geotherm Res 151:279-307, 2006; Dixon et al. in J Pet 38:911-939, 1997), the early Kilauea basanite-nephelinite glasses are interpreted as olivine fractionation products from primary magnesian alkalic liquids. For early Kilauea, these were saturated with a garnet-phlogopite-sulfide peridotite assemblage, with elevated dissolved CO2 contents responsible for the liquids' distinctly low-SiO2 concentrations. Reconstructed primitive liquids for early Kilauea and other Hawaiian strongly alkalic localities are similar to experimental 3 GPa low-degree melts of moderately carbonated garnet lherzolite, and estimated parent magma temperatures of 1,350-1,400??C (olivine-liquid geothermometry) match the ambient upper mantle geotherm shortly beneath the base of the lithosphere. The ???3 GPa source regions were too hot for stable crystalline carbonate and may have consisted of ambient upper mantle peridotite containing interstitial carbonate-silicate or carbonatitic liquid, possibly (Dixon et al. in Geochem Geophys Geosyst 9(9):Q09005, 2008), although not necessarily, from the Hawaiian mantle plume. Carbonate-enriched domains were particularly susceptible to further melting upon modest decompression during upward lithospheric flexure beneath the advancing Hawaiian Arch, or by conductive heating or upward drag by the Hawaiian mantle plume. The early Kilauea basanite-nephelinite suite has a HIMU-influenced isotopic character unlike other Hawaiian magmas (Shimizu et al. in EOS Tran Amer Geophys Union 82(47): abstr V12B-0962, 2001; Shimizu et al. in Geochim Cosmochim Acta 66(15A):710, 2002) but consistent with oceanic carbonatite involvement (Hoernle et al. in Contrib Mineral Petrol 142:520-542, 2002). It may represent the melting products of a fertile domain in the ambient upper mantle impinged upon and perturbed by the sustained plume source that feeds later shield-stage magmatism. ?? US Government 2009.

Sisson, T.W.; Kimura, J.-I.; Coombs, M.L.

2009-01-01

374

Synthesis of nano zerovalent iron nanoparticles--graphene composite for the treatment of lead contaminated water.  

PubMed

A Nano zerovalent iron nanoparticles graphene composite (G-nZVI) was prepared via a sodium borohydride reduction of graphene oxide and iron chloride under an argon atmosphere. Powder X-ray diffraction patterns showed the formation of the magnetic graphene/nanoscale-zerovalent-iron (G-nZVI) composites and bare nanoscale-zerovalent-iron (nZVI) particles. TEM analysis shows the formation of ~10 nm particles. Adsorption experiments show a maximum Pb(II) adsorption capacity for the G-nZVI composite with 6 wt% graphene oxide loading. Additionally the effects of pH, temperature, contact time, ionic strength and initial metal ion concentration on Pb(II) ion removal were studied. X-ray photoelectron spectroscopy analysis after adsorption results confirmed the composite's ability to adsorb and immobilize lead more efficiently in its zerovalent and bivalent forms, as compared to bare iron nanoparticles. The adsorption of Pb(II) ions fit a pseudo-second-order kinetic model, and adsorption isotherms can be described using the Freundlich equations. G-nZVI shows great potential as an efficient adsorbent for lead immobilization from water, as it exhibits stability, reducing power, a large surface area, and magnetic separation. PMID:24184984

Jabeen, Humera; Kemp, K Christian; Chandra, Vimlesh

2013-11-30

375

Actin Filaments at the Leading Edge of Cancer Cells Are Characterized by a High Mobile Fraction and Turnover Regulation by Profilin I  

PubMed Central

Cellular motility is the basis for cancer cell invasion and metastasis. In the case of breast cancer, the most common type of cancer among women, metastasis represents the most devastating stage of the disease. The central role of cellular motility in cancer development emphasizes the importance of understanding the specific mechanisms involved in this process. In this context, tumor development and metastasis would be the consequence of a loss or defect of the mechanisms that control cytoskeletal remodeling. Profilin I belongs to a family of small actin binding proteins that are thought to assist in actin filament elongation at the leading edge of migrating cells. Traditionally, Profilin I has been considered to be an essential control element for actin polymerization and cell migration. Expression of Profilin I is down-regulated in breast and various other cancer cells. In MDA-MB-231 cells, a breast cancer cell line, further inhibition of Profilin I expression promotes hypermotility and metastatic spread, a finding that contrasts with the proposed role of Profilin in enhancing polymerization. In this report, we have taken advantage of the fluorescence recovery after photobleaching (FRAP) of GFP-actin to quantify and compare actin dynamics at the leading edge level in both cancer and non-cancer cell models. Our results suggest that (i) a high level of actin dynamics (i.e., a large mobile fraction of actin filaments and a fast turnover) is a common characteristic of some cancer cells; (ii) actin polymerization shows a high degree of independence from the presence of extracellular growth factors; and (iii) our results also corroborate the role of Profilin I in regulating actin polymerization, as raising the intracellular levels of Profilin I decreased the mobile fraction ratio of actin filaments and slowed their polymerization rate; furthermore, increased Profilin levels also led to reduced individual cell velocity and directionality. PMID:24465723

Lorente, Gisela; Syriani, Emilio; Morales, Miguel

2014-01-01

376

Lubricating Properties of Lead-Monoxide-Base Coatings of Various Compositions at Temperatures to 1250 F  

NASA Technical Reports Server (NTRS)

A number of ceramic coatings of different compositions containing lead monoxide (PbO) were studied to determine their relative merits as dry-film lubricants. Lead monoxide is known to be an effective solid lubricant at elevated temperatures, and this oxide was the main component in all compositions studied. Friction and wear properties were determined at temperatures from 750 to 1250 F, at a sliding velocity of 430 feet per minute, and at a normal load of 1 kilogram. In all of the coatings, PbO was the component primarily responsible for the lubricating properties. Oxides other than PbO had an indirect effect on lubrication by influencing such properties as adhesion, hardness, vitrifying or glaze-forming tendency, melting or softening point, and chemical stability of the coatings. Notable among these oxides were magnetite (Fe3O4.), which had generally a beneficial influence on ceramic- to-metal adhesion, and silica (SiO2), which inhibited the oxidation of PbO and enhanced the tendency for glaze formation on the sliding surfaces. Several of the compositions studied provided protection against metal-to-metal adhesive wear, galling, or seizure at test temperatures from 750 to 1250 F. Coating friction coefficients ranged from 0.20 to 0.37 at 75 F but were around 0.08 to 0.20 at temperatures of 1250 F.

Sliney, Harold E.

1959-01-01

377

Reaction of YBa2Cu3O(7-beta) with Gold, Silver, Bismuth and Lead: Substitution Chemistry and Composite Fabrication  

NASA Technical Reports Server (NTRS)

The reaction of YBa2Cu3O(7-beta) with Au, Ag, Bi, and Ph ions or metal is described. Three types of materials were produced: a well-defined series of homogeneous superconductors was obtained for Au ion substitution with little effect on T(sub c); attempted Ag and Bi ion substitution resulted in multi-phase samples with slightly enhanced T(sub c); finally, attempts to produce superconducting metal/superconducting ceramic composites with Pb and Bi powders resulted in multi-phase samples with drastically diminished superconducting properties. For Au- substituted superconductors, YBa2(Cu(l-x)Au(x))3O(7-beta), a substitution series (x = 0 - 0.1) has been synthesized. For x = 0.1 there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. The valence of Cu and Au in YBa2Au(0.3)Cu(2.7)O(7-beta) was investigated using X-ray Absorption Near-Edge Structure (XANES). X-ray studies indicate that Au goes into the Cu(l) site and Cu K edge XANES shows that this has little effect on the oxidation state of the remaining copper. A small effect on T(sub c) is observed (T(sub c) = 89 K for x = 0.10). Ag and Bi addition results in a rise in T(sub c) and a decrease in (delta)T(sub c) at low levels (x = 0.10 Ag, T(sub c) = 94 K and (delta)T(sub c) = 0.5 K; x = 0.02 Bi, T(sub c) = 94 K and (delta)T(sub c) = 1K) relative to typical values for YBa2Cu3O(7-beta) (T(sub c) = 91 K, (delta)T(sub c) = 2 K). Attempts at fabrication of Pb- and Pb(1-x)Bi(x)-superconductor composites are described. Cold pressing followed by low temperature (200 C) sintering resulted in a composite which excluded flux below 90 K but did not show zero electrical resistance until the metal (alloy) superconducting transition. X-ray diffraction showed the presence of pervoskite and metal. Processing at moderate (450 C) or high (950 C) temperatures resulted in oxygen-depleted pervoskite and/or metal oxides. These materials displayed greatly degraded superconducting properties. Processing at 800 C resulted in high T(sub c) only for composites containing greater than 90% weight fraction ceramic. Reaction of metal with YBa2Cu3O(7-beta) formed superconducting lead/bismuth-based oxides and other binary oxides.

Hepp, Aloysius F.; Gaier, James R.

1993-01-01

378

Leading Edge Cellular Strategies for  

E-print Network

.h.dekker@tudelft.nl DOI 10.1016/j.cell.2010.08.001 Entangling and twisting of cellular DNA (i.e., supercoiling, DNA replication, and chromo- somal segregation. Consequently the cell must fine-tune supercoiling free rotation of the DNA strands, so that, in the context of circular bacterial chromosomes

Dekker, Nynke

379

The Leading Edge: Data Mining  

NASA Video Gallery

When an airplane flies, hundreds of data streams fly from it every secondâ??pilot reports, incident reports, control positions, instrument positions, warning modes. NASA is mining terabytes of avia...

380

Leading Edge Slicing across Kingdoms  

E-print Network

.01.040 Multicellular organisms possessing relatively long life spans are subjected to diverse, constant, and often the existence of the other, but rarely do they come in direct contact. Regenera- tion provided one of those that these organisms were plants. On November 25, 1740 I sectioned a polyp for the first time.the first polyps I cut

Alvarado, Alejandro Sánchez

381

Leading Edge Network Medicine Strikes  

E-print Network

-based attacks targeting dynamic network states. Lee et al. now reveal how the progres- sive rewiring and colleagues take the bull by the horns, monitoring the dynamic network response of breast cancer cells

382

Leading Edge Chemoaffinity Revisited: Dscams,  

E-print Network

, USA 2Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University.R.S.) DOI 10.1016/j.cell.2010.10.009 The chemoaffinity hypothesis for neural circuit assembly posits on regeneration following nerve injury in adults rather than development. In the first, John Langley (Langley

Zipursky, Lawrebce

383

Leading Edge In This Issue  

E-print Network

pole is caused by the hydrodynamic flow force produced by the forward swimming of the cell. Thus that this type of protein redistribution may occur on other cell surfaces, such as the epithelial cells lining with the Flow PAGE 505 While in the circulatory system of its host, African trypanosomes are under constant

Rohs, Remo

384

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Volume 1; Sharp Leading Edge; [conducted in the Langley National Transonic Facility (NTF)  

NASA Technical Reports Server (NTRS)

An experimental wind tunnel test of a 65 deg delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 36 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at a Reynolds number of 6 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

385

Lithospheric structure at the leading edge of the North American craton: Imaging the Shield-Cordillera transition in western Canada by teleseismic Rayleigh-wave analysis  

NASA Astrophysics Data System (ADS)

The tectonics of southwestern Canada is characterized by a transition from the Mesozoic-Cenozoic Cordilleran orogen to the Archean-Proterozoic craton, making this region an excellent natural laboratory to study episodic growth of continents. Here, we explore regional lithospheric structure using fundamental Rayleigh waves recorded by broadband seismometers from CNSN and various temporary networks (ATSN, CRANE, USArray) from 2006 to the present. Using a two-station cross-correlation technique, we extract phase velocities at periods ranging from 20 s to more than 200 s. Phase velocities for the region west of the deformation front are significantly lower than those of the region to the east, especially at periods of 30-200 s, reflecting strong lateral variations in lithosphere structure due to thermal and compositional differences. Our analysis is particularly focused on characterizing the lithosphere-asthenosphere boundary (LAB) across the transition, and identifying small-scale convection associated with the edge of the craton. Detailed 3-D lithospheric structural models developed in the near feature will shed more new lights on the transition from backarc to craton lithosphere and their geodynamical interactions.

Bao, X.; Eaton, D. W.

2013-12-01

386

Composite lead for conducting an electrical current between 75--80K and 4. 5K temperatures  

DOEpatents

A composite lead is provided which electrically links and conducts a current between about 75-80K and liquid helium temperature of about 4.5K. The composite lead may be employed singly or in multiples concurrently to provide conduction of electrical current from normal conductors and semi-conductors at room temperature to superconductors operating at 4.5K. In addition, a variety of organizational arrangements and assemblies are provided by which the mechanical strength and electrical reliability of the composite lead is maintained. 12 figures.

Negm, Y.; Zimmerman, G.O.; Powers, R.E. Jr.; McConeghy, R.J.; Kaplan, A.

1994-12-27

387

Composite lead for conducting an electrical current between 75-80K and 4.5K temperatures  

DOEpatents

A composite lead is provided which electrically links and conducts a current between about 75-80K. and liquid helium temperature of about 4.5K. The composite lead may be employed singly or in multiples concurrently to provide conduction of electrical current from normal conductors and semi-conductors at room temperature to superconductors operating at 4.5K. In addition, a variety of organizationl arrangements and assemblies are provided by which the mechanical strength and electrical reliability of the composite lead is maintained.

Negm, Yehia (Braintree, MA); Zimmerman, George O. (South Hamilton, MA); Powers, Jr., Robert E. (East Boston, MA); McConeghy, Randy J. (Waxahachie, TX); Kaplan, Alvaro (Brookline, MA)

1994-12-27

388

Large-sized cylinder of Bi-2223/Ni meshes composite bulk for current lead  

NASA Astrophysics Data System (ADS)

In order to improve the critical current density ( Jc) and mechanical property of Bi-2223 sintered bulk, Ni wire meshes were added in the bulk. For fabricating large-sized cylindrical Bi-2223/Ni meshes composite, composing meshes are easy to produce compared with adding a lot of wires. The mesh concentration was 18 × 18 meshes/cm 2 using Ni wires of 0.25 mm in diameter. The Ni meshes were plated with Ag by 0.03 mm in thickness. We prepared the cylindrical sintered bulk for a current lead, 32 mm in outer diameter, 2 mm in thickness and 110 mm in length using a cold isostatic pressing (CIP) method. The samples were sintered at 845 °C for 50 h. After treatment again with CIP as an intermediate pressing, the samples were re-sintered. Small species were cut from the cylinder for measurement of critical current density ( Jc) at 77 K under self-field. There existed higher Jc portions and low Jc portions in the composite cylinder. Scanning electron microscope (SEM) observation showed that highly c-axis oriented and densely structured Bi-2223 plate-like grains could be formed around the interfacial region between the superconducting oxide and the Ag-plated Ni wires. There observed structural dislocation, which lead to low Jc portions in the cylinder.

Sakamoto, M.; Yoshizawa, S.; Hishinuma, Y.; Nishimura, A.; Yamazaki, S.; Kojima, S.

2006-10-01

389

Leading-Edge Votex-System Details Obtained on F-106B Aircraft Using a Rotating Vapor Screen and Surface Techniques  

NASA Technical Reports Server (NTRS)

A flight research program to study the flow structure and separated-flow origins over an F-106B aircraft wing is described. The flight parameters presented include Mach numbers from 0.26 to 0.81, angles of attack from 8.5 deg to 22.5 deg, Reynolds numbers from 22.6 x 10(exp 6) to 57.3 x 10(exp 6) and load factors from 0.9 to 3.9 times the acceleration due to gravity. Techniques for vapor screens, image enhancement, photogrammetry, and computer graphics are integrated to analyze vortex-flow systems. Emphasis is placed on the development and application of the techniques. The spatial location of vortex cores and their tracks over the wing are derived from the analysis. Multiple vortices are observed and are likely attributed to small surface distortions in the wing leading-edge region. A major thrust is to correlate locations of reattachment lines obtained from the off-surface (vapor-screen) observations with those obtained from on-surface oil-flow patterns and pressure-port data. Applying vapor-screen image data to approximate reattachment lines is experimental, but depending on the angle of attack, the agreement with oil-flow results is generally good. Although surface pressure-port data are limited, the vapor-screen data indicate reattachment point occurrences consistent with the available data.

Lamar, John E.; Brandon, Jay; Stacy, Kathryn; Johnson, Thomas D., Jr.; Severance, Kurt; Childers, Brooks A.

1993-01-01

390

Lead isotope studies of the Guerrero composite terrane, west-central Mexico: implications for ore genesis  

NASA Astrophysics Data System (ADS)

New thermal ionization mass spectrometry and multi-collector inductively coupled plasma mass spectrometry Pb isotope analyses of three Cenozoic ores from the La Verde porphyry copper deposit located in the Zihuatanejo-Huetamo subterrane of the Guerrero composite terrane are presented and the metal sources are evaluated. Lead isotope ratios of 3 Cenozoic ores from the El Malacate and La Esmeralda porphyry copper deposits located in the Zihuatanejo-Huetamo subterrane and of 14 ores from the Zimapan and La Negra skarn deposits from the adjoining Sierra Madre terrane are also presented to look for systematic differences in the lead isotope trends and ore metal sources among the proposed exotic tectonostratigraphic terranes of southern Mexico. Comparison among the isotopic signatures of ores from the Sierra Madre terrane and distinct subterranes of the Guerrero terrane supports the idea that there is no direct correlation between the distinct suspect terranes of Mexico and the isotopic signatures of the associated Cenozoic ores. Rather, these Pb isotope patterns are interpreted to reflect increasing crustal contribution to mantle-derived magmas as the arc advanced eastward onto a progressively thicker continental crust. The lead isotope trend observed in Cenozoic ores is not recognized in the ores from Mesozoic volcanogenic massive sulfide and sedimentary exhalative deposits. The Mesozoic ores formed prior to the amalgamation of the Guerrero composite terrane to the continental margin, which took place during the Late Cretaceous, in intraoceanic island arc and intracontinental marginal basin settings, while the Tertiary deposits formed after this event in a continental arc setting. Lead isotope ratios of the Mesozoic and Cenozoic ores appear to reflect these differences in tectonic setting of ore formation. Most Pb isotope values of ores from the La Verde deposit (206Pb/204Pb = 18.674-18.719) are less radiogenic than those of the host igneous rocks, but plot within the field defined by the Huetamo Sequence, suggesting that these ores may also contain metals from the sedimentary rocks. The Pb isotope ratios of ore samples from the Zimapan deposit (206Pb/204Pb = 18.771-18.848) are substantially higher than the whole-rock Pb isotope compositions of the basement rocks. The similarity of ore Pb to igneous rock Pb in the Zimapan district (206Pb/204Pb = 18.800-18.968) may indicate that the proximal source of ore metals in the hydrothermal system was the igneous activity.

Potra, Adriana; Macfarlane, Andrew W.

2014-01-01

391

The design of a functionally graded composite for service in high temperature lead and lead-bismuth cooled nuclear reactors  

E-print Network

A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C would be an enabling technology for LBE-cooled reactors. No single alloy currently exists that can economically meet the required ...

Short, Michael Philip

2010-01-01

392

Lead concentration and isotopic composition in five peridotite inclusions of probable mantle origin  

USGS Publications Warehouse

The lead content of five whole-rock peridotite inclusions (four lherzolites and one harzburgite) in alkali basalt ranges from 82 to 570 ppb (parts per billion). Approximately 30-60 ppb of this amount can be accounted for by analyzed major silicate minerals (olivine ??? 10 ppb; enstatite 5-28 ppb; chrome diopside ???400 ppb). Through a series of acid leaching experiments, the remainder of the lead is shown to be quite labile and to reside in either glassy or microcrystalline veinlets or accessory mineral phases, such as apatite and mica. The lead isotopic composition of the peridotites (206Pb/204Pb = 18.01-18.90; 207Pb/204Pb = 15.52-15.61; 208Pb/204Pb = 37.80-38.86) lies within the range of values defined by many modern volcanic rocks and, in particular, is essentially coextensive with the abyssal tholeiite field. In all but one instance, isotopic differences were found between the peridotite and its host alkali basalt. Two of the peridotites clearly demonstrated internal isotopic heterogeneity between leachable and residual fractions that could not simply be due to contamination by the host basalt. However, there is no evidence that these ultramafic rocks form some layer in the mantle with isotopic characteristics fundamentally different from those of the magma sources of volcanic rocks. ?? 1973.

Zartman, R.E.; Tera, F.

1973-01-01

393

Study of BNKLBT-1.5 lead-free ceramic/epoxy 1-3 composites  

SciTech Connect

Bismuth sodium titanate based lead-free ceramic fiber with the chemical formula of 0.885(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-0.05(Bi{sub 0.5}K{sub 0.5})TiO{sub 3}-0.015(Bi{sub 0.5}Li{sub 0.5}= )TiO{sub 3}-0.05BaTiO{sub 3}, BNKLBT-1.5, has been fabricated by a powder-based extrusion method. The ceramic fibers with 400 {mu}m diameter were well crystallized after being calcined at 800 deg. C and sintered at 1170 deg. C. The piezoelectric and ferroelectric properties of the single fiber were found to be 155 pC/N and {approx}34.5 {mu}C/cm{sup 2}, respectively, which is comparable with that in bulk sample. 1-3 ceramic/polymer composites were fabricated by two routes, including dice and filled method and fiber pick-and-place method. Theoretical models were used to calculate the piezoelectric properties of the composites and compared with experimental results.

Choy, S. H.; Li, W. K.; Li, H. K.; Lam, K. H.; Chan, H. L. W. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong (China)

2007-12-01

394

The effects of edge sealing treatment applied to wood-based composites on formaldehyde emission by desiccator test method  

Microsoft Academic Search

Formaldehyde emissions were measured with the Japanese industrial standard desiccator (JIS A 1460) method for particleboard (PB) and medium density fiberboard (MDF) as furniture materials, 8mm laminate flooring, and engineered flooring as flooring materials. To measure the formaldehyde surface emissions, the edge of each sample was sealed with either parafilm, polyethylene wax or aluminum foil. To determine the effect of

Sumin Kim; Jin-A Kim; Hyun-Joong Kim; Hwa Hyoung Lee; Dong-Won Yoon

2006-01-01

395

The Use of Pristine and Intercalated Graphite Fiber Composites as Buss Bars in Lead-Acid Batteries  

NASA Technical Reports Server (NTRS)

This study was conducted as a part of the Firefly Energy Space Act Agreement project to investigate the possible use of composite materials in lead acid batteries. Specifically, it examined the use of intercalated graphite composites as buss bars. Currently, buss bars of these batteries are made of lead, a material that is problematic for several reasons. Over time, the lead is subject to both corrosion at the positive plate and sulfation at the negative plate, resulting in decreased battery life. In addition, the weight and size of the lead buss bars make for a heavy and cumbersome battery that is undesirable. Functionality and practicality of lead buss bars is adequate at best; consequently, investigation of more efficient composite materials would be advantageous. Practically speaking, graphite composites have a low density that is nearly one fourth that of its lead counterpart. A battery made of less dense materials would be more attractive to the consumer and the producer because it would be light and convenient. More importantly, low weight would be especially beneficial because it would result in greater overall power density of the battery. In addition to power density, use of graphite composite materials can also increase the life of the battery. From a functional standpoint, corrosion and sulfation at the positive and negative plates are major obstacles when considering how to extend battery life. Neither of these reactions are a factor when graphite composites replace lead parts because graphite is chemically non-reactive with the electrolyte within the battery. Without the problem of corrosion or sulfation, battery life expectancy can be almost doubled. The replacement of lead battery parts with composite materials is also more environmentally favorable because of easy disposal of organic materials. For this study, both pristine and bromine intercalated single-ply graphite fiber composites were created. The composites were fabricated in such a way as to facilitate their use in a 3" x 1/2" buss bar test cell. The prime objective of this investigation was to examine the effectiveness of a variety of graphite composite materials to act as buss bars and carry the current to and from the positive and negative battery plates. This energy transfer can be maximized by use of materials with high conductivity to minimize the buss resistance. Electrical conductivity of composites was measured using both a contactless eddy current probe and a four point measurement. In addition, the stability of these materials at battery-use conditions was characterized.

Opaluch, Amanda M.

2004-01-01

396

Nonlinear absorption of laser radiation by zinc and lead phthalocyanines and zinc porphyrin in a nanoporous-glass/polymer composite  

SciTech Connect

We have studied the nonlinear absorption of nanosecond 532-nm laser pulses by zinc phthalocyanine (PcZn), lead phthalocyanine (PcPb) and zinc porphyrin (PrZn) incorporated into a nanoporous-glass/polymer composite and determined the basic nonlinear absorption characteristics of these compounds in the composite host. The composite is shown to be suitable for designing nonlinear optical elements activated with organic compounds. The correlation between the characteristics of the three compounds in the composite host and liquid solvents is analysed.

Dolotov, S M; Koldunov, L M; Koldunov, M F; Petukhov, A V; Sizyukhin, A V

2012-01-31

397

Lead isotopic composition of fly ash and flue gas residues from municipal solid waste combustors in France: implications for atmospheric lead source tracing.  

PubMed

Fly ash and flue gas residues from eight municipal solid waste combustors (MSWC) in France (1992--93 and 1998/ 2002) were analyzed for their Pb isotopic composition. Fly ashes are more representative of solid residual particles, whereas flue gas residues reflect mostly the composition of gas phases. Both sample types contain hundreds to thousands of micrograms of metals per gram. Leaching experiments showed that metals are present in condensed phases, probably as sulfates and chlorides, and suggest that Cd, Pb, and Zn are highly fractionated from one another during volatilization/condensation processes occurring during combustion. Although all the samples analyzed define a fairly restricted range in Pb isotopic compositions (206Pb/207Pb = 1.148-1.158 and 208Pb/206Pb = 2.101-2.114) compared to other environmental samples, some MSWC produce materials having distinct isotopic compositions, whereas others display very similar ones. Isotopic heterogeneity is also measured between samples from a single MSWC. This is interpreted as resulting from the heterogeneity of the waste source materials. The range of Pb isotopic composition of incinerator materials form a well-defined linear array in the 208Pb/206Pb versus 206Pb/207Pb diagram. This array is compatible with the previously reported European standard pollution (ESP) line and most probably represent the average lead isotopic composition of industrial atmospheric emissions in France, with the following ratios: 206Pb/207Pb = 1.154+/-0.003 and 208Pb/206Pb = 2.107+/-0.003 (1sigma). PMID:15871232

Carignan, Jean; Libourel, Guy; Cloquet, Christophe; Le Forestier, Lydie

2005-04-01

398

Effects of Elastic Edge Restraints and Initial Prestress on the Buckling Response of Compression-Loaded Composite Panels  

NASA Technical Reports Server (NTRS)

A parametric study of the effects of test-fixture-induced initial prestress and elastic edge restraints on the prebuckling and buckling responses of a compression-loaded, quasi-isotropic curved panel is presented. The numerical results were obtained by using a geometrically nonlinear finite element analysis code with high-fidelity models. The results presented show that a wide range of prebuckling and buckling behavior can be obtained by varying parameters that represent circumferential loaded-edge restraint and rotational unloaded-edge restraint provided by a test fixture and that represent the mismatch in specimen and test-fixture radii of curvature. For a certain range of parameters, the panels exhibit substantial nonlinear prebuckling deformations that yield buckling loads nearly twice the corresponding buckling load predicted by a traditional linear bifurcation buckling analysis for shallow curved panels. In contrast, the results show another range of parameters exist for which the nonlinear prebuckling deformations either do not exist or are relatively benign, and the panels exhibit buckling loads that are nearly equal to the corresponding linear bifurcation buckling load. Overall, the results should also be of particular interest to scientists, engineers, and designers involved in simulating flight-hardware boundary conditions in structural verification and certification tests, involved in validating structural analysis tools, and interested in tailoring buckling performance.

Hilburger, Mark W.; Nemeth, Michael P.; Riddick, Jaret C.; Thornburgh, Robert P.

2004-01-01

399

The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates  

NASA Technical Reports Server (NTRS)

The isotopic compositions of uranium and lead in Ca-Al-rich inclusions from the Allende chondrite and in whitlockite from the St. Severin chondrite and the Angra dos Reis achondrite are reported. Isoptopic analysis of acid soluble fractions of the Allende inclusions and the meteoritic whitlockite, which show isotopic anomalies in other elements, reveals U-235/U-238 ratios from 1/137.6 to 1/138.3, within 20 per mil of normal terrestrial U abundances. The Pb isotopic compositions of five coarse-grained Allende inclusions give a mean Pb-207/Pb-206 model age of 4.559 + or - 0.015 AE, in agreement with the U results. Pb isotope ratios of two fine-grained inclusions and a coarse-grained inclusion with strong mass fractionation and some nonlinear isotopic anomalies indicate that the U-Pb systems of these inclusions have evolved differently from the rest of Allende. Th/U abundance ratios in the Allende inclusions and meteoritic phosphate are found to range from 3.8 to 96, presumably indicating an optimal case for Cm/U fractionation, although the normal U concentrations do not support claims of abundant live Cm-247 or Cm-247/U-238 fractionation at the time of meteorite formation, in contrast to previous results. A limiting Cm-247/U-235 ratio of 0.004 at the time of meteorite formation is calculated which implies that the last major r process contribution at the protosolar nebula was approximately 100 million years prior to Al-26 formation and injection.

Chen, J. H.; Wasserburg, G. J.

1981-01-01

400

Surface plasmon resonance sensing detection of mercury and lead ions based on conducting polymer composite.  

PubMed

A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (?RU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb(2+) and Hg(2+) ions. The Pb(2+) ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb(2+) compared to Hg(2+). The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system. PMID:21931763

Abdi, Mahnaz M; Abdullah, Luqman Chuah; Sadrolhosseini, Amir R; Mat Yunus, Wan Mahmood; Moksin, Mohd Maarof; Tahir, Paridah Md

2011-01-01

401

Manufacturing and analysis of a LIGA heat exchanger for the surface of a cylinder: a cooling simulation of the leading edge region of a turbine blade  

Microsoft Academic Search

The presence a pin fins array in a channel has the ability to enhance heat transfer greatly. That concept is already used in the internal cooling channel present in the trailing edge of some turbine blades. The reasons why fins enhance heat transfer are numerous: i) their presence increases the wetted surface area available to heat transfer ii) they promote

Christophe Marques; Kevin Kelly

2002-01-01

402

Wind-tunnel investigation of effects of wing-leading-edge modifications on the high angle-of-attack characteristics of a T-tail low-wing general-aviation aircraft  

NASA Technical Reports Server (NTRS)

Exploratory tests have been conducted in the NASA-Langley Research Center's 12-Foot Low-Speed wind Tunnel to evaluate the application of wing-leading-edge devices on the stall-departure and spin resistance characteristics of a 1/6-scale model of a T-tail general-aviation aircraft. The model was force tested with an internal strain-gauge balance to obtain aerodynamic data on the complete configuration and with a separate wing balance to obtain aerodynamic data on the outer portion of the wing. The addition of the outboard leading-edge droop eliminated the abrupt stall of the windtip and maintained or increased the resultant-force coefficient up to about alpha = 32 degrees. This change in slope of the resultant-force coefficient curve with angle of attack has been shown to be important for eliminating autorotation and for providing spin resistance.

White, E. R.

1982-01-01

403

Effect of Ice Formations on Section Drag of Swept NACA 63A-009 Airfoil with Partical-span Leading-edge Slat for Various Modes of Thermal Ice Protection  

NASA Technical Reports Server (NTRS)

Studies were made to determine the effect of ice formations on the section drag of a 6.9-foot-chord 36 degree swept NACA 63A-009 airfoil with partial-span leading-edge slat. In general, the icing of a thin swept airfoil will result in greater aerodynamic penalties than for a thick unswept airfoil. Glaze-ice formations at the leading edge of the airfoil caused large increases in section drag even at liquid-water content of 0.39 gram per cubic meter. The use of an ice-free parting strip in the stagnation region caused a negligible change in drag compared with a completely unheated airfoil. Cyclic de-icing when properly applied caused the drag to decrease almost to the bare-airfoil drag value.

Von Glahn, Uwe H; Gray, Vernon H

1954-01-01

404

Isotopic composition of lead in moss and soil of the European Arctic  

NASA Astrophysics Data System (ADS)

Moss, O and C horizons of podzols, mainly forming complementary sample triplets, as well as filter residues of molten snow from northern Norway, northern Finland and NW Russia have been analyzed by TIMS for their Pb isotopic composition in order to study the impacts of local geogenic/anthropogenic sources and long range atmospheric transport on the Pb balance in the European Arctic. Samples were taken along two N-S transects covering an area of ˜188.000 km 2, including both pristine environments in the W and certain regions towards the E severely contaminated by heavy metal emissions originating from large nickel smelters and processing plants in NW Russia. The lead in moss and O horizon samples clearly reflects atmospheric deposition, as it displays overall uniform isotope ratios and is decoupled from the geogenic background, i.e. the underlying mineral soils in the C horizon. Moss and O horizon samples from the eastern N-S transect are isotopically indistinguishable from those taken along the western transect but their Pb concentrations tend to be ˜2 times higher. This points to considerable contamination originating from the nearby Russian industrial and urban centers. However, isotopic signals of emissions from individual industrial point sources cannot be unambiguously identified because they lack characteristic isotope signatures. Pb derived from gasoline additives is swamped by Pb from other sources and can also be excluded as a major contributor to the environmental Pb in the European Arctic. Overall, the Pb isotopic signatures of moss and O horizon overlap values recorded in atmospheric lead all over central and southern Europe, more than 2000 km south of the study area. This may be taken as indicating continent-wide mixing of Pb derived from similar sources in the atmosphere or as reflecting economic globalization, or both. O horizon samples, which accumulate lead over 20-30 yr, conform to a distinct Pb isotope reference line in 207Pb/ 206Pb vs. 208Pb/ 206Pb space ("European Standard Pollution," ESP) defined by atmospheric Pb considered to be representative for the technical civilization in Europe. Conversely, the Arctic moss samples with a lifetime of <3 yr display a deviating linear trend reflecting a recent change of atmospheric input towards significantly more radiogenic Pb derived from Mississippi Valley-type ores in the U.S., fully compatible with signatures found in epiphytic lichens from Canada, but also in Pb from urban waste incinerators in central Europe. Considering the elevated Pb concentrations in moss collected along the eastern N-S transect, this congruence indicates that the Pb in moss of the European Arctic most probably originates from the nearby Russian centers of urbanization and not from transatlantic transport. We therefore suspect imported industrial goods and their subsequent attrition to be a more plausible explanation for the appearance of MVT lead in Europe.

Haack, U.; Kienholz, B.; Reimann, C.; Schneider, J.; Stumpfl, E. F.

2004-06-01

405

Isotopic compositions of gangue versus ore minerals in the Upper Mississippi Valley zinc-lead district  

SciTech Connect

Four successive stages of gangue calcite occur after sulfide mineralization in the Upper Mississippi Valley zinc-lead district. These are commonly interpreted to represent the waning stage of MTV mineralization, because of spatial association and a smooth transition of decreasing fluid inclusion temperatures from late stage sphalerite through calcites 2 to 4. U-Pb systematics in two calcite 2 crystals suggests an age of 162 Ma, with [mu] values sufficiently great (1,175 and 1,611) that the indicated age is insensitive to initial [sup 206]Pb/[sup 204]Pb. This age for calcite formation is [approx] 100 Ma after that of sulfide mineralization and thus represents recurrent fluid activity along fracture zones. Initial [sup 87]Sr/[sup 86]Sr isotopic composition for three calcite 2 crystals range from 0.70956--0.70961, consist with initial [sup 87]Sr/[sup 86]Sr in the 270 Ma sphalerites. The initial [sup 87]Sr/[sup 86]Sr for two calcite 3 crystals and one calcite 4 crystal range from 0.70845--0.70875, consistent with mid-Ordovician seawater and the host carbonates of that age. The authors propose a hypothesis which is consistent with the Sr and U-Pb isotopic data. 162 Ma ago fluids flushed the existing pore fluids (left over from 270 Ma MVT event) from carbonate strata and deposited calcite 2. Subsequently, additional fluids containing [sup 87]Sr/[sup 86]Sr consistent with that derived from mid-Ordovician carbonates deposited calcite 3 and 4. If this hypothesis is correct the paragenetic connection between ore and gangue mineralization at UMV is weak and geochemical study of the gangue minerals may provide only limited information about the fluid which formed the ores.

Brannon, J.C.; Podosek, F.A. (Washington Univ., St. Louis, MO (United States). Dept. of Earth Planetary Sciences); McLimans, R.K. (E.I. DuPont de Nemours Co., Deepwater, NJ (United States). Jackson Research Lab.)

1993-03-01

406

Entrepreneurial Edge  

NSDL National Science Digital Library

Published by the Edward Lowe Foundation, Entrepreneurial Edge Online is the electronic counterpart to the small business training magazine by the same name. Site features beyond selected Entrepreneurial Edge articles include the self-training modules--Business Builders, an Interactive Toolbox of budget, balance sheet, and cash flow calculators, and a list of discussion forums entitled Virtual Network.

1998-01-01

407

Influence of Chemical Composition Heterogeneity on the Spectral Position of the Fundamental Absorption Edge of Cu(In, Ga)Se2 Solid Solutions  

NASA Astrophysics Data System (ADS)

Optical parameters of Cu(In,Ga)Se2 (CIGS) thin films were determined by measuring optical transmission and reflectance spectra at room temperature. CIGS thin films with average Ga/(Ga + In) ratio ~0.45 were deposited on glass substrates using a three-stage process. The films had thickness d ~ 1.6 ?m and refractive index n ~ 2.38-2.53 in the transparency range. The band-gap energy Eg of the CIGS thin films was ~1.36 eV at 293 K. The influence of chemical composition heterogeneity along the depth of the absorbing layers on the spectral position of the fundamental absorption edge of the CIGS solid solutions was discussed.

Refahati, N.; Mudryi, A. V.; Zhivulko, V. D.; Yakushev, M. V.; Martin, R.

2014-07-01

408

Isotopic composition as a natural tracer of lead in the environment  

Microsoft Academic Search

The object of this research was to determine if the isotope ratios of lead were significantly different in various environmental media and if such differences could be used to distinguish the lead in the media. Significant differences in the lead isotopic ratios in rock and soils, grasses, tree leaves and tree rings, air particulate, and in some industrial products such

Wayne U. Ault; Ronald G. Senechal; Woodland E. Erlebach

1970-01-01

409

The lead susceptibility of fuels and its dependence on the chemical composition  

NASA Technical Reports Server (NTRS)

The fact that by the use of tetraethyl lead a number of otherwise unsuitable fuels could be made to meet engine requirements was not sufficiently appreciated. While use of tetraethyl lead is limited, the addition of special leaded fuels that increase the octane number is a requirement for many fuels. In this connection, the extent to which the action of tetraethyl lead through the addition of knock-resistant hydrocarbons to the base gasoline is influenced, is quite important. To the elucidation of this problem and of the storage stability of leaded fuels, the present report is dedicated.

Widmaier, O

1940-01-01

410

NOVEL LEAD ZIRCONATE TITANATE COMPOSITE VIA FREEZING TECHNOLOGY FOR HIGH FREQUENCY TRANSDUCER APPLICATIONS  

PubMed Central

Novel PZT-5A ceramic-polymer composite was prepared via freezing technology. This composite exhibited good dielectric and ferroelectric behaviors. At 1 kHz, the dielectric constant and the dielectric loss were 546 and 0.046, respectively, while the remnant polarization was 13.0 ?C/cm2 at room temperature. The electromechanical coupling coefficient (kt) of PZT-5A composite was measured to be 0.54, which is similar to that of PZT piezoelectric ceramic. The piezoelectric coefficient (d33) of PZT-5A composite was determined to be ~250 pC/N. Using this composite, a 58MHz single element transducer with the bandwidth of 70% at ?6dB was built, and the insertion loss was tested to be ?29dB around the central frequency. PMID:21785672

ZHU, B. P.; ZHOU, Q. F.; HU, C. H.; SHUNG, K. K.; GORZKOWSKI, E. P.; PAN, M. J.

2011-01-01

411

Electron microscopy characterization of lead zirconate titanate ceramics at the morphotropic phase boundary composition  

SciTech Connect

The structure and chemical composition of PZT ceramics prepared by conventional ceramic processing has been analyzed by electron microscopy. Lattice parameters obtained from x-ray diffraction indicate that the T and R phases are only very slightly distorted from cubic symmetry at the MPB composition. Convergent beam diffraction (CBD) has been used to analyze the structure at te MPB composition using the fact that the symmetry of the CBD pattern is sensitive to the point group of the space lattice. It has been established that both T and R phases are present at the MPB composition. Microanalysis using energy dispersive x-ray spectroscopy has been carried out in conjunction with the structure analysis to establish the chemical composition of the different phases present.

Dass, M.L.A.; Dehmen, U.; Thomas, G.; Yamamoto, T.; Okazaki, K.

1986-06-01

412

Determination of the age of the earth from the isotopic composition of meteoritic lead  

Microsoft Academic Search

Summary  Under the assumption thata) the isotopic constitution of lead at the time of the formation of the lithosphére is represented by the figures found for\\u000a lead from the troilite phase of the Cafion-Diablo meteorite [Pat 53] andb) the majority of tertiary lead ores analysed for isotopic constitution has been formed according to the simple model of primary\\u000a origin (equ. 3),

F. G. Houtermans

1953-01-01

413

High-strain actuation of lead-free perovskites : compositional effects, phenomenology and mechanism  

E-print Network

An experimental study was carried out to map the compositional dependence of electromechanical behavior and ferroelectric phase stability in the barium, zirconium-codoped sodium bismuth titanate (BNBZT) system for barium ...

Soukhojak, Andrey N. (Andrey Nestorovich), 1972-

2002-01-01

414

The phase composition and degree of dispersion of lead powders produced by electroerosion dispersion and used in storage battery plates  

Microsoft Academic Search

The primary criterion in selection of the optimum method of forming of the plate mixture for lead-acid storage batteries is obtaining of a certain phase composition of the plates with a sufficiently uniform distribution of finely dispersed oxide phases in them. Development of new methods of production of storage battery plates satisfying the requirements of GOST`s 959-0-84 to 959.25-84 is

G. N. Dubrovskaya; A. V. Pukalenko; N. V. Olekseenko; D. P. Semkin; V. T. Khimich

1995-01-01

415

Lead zirconate titanate-nickel zink ferrite thick-film composites: obtaining by the screen printing technique and magnetoelectric properties  

NASA Astrophysics Data System (ADS)

Layered thick-film composites containing one lead zirconate titanate (PZT) layer, one nickel zinc ferrite (NZF) layer, two PZT-NZF layers, or three PZT-NZF-PZT layers each 40-50 ?m thick are prepared. The layers are applied by screen printing on a ceramic aluminum oxide substrate with a preformed contact (conducting) layer. The dielectric properties of the composites are studied in the temperature interval 80-900 K and the frequency interval 25 Hz-1 MHz. Polarized samples exhibit piezoelectric, pyroelectric, and magnetoelectric effects. In tangentially magnetized two- and three-layer composites, the magnetoelectric conversion factor equals 57 kV/(m T) at low frequencies and reaches 2000 kV/(m T) at the mechanical resonance frequency.

Bush, A. A.; Shkuratov, V. Ya.; Chernykh, I. A.; Fetisov, Y. K.

2010-03-01

416

Modeling of dielectric relaxation response of ceramic\\/polymer composite based on lead titanate  

Microsoft Academic Search

The dielectric behavior of the [(Pb0.88Sm0.08)(Ti0.99Mn0.01)O3]\\/polyetherketoneketone (PSTM\\/PEKK) ceramic\\/polymer composite is presented. The main contribution to the total dielectric relaxation response is due to the ceramic phase. Two important relaxation processes are observed, whose behavior suggest that the Jonscher’s power law holds for the composite. The results are also explained considering the intra-cluster motion and inter-cluster exchange mechanisms, as proposed by

A. Peláiz-Barranco

2006-01-01

417

Wind-tunnel and Flight Investigations of the Use of Leading-Edge Area Suction for the Purpose of Increasing the Maximum Lift Coefficient of a 35 Degree Swept-Wing Airplane  

NASA Technical Reports Server (NTRS)

An investigation was undertaken to determine the increase in maximum lift coefficient that could be obtained by applying area suction near the leading edge of a wing. This investigation was performed first with a 35 degree swept-wing model in the wind tunnel, and then with an operational 35 degree swept-wing airplane which was modified in accord with the wind-tunnel results. The wind-tunnel and flight tests indicated that the maximum lift coefficient was increased more than 50 percent by the use of area suction. Good agreement was obtained in the comparison of the wind-tunnel results with those measured in flight.

Holzhauser, Curt A; Bray, Richard S

1956-01-01

418

Protist community composition during spring in an Arctic flaw lead polynya  

Microsoft Academic Search

The overwintering deployment of an icebreaker during the Canadian Flaw Lead study provided an opportunity to evaluate how\\u000a protist communities (phytoplankton and other single-celled eukaryotes) respond to changing spring irradiance conditions in\\u000a flaw lead polynyas, where open water persists between the central pack ice and land fast ice. We combined microscopic analysis\\u000a of the protist communities (all cell sizes) with

Ramon Terrado; Emmanuelle Medrinal; Cindy Dasilva; Mary Thaler; Warwick F. Vincent; Connie Lovejoy

419

A multispectroscopic structural study of lead silicate glasses over an extended range of compositions  

Microsoft Academic Search

A series of lead silicate glasses, spanning the broadest reported range of lead contents (up to 83mol% PbO), were prepared, on which the following spectroscopic observations were made: 29Si magic angle spinning nuclear magnetic resonance, time of flight mass spectroscopy, raman spectroscopy and fourier transform infrared spectroscopy. For bulk, splat-quenched samples, infrared results indicate that the lever rule is approximately

S. Feller; G. Lodden; A. Riley; T. Edwards; J. Croskrey; A. Schue; D. Liss; D. Stentz; S. Blair; M. Kelley; G. Smith; S. Singleton; M. Affatigato; D. Holland; M. E. Smith; E. I. Kamitsos; C. P. E. Varsamis; E. Ioannou

2010-01-01