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1

Leading edge protection for composite blades  

NASA Technical Reports Server (NTRS)

A laminated filament composite structure, such as an airfoil for use in an environment in which it is subjected to both foreign object impact and bending is provided with improved leading edge protection. At least one fine wire mesh layer is partially bonded within the composite structure along its neutral bending axis. A portion of the wire mesh layer extends beyond the neutral bending axis and partially around the leading edge where it is bonded to the outer periphery of the primary composite structure. The wire mesh is clad with a metal such as nickel to provide an improved leading edge protective device which is firmly anchored within the composite structure. Also described is a novel method of constructing a composite airfoil so as to further minimize the possibility of losing the leading edge protective device due to delamination caused by impact and bending.

Brantley, J. W.; Irwin, T. P. (inventors)

1977-01-01

2

Ultra-High Temperature Ceramic Composites for Leading Edges  

NASA Technical Reports Server (NTRS)

Issues associated with the development and use of Ultra-High Temperature Ceramic Composites (UHTCC) for leading edges of hypersonic vehicles will be discussed. These include attachments, constituent selection, processing, oxidation, physical and mechanical properties, and attachments.

Levine, Stanley R.

2004-01-01

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

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

5

Ultra-High Temperature Ceramic Composites for Leading Edges  

NASA Technical Reports Server (NTRS)

Ultra-high 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 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. In particular, initial tests of tantalum additions have shown potential for major improvement. Results for additional tests at higher temperatures will be presented. These oxidation improvements are being incorporated in the composites approaches. Two fabrication approaches are being persued to produce carbon fiber reinforced UHTC composites: prepregging and rigid perform infiltration. Fabrication procedures, microstructures, and initial mechanical property and oxidation results for composites will be reported.

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

2003-01-01

6

Ultra-High Temperature Ceramic Composites for Leading Edges  

NASA Technical Reports Server (NTRS)

Ultra-high 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 UHTC. If these deficiencies are overcome, we are still faced with poor oxidation resistance as a limitation on UHT 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. In particular, initial tests of tantalum additions have shown potential for major improvement. Less promising results of additional tests at higher temperatures will be presented. Two fabrication approaches are being pursued to produce carbon fiber reinforced UHTC composites: prepregging and rigid perform infiltration. Fabrication procedures and microstructures for composites will be reported.

Levine, Stanley R.; Singh, Mrityunjay; Opila, Elizabeth J.; Lorincz, Jonathan A.; Petko, Jeanne; Ellerby, Donald T.; Gasch, Matthew J.

2003-01-01

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

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

9

Experimental investigation on the composite cooling of a semicylinder leading edge  

NASA Astrophysics Data System (ADS)

Composite cooling of the leading edge region of a semicylinder simulating a turbine vane was studied experimentally. The cylinder's inner surface served as an impingement target for studying impingement cooling; the outer surface was used to study the film cooling effectiveness. The equipment for composite cooling was a sucked-wind tunnel with the test section of 140 x 200-sq m in cross section and with transparent windows for flow visualization. Three test models and five different impingement tubes were used. The effects of geometrical parameters of the test models and impingement tubes and of the location and direction of the film holes on both the impingement and the film cooling are described.

Cheng, Ji-Rui; Ji, Hong-Hu

10

The preparation of a composite structure for a first large scale ground test of a smart and gapless wing leading edge  

Microsoft Academic Search

At the Institute of Composite Structures and Adaptive Systems (FA, Prof. Wiedemann) of the DLR the structure of a flexible and gapless wing leading edge has been developed for testing in large scale structure-system ground tests. The absence of gaps in a flexible wing leading edge allows for a significant noise reduction and provides an additional key technology for realizing

Olaf Heintze; Sebastian Geier; Daniel Hartung; Markus Kintscher

2011-01-01

11

Icing tunnel tests of a composite porous leading edge for use with a liquid anti-ice system. [Lewis icing research tunnel  

NASA Technical Reports Server (NTRS)

The efficacy of liquid ice protection systems which distribute a glycol-water solution onto leading edge surfaces through a porous skin was demonstrated in tests conducted in the NASA Lewis icing research tunnel using a composite porous leading edge panels. The data obtained were compared with the performance of previously tested stainless steel leading edge with the same geometry. Results show: (1) anti-ice protection of a composite leading edge is possible for all the simulated conditions tested; (2) the glycol flow rates required to achieve anti-ice protection were generally much higher than those required for a stainless steel panel; (3) the low reservoir pressures of the glycol during test runs indicates that more uniform distribution of glycol, and therefore lower glycol flow rates, can probably be achieved by decreasing the porosity of the panel; and (4) significant weight savings can be achieved in fluid ice protection systems with composite porous leading edges. The resistance of composite panels to abrasion and erosion must yet be determined before they can be incorporated in production systems.

Kohlman, D. L.

1981-01-01

12

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

13

The preparation of a composite structure for a first large scale ground test of a smart and gapless wing leading edge  

NASA Astrophysics Data System (ADS)

At the Institute of Composite Structures and Adaptive Systems (FA, Prof. Wiedemann) of the DLR the structure of a flexible and gapless wing leading edge has been developed for testing in large scale structure-system ground tests. The absence of gaps in a flexible wing leading edge allows for a significant noise reduction and provides an additional key technology for realizing wings with a fully natural laminar flow. In the years 2009 and 2010 the work in the project SmartLED within the 4th German Aviation Research Program (LuFo) was focused on the preparation and realization of the first ground test of the in the project developed overall system. The overall smart droop nose concept arose from the cooperation of Airbus and EADS, whereas the DLR Institute FA dealt with the structural design, the test of the material systems, the simulation of the overall system, and the development of manufacturing technologies for the composite structures to be employed in the planned tests. The detailed presentation of this work forms the content of this paper which has been made possible through the application of the process chain for composite structures established at the Institute FA of the DLR.

Heintze, Olaf; Geier, Sebastian; Hartung, Daniel; Kintscher, Markus

2011-03-01

14

Improvement in oxidation resistance of the leading edge thermal protection for a space shuttle. [carbon-carbon composite  

NASA Technical Reports Server (NTRS)

To improve the oxidation resistance of a carbon-carbon composite, impregnations were performed using pitches, polyfurfuryl alcohols, and phenolic resins, including a silicon-doped phenolic resin. Oxidation resistance and strength increased for all of the composites as the impregnant-carbon residue increased. The properties of the composites impregnated with the nonsilicon-bearing resins were nearly identical and depended only on the amount of impregnant residue present. However, for equivalent residue concentrations, composites produced with the silicon-bearing resin gave higher strengths and at least 100% better oxidation resistance than was observed for the other composites or for a prototype control material.

Williams, J. M.; Imprescia, R. J.

1975-01-01

15

Leading-edge receptivity by adjoint methods  

NASA Astrophysics Data System (ADS)

The properties of adjoint operators and the method of composite expansion are used to study the generation of Tollmien Schlichting (TS) waves in the leading-edge region of an incompressible, flat-plate boundary layer. Following the classical asymptotic approach, the flow field is divided into an initial receptivity region, where the unsteady motion is governed by the linearized unsteady boundary-layer equation (LUBLE), and a downstream linear amplification area, where the evolution of the unstable mode is described by the classical Orr Sommerfeld equation (OSE). The large bar{x} behaviour of the LUBLE is analysed using a multiple-scale expansion which leads to a set of composite differential equations uniformly valid in the wall-normal direction. These are solved numerically as an eigenvalue problem to determine the local properties of the Lam and Rott eigensolutions. The receptivity coefficient for an impinging acoustic wave is extracted by projecting the numerical solution of the LUBLE onto the adjoint of the Lam and Rott eigenfunction which, further downstream, turns into an unstable TS wave. In the linear amplification region, the main characteristics of the instability are recovered by using a multiple-scale expansion of the Navier Stokes equations and solving numerically the derived eigenvalue problems. A new matching procedure, based on the properties of the adjoint Orr Sommerfeld operator, is then used to check the existence and the extent of an overlapping domain between the two asymptotic regions. Results for different frequencies are discussed.

Giannetti, Flavio; Luchini, Paolo

16

Improved prediction of laminar leading edge separation  

NASA Technical Reports Server (NTRS)

Research was conducted to provide a definite criterion for the prediction of the bubble burst on airfoils typical of those used for fighter wings. The approach taken was to correlate existing airfoil bubble burst data using various parameters at the laminar separation point. The method due to Weber was modified to provide a continuous analytic solution for the velocity distribution around the airfoil leading edge. Coupling the modified Weber method with the Stratford laminar separation prediction method leads to a universal chart giving the conditions at separation as a function of stagnation location and leading edge radius. Application of the combined method to available two-dimensional airfoil data resulted in an empirical criterion presenting the limiting local velocity gradient at separation as a function of the boundary layer momentum thickness at separation for bubble burst. The correlation leads as well to the qualitative explanation of two types of laminar stall: thin airfoil and leading edge. The validity of the correlation is demonstrated by predicting the lift coefficient and angle of attack for stall on airfoils with leading edge or trailing edge flaps.

Herring, R. N.; Ely, W. L.

1979-01-01

17

Development of Columbia Leading Edge Reconstruction System  

NASA Technical Reports Server (NTRS)

After the loss of Columbia in 2003, the Columbia Accident Investigation Board and NASA KSC directed personnel at the Launch Equipment Test Facility (LETF) to design and build high fidelity mock-ups of Columbia's left wing leading edges. These leading edge segments, constructed of reinforced carbon-carbon, were a major point of inquiry by the investigation team. The LETF engineers developed a concept of building a clear Lexan panel with an aluminum support structure ten percent larger than the original panel. The leading edge debris are attached to the Lexan panels and both the front and back side of each panel are visible for inspection. The entire assembly can be rotated, to provide visual access to the entire panel. Six carts were fabricated to support the thirteen panels. These carts could be set up in order, next to each other, to provide the desired inspection access. The carts and attached debris are currently located in the Vehicle Assembly Building at KSC.

Trautwein, John; Wegerif, Dan

2004-01-01

18

Wing Leading Edge Concepts for Noise Reduction  

NASA Technical Reports Server (NTRS)

This study focuses on the development of wing leading edge concepts for noise reduction during high-lift operations, without compromising landing stall speeds, stall characteristics or cruise performance. High-lift geometries, which can be obtained by conventional mechanical systems or morphing structures have been considered. A systematic aerodynamic analysis procedure was used to arrive at several promising configurations. The aerodynamic design of new wing leading edge shapes is obtained from a robust Computational Fluid Dynamics procedure. Acoustic benefits are qualitatively established through the evaluation of the computed flow fields.

Shmilovich, Arvin; Yadlin, Yoram; Pitera, David M.

2010-01-01

19

Cascade with subsonic leading-edge locus  

NASA Technical Reports Server (NTRS)

The paper investigates a two-dimensional oscillating cascade with a subsonic leading edge locus in a supersonic flow. The blades are assumed to be of small thickness and camber, and are undergoing small amplitude-harmonic oscillations. The problem is reduced to the solution of a functional integral equation, and an expression is given for the kernel function.

Goldstein, M. E.

1975-01-01

20

Analysis of airfoil leading edge separation bubbles  

NASA Technical Reports Server (NTRS)

A local inviscid-viscous interaction technique was developed for the analysis of low speed airfoil leading edge transitional separation bubbles. In this analysis an inverse boundary layer finite difference analysis is solved iteratively with a Cauchy integral representation of the inviscid flow which is assumed to be a linear perturbation to a known global viscous airfoil analysis. Favorable comparisons with data indicate the overall validity of the present localized interaction approach. In addition numerical tests were performed to test the sensitivity of the computed results to the mesh size, limits on the Cauchy integral, and the location of the transition region.

Carter, J. E.; Vatsa, V. N.

1982-01-01

21

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

22

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

23

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

24

Textbook Multigrid Efficiency for Leading Edge Stagnation  

NASA Technical Reports Server (NTRS)

A multigrid solver is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work which is a small (less than 10) multiple of the operation count in evaluating the discrete residuals. TME in solving the incompressible inviscid fluid equations is demonstrated for leading-edge stagnation flows. The contributions of this paper include (1) a special formulation of the boundary conditions near stagnation allowing convergence of the Newton iterations on coarse grids, (2) the boundary relaxation technique to facilitate relaxation and residual restriction near the boundaries, (3) a modified relaxation scheme to prevent initial error amplification, and (4) new general analysis techniques for multigrid solvers. Convergence of algebraic errors below the level of discretization errors is attained by a full multigrid (FMG) solver with one full approximation scheme (FAS) cycle per grid. Asymptotic convergence rates of the FAS cycles for the full system of flow equations are very fast, approaching those for scalar elliptic equations.

Diskin, Boris; Thomas, James L.; Mineck, Raymond E.

2004-01-01

25

Textbook Multigrid Efficiency for Leading Edge Stagnation  

NASA Technical Reports Server (NTRS)

A multigrid solver is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work which is a small (less than 10) multiple of the operation count in evaluating the discrete residuals. TME in solving the incompressible inviscid fluid equations is demonstrated for leading- edge stagnation flows. The contributions of this paper include (1) a special formulation of the boundary conditions near stagnation allowing convergence of the Newton iterations on coarse grids, (2) the boundary relaxation technique to facilitate relaxation and residual restriction near the boundaries, (3) a modified relaxation scheme to prevent initial error amplification, and (4) new general analysis techniques for multigrid solvers. Convergence of algebraic errors below the level of discretization errors is attained by a full multigrid (FMG) solver with one full approximation scheme (F.4S) cycle per grid. Asymptotic convergence rates of the F.4S cycles for the full system of flow equations are very fast, approaching those for scalar elliptic equations.

Diskin, Boris; Thomas, James L.; Mineck, Raymond E.

2004-01-01

26

Separation bubble around a leading edge of compressor blade  

Microsoft Academic Search

This paper presents an experimental study of the influence of 2D leading-edge geometry on transition and performance. The measurements were conducted on a special large-scale experimental facility, the pressure distribution and flow field were measured. The test model used in this study consists of circular leading edge and elliptic leading edge. Results are presented for a range of incidence. The

Huo-xing Liu; Bao-jie Liu; Ling Li; Hao-Kang Jiang

2003-01-01

27

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

28

Development of X-43A Mach 10 Leading Edges  

NASA Technical Reports Server (NTRS)

The nose leading edge of the Hyper-X Mach 10 vehicle was orginally anticipated to reach temperatures near 4000 F at the leading-edge stagnation line. A SiC coated carbon/carbon (C/C) leading-edge material will not survive that extreme temperature for even a short duration single flight. To identify a suitable leading edge for the Mach 10 vehicle, arc-jet testing was performed on thirteen leading-edge segments fabricated from different material systems to evaluate their performance in a simulated flight environment. Hf, Zr, Si, and Ir based materials, in most cases as a coating on C/C, were included in the evaluation. Afterwards, MER, Tucson, AZ was selected as the supplier of the flight vehicle leading edges. The nose and the vertical and horizontal tail leading edges were fabricated out of a 3:1 biased high thermal conductivity C/C. The leading edges were coated with a three layer coating comprised of a SiC conversion of the top surface of the C/C, followed by a chemical vapor deposited layer of SiC, followed by a thin chemical vapor deposited layer of HfC. This paper will describe the fabrication of the Mach 10 C/C leading edges and the testing performed to validate performance.

Ohlhorst, Craig W.; Glass, David E.; Bruce, Walter E., III; Lindell, Michael C.; Vaughn, Wallace L.; Dirling, R. B., Jr.; Hogenson, P. A.; Nichols, J. M.; Risner, N. W.; Thompson, D. R.

2005-01-01

29

Separation bubble around a leading edge of compressor blade  

NASA Astrophysics Data System (ADS)

This paper presents an experimental study of the influence of 2D leading-edge geometry on transition and performance. The measurements were conducted on a special large-scale experimental facility, the pressure distribution and flow field were measured. The test model used in this study consists of circular leading edge and elliptic leading edge. Results are presented for a range of incidence. The measurement result indicated that the leading edge shape has a large influence on flow details, separation and transition as well as the boundary layer properties after reattached point.

Liu, Huo-xing; Liu, Bao-jie; Li, Ling; Jiang, Hao-Kang

2003-04-01

30

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

31

Composition of Lead Sinter.  

National Technical Information Service (NTIS)

Microscopic and electroprobe studies of lead sinters and roasted mixtures of lead sulfide with varying amounts of SiO2, CaO, Fe2O3, and ZnS are presented. The studies show that lead silicates, lead-zinc silicate, calcium-zinc silicate, and spinels or ferr...

W. M. Dressel E. R. Cole P. G. Barnard W. C. Clinton

1975-01-01

32

Edge effects in composites by moire interferometry  

NASA Technical Reports Server (NTRS)

The very high sensitivity of moire interferometry has permitted the present edge effect experiments to be conducted at a low average stress and strain level, assuring linear and elastic behavior in the composite material samples tested. Sensitivity corresponding to 2450 line/mm moire was achieved with a 0.408 micron/fringe. Simultaneous observations of the specimen face and edge displacement fields showed good fringe definition despite the 1-mm thickness of the specimens and the high gradients, and it is noted that the use of a carrier pattern and optical filtering was effective in even these conditions. Edge effects and dramatic displacement gradients were confirmed in angle-ply composite laminates.

Czarnek, R.; Post, D.; Herakovich, C.

1983-01-01

33

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

34

Robust UHTC for Sharp Leading Edge Applications  

NASA Technical Reports Server (NTRS)

Ultrahigh temperature ceramics 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 UHTCs. 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 UHTCs for the past year via a small task at GRC that is part of the 3rd Gen TPS effort. Our focus is on composite constructions and functional grading to address the mechanical issues and on composition modification to address the oxidation issue. The approaches and progress will be reported.

Levine, Stanley R.; Singh, Mrityunjay; Opila, Elizabeth J.

2003-01-01

35

Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge. The Wing Leading Edge Impact Detection System (WLE IDS) and the Impact Analysis Process are also described to monitor WLE debris threats. The contents include: 1) Risk Management via SHM; 2) Hardware Overview; 3) Instrumentation; 4) Sensor Configuration; 5) Debris Hazard Monitoring; 6) Ascent Response Summary; 7) Response Signal; 8) Distribution of Flight Indications; 9) Probabilistic Risk Analysis (PRA); 10) Model Correlation; 11) Impact Tests; 12) Wing Leading Edge Modeling; 13) Ascent Debris PRA Results; and 14) MM/OD PRA Results.

Yap, Keng C.

2010-01-01

36

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

37

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

38

Design and Analysis of UHTC Leading Edge Attachment.  

National Technical Information Service (NTIS)

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 becaus...

D. J. Thomas

2002-01-01

39

Symmetric airfoil geometry effects on leading edge noise.  

PubMed

Computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. Single frequency harmonic gusts are interacted with various airfoil geometries at zero angle of attack. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and independently for the first time, at higher frequencies than previously used in computational methods. Increases in both leading edge radius and thickness are found to reduce the predicted noise. This noise reduction effect becomes greater with increasing frequency and Mach number. The dominant noise reduction mechanism for airfoils with real geometry is found to be related to the leading edge stagnation region. It is shown that accurate leading edge noise predictions can be made when assuming an inviscid meanflow, but that it is not valid to assume a uniform meanflow. Analytic flat plate predictions are found to over-predict the noise due to a NACA 0002 airfoil by up to 3 dB at high frequencies. The accuracy of analytic flat plate solutions can be expected to decrease with increasing airfoil thickness, leading edge radius, gust frequency, and Mach number. PMID:24116405

Gill, James; Zhang, X; Joseph, P

2013-10-01

40

Task 4 supporting technology. Part 1: Detailed test plan for leading edge tile development. Leading edge material development and testing  

NASA Technical Reports Server (NTRS)

This task develops two alternative candidate tile materials for leading edge applications: coated alumina enhanced thermal barrier (AETB) tile and silicone impregnated reusable ceramic ablator (SIRCA) tile. Upon reentry of the X-33/RLV space vehicle, the leading edges experience the highest heating rates and temperatures. The wing leading edge and nose cap experience peak temperatures in the range 2000 to 2700 F. Replacing reinforced carbon-carbon (RCC) with tile-based thermal protection system (TPS) materials is the primary objective. Weight, complexity, coating impact damage, and repairability are among the problems that this tile technology development addresses. The following subtasks will be performed in this development effort: tile coating development; SIRCA tile development; robustness testing of tiles; tile repair development; tile operations/processing; tile leading edge configuration; and life cycle testing.

Hogenson, P. A.; Staszak, Paul; Hinkle, Karrie

1995-01-01

41

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

42

Effect of Leading Edge Tubercles on Marine Tidal Turbine Blades  

NASA Astrophysics Data System (ADS)

This project investigated the impact that the addition of leading edge protuberances (tubercles) have on the effectiveness of marine tidal turbine blades, especially at lower flow speeds. The addition of leading edge tubercles to lifting foils has been shown, in previous research, to delay the onset of stall without significant hydrodynamic costs. The experimental results obtained utilizing three different blade designs (baseline and two tubercle modified) are compared. All blades were designed in SolidWorks and manufactured utilizing rapid prototype techniques. All tests were conducted in the 120 ft tow tank at the U.S. Naval Academy using a specifically designed experimental apparatus. Results for power coefficients are presented for a range of tip speed ratios. Cut-in velocity is also compared between the blade designs. For all test criteria, the tubercle modified blades significantly outperformed the smooth leading edge baseline design blades.

Murray, Mark; Gruber, Timothy; Fredriksson, David

2010-11-01

43

Aerothermal Performance Constraint Analysis of Sharp Nosecaps and Leading Edges.  

National Technical Information Service (NTIS)

The main objective of this work is to predict the Aerothermal Performance Constraint (APC) for a class of Crew Transfer Vehicles (CTV) with shap noses and wing leading edges made out of UHTC which is a family of Ultra High Temperature Ceramics materials d...

Y. Rizk K. Gee

2004-01-01

44

The leading edge is a lipid diffusion barrier  

Microsoft Academic Search

Actin polymerization drives many cellular events, including endocytosis, pathogen rocketing, and cell spreading. Force generation and polymerization regulation are intimately linked where an actin meshwork attaches to, and pushes against, an interface. We reasoned that interaction with actin filament plus-ends might stabilize the position of components within the plasma membrane at the leading edge, thereby slowing the diffusion of lipids

Ina Weisswange; Till Bretschneider; Kurt I. Anderson

2005-01-01

45

Direct numerical simulation of leading edge receptivity to sound  

NASA Astrophysics Data System (ADS)

Numerical simulations of leading-edge acoustic receptivity are performed for a flat plate with a modified-super-elliptic (MSE) leading edge. For small freestream amplitude, the agreement between Branch I receptivity coefficients predicted from the DNS and the experiments of Saric and White (AIAA-98-2645, 1998) for acoustic waves at zero incidence is excellent. The effect of angle of incidence of the impinging wave is investigated and found to produce higher receptivity coefficients than in the symmetric case. The slope of leading-edge receptivity coefficient versus angle of incidence of the impinging wave is found to be less than 1/4 of the slope predicted by zero-thickness flat-plate theory. However, there is excellent agreement between the DNS and finite-nose-radius theory of Hammerton and Kerschen (J. Fluid Mech. 310, 243-267, 1996). These results clearly demonstrate the importance of including the effects of the finite nose radius in any receptivity study. Finally, downstream of the leading-edge region, linear stability theory is found to accurately reproduce the characteristics of the instability waves. At higher freestream forcing, an instability wave generated by nonlinear interaction is found at double the frequency of the forcing.

Reed, H. L.; Fuciarelli, D. A.; Lyttle, I. J.

1998-11-01

46

Contact angle at the leading edge controls cell protrusion rate.  

PubMed

Plasma membrane tension and the pressure generated by actin polymerization are two antagonistic forces believed to define the protrusion rate at the leading edge of migrating cells [1-5]. Quantitatively, resistance to actin protrusion is a product of membrane tension and mean local curvature (Laplace's law); thus, it depends on the local geometry of the membrane interface. However, the role of the geometry of the leading edge in protrusion control has not been yet investigated. Here, we manipulate both the cell shape and substrate topography in the model system of persistently migrating fish epidermal keratocytes. We find that the protrusion rate does not correlate with membrane tension, but, instead, strongly correlates with cell roundness, and that the leading edge of the cell exhibits pinning on substrate ridges-a phenomenon characteristic of spreading of liquid drops. These results indicate that the leading edge could be considered a triple interface between the substrate, membrane, and extracellular medium and that the contact angle between the membrane and the substrate determines the load on actin polymerization and, therefore, the protrusion rate. Our findings thus illuminate a novel relationship between the 3D shape of the cell and its dynamics, which may have implications for cell migration in 3D environments. PMID:24794299

Gabella, Chiara; Bertseva, Elena; Bottier, Céline; Piacentini, Niccolň; Bornert, Alicia; Jeney, Sylvia; Forró, László; Sbalzarini, Ivo F; Meister, Jean-Jacques; Verkhovsky, Alexander B

2014-05-19

47

Laminar flow control leading edge glove flight test article development  

NASA Technical Reports Server (NTRS)

A laminar flow control (LFC) flight test article was designed and fabricated to fit into the right leading edge of a JetStar aircraft. The article was designed to attach to the front spar and fill in approx. 70 inches of the leading edge that are normally occupied by the large slipper fuel tank. The outer contour of the test article was constrained to align with an external fairing aft of the front spar which provided a surface pressure distribution over the test region representative of an LFC airfoil. LFC is achieved by applying suction through a finely perforated surface, which removes a small fraction of the boundary layer. The LFC test article has a retractable high lift shield to protect the laminar surface from contamination by airborne debris during takeoff and low altitude operation. The shield is designed to intercept insects and other particles that could otherwise impact the leading edge. Because the shield will intercept freezing rain and ice, a oozing glycol ice protection system is installed on the shield leading edge. In addition to the shield, a liquid freezing point depressant can be sprayed on the back of the shield.

Pearce, W. E.; Mcnay, D. E.; Thelander, J. A.

1984-01-01

48

SiC/SiC Leading Edge Turbine Airfoil Tested Under Simulated Gas Turbine Conditions  

NASA Technical Reports Server (NTRS)

Silicon-based ceramics have been proposed as component materials for use in gas turbine engine hot-sections. A high pressure burner rig was used to expose both a baseline metal airfoil and ceramic matrix composite leading edge airfoil to typical gas turbine conditions to comparatively evaluate the material response at high temperatures. To eliminate many of the concerns related to an entirely ceramic, rotating airfoil, this study has focused on equipping a stationary metal airfoil with a ceramic leading edge insert to demonstrate the feasibility and benefits of such a configuration. Here, the idea was to allow the SiC/SiC composite to be integrated as the airfoil's leading edge, operating in a "free-floating" or unrestrained manner. and provide temperature relief to the metal blade underneath. The test included cycling the airfoils between simulated idle, lift, and cruise flight conditions. In addition, the airfoils were air-cooled, uniquely instrumented, and exposed to the same internal and external conditions, which included gas temperatures in excess of 1370 C (2500 F). Results show the leading edge insert remained structurally intact after 200 simulated flight cycles with only a slightly oxidized surface. The instrumentation clearly suggested a significant reduction (approximately 600 F) in internal metal temperatures as a result of the ceramic leading edge. The object of this testing was to validate the design and analysis done by Materials Research and Design of Rosemont, PA and to determine the feasibility of this design for the intended application.

Robinson, R. Craig; Hatton, Kenneth S.

1999-01-01

49

Vortex interaction with a leading-edge of finite thickness  

NASA Technical Reports Server (NTRS)

Vortex interaction with a thick elliptical leading-edge at zero relative offset produces a pronounced secondary vortes of opposite sense that travels with the same phase speed as the primaty vortex along the lower surface of the edge. The edge thickness (scale) relative to the incident vorticity field has a strong effect on the distortion of the incident primary vortex during the impingement processs. When the thickness is sufficiently small, there is a definite severing of the incident vortex and the portion of the incident vortex that travels along the upper part of the elliptical surface has a considerably larger phase speed than that along the lower surface; this suggests that the integrated loading along the upper surface is more strongly correlated. When the thickness becomes too large, then most, if not all, of the incident vortex passes below the leading-edge. On the other hand, the relative tranverse offset of the edge with respect to the center of the incident vortex has a significant effect on the secondary vortex formation.

Sohn, D.; Rockwell, Donald

1987-01-01

50

Numerical simulations of leading-edge acoustic receptivity  

NASA Astrophysics Data System (ADS)

Numerical simulations of leading-edge acoustic receptivity are performed for a flat-plate with an elliptical leading-edge. The Modified Super Ellipse is chosen as the leading-edge geometry. The flow is simulated by solving the incompressible Navier-Stokes equations in a general curvilinear coordinate system in stream-function/vorticity form. The Modified Strongly Implicit Procedure is the second-order-accurate, robust, and memory-conservative numerical scheme used. A time-harmonic formulation of the disturbance equations is implemented to promote a more efficient means for solving the equations. Small-amplitude velocity oscillations are imposed at the far-field boundary location to simulate a long-wavelength acoustic wave. A buffer-domain technique is implemented to eliminate wave reflection from the outflow computational boundary. The effect of angle of incidence of the impinging acoustic wave is investigated and found to produce higher receptivity coefficients than symmetric acoustic waves. The increase is found to be significantly lower than that predicted by theoretical investigations of acoustic receptivity. Detailed results of the symmetric forcing are presented in an effort to provide a database for future investigations including a term-by-term analysis of the linearized disturbance equations. Non-linear simulations are performed and the presence of harmonics generated by non-linear interaction in the leading-edge region is found. Downstream of the leading-edge region the locally parallel Orr-Sommerfeld equation is found to reproduce the characteristics of the instability waves in an accurate manner in both the linear and non-linear simulations.

Fuciarelli, David A.

51

Surface analysis of bileaflet prosthetic heart valve leaflet leading edge.  

PubMed

In 1991 and 1992, two patients presented with persistent clinical hemolysis after mitral valve replacement with bileaflet valves, in the absence of paravalvular leaks. When each valve was replaced, the hemolysis disappeared. The first valve was not examined in the laboratory owing to its loss, but it looked normal. The second valve was tested and found to have normal hemodynamics and a normal appearance by light microscopy (LM) and scanning electron microscopy (SEM), but fringe pattern interferometry (FPI) showed its leading leaflet edges to be flatter and rougher than another St. Jude Medical valves (SJMV). This led the authors to collect 17 bileaflet valves (14 SJMV and 3 Carbomedics) for examination of their surface characteristics to see if there was any correlation with hemolysis. All valves were examined by LM, SEM, and FPI. However, only FPI indicated the presence of notable differences in surface roughness and convexity of the leading leaflet edges. Further, convexity of an edge tended to vary inversely with its roughness, and the flat inlet surfaces of most leaflets were consistently less rough than the adjacent edge. The authors' hemolytic valve had one of the flattest and roughest edges of the series. Roughness of the leading edge may contribute to hemolysis by presenting an abrasive surface to the antegrade flow of blood, and by forming the sides of the gap between the leaflets, through which blood is squeezed during closed regurgitation, generating substantial shear forces and causing hemolysis. FPI is a noncontact, sensitive modality, useful in screening pyrolytic carbon surfaces but, unlike other current methods, it is reproducible, does not require modification of the surface, and causes no alteration of the surface texture. PMID:9682955

Barmada, H; Cohen, D

1998-01-01

52

The fish tail motion forms an attached leading edge vortex  

PubMed Central

The tail (caudal fin) is one of the most prominent characteristics of fishes, and the analysis of the flow pattern it creates is fundamental to understanding how its motion generates locomotor forces. A mechanism that is known to greatly enhance locomotor forces in insect and bird flight is the leading edge vortex (LEV) reattachment, i.e. a vortex (separation bubble) that stays attached at the leading edge of a wing. However, this mechanism has not been reported in fish-like swimming probably owing to the overemphasis on the trailing wake, and the fact that the flow does not separate along the body of undulating swimmers. We provide, to our knowledge, the first evidence of the vortex reattachment at the leading edge of the fish tail using three-dimensional high-resolution numerical simulations of self-propelled virtual swimmers with different tail shapes. We show that at Strouhal numbers (a measure of lateral velocity to the axial velocity) at which most fish swim in nature (approx. 0.25) an attached LEV is formed, whereas at a higher Strouhal number of approximately 0.6 the LEV does not reattach. We show that the evolution of the LEV drastically alters the pressure distribution on the tail and the force it generates. We also show that the tail's delta shape is not necessary for the LEV reattachment and fish-like kinematics is capable of stabilising the LEV. Our results suggest the need for a paradigm shift in fish-like swimming research to turn the focus from the trailing edge to the leading edge of the tail.

Borazjani, Iman; Daghooghi, Mohsen

2013-01-01

53

The fish tail motion forms an attached leading edge vortex.  

PubMed

The tail (caudal fin) is one of the most prominent characteristics of fishes, and the analysis of the flow pattern it creates is fundamental to understanding how its motion generates locomotor forces. A mechanism that is known to greatly enhance locomotor forces in insect and bird flight is the leading edge vortex (LEV) reattachment, i.e. a vortex (separation bubble) that stays attached at the leading edge of a wing. However, this mechanism has not been reported in fish-like swimming probably owing to the overemphasis on the trailing wake, and the fact that the flow does not separate along the body of undulating swimmers. We provide, to our knowledge, the first evidence of the vortex reattachment at the leading edge of the fish tail using three-dimensional high-resolution numerical simulations of self-propelled virtual swimmers with different tail shapes. We show that at Strouhal numbers (a measure of lateral velocity to the axial velocity) at which most fish swim in nature (approx. 0.25) an attached LEV is formed, whereas at a higher Strouhal number of approximately 0.6 the LEV does not reattach. We show that the evolution of the LEV drastically alters the pressure distribution on the tail and the force it generates. We also show that the tail's delta shape is not necessary for the LEV reattachment and fish-like kinematics is capable of stabilising the LEV. Our results suggest the need for a paradigm shift in fish-like swimming research to turn the focus from the trailing edge to the leading edge of the tail. PMID:23407826

Borazjani, Iman; Daghooghi, Mohsen

2013-04-01

54

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

55

Leading-edge vortex shedding from rotating wings  

NASA Astrophysics Data System (ADS)

This paper presents a numerical investigation of the leading-edge vortices generated by rotating triangular wings at Reynolds number Re = 250. A series of three-dimensional numerical simulations have been carried out using a Fourier pseudo-spectral method with volume penalization. The transition from stable attachment of the leading-edge vortex to periodic vortex shedding is explored, as a function of the wing aspect ratio and the angle of attack. It is found that, in a stable configuration, the spanwise flow in the recirculation bubble past the wing is due to the centrifugal force, incompressibility and viscous stresses. For the flow outside of the bubble, an inviscid model of spanwise flow is presented.

Kolomenskiy, Dmitry; Elimelech, Yossef; Schneider, Kai

2014-06-01

56

Applications of Euler equations to sharp edge delta wings with leading edge vortices  

NASA Technical Reports Server (NTRS)

Studies on the solution of discrete Euler equations past swept delta wing configurations with sharp leding edges are presented. Freestream Mach numbers range from zero to supersonic, although the Mach number normal to the leading edge is subsonic for all cases discussed. A few examples are given to show the application of the numerical methods to representative problems. The major dicussion is directed at the application of Computational Fluid Dynamics to the understanding of the fundamental fluid mechanic mechanisms of this class of flows.

Murman, Earll M.; Rizzi, Arthur

1986-01-01

57

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

58

Wake of forced flow around elliptical leading edge plates  

Microsoft Academic Search

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

R. Mills; J. Sheridan; K. Hourigan

2005-01-01

59

Copper Ball Bonding Advances for Leading Edge Packaging  

Microsoft Academic Search

The Graphic Processing Unit (GPU) represents the leading edge in assembly technology, eclipsing the Central Processing Unit (CPU) as the most challenging semiconductor device. This paper will explore ways in which GPUs are advancing the state-of -the-art in assembly with its low cost manufacturing requirements, high number of interconnects (now approaching 1,000 interconnects\\/device) and demanding electrical requirements. In addition to

Michael Deley; Lee Levine

2005-01-01

60

Receptivity to surface roughness near a swept leading edge  

Microsoft Academic Search

The formation of stationary crossflow vortices in a three-dimensional boundary layer due to surface roughness located near the leading edge of a swept wing is investigated using numerical solutions of the compressible Navier{Stokes equations. The numerical solutions are used to evaluate the accuracy of theoretical receptivity predictions which are based on the parallel-flow approximation. By reformulating the receptivity theory to

S. S COTT C OLLIS; SANJIVA K. L ELE

1999-01-01

61

Aerothermal Performance Constraint Analysis of Sharp Nosecaps and Leading Edges  

NASA Technical Reports Server (NTRS)

The main objective of this work is to predict the Aerothermal Performance Constraint (APC) for a class of Crew Transfer Vehicles (CTV) with shap noses and wing leading edges made out of UHTC which is a family of Ultra High Temperature Ceramics materials developed at NASA Ames. The APC is based on the theoretical temperature limit of the material which is usually encountered at the CTV nose or wing leading edge. The APC places a lower limit on the trajectory of the CTV in the altitude velocity space. The APC is used as one of the constraints in developing reentry and abort trajectories for the CTV. The trajectories are then used to generate transient thermal response of the nosecaps and wing leading edges which are represented as either a one piece of UHTC or two piece (UHTC + RCC) with perfect axial contact. The final paper will include more details about the analysis procedure and will also include results for reentry and abort design trajectories.

Rizk, Yehia; Gee, Ken

2004-01-01

62

Leading-Edge Receptivity to Oblique Acoustic Waves  

NASA Astrophysics Data System (ADS)

Numerical simulations of leading-edge acoustic receptivity are performed for a flat-plate with a modified-super-elliptic (MSE) leading edge. For small freestream amplitude, the effect of angle of incidence of the impinging wave is investigated and found to produce higher receptivity coefficients than in the symmetric case. The slope of receptivity coefficient versus angle of incidence of the impinging wave is found to be less than 1/4 of the theoretically predicted slope. This result is not explained by accounting for the finite nose radius of the 6:1 MSE since the Strouhal number based upon the nose radius for these simulations is very small and therefore theory predicts that the receptivity coefficients should be very nearly the same as those for the zero-nose-radius flat plate. There is a small oscillating tangential-velocity component at the attachment line in the simulations. Downstream of the leading-edge region, linear stability theory is found to accurately reproduce the characteristics of the instability waves. At higher, 1% freestream forcing, an instability wave generated by nonlinear interaction is found at double the frequency of the forcing.

Reed, Helen

1997-11-01

63

At the leading edge of three-dimensional cell migration  

PubMed Central

Summary Cells migrating on flat two-dimensional (2D) surfaces use actin polymerization to extend the leading edge of the plasma membrane during lamellipodia-based migration. This mode of migration is not universal; it represents only one of several mechanisms of cell motility in three-dimensional (3D) environments. The distinct modes of 3D migration are strongly dependent on the physical properties of the extracellular matrix, and they can be distinguished by the structure of the leading edge and the degree of matrix adhesion. How are these distinct modes of cell motility in 3D environments related to each other and regulated? Recent studies show that the same type of cell migrating in 3D extracellular matrix can switch between different leading edge structures. This mode-switching behavior, or plasticity, by a single cell suggests that the apparent diversity of motility mechanisms is integrated by a common intracellular signaling pathway that governs the mode of cell migration. In this Commentary, we propose that the mode of 3D cell migration is governed by a signaling axis involving cell–matrix adhesions, RhoA signaling and actomyosin contractility, and that this might represent a universal mechanism that controls 3D cell migration.

Petrie, Ryan J.; Yamada, Kenneth M.

2012-01-01

64

Leading-edge vortex solutions with large total pressure losses  

NASA Technical Reports Server (NTRS)

Computations are presented for a Lambda = 75 deg delta wing in a supersonic freestream under two conditions which lead to leading-edge vortices. For one condition, analysis of the computed vortical flow reveals a closed streamline in the core. From varying computational parameters, it appears that this is due to truncation error of the convective derivatives. For the other condition, comparisons are made with wind-tunnel data, and good agreement is noted for pitot pressure distributions, flow angles on the symmetry plane, and the position of an embedded shock. Many of the aerodynamic parameters are shown to be insensitive to grid spacing.

Murman, Earll M.; Powell, Kenneth G.; Goodsell, Aga M.; Landahl, Marten T.

1987-01-01

65

Optimization of the leading edge segment of a corrugated wing  

NASA Astrophysics Data System (ADS)

Insect wings consist of flat plates of membranes stiffened by spars. The effect of this structure is that the wings appear as corrugated surfaces when considered on chordwise sections. We know that aerodynamically efficient insects such as a dragonfly engage in fixed wing flight modes for extended periods. The analysis in the literature has shown that the aerodynamic efficiency (cl/cd) of a corrugated aerofoil is sensitive to Reynolds number (Re) and angle-of-attack (AoA), yet the conclusions established are on the basis of flow analysis on a single baseline shape only. The sample size of the aerofoils must be extended further so that the influence and merits of corrugated shape features can be established. In this work, a design-of-experiments (DoE) approach is applied to induce systematic shape perturbations on a select, off-the-shelf baseline shape one feature at a time over a set number of increments. At each shape increment, the aerodynamic forces are established using a high fidelity CFD solver. The design space is modeled at a Re of 20,000 and 34,000 and at flow angle of 4.0° to represent a Micro Air Vehicle (MAV) in glide. The results confirmed the importance of the leading and trailing edge deflections on cl/cd. At Re = 20, 000, cl/cd of a corrugated aerofoil with deflection at the leading edge region only is 16% higher than the baseline shape, and 39% higher than the flat plate. At Re = 34, 000, cl/cd performance is sensitive to the trailing edge deflection. At the optimum deflection setting, cl/cd is 18% higher than the baseline shape and 23% higher than the flat plate. The results confirm that the leading and trailing edge deflections are critical to cl/cd for a MAV in glide.

Khurana, Manas; Chahl, Javaan

2014-03-01

66

Edge Effects on Thermally Induced Stresses in Composite Laminates  

Microsoft Academic Search

Thermally induced stresses in fiber composite laminates play an important role in the strength and failure of such laminates as load carrying members. When laminates have free edges, cutouts or holes, interlaminar stress concentration will usually develop near the free-edge region under service loads. An accurate evaluation of thermally induced edge stresses will further the understanding of the laminates' behavior.

A. S. D. Wang; Frank W. Crossman

1977-01-01

67

Leading edge vortex dynamics on a pitching delta wing  

NASA Technical Reports Server (NTRS)

A study of the dynamic behavior of the leading edge vortices on a delta wing undergoing oscillatory pitching motion is presented. A sharp edge, flat plate, delta wing having a sweep angle of 70 deg was used in this investigation. The wing was sinusoidally pitched about its 1/2 chord position at reduced frequencies ranging from k = 2(pi)fc/u = 0.05 to 0.30 at chord Reynolds numbers between 90,000 and 350,000, for angle of attack ranges of 29 to 39 deg and 0 to 45 deg. During these dynamic motions, visualization of the leading edge vortices was obtained by marking the vortices with TiCl4 introduced through ports located near the model apex. The location of vortex breakdown was recorded using high speed motion picture photography. The motion picture records were analyzed to determine vortex trajectory and breakdown position as a function of angle of attack. When the wing was sinusoidally pitched, a hysteresis was observed in the location of breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing, and the phase lag between model motion and breakdown location were also determined. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases.

Lemay, S. P.; Batill, S. M.; Nelson, R. C.

1988-01-01

68

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

69

Pulsed film cooling on a turbine blade leading edge  

NASA Astrophysics Data System (ADS)

Unsteadiness in gas turbine film cooling jets may arise due to inherent unsteadiness of the flow through an engine or may be induced as a means of flow control. The traditional technique used to evaluate the performance of a steady film cooling scheme is demonstrated to be insufficient for use with unsteady film cooling and is modified to account for the cross coupling of the time dependent adiabatic effectiveness and heat transfer coefficient. The addition of a single term to the traditional steady form of the net heat flux reduction equation with time averaged quantities accounts for the unsteady effects. An experimental technique to account for the influence of the new term was devised and used to measure the influence of a pulsating jet on the net heat flux in the leading edge region of a turbine blade. High spatial resolution data was acquired in the near-hole region using infrared thermography coupled with experimental techniques that allowed application of the appropriate thermal boundary conditions immediately adjacent to the film cooling hole. The turbine blade leading edge was simulated by a half cylinder in cross flow with a blunt afterbody. The film cooling geometry consisted of a coolant hole located 21.5° from the leading edge, angled 20° to the surface and 90° from the streamwise direction. Investigated parameters include pulsation frequency, duty cycle, and waveform shape. Separate experiments were conducted in a water channel to provide visualization of the unsteady coolant propagation behavior. Further insight into the flow physics was obtained through computational simulations of the experimental apparatus. The computational results afforded time resolved flow field and net heat flux reduction data unobtainable with the experimental techniques. A technique to predict the performance of an unsteady film cooling scheme through knowledge of only the steady film cooling behavior was developed and demonstrated to be effective.

Rutledge, James L.

70

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

71

Analysis of airfoil leading-edge separation bubbles  

NASA Technical Reports Server (NTRS)

A local inviscid-viscous interaction technique was developed for the analysis of low speed airfoil leading edge transitional separation bubbles. In this analysis an inverse boundary layer finite difference analysis is solved iteratively with a Cauchy integral representation of the inviscid flow which is assumed to be a linear perturbation to a known global viscous airfoil analysis. Favorable comparisons with data indicate the overall validity of the present localized interaction approach. In addition numerical tests were performed to test the sensitivity of the computed results to the mesh size, limits on the Cauchy integral, and the location of the transition region.

Vatsa, V. N.; Carter, J. E.

1984-01-01

72

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

73

Stability of the Leading Edge Vortex on Insect Wings  

NASA Astrophysics Data System (ADS)

A defining characteristic of the flowfield associated with insect flight is a stable leading edge vortex that persists over a majority of the flapping stroke. While it is known that spanwise flow, coupled with the effect of wing rotation and interaction with the tip vortex can result in stability, the specific mechanisms by which this stability is achieved have not been clearly identified. Towards a clarification of this issue, two idealized cases are computationally simulated. First, computations of the flow over a rectangular plate in linear translation are compared with experimental data to provide both code validation and a basis for comparison with the rotational cases. Secondly, a model wing, similar in planform to a fruit fly (Drosophila), is simulated both in steady translation and in an impulsively started steady rotation at a constant angle of attack. The stability of the resulting vortex system is compared against the translational cases at various Reynolds numbers and angles of attack to better understand the role that rotation and planform shape play in the leading edge vortex development and stability.

Bush, B.; Duraisamy, K.; Baeder, J.

2007-11-01

74

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

75

Boundary Layer Leading Edge Receptivity to Sound at Incidence Angles.  

NASA Astrophysics Data System (ADS)

The leading edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier-Stokes equations in vorticity/stream function form in parabolic 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(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. We primarily investigated the effect of frequency and angle of incidence (-180^circ <= ? <= 180^circ) of the acoustic waves on the leading edge receptivity. The results at ?=0^circ were found to be in quantitative agreement with those of Haddad & Corke, and substantiated the Strouhal number scaling based on the nose radius. The results with sound waves at angles of incidence agreed qualitatively with the analysis of Hammerton & Kerschen (1992). These included a maximum receptivity at ?=90^circ, and an asymmetric variation in the receptivity with sound incidence angle, with minima at angles which were slightly less than ?=0^circ and 180^circ.

Erturk, E.; Corke, T. C.

1999-11-01

76

Leading Edge Material Thermal and Ablation Test Evaluations for Extended Range Reentry Missions.  

National Technical Information Service (NTIS)

Arc-heater tests were conducted on candidate Air Force leading edge materials for extended range reentry applications. The objectives were to obtain thermal and ablation data on leading edge materials at a swept angle representative of the operational sys...

H. L. Moody C. M. Graves D. S. Moody J. L. Deleget

1995-01-01

77

Seven hole probe measurement of leading edge vortex flows  

NASA Technical Reports Server (NTRS)

This paper discusses the use of a seven-hole probe on measurements of leading edge vortices of highly sweep delta wing planforms. Intrusive probe data taken with the pressure probe were compared with nonintrusive measurements made with laser Doppler anemometry system. In addition to probe size, the natural position of breakdown and the sweep angle of the wing are also factors in determining sensitivity of the flow to probe interference. At low angles of attach vortex breakdown does not occur in the vicinity of the model and the seven hole probe was found to yield reasonably accurate measurements. When the angle of attack of the model was increased so that vortex breakdown was near the trailing edge, introducing the probe over the wing would cause the breakdown position to move ahead of the probe. However, when breakdown naturally occurred ahead of the mid-chord of the wing the vortices were found to be less sensitive to a probe placed behind the breakdown point. Vortex breakdown on a lower swept wing is found to be more sensitive to interference. Near the breakdown region, seven hole probe measurement is less accurate due to a combination of probe interference and flow reversal.

Payne, F. M.; Ng, T. T.; Nelson, R. C.

1989-01-01

78

Method for Computing the Leading-Edge Suction in a Higher-Order Panel Method.  

National Technical Information Service (NTIS)

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...

F. E. Ehlers M. E. Manro

1984-01-01

79

A method for computing leading-edge loads  

NASA Technical Reports Server (NTRS)

In this report a formula is developed that enables the determination of the proper design load for the portion of the wing forward of the front spar. The formula is inherently rational in concept, as it takes into account the most important variables that affect the leading-edge load, although theoretical rigor has been sacrificed for simplicity and ease of application. Some empirical corrections, based on pressure distribution measurements on the PW-9 and M-3 airplanes have been introduced to provide properly for biplanes. Results from the formula check experimental values in a variety of cases with good accuracy in the critical loading conditions. The use of the method for design purposes is therefore felt to be justified and is recommended.

Rhode, Richard V; Pearson, Henry A

1933-01-01

80

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

81

Experimental and Numerical Study of CMC Leading Edges in Hypersonic Flows  

NASA Astrophysics Data System (ADS)

Future transportation concepts aim at high supersonic or hypersonic speeds, where the formerly sharp boundaries between aeronautic and aerospace applications become blurred. One of the major issues involved to high speed flight are extremely high aerothermal loads, which especially appear at the leading edges of the plane's wings and at sharp edged air intake components of the propulsion system. As classical materials like metals or simple ceramics would thermally and structurally fail here, new materials have to be applied. In this context, lightweight ceramic matrix composites (CMC) seem to be prospective candidates as they are high-temperature resistant and offer low thermal expansion along with high specific strength at elevated temperature levels. A generic leading edge model with a ceramic wing assembly with a sweep back angle of 53° was designed, which allowed for easy leading edge sample integration of different CMC materials. The samples consisted of the materials C/C-SiC (non-oxide), OXIPOL and WHIPOX (both oxide) with a nose radius of 2 mm. In addition, a sharp edged C/C-SiC sample was prepared to investigate the nose radius influence. Overall, 13 thermocouples were installed inside the entire model to measure the temperature evolution at specific locations, whereby 5 thermocouples were placed inside the leading edge sample itself. In addition, non-intrusive techniques were applied for surface temperature measurements: An infrared camera was used to measure the surface temperature distribution and at specific spots, the surface temperature was also measured by pyrometers. Following, the model was investigated in DLR's arc-heated facility L3K at a total enthalpy of 8.5 MJ/kg, Mach number of 7.8, different angles of attack and varying wing inclination angles. These experiments provide a sound basis for the simulation of aerothermally loaded CMC leading edge structures. Such fluid-structure coupled approaches have been performed by FOI, basing on a modal approach for the conduction model. Results show, that the temperature profiles are correctly depicted dependent on the model's angle of attack.

Kuhn, M.; Esser, B.; Gülhan, A.; Dalenbring, M.; Cavagna, L.

2011-08-01

82

Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings  

NASA Technical Reports Server (NTRS)

This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar flow wings. Based on a known laminar cruise airfoil that incorporated an NGAS-developed integrated slot design, this effort involved using Computational Fluid Dynamics (CFD) analysis and quality function deployment (QFD) analysis on several leading edge concepts, and subsequently down-selected to two blown leading-edge concepts for testing. A 7-foot-span AHLLE airfoil model was designed and fabricated at NGAS and then tested at the NGAS 7 x 10 Low Speed Wind Tunnel in Hawthorne, CA. The model configurations tested included: baseline, deflected trailing edge, blown deflected trailing edge, blown leading edge, morphed leading edge, and blown/morphed leading edge. A successful demonstration of high lift leading edge technology was achieved, and the target goals for improved lift were exceeded by 30% with a maximum section lift coefficient (Cl) of 5.2. Maximum incremental section lift coefficients ( Cl) of 3.5 and 3.1 were achieved for a blown drooped (morphed) leading edge concept and a non-drooped leading edge blowing concept, respectively. The most effective AHLLE design yielded an estimated 94% lift improvement over the conventional high lift Krueger flap configurations while providing laminar flow capability on the cruise configuration.

Bright, Michelle M.; Korntheuer, Andrea; Komadina, Steve; Lin, John C.

2013-01-01

83

Mechanisms of leading edge protrusion in interstitial migration  

NASA Astrophysics Data System (ADS)

While the molecular and biophysical mechanisms underlying cell protrusion on two-dimensional substrates are well understood, our knowledge of the actin structures driving protrusion in three-dimensional environments is poor, despite relevance to inflammation, development and cancer. Here we report that, during chemotactic migration through microchannels with 5??m × 5??m cross-sections, HL60 neutrophil-like cells assemble an actin-rich slab filling the whole channel cross-section at their front. This leading edge comprises two distinct F-actin networks: an adherent network that polymerizes perpendicular to cell-wall interfaces and a ‘free’ network that grows from the free membrane at the cell front. Each network is polymerized by a distinct nucleator and, due to their geometrical arrangement, the networks interact mechanically. On the basis of our experimental data, we propose that, during interstitial migration, medial growth of the adherent network compresses the free network preventing its retrograde movement and enabling new polymerization to be converted into forward protrusion.

Wilson, Kerry; Lewalle, Alexandre; Fritzsche, Marco; Thorogate, Richard; Duke, Tom; Charras, Guillaume

2013-12-01

84

Mechanisms of leading edge protrusion in interstitial migration  

PubMed Central

While the molecular and biophysical mechanisms underlying cell protrusion on two-dimensional substrates are well understood, our knowledge of the actin structures driving protrusion in three-dimensional environments is poor, despite relevance to inflammation, development and cancer. Here we report that, during chemotactic migration through microchannels with 5??m × 5??m cross-sections, HL60 neutrophil-like cells assemble an actin-rich slab filling the whole channel cross-section at their front. This leading edge comprises two distinct F-actin networks: an adherent network that polymerizes perpendicular to cell-wall interfaces and a ‘free’ network that grows from the free membrane at the cell front. Each network is polymerized by a distinct nucleator and, due to their geometrical arrangement, the networks interact mechanically. On the basis of our experimental data, we propose that, during interstitial migration, medial growth of the adherent network compresses the free network preventing its retrograde movement and enabling new polymerization to be converted into forward protrusion.

Wilson, Kerry; Lewalle, Alexandre; Fritzsche, Marco; Thorogate, Richard; Duke, Tom; Charras, Guillaume

2013-01-01

85

Characteristics of surface roughness associated with leading edge ice accretion  

NASA Technical Reports Server (NTRS)

Detailed size measurements of surface roughness associated with leading edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data was obtained from icing tests conducted in the Icing Research Tunnel (IRT) at NASA Lewis Research Center (LeRC) using a NACA 0012 airfoil. Measurements include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The height of roughness grows as the air temperature and the liquid water content increase, however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very initial stage of the ice accretion process.

Shin, Jaiwon

1994-01-01

86

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

87

Leading-edge force features of the aerodynamic finite element method.  

NASA Technical Reports Server (NTRS)

Description of a practical procedure for computing the wing leading-edge thrust distribution by the finite element method. When incorporated into a wing-body aerodynamic computer program, the technique is capable of predicting (at subsonic and supersonic speeds) the leading-edge thrust distribution (and therefore, the lateral-directional stability derivatives due to roll) and the nonlinear aerodynamic characteristics of low aspect-ratio wings with leading edge separation due to the application of suction technology.

Lan, C.-T.; Roskam, J.

1972-01-01

88

Modulation of leading edge vorticity and aerodynamic forces in flexible flapping wings.  

PubMed

In diverse biological flight systems, the leading edge vortex has been implicated as a flow feature of key importance in the generation of flight forces. Unlike fixed wings, flapping wings can translate at higher angles of attack without stalling because their leading edge vorticity is more stable than the corresponding fixed wing case. Hence, the leading edge vorticity has often been suggested as the primary determinant of the high forces generated by flapping wings. To test this hypothesis, it is necessary to modulate the size and strength of the leading edge vorticity independently of the gross kinematics while simultaneously monitoring the forces generated by the wing. In a recent study, we observed that forces generated by wings with flexible trailing margins showed a direct dependence on the flexural stiffness of the wing. Based on that study, we hypothesized that trailing edge flexion directly influences leading edge vorticity, and thereby the magnitude of aerodynamic forces on the flexible flapping wings. To test this hypothesis, we visualized the flows on wings of varying flexural stiffness using a custom 2D digital particle image velocimetry system, while simultaneously monitoring the magnitude of the aerodynamic forces. Our data show that as flexion decreases, the magnitude of the leading edge vorticity increases and enhances aerodynamic forces, thus confirming that the leading edge vortex is indeed a key feature for aerodynamic force generation in flapping flight. The data shown here thus support the hypothesis that camber influences instantaneous aerodynamic forces through modulation of the leading edge vorticity. PMID:21852729

Zhao, Liang; Deng, Xinyan; Sane, Sanjay P

2011-09-01

89

Suppression of edge cracking in layered ceramic composites by edge coating  

Microsoft Academic Search

A strategy is proposed to reduce surface tensile stresses that develop in ceramic microlaminate structures. As a specific example, surface stresses, which can lead to unwanted edge cracking, appear within a thin alumina\\/mullite layer bounded by thicker alumina layers after fabrication at some elevated temperature and subsequent cooling. A stress analysis is performed using the finite element method on a

Adam J. Monkowski; Glenn E. Beltz

2005-01-01

90

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

91

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

92

Application of a Flush Airdata Sensing System to a Wing Leading Edge (LE-FADS).  

National Technical Information Service (NTIS)

The feasibility of locating a flush airdata sensing (FADS) system on a wing leading edge where the operation of the avionics or fire control radar system will not be hindered is investigated. The leading-edge FADS system (LE-FADS) was installed on an unsw...

S. A. Whitmore T. R. Moes M. W. Czerniejewski D. A. Nichols

1993-01-01

93

Case Studies of Leading Edge Small Urban High Schools. Relevance Strategic Designs: 4. Boston Arts Academy  

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

94

Compositional variation in bullet lead manufacture.  

PubMed

The concentrations of antimony, copper, tin, arsenic, silver, bismuth, and cadmium in lead alloys produced by two smelters and one ammunition manufacturer were determined using inductively coupled plasma-atomic emission spectrometry. These element concentrations were used to measure the variations in composition of lead products that result from various processes involved in the manufacture of lead projectiles. In general, when a pot containing molten lead is used to cast a number of objects, these objects are similar, although not necessarily analytically indistinguishable in their elemental compositions. In each subsequent step in the processing of lead at the smelter and at the ammunition manufacturer, the size of an individual homogeneous melt of lead decreases as more distinct compositions are formed as a result of remelting and mixing of sources, including lead scrap. The ammunition manufacturer in this study produced at least 10 compositionally distinguishable groups of bullet wire in a 19.7-h period. The largest group could potentially be used to produce a maximum of 1.3 million compositionally indistinguishable 40 grain bullets. PMID:12353580

Koons, Robert D; Grant, Diana M

2002-09-01

95

Reducing edge delamination stresses in composite plates using multiobjective optimization  

NASA Astrophysics Data System (ADS)

This paper addresses the development of an optimization procedure for the reduction of interlaminar stresses in composite plates. The goal is to reduce the interlaminar stress trends at the free edges of composite plates subjected to a uniaxial compressive loading or a bending moment. A simplified analytical method is used for predicting the free edge delamination stresses. Ply orientations are used as design variables and constraints are imposed upon the in-plane material-axis ply stresses, the buckling load and the interlaminar normal stress at the interior of the plate. The problem is formulated with multiple design objectives and the Kreisselmeier-Steinhauser multiobjective optimization technique is used to solve the nonlinear problem. The procedure yields reductions in interlaminar stresses. Results are presented and compared with a reference or baseline design for four Gr/Ep composite plates with symmetric ply arrangements.

Ferreira, Jay M.; Chattopadhyay, Aditi; Pringnitz, Steven J.

1993-02-01

96

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

97

Edge Effects in Angle-Ply Composite Laminates  

Microsoft Academic Search

This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation tech niques and a limiting free body approach. The general solution for [±?]laminates is applied to the special case of a [±45]s graphite\\/epoxy lamin ate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio h\\/b and compared

Peter W. Hsu; Carl T. Herakovich

1977-01-01

98

Aerothermal Performance Envelopes for Hypersonic Small Radius Unswept Leading Edges and Nosetips  

NASA Technical Reports Server (NTRS)

Small radius leading edges and nosetips were utilized to minimize wave drag in early hypersonic vehicle concepts until further analysis demonstrated that extreme aerothermodynamic heating would cause severe ablation or blunting of the available thermal protection system materials. Recent studies indicate that diboride composite materials are shape stable under extreme aerothermodynamic heating at ultra high temperatures. Aerothermal performance envelopes for sharp components made from these materials are presented in this work to demonstrate the effects of convective blocking, surface catalycity, surface emissivity, and rarefied flow effects on steady state operation at altitudes from sea level to 90 km. These components are capable of steady state operation at velocities up to 7.9 km/s at altitudes near 90 km.

Kolodziej, Paul; Rasky, Daniel J. (Technical Monitor)

1995-01-01

99

Convergence of Strain Energy Release Rate Components for Edge-Delaminated Composite Laminates.  

National Technical Information Service (NTIS)

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strai...

I. S. Raju J. H. Crews M. A. Aminpour

1987-01-01

100

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

101

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

102

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

103

Delta wing with blunted leading edges at angle of attack in hypersonic flow  

NASA Astrophysics Data System (ADS)

A hypersonic rarefied diatomic gas flow around a delta wing with a blunted leading edge at an angle of attack of 10° is considered. Flow fields on the leeward and windward sides are obtained. Specific features of surface distributions of thermal characteristics on the side edge are studied.

Vashchenkov, P.; Kashkovsky, A.; Ivanov, M.

2013-06-01

104

Reynolds Number Effects on Leading Edge Radius Variations of a Supersonic Transport at Transonic Conditions  

NASA Technical Reports Server (NTRS)

A computational study focused on leading-edge radius effects and associated Reynolds number sensitivity for a High Speed Civil Transport configuration at transonic conditions was conducted as part of NASA's High Speed Research Program. The primary purposes were to assess the capabilities of computational fluid dynamics to predict Reynolds number effects for a range of leading-edge radius distributions on a second-generation supersonic transport configuration, and to evaluate the potential performance benefits of each at the transonic cruise condition. Five leading-edge radius distributions are described, and the potential performance benefit including the Reynolds number sensitivity for each is presented. Computational results for two leading-edge radius distributions are compared with experimental results acquired in the National Transonic Facility over a broad Reynolds number range.

Rivers, S. M. B.; Wahls, R. A.; Owens, L. R.

2001-01-01

105

Aerothermal Performance Constraints for Hypervelocity Small Radius Unswept Leading Edges and Nosetips.  

National Technical Information Service (NTIS)

Small radius leading edges and nosetips were utilized to minimize wave drag in early hypervelocity vehicle concepts until further analysis demonstrated that extreme aerothermodynamic heating would cause severe ablation or blunting of the available thermal...

P. Kolodziej

1997-01-01

106

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

107

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.

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

2013-01-01

108

Numerical Study of Leading-Edge Heat Transfer Under Free-Stream Turbulence.  

National Technical Information Service (NTIS)

The effect of incoming organized disturbance and free-stream turbulence on leading-edge heat transfer is investigated numerically. An optimum length scale is found to give the maximum heat transfer enhancement for the organized disturbance case. Beyond th...

S. K. Lele Z. Xiong

2000-01-01

109

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

110

Theory of step on leading edge of negative corona current pulse  

NASA Astrophysics Data System (ADS)

Theoretical models taking into account different feedback source terms (e.g., ion-impact electron emission, photo-electron emission, field emission, etc) have been proposed for the existence and explanation of the shape of negative corona current pulse, including the step on the leading edge. In the present work, a negative corona current pulse with the step on the leading edge is obtained in the presence of ion-impact electron emission feedback source only. The step on the leading edge is explained in terms of the plasma formation process and enhancement of the feedback source. Ionization wave-like movement toward the cathode is observed after the step. The conditions for the existence of current pulse, with and without the step on the leading edge, are also described. A qualitative comparison with earlier theoretical and experimental work is also included.

Gupta, Deepak K.; Mahajan, Sangeeta; John, P. I.

2000-03-01

111

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

112

Design and fabrication of a high temperature leading edge heating array, phase 1  

NASA Technical Reports Server (NTRS)

Progress during a Phase 1 program to design a high temperature heating array is reported for environmentally testing full-scale shuttle leading edges (30 inch span, 6 to 15 inch radius) at flight heating rates and pressures. Heat transfer analyses of the heating array, individual modules, and the shuttle leading edge were performed, which influenced the array design, and the design, fabrication, and testing of a prototype heater module.

1972-01-01

113

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

114

Rapid de-localization of actin leading edge components with BDM treatment  

PubMed Central

Background 2,3-Butanedione monoxime (BDM) has been widely used as a non-muscle myosin inhibitor to investigate the role of non-muscle myosinII in the process of actin retrograde flow and other actin cytoskeletal processes. Recent reports show that BDM does not inhibit any non-muscle myosins so far tested, including nm-myosinII, prompting the question, how were these process affected in BDM studies? Results We have found that treatment of mammalian cells with BDM for only 1 min blocks actin incorporation at the leading edge in a permeabilized cell system. We show that inhibition of actin incorporation occurs through de-localization of leading edge proteins involved in actin polymerization – the Arp2/3 complex, WAVE, and VASP – that de-localize concomitantly with the leading edge actin network. Conclusion De-localization of actin leading edge components by BDM treatment is a newly described effect of this compound. It may explain many of the results previously ascribed to inhibition of non-muscle myosinII by BDM, particularly in studies of leading edge dynamics. Though this effect of BDM is intriguing, future studies probing actin dynamics at the leading edge should use more potent and specific inhibitors.

Yarrow, Justin C; Lechler, Terry; Li, Rong; Mitchison, Timothy J

2003-01-01

115

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

116

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

117

Formation of Leading-Edge Pinholes in the Space Shuttle Wings Investigated  

NASA Technical Reports Server (NTRS)

The space shuttle wing leading edge and nose cap are composed of a carbon/carbon composite that is protected by silicon carbide. The coefficient of thermal expansion mismatch leads to cracks in the silicon carbide. The outer coating of the silicon carbide is a sodium-silicate-based glass that becomes fluid at the shuttles high reentry temperatures and fills these cracks. Small pinholes roughly 0.1 mm in diameter have been observed on these materials after 12 or more flights. These pinholes have been investigated by researchers at the NASA Johnson Space Center, Rockwell International, the Boeing Company, Lockheed Martin Corporation, and the NASA Glenn Research Center at Lewis Field to determine the possible sources and the extent of damage. A typical pinhole is illustrated in the photomicrographs. These pinholes are found primarily on the wing leading edges and not on the nose cap, which is covered when the orbiter is on the launch pad. The pinholes are generally associated with a bead of zincrich glass. Examination of the orbiter and launch structure indicates that weathering paint on the launch structure leads to deposits of zinc-containing paint flakes on the wing leading edge. These may become embedded in the crevices of the wing leading edge and form the observed zinc-rich glass. Laboratory experiments indicate that zinc oxide reacts vigorously with the glass coating on the silicon carbide. Thus, it is likely that this is the reaction that leads to pinhole formation (Christensen, S.V.: Reinforced Carbon/Carbon Pin Hole Formation Through Zinc Oxide Attack. Rockwell International Internal Letter, RDW 96 057, May 1996). Cross-sectional examination of pinholes suggests that they are enlarged thermal expansion mismatch cracks. This is illustrated in the photomicrographs. A careful microstructural analysis indicates that the pinhole walls consist of layers of zinc-containing glass. Thus, pinholes are likely formed by zinc oxide particles lodging in crevices and forming a corrosive zinc-rich glass that enlarges existing cracks. Having established the likely source of the pinholes, we next needed to model the damage. Our concern was that if a pinhole went through the silicon carbide to the carbon/carbon substrate, oxygen would have a clear path to oxidize the carbon at high temperatures. This possibility was examined with studies in a laboratory furnace. An ultrasonic drill was used to make artificial pinholes in a sample of protected carbon/carbon. After exposure, the specimens were weighed and cross-sectioned to quantify the extent of oxidation below the pinhole. The results at higher temperatures showed good agreement with a simple diffusion-control model. This model is based on the two-step oxidation of carbon to carbon monoxide and carbon dioxide. The fluxes are illustrated in the final figure. The model indicates a strong dependence on pinhole diameter. For smaller diameters and short times, the oxidation of carbon is very limited.

Jacobson, Nathan S.

2000-01-01

118

Experimental investigation of cut-edge effect on mechanical properties of three-dimensional braided composites  

Microsoft Academic Search

Experimental characterization of the effect of cut-edge on the tensile, compressive and flexure properties in the braiding direction of the 3D braided composites is presented. The geometrical microstructure models of the uncut-edge and cut-edge composites are established for calculating the remainder lengths of braider yarns in the composites. The integrity of fiber architecture as reinforcement is destroyed for the cut-edge

Jialu Li; Yanan Jiao; Ying Sun; Limei Wei

2007-01-01

119

Interchange Instability at the Leading Edge of Reconnection Jets  

NASA Astrophysics Data System (ADS)

The leading part of a reconnection jet is known to be unstable to an interchange instability as the jet interacts with the standing plasma ahead of it. We have conducted three-dimensional MHD and Hall-MHD simulations and have clarified the nature of this instability. From MHD simulation results, we have found the driving mechanism of the instability to be essentially the same as the Richtmyer-Meshkov instability that grows at colliding fluid interfaces producing mushroom-like pattern of the magnetic normal component on the current sheet plane. By comparing a number of single-mode runs, the growth speeds of the mushrooms are compared and we find the shorter wavelength mode to grow faster. While the driving mechanism seems to stay the same, Hall-MHD simulation results show more complicated structures and development to turbulence-like state is observed even when starting from a single mode initial disturbance. We have also found the fastest growing wavelength to show quite a peculiar feature in Hall-MHD: Shorter wavelenght is preferred as the thickness of the current sheet is increased.

TanDokoro, R.; Fujimoto, M.; Nakamura, M.

2001-12-01

120

Shuttle Wing Leading Edge Root Cause NDE Team Findings and Implementation of Quantitative Flash Infrared Thermography  

NASA Technical Reports Server (NTRS)

Comparison metrics can be established to reliably and repeatedly establish the health of the joggle region of the Orbiter Wing Leading Edge reinforced carbon carbon (RCC) panels. Using these metrics can greatly reduced the man hours needed to perform, wing leading edge scanning for service induced damage. These time savings have allowed for more thorough inspections to be preformed in the necessary areas with out affecting orbiter flow schedule. Using specialized local inspections allows for a larger margin of safety by allowing for more complete characterizations of panel defects. The presence of the t-seal during thermographic inspection can have adverse masking affects on ability properly characterize defects that exist in the joggle region of the RCC panels. This masking affect dictates the final specialized inspection should be preformed with the t-seal removed. Removal of the t-seal and use of the higher magnification optics has lead to the most effective and repeatable inspection method for characterizing and tracking defects in the wing leading edge. Through this study some inadequacies in the main health monitoring system for the orbiter wing leading edge have been identified and corrected. The use of metrics and local specialized inspection have lead to a greatly increased reliability and repeatable inspection of the shuttle wing leading edge.

Burke, Eric R.

2009-01-01

121

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

122

Extension of leading-edge-suction analogy to wings with separated flow around the side edges at subsonic speeds  

NASA Technical Reports Server (NTRS)

A method for determining the lift, drag, and pitching moment for wings which have separated flow at the leading and side edges with subsequently reattached flow downstream and inboard is presented. Limiting values of the contribution to lift of the side-edge reattached flow are determined for rectangular wings. The general behavior of this contribution is computed for rectangular, cropped-delta, cropped-diamond, and cropped-arrow wings. Comparisons of the results of the method and experiment indicate reasonably good correlation of the lift, drag, and pitching moment for a wide planform range. The agreement of the method with experiment was as good as, or better than, that obtained by other methods. The procedure is computerized and is available from COSMIC as NASA Langley computer program A0313.

Lamar, J. E.

1974-01-01

123

Interplay between phosphoinositide lipids and calcium signals at the leading edge of chemotaxing ameboid cells.  

PubMed

The chemotactic migration of eukaryotic ameboid cells up concentration gradients is among the most advanced forms of cellular behavior. Chemotaxis is controlled by a complex network of signaling proteins bound to specific lipids on the cytoplasmic surface of the plasma membrane at the front of the cell, or the leading edge. The central lipid players in this leading edge signaling pathway include the phosphoinositides PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3), both of which play multiple roles. The products of PI(4,5)P2 hydrolysis, diacylglycerol (DAG) and Ins(1,4,5)P3 (IP3), are also implicated as important players. Together, these leading edge phosphoinositides and their degradation products, in concert with a local Ca(2+) signal, control the recruitment and activities of many peripheral membrane proteins that are crucial to the leading edge signaling network. The present critical review summarizes the current molecular understanding of chemotactic signaling at the leading edge, including newly discovered roles of phosphoinositide lipids and Ca(2+), while highlighting key questions for future research. PMID:24451847

Falke, Joseph J; Ziemba, Brian P

2014-09-01

124

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

125

Acoustic Receptivity of Mach 4.5 Boundary Layer with Leading- Edge Bluntness  

NASA Technical Reports Server (NTRS)

Boundary layer receptivity to two-dimensional slow and fast acoustic waves is investigated by solving Navier-Stokes equations for Mach 4.5 flow over a flat plate with a finite-thickness leading edge. Higher order spatial and temporal schemes are employed to obtain the solution whereby the flat-plate leading edge region is resolved by providing a sufficiently refined grid. The results show that the instability waves are generated in the leading edge region and that the boundary-layer is much more receptive to slow acoustic waves (by almost a factor of 20) as compared to the fast waves. Hence, this leading-edge receptivity mechanism is expected to be more relevant in the transition process for high Mach number flows where second mode instability is dominant. Computations are performed to investigate the effect of leading-edge thickness and it is found that bluntness tends to stabilize the boundary layer. Furthermore, the relative significance of fast acoustic waves is enhanced in the presence of bluntness. The effect of acoustic wave incidence angle is also studied and it is found that the receptivity of the boundary layer on the windward side (with respect to the acoustic forcing) decreases by more than a factor of 4 when the incidence angle is increased from 0 to 45 deg. However, the receptivity coefficient for the leeward side is found to vary relatively weakly with the incidence angle.

Malik, Mujeeb R.; Balakumar, Ponnampalam

2007-01-01

126

The three-dimensional leading-edge vortex of a 'hovering' model hawkmoth  

PubMed Central

Recent flow visualisation experiments with the hawkmoth, Manduca sexta, revealed small but clear leading-edge vortex and a pronounced three-dimensional flow. Details of this flow pattern were studied with a scaled-up, robotic insect ('the flapper') that accurately mimicked the wing movements of a hovering hawkmoth. Smoke released from the leading edge of the flapper wing confirmed the existence of a small, strong and stable leading-edge vortex, increasing in size from wingbase to wingtip. Between 25 and 75 per cent of the wing length, its diameter increased approximately from 10 to 50 per cent of the wing chord. The leading-edge vortex had a strong axial flow veolocity, which stabilized it and reduced its diamater. The vortex separated from the wing at approximately 75 per cent of the wing length and thus fed vorticity into a large, tangled tip vortex. If the circulation of the leading-edge vortex were fully used for lift generation, it could support up to two-thirds of the hawkmoth's weight during the downstroke. The growth of this circulation with time and spanwise position clearly identify dynamic stall as the unsteady aerodynamic mechanism responsible for high lift production by hovering hawkmoths and possibly also by many other insect species.

Berg, C. van den; Ellington, C.P.

1997-01-01

127

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

128

The Performance of Finite-span Hydrofoils with Humpback Whale-like Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

The effects of leading edge protuberances on the lift and drag performance of finite-span hydrofoils were examined in a series of water tunnel experiments. The leading edge protuberances are analogous to the tubercles on humpback whale pectoral flippers. The hydrofoils have a rectangular planform and an aspect ratio of 4. The hydrofoil section profile is based on NACA 63(4)-021, and the leading edge has a sinusoidal geometry with constant amplitude and wavelength. The hydrofoil angle of attack was varied up to 30 , and the freestream velocity ranged from 1.8 to 5.4 m/s. Results indicate that the hydrofoils with leading edge protuberances do not stall in the traditional manner. Below 12 lift increased linearly with angle of attack. Beyond this angle, the lift either attained a nearly constant value or increased slowly up to 30 depending on the Reynolds number. Drag increased continuously with the angle of attack, and was not dependent on the Reynolds number. These observations are consistent with our previous infinite span hydrofoil data, and may be explained in terms of the flow modifications created by the leading edge protuberances.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2010-11-01

129

Receptivity to Sound of an Elliptic Leading Edge on a Flat Plate.  

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(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. The motivation for the work comes from physical experiments by Wei(M.S. Thesis, Arizona State Univ., 1994) and Rasmussen(M.S. Thesis, Arizona State Univ., 1992) for flat plates with elliptic leading edges, which showed frequency bands of higher Branch I receptivity. We investigated the same conditions in our simulations, as well as on a parabolic leading edge. The numerical simulations documented higher receptivity in frequency bands which were similar to the experiments. These however did not appear for the parabolic body. The results suggest an influence of the elliptic leading-edge/flat-plate joint as an additional site of receptivity which, along with the leading edge, provides a wave-length selection mechanism which favors certain frequencies through linear superposition.

Wanderley, J.; Corke, T. C.

1998-11-01

130

The Influence of Clocking Angle of the Projectile on the Simulated Impact Response of a Shuttle Leading Edge Wing Panel  

NASA Technical Reports Server (NTRS)

An analytical study was conducted to determine the influence of clocking angle of a foam projectile impacting a space shuttle leading edge wing panel. Four simulations were performed using LS-DYNA. The leading edge panels are fabricated of multiple layers of reinforced carbon-carbon (RCC) material. The RCC material was represented using Mat 58, which is a material property that can be used for laminated composite fabrics. Simulations were performed of a rectangular-shaped foam block, weighing 0.23-lb., impacting RCC Panel 9 on the top surface. The material properties of the foam were input using Mat 83. The impact velocity was 1,000 ft/s along the Orbiter X-axis. In two models, the foam impacted on a corner, in one model the foam impacted the panel initially on the 2-in.-long edge, and in the last model the foam impacted the panel on the 7-in.- long edge. The simulation results are presented as contour plots of first principal infinitesimal strain and time history plots of contact force and internal and kinetic energy of the foam and RCC panel.

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

2005-01-01

131

The contribution of the leading edge vortex for the total lift in small insect flight  

NASA Astrophysics Data System (ADS)

The existence of a leading edge vortex in small insect flight is studied, and its importance for the generation of lift is investigated. A 2D approximation of small insect flight is calculated with a high-order, immersed boundary, incompressible Navier-Stokes flow solver. The simulated motion of the model wing is a simplification of the flight of Drosophila melanogaster, and was done in line with previous numerical simulations. This study uses results from the time-periodic steady state regime. Above the critical Reynolds number for which flapping flight is possible, vortices are alternately shed during wing translation. Before the leading edge vortex is shed, it remains close to the leading edge region for a considerable part of the wing translation. This attachment can be a significant mechanism for the augmentation of lift in 2D flapping flight.

Ferreira de Sousa, Paulo; Allen, James

2007-03-01

132

Test and Analysis Correlation of Form Impact onto Space Shuttle Wing Leading Edge RCC Panel 8  

NASA Technical Reports Server (NTRS)

Soon after the Columbia Accident Investigation Board (CAIB) began their study of the space shuttle Columbia accident, "physics-based" analyses using LS-DYNA were applied to characterize the expected damage to the Reinforced Carbon-Carbon (RCC) leading edge from high-speed foam impacts. Forensic evidence quickly led CAIB investigators to concentrate on the left wing leading edge RCC panels. This paper will concentrate on the test of the left-wing RCC panel 8 conducted at Southwest Research Institute (SwRI) and the correlation with an LS-DYNA analysis. The successful correlation of the LS-DYNA model has resulted in the use of LS-DYNA as a predictive tool for characterizing the threshold of damage for impacts of various debris such as foam, ice, and ablators onto the RCC leading edge for shuttle return-to-flight.

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

2004-01-01

133

Improved Method for Prediction of Attainable Wing Leading-Edge Thrust  

NASA Technical Reports Server (NTRS)

Prediction of the loss of wing leading-edge thrust and the accompanying increase in drag due to lift, when flow is not completely attached, presents a difficult but commonly encountered problem. A method (called the previous method) for the prediction of attainable leading-edge thrust and the resultant effect on airplane aerodynamic performance has been in use for more than a decade. Recently, the method has been revised to enhance its applicability to current airplane design and evaluation problems. The improved method (called the present method) provides for a greater range of airfoil shapes from very sharp to very blunt leading edges. It is also based on a wider range of Reynolds numbers than was available for the previous method. The present method, when employed in computer codes for aerodynamic analysis, generally results in improved correlation with experimental wing-body axial-force data and provides reasonable estimates of the measured drag.

Carlson, Harry W.; McElroy, Marcus O.; Lessard, Wendy B.; McCullers, L. Arnold

1996-01-01

134

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

135

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

136

An analytical design procedure for the determination of effective leading edge extensions on thick delta wings  

NASA Technical Reports Server (NTRS)

An analytical design procedure for leading edge extensions (LEE) was developed for thick delta wings. This LEE device is designed to be mounted to a wing along the pseudo-stagnation stream surface associated with the attached flow design lift coefficient of greater than zero. The intended purpose of this device is to improve the aerodynamic performance of high subsonic and low supersonic aircraft at incidences above that of attached flow design lift coefficient, by using a vortex system emanating along the leading edges of the device. The low pressure associated with these vortices would act on the LEE upper surface and the forward facing area at the wing leading edges, providing an additional lift and effective leading edge thrust recovery. The first application of this technique was to a thick, round edged, twisted and cambered wing of approximately triangular planform having a sweep of 58 deg and aspect ratio of 2.30. The panel aerodynamics and vortex lattice method with suction analogy computer codes were employed to determine the pseudo-stagnation stream surface and an optimized LEE planform shape.

Ghaffari, F.; Chaturvedi, S. K.

1984-01-01

137

Reynolds Number and Leading-Edge Bluntness Effects on a 65 Deg Delta Wing  

NASA Technical Reports Server (NTRS)

A 65 deg delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at subsonic speeds (M = 0.4) from this data set. The results show significant effects of both these parameters on the onset and progression of leading-edge vortex separation.

Luckring, J. M.

2002-01-01

138

Transonic Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing  

NASA Technical Reports Server (NTRS)

A 65 degree delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated a systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at transonic speeds (M = 0.85) from this data set. The results show significant effects of both these parameters on the onset and progression of leading edge vortex separation.

Luckring, J. M.

2003-01-01

139

Transonic Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing  

NASA Technical Reports Server (NTRS)

A 65 deg delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated a systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at transonic speeds (M = 0.85) from this data set. The results show significant effects of both these parameters on the onset and progression of leading- edge vortex separation.

Luckring, J. M.

2003-01-01

140

Transonic Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing  

NASA Technical Reports Server (NTRS)

A 65 deg delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated a systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at transonic speeds (M=0.85) from this data set. The results show significant effects of both these parameters on the onset and progression of leading-edge vortex separation.

Luckring, J. M.

2003-01-01

141

Reynolds Number, Compressibility, and Leading-Edge Bluntness Effects on Delta-Wing Aerodynamics  

NASA Technical Reports Server (NTRS)

An overview of Reynolds number, compressibility, and leading edge bluntness effects is presented for a 65 degree delta wing. The results of this study address both attached and vortex-flow aerodynamics and are based upon a unique data set obtained in the NASA-Langley National Transonic Facility (NTF) for i) Reynolds numbers ranging from conventional wind-tunnel to flight values, ii) Mach numbers ranging from subsonic to transonic speeds, and iii) leading-edge bluntness values that span practical slender wing applications. The data were obtained so as to isolate the subject effects and they present many challenges for Computational Fluid Dynamics (CFD) studies.

Luckring, James M.

2004-01-01

142

Experimental study of delta wing leading-edge devices for drag reduction at high lift  

NASA Technical Reports Server (NTRS)

The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred.

Johnson, T. D., Jr.; Rao, D. M.

1982-01-01

143

Impingement cooling with film coolant extraction in the airfoil leading edge regions  

NASA Astrophysics Data System (ADS)

An extensive experimental study is conducted to determine the heat transfer characteristics of arrays of air jets impinging on perforated target surfaces in turbine blade leading edge regions by six large-scale models. The relations of pressure loss and Nusselt number to jet Reynolds number are obtained in a wide range of parameter combinations of interest in cooled airfoil practice for various models, respectively. These parameter combinations are covered in a test matrix, including combinations of variations in jet Reynolds number, airfoil leading edge curvature radius-to-diameter ratio, jet pitch-to-diameter ratio, and jet impingement gap-to-diameter ratio.

Li, Liguo; Li, Zhaohui

144

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

145

Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing  

NASA Technical Reports Server (NTRS)

A 65 degree delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at subsonic speeds (M = 0.4) from this data set. The results show significant effects of both these parameters on the onset and progression of leading-edge vortex separation.

Luckring, J. M.

2002-01-01

146

Effect of leading-edge geometry on boundary-layer receptivity to freestream sound  

NASA Technical Reports Server (NTRS)

The receptivity to freestream sound of the laminar boundary layer over a semi-infinite flat plate with an elliptic leading edge is simulated numerically. The incompressible flow past the flat plate is computed by solving the full Navier-Stokes equations in general curvilinear coordinates. A finite-difference method which is second-order accurate in space and time is used. Spatial and temporal developments of the Tollmien-Schlichting wave in the boundary layer, due to small-amplitude time-harmonic oscillations of the freestream velocity that closely simulate a sound wave travelling parallel to the plate, are observed. The effect of leading-edge curvature is studied by varying the aspect ratio of the ellipse. The boundary layer over the flat plate with a sharper leading edge is found to be less receptive. The relative contribution of the discontinuity in curvature at the ellipse-flat-plate juncture to receptivity is investigated by smoothing the juncture with a polynomial. Continuous curvature leads to less receptivity. A new geometry of the leading edge, a modified super ellipse, which provides continuous curvature at the juncture with the flat plate, is used to study the effect of continuous curvature and inherent pressure gradient on receptivity.

Lin, Nay; Reed, Helen L.; Saric, W. S.

1991-01-01

147

Visualization of the separation and subsequent transition near the leading edge of airfoils  

NASA Technical Reports Server (NTRS)

A visual study was performed using the low speed smoke wind tunnels with the objective of obtaining a better understanding of the structure of leading edge separation bubbles on airfoils. The location of separation, transition and reattachment for a cylindrical nose constant-thickness airfoil model were obtained from smoke photographs and surface oil flow techniques. These data, together with static pressure distributions along the leading edge and upper surface of the model, produced the influence of Reynolds number, angle of attack, and trailing edge flap angle on the size and characteristics of the bubble. Additional visual insight into the unsteady nature of the separation bubble was provided by high speed 16 mm movies. The 8 mm color movies taken of the surface oil flow supported the findings of the high speed movies and clearly showed the formation of a scalloped spanwise separation line at the higher Reynolds number.

Arena, A. V.; Mueller, T. J.

1978-01-01

148

Critique of the Hughes Aircraft shuttle Ku band leading edge bit synchronizer  

NASA Technical Reports Server (NTRS)

A bit synchronizer is analyzed via timing diagrams in a noise-free environment. It is believed that this new bit synchronizer will track the rising edge of the data bits with 25% asymmetry and up to a 90 deg phase shift between the received clock and data bit timing. In addition, the data bits will be demodulated correctly. It is not true that phase shifts larger than 90 deg will necessarily be corrected by this bit synchronizer. However, the specifications currently require the loop to operate over only a + or - 75 deg phase shift between the received data stream leading edges and the bit synchronizer leading edges; consequently, there should be no problem.

Holmes, J. K.

1980-01-01

149

Ultra-High Temperature Ceramic Composites for Leading Edges.  

National Technical Information Service (NTIS)

Ultra-high 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 UHTC. If these deficiencies are overcome...

S. R. Levine M. Singh E. J. Opila J. A. Lorincz J. Petko D. T. Ellerby M. J. Gasch

2003-01-01

150

Ultra-High Temperature Ceramic Composites for Leading Edges-2004.  

National Technical Information Service (NTIS)

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 UHTC. If these deficiencies are overcome,...

S. R. Levine E. J. Opila J. A. Lorincz M. Singh R. C. Robinson

2004-01-01

151

PIV Analysis of a Delta Wing Flow with or without LEX(Leading Edge Extension)  

Microsoft Academic Search

Highly swept leading edge extensions(LEX) applied to delta wings have greatly improved the subsonic maneuverability of contemporary fighters. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of

Jung-Hwan KIM; Beom-Seok KIM

152

Method for Computing the Core Flow in Three-Dimensional Leading-Edge Vortices.  

National Technical Information Service (NTIS)

A theory is presented for calculating the flow in the core of a separation-induced leading-edge vortex. The method is based on matching inner and outer representations of the vortex. The inner model of the vortex is based on the quasicylindrical Navier-St...

J. M. Luckring

1985-01-01

153

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

154

Flow Visualization Study of Passive Flow Control Features on a Film- Cooled Turbine Blade Leading Edge.  

National Technical Information Service (NTIS)

A flow visualization study was conducted on a model of a film-cooled turbine blade leading edge in a closed-loop water channel at ReD = 30k. The model consisted of an 8.89 cm diameter half cylinder with flat afterbody joined at the ninety-degree point. A ...

D. R. Carroll

2009-01-01

155

Finite element analysis of large wavelength antenna radome problems for leading edge and radar phased arrays  

Microsoft Academic Search

A method for determining the RF performance from antenna radome configurations based on a frequency-domain finite-element method is presented. The application of this analysis on the design of antenna arrays in aircraft leading edges and radar radomes is discussed. The modeled antenna array elements can be driven with arbitrary amplitude and phase weighting for sidelobe tapering and phased steering of

Mark J. Povinelli; John D'Angelo

1991-01-01

156

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

National Technical Information Service (NTIS)

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 t...

R. C. Robinson K. S. Hatton

2000-01-01

157

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

158

New American High Schools: Profiles of the Nation's Leading Edge Schools.  

ERIC Educational Resources Information Center

This booklet profiles "leading edge" schools committed to ensuring that all students meet challenging academic standards and are prepared for college and careers. In 1996, these 10 New American High Schools were chosen by the U.S. Department of Education for their innovation and commitment to academic excellence. As these award-winning,…

Department of Education, Washington, DC.

159

Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings.  

National Technical Information Service (NTIS)

A survey is presented of factors affecting blunt leading-edge separation for swept and semi-slender wings. This class of separation often results in the onset and progression of separation-induced vortical flow over a slender or semi-slender wing. The ter...

J. M. Luckring

2010-01-01

160

Closed-loop control of leading-edge and tip vortices for small UAV  

Microsoft Academic Search

Summary We present plans and preliminary results for a recently initiated multidis- ciplinary research effort aimed at closed-loop control of three-dimensional leading edge and tip vortices on low aspect ratio wings relevant to micro and small unmanned air vehicles. The goal of control is to extend the parameter space for which steady lift can be maintained at high angles of

Tim Colonius; Clarence W. Rowley; Gilead Tadmor; David R. Williams; Kunihiko Taira; Will B. Dickson; Morteza Gharib; Michael Dickinson

161

Leading-edge tubercles delay stall on humpback whale ŃMegaptera novaeangliaeÖ flippers  

Microsoft Academic Search

The humpback whale ~Megaptera novaeangliae! is exceptional among the baleen whales in its ability to undertake acrobatic underwater maneuvers to catch prey. In order to execute these banking and turning maneuvers, humpback whales utilize extremely mobile flippers. The humpback whale flipper is unique because of the presence of large protuberances or tubercles located on the leading edge which gives this

D. S. Miklosovic; M. M. Murray; L. E. Howle

2004-01-01

162

Project 2000-3 Leading Edge Enterprise: Insights into Employment and Training Practices. Working Paper.  

ERIC Educational Resources Information Center

Leading-edge firms (LEFs)--at the forefront of their industry in terms of growth or market share--may influence skill development through diffusion of technology, products, or practices and use of market power to set standards or change customer businesses. Study of LEFs can identify the type and mix of skills needed in the industry. LEFs are…

Long, Michael; Fischer, John

163

Space shuttle wing leading edge heating environment prediction derived from development flight data  

NASA Technical Reports Server (NTRS)

An analytical program is in progress at Rockwell International to revise wing leading edge heating predictions in order to improve correlation with STS-1 to -5 flight radiometer data. This paper discusses the methods that have been used to improve agreement between prediction and flight and summarizes the aerodynamic correlations which, when updated, will be used to analyze future orbiter missions.

Cunningham, J. A.; Haney, J. W., Jr.

1983-01-01

164

Integrin-mediated Protein Kinase A Activation at the Leading Edge of Migrating Cells  

PubMed Central

cAMP-dependent protein kinase A (PKA) is important in processes requiring localized cell protrusion, such as cell migration and axonal path finding. Here, we used a membrane-targeted PKA biosensor to reveal activation of PKA at the leading edge of migrating cells. Previous studies show that PKA activity promotes protrusion and efficient cell migration. In live migrating cells, membrane-associated PKA activity was highest at the leading edge and required ligation of integrins such as ?4?1 or ?5?1 and an intact actin cytoskeleton. ?4 integrins are type I PKA-specific A-kinase anchoring proteins, and we now find that type I PKA is important for localization of ?4?1 integrin-mediated PKA activation at the leading edge. Accumulation of 3? phosphorylated phosphoinositides [PtdIns(3,4,5)P3] products of phosphatidylinositol 3-kinase (PI3-kinase) is an early event in establishing the directionality of migration; however, polarized PKA activation did not require PI3-kinase activity. Conversely, inhibition of PKA blocked accumulation of a PtdIns(3,4,5)P3-binding protein, the AKT-pleckstrin homology (PH) domain, at the leading edge; hence, PKA is involved in maintaining cell polarity during migration. In sum, we have visualized compartment-specific PKA activation in migrating cells and used it to reveal that adhesion-mediated localized activation of PKA is an early step in directional cell migration.

Lim, Chinten J.; Kain, Kristin H.; Tkachenko, Eugene; Goldfinger, Lawrence E.; Gutierrez, Edgar; Allen, Michael D.; Groisman, Alex; Zhang, Jin

2008-01-01

165

First experimental assessment of RCS plume-flow field interaction on Hermes leading edge thruster configuration  

Microsoft Academic Search

Glow discharge flow visualization experiments are demonstrated which have been performed to enable a first assessment of the HERMES 1.0 leading edge thruster configuration concerning interference between the thruster plumes of the reaction control system (RCS) and the surrounding flow field. The results of the flow visualization tests are presented in exemplary selected photographs. Additional Pitot pressure measurements support assumptions

T. Poertner

1993-01-01

166

A role for actin arcs in the leading edge advance of migrating cells  

PubMed Central

The migration of epithelial cells requires coordination of two actin modules at the leading edge: one in the lamellipodium and one in the lamella. How the two modules connect mechanistically to regulate directed edge motion is not understood. Using a combination of live-cell imaging and photoactivation approaches, we demonstrate that the actin network of the lamellipodium evolves spatio-temporally into the lamella. This occurs during the retraction phase of edge motion when myosin II redistributes to the cell edge and condenses the lamellipodial-actin into an arc-like bundle (i.e., actin arc) parallel to the edge. The newly formed actin arc moves rearward and couples to focal adhesions as it enters the lamella. We propose net edge extension occurs by nascent focal adhesions advancing the site at which new actin arcs slow down and form the base of the next protrusion event. The actin arc thus serves as a structural element underlying the temporal and spatial connection between the lamellipodium and lamella to drive directed cell motion.

Burnette, Dylan T.; Manley, Suliana; Sengupta, Prabuddha; Sougrat, Rachid; Davidson, Michael W.; Kachar, Bechara; Lippincott-Schwartz, Jennifer

2013-01-01

167

Modelling bird impacts on an aircraft wing – Part 1: Material modelling of the fibre metal laminate leading edge material with continuum damage mechanics  

Microsoft Academic Search

In a collaborative research project, aircraft wing leading edge structures with a glass-based Fibre Metal Laminate (FML) skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. Fibre Metal Laminates have layers of aluminium alloy and high strength glass fibre composite and have been reported to possess excellent impact properties. In

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

2005-01-01

168

Design & fabrication of two seated aircraft with an advanced rotating leading edge wing  

NASA Astrophysics Data System (ADS)

The title of this thesis is "Design & Fabrication of two Seated Aircraft with an Advanced Rotating Leading Edge Wing", this gives almost a good description of the work has been done. In this research, the moving surface boundary-layer control (MSBC) concept was investigated and implemented. An experimental model was constructed and tested in wind tunnel to determine the aerodynamic characteristics using the leading edge moving surface of modified semi-symmetric airfoil NACA1214. The moving surface is provided by a high speed rotating cylinder, which replaces the leading edge of the airfoil. The angle of attack, the cylinder surfaces velocity ratio Uc/U, and the flap deflection angle effects on the lift and drag coefficients and the stall angle of attack were investigated. This new technology was applied to a 2-seat light-sport aircraft that is designed and built in the Aerospace Engineering Department at KFUPM. The project team is led by the aerospace department chairman Dr. Ahmed Z. AL-Garni and Dr. Wael G. Abdelrahman and includes graduate and under graduate student. The wing was modified to include a rotating cylinder along the leading edge of the flap portion. This produced very promising results such as the increase of the maximum lift coefficient at Uc/U=3 by 82% when flaps up and 111% when flaps down at 40° and stall was delayed by 8degrees in both cases. The laboratory results also showed that the effective range of the leading-edge rotating cylinder is at low angles of attack which reduce the need for higher angles of attack for STOL aircraft.

Al Ahmari, Saeed Abdullah Saeed

169

Effect of coolant–mainstream blowing ratio on leading edge film cooling flow and heat transfer – LES investigation  

Microsoft Academic Search

Large Eddy Simulation (LES) is used to analyze and quantify the effects of the coolant-to-mainstream blowing ratio in leading edge film cooling. A cylindrical leading edge with a flat after-body represents the blade leading edge, where coolant is injected with a 30° compound angle. Three blowing ratios of 0.4, 0.8, and 1.2 are studied. Free-stream Reynolds number is 100,000 and

Ali Rozati; Danesh K. Tafti

2008-01-01

170

Spanwise flow and the attachment of the leading-edge vortex on insect wings  

NASA Astrophysics Data System (ADS)

The flow structure that is largely responsible for the good performance of insect wings has recently been identified as a leading-edge vortex. But because such vortices become detached from a wing in two-dimensional flow, an unknown mechanism must keep them attached to (three-dimensional) flapping wings. The current explanation, analogous to a mechanism operating on delta-wing aircraft, is that spanwise flow through a spiral vortex drains energy from the vortex core. We have tested this hypothesis by systematically mapping the flow generated by a dynamically scaled model insect while simultaneously measuring the resulting aerodynamic forces. Here we report that, at the Reynolds numbers matching the flows relevant for most insects, flapping wings do not generate a spiral vortex akin to that produced by delta-wing aircraft. We also find that limiting spanwise flow with fences and edge baffles does not cause detachment of the leading-edge vortex. The data support an alternative hypothesis-that downward flow induced by tip vortices limits the growth of the leading-edge vortex.

Birch, James M.; Dickinson, Michael H.

2001-08-01

171

A theoretical investigation of the aerodynamics of low-aspect-ratio wings with partial leading-edge separation  

NASA Technical Reports Server (NTRS)

A numerical method is developed to predict distributed and total aerodynamic characteristics for low aspect-ratio wings with partial leading-edge separation. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the quasi-vortex-lattice method. The leading-edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at mid-points to satisfy the force free condition. The wake behind the trailing-edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading- and trailing-edges. Comparison of the predicted results with complete leading-edge separation has shown reasonably good agreement. For cases with partial leading-edge separation, the lift is found to be highly nonlinear with angle of attack.

Mehrotra, S. C.; Lan, C. E.

1978-01-01

172

Effect of a round airfoil nose on leading-edge suction  

NASA Technical Reports Server (NTRS)

Kulfan (1979) assumed that the angle of attack for initial vortex separation on a slender wing with rounded leading edges could be obtained by equating the leading-edge suction (LES) and nose drag coefficients. In the present study, this assumption is examined and is shown to predict reasonably well the initial angle of attack at which laminar separation occurs near the airfoil nose. However, the assumption is shown to be slightly less accurate for thick or cambered airfoils. Attainable LES estimated by Kulfan's method seemed to agree well with that obtained from an airfoil aerodynamics code and experimental data on a NACA 64A009 airfoil at M = 0.4 and Re = 0.86 x 10 to the 6th.

Lan, C. Edward; Su, Ingchung

1987-01-01

173

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

174

Comparison of computations and experimental data for leading edge vortices - Effects of yaw and vortex flaps  

NASA Technical Reports Server (NTRS)

Computations are presented using the conical Euler equations for swept delta wings with leading edge vortices. All the wings have sharp leading edges swept at 75 degrees to the freestream. In addition to an idealized flat plate model, geometrical features also included are thickness, centerbody, and two vortex flaps. Freestream Mach numbers of 1.7 to 2.8, angles of attack of 10 and 12 degrees, and angles of yaw of 0 and 8 degrees are considered. The computations are compared with pitot pressure traverses for one case. Other calculations are compared with surface pressure data and vapor screen pictures recently obtained at NASA Langley Research Center. The comparisons indicate that the dominant features of these flows are adequately modeled by the Euler equations, but viscous models are needed for the surface boundary layer and secondary separations.

Murman, E. M.; Powell, K. G.; Miller, D. S.; Wood, R. M.

1986-01-01

175

Comparison of computations and experimental data for leading edge vortices - Effects of yaw and vortex flaps  

NASA Technical Reports Server (NTRS)

Computations are presented using the conical Euler equations for swept delta wings with leading edge vortices. All the wings have sharp leading edges swept at 75 degrees to the freestream. In addition to an idealized flat plate model, geometrical features also included are thickness, centerbody, and two vortex flaps. Freestream Mach numbers of 1.7 to 2.8, angles of attack of 10 and 12 degrees, and angles of yaw of 0 and 8 degrees are considered. The computations are compared with pitot pressure traverses for one case. Other calculations are compared with pitot pressure traverses for one case. Other calculations are compared with surface pressure data and vapor screen pictures recently obtained at NASA Langley Research Center. The comparisons indicate that the dominant features of these flows are adequately modeled by the Euler equations, but viscous models are needed for the surface boundary layer and secondary separations.

Murman, E. M.; Powell, K. G.; Miller, D. S.; Wood, R. M.

1986-01-01

176

Effects of leading-edge flap oscillation on unsteady delta wing flow and rock control  

NASA Technical Reports Server (NTRS)

The isolated and interdisciplinary problems of unsteady fluid dynamics and rigid-body dynamics and control of delta wings with and without leading-edge flap oscillation are considered. For the fluid dynamics problem, the unsteady, compressible, thin-layer Navier-Stokes (NS) equations, which are written relative to a moving frame of reference, are solved along with the unsteady, linearized, Navier-displacement (ND) equations. The NS equations are solved for the flowfield using an implicit finite-volume scheme. The ND equations are solved for the grid deformation, if the leading-edge flaps oscillate, using an ADI scheme. For the dynamics and control problem, the Euler equation of rigid-body rolling motion for a wing and its flaps are solved interactively with the fluid dynamics equations for the wing-rock motion and subsequently for its control. A four-stage Runge-Kutta scheme is used to explicitly integrate the dynamics equation.

Kandil, Osama A.; Salman, Ahmed A.

1991-01-01

177

Aerothermal Performance Constraints for Hypervelocity Small Radius Unswept Leading Edges and Nosetips  

NASA Technical Reports Server (NTRS)

Small radius leading edges and nosetips were utilized to minimize wave drag in early hypervelocity vehicle concepts until further analysis demonstrated that extreme aerothermodynamic heating would cause severe ablation or blunting of the available thermal protection system materials. Recent studies indicate that ultrahigh temperature ceramic (UHTC) materials are shape stable at temperatures approaching 3033 K and will be available for use as sharp UHTC leading edge components in the near future. Aerothermal performance constraints for sharp components made from these materials are presented in this work to demonstrate the effects of convective blocking, surface catalycity, surface emissivity, and rarefied flow effects on steady state operation at altitudes from sea level to 90 km. These components are capable of steady state operation at velocities up to 7.9 km/s at attitudes near 90 km.

Kolodziej, Paul

1997-01-01

178

Studies on laminar boundary-layer receptivity to freestream turbulence near a leading edge  

NASA Technical Reports Server (NTRS)

An experimental study of the generation of Tollmien-Schlichting waves and wave packets in a flat-plate boundary-layer by weak freestream turbulence has been conducted with the intent of clarifying receptivity mechanisms. Emphasis was placed upon the properties of such waves at stations as far forward as the minimum critical Reynolds number. It was found that alteration of the flow about the leading edge, due either to an asymmetry associated with lift, or due to a change of the fineness ratio of the leading edge, altered the T-S wave amplitude at early stations. The subsequent growth of the waves proceeded faster than expected according to certain stability theory results. Speculation regarding receptivity mechanisms is made.

Kendall, James M.

1991-01-01

179

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

180

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

181

Experimental unsteady pressures on an oscillating cascade with supersonic leading edge locus  

NASA Technical Reports Server (NTRS)

The first experimental data for an oscillating cascade with a supersonic leading edge locus (SLEL) at zero stagger angle is presented which were obtained in the NASA/OSU supersonic oscillating cascade facility. Reduced frequencies from .093 to .146, based on half chord were investigated. An influence coefficient technique for a linear oscillating cascade with constant interblade phase angle has been extended to a cascade with a SLEL.

Erwin, Daniel; Gregorek, G. M.; Ramsey, John

1992-01-01

182

Lessons from the experiences of leading-edge object technology projects in Hewlett-Packard  

Microsoft Academic Search

A study of leading-edge HP object technology projects was conducted to understand the current state of object-oriented practice, and projects' object-oriented analysis and design method needs. In this paper, we distill general best practices and pitfalls from the lessons learned in these projects. We also consider how the OOA\\/D methods support what the businesses have set out to accomplish, where

Ruth Malan; Derek Coleman; Reed Letsinger

1995-01-01

183

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

184

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

Microsoft Academic Search

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

V. Nirmalan; L. D. Hylton

1989-01-01

185

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

Microsoft Academic Search

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

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

1988-01-01

186

Application of a flush airdata sensing system to a wing leading edge (LE-FADS)  

NASA Technical Reports Server (NTRS)

The feasibility of locating a flush airdata sensing (FADS) system on a wing leading edge where the operation of the avionics or fire control radar system will not be hindered is investigated. The leading-edge FADS system (LE-FADS) was installed on an unswept symmetrical airfoil and a series of low-speed wind-tunnel tests were conducted to evaluate the performance of the system. As a result of the tests it is concluded that the aerodynamic models formulated for use on aircraft nosetips are directly applicable to wing leading edges and that the calibration process is similar. Furthermore, the agreement between the airdata calculations for angle of attack and total pressure from the LE-FADS and known wind-tunnel values suggest that wing-based flush airdata systems can be calibrated to a high degree of accuracy. Static wind-tunnel tests for angles of attack from -50 deg to 50 deg and dynamic pressures from 3.6 to 11.4 lb/sq ft were performed.

Whitmore, Stephen A.; Moes, Timothy R.; Czerniejewski, Mark W.; Nichols, Douglas A.

1993-01-01

187

Application of a flush airdata sensing system to a wing leading edge (LE-FADS)  

NASA Technical Reports Server (NTRS)

This paper investigates the feasibility of locating a flush air-data sensing (FADS) system on a wing leading edge where the operation of the avionics or fire control radar system will not be hindered. The leading-edge FADS system (LE-FADS) was installed on an unswept symmetrical airfoil, and a series of low-speed wind-tunnel tests were conducted to evaluate the performance of the system. As a result of the tests it is concluded that the aerodynamic models formulated for use on aircraft nosetips are directly applicable to wing leading edges and that the calibration process is similar. Furthermore, the agreement between the air-data calculations for angle of attack and total pressure from the LE-FADS and known wind-tunnel values suggest that wing-based flush air-data systems can be calibrated to a high degree of accuracy. Static wind-tunnel tests for angles of attack from -50 to 50 deg and dynamic pressures from 3.6 to 11.4 lb/sq ft were performed.

Whitmore, Stephen A.; Moes, Timothy R.; Czerniejewski, Mark W.; Nichols, Douglas A.

1993-01-01

188

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

National Technical Information Service (NTIS)

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 stud...

F. Ghaffari

2005-01-01

189

A Reynolds Number Study of Wing Leading-Edge Effects on a Supersonic Transport Model at Mach 0.3  

NASA Technical Reports Server (NTRS)

A representative supersonic transport design was tested in the National Transonic Facility (NTF) in its original configuration with small-radius leading-edge flaps and also with modified large-radius inboard leading-edge flaps. Aerodynamic data were obtained over a range of Reynolds numbers at a Mach number of 0.3 and angles of attack up to 16 deg. Increasing the radius of the inboard leading-edge flap delayed nose-up pitching moment to a higher lift coefficient. Deflecting the large-radius leading-edge flap produced an overall decrease in lift coefficient and delayed nose-up pitching moment to even higher angles of attack as compared with the undeflected large- radius leading-edge flap. At angles of attack corresponding to the maximum untrimmed lift-to-drag ratio, lift and drag coefficients decreased while lift-to-drag ratio increased with increasing Reynolds number. At an angle of attack of 13.5 deg., the pitching-moment coefficient was nearly constant with increasing Reynolds number for both the small-radius leading-edge flap and the deflected large-radius leading-edge flap. However, the pitching moment coefficient increased with increasing Reynolds number for the undeflected large-radius leading-edge flap above a chord Reynolds number of about 35 x 10 (exp 6).

Williams, M. Susan; Owens, Lewis R., Jr.; Chu, Julio

1999-01-01

190

An ?4 integrin–paxillin–Arf-GAP complex restricts Rac activation to the leading edge of migrating cells  

Microsoft Academic Search

Formation of a stable lamellipodium at the front of migrating cells requires localization of Rac activation to the leading edge. Restriction of ?4 integrin phosphorylation to the leading edge limits the interaction of ?4 with paxillin to the sides and rear of a migrating cell. The ?4–paxillin complex inhibits stable lamellipodia, thus confining lamellipod formation to the cell anterior. Here

Naoyuki Nishiya; William B. Kiosses; Jaewon Han; Mark H. Ginsberg

2005-01-01

191

Case Studies of Leading Edge Small Urban High Schools. Core Academic Strategic Designs: 1. Academy of the Pacific Rim  

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

192

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

193

Case Studies of Leading Edge Small Urban High Schools. Core Academic Strategic Designs: 3. University Park Campus 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

194

Case Studies of Leading Edge Small Urban High Schools. Relevance Strategic Designs: 7. TechBoston Academy  

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

195

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

196

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

197

Characterization of Unsteady Flow Structures Near Leading-Edge Slat. Part 1; PIV Measurements  

NASA Technical Reports Server (NTRS)

A comprehensive computational and experimental study has been performed at the NASA Langley Research Center as part of the Quiet Aircraft Technology (QAT) Program to investigate the unsteady flow near a leading-edge slat of a two-dimensional, high-lift system. This paper focuses on the experimental effort conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART) where Particle Image Velocimetry (PIV) data was acquired in the slat cove and at the slat trailing edge of a three-element, high-lift model at 4, 6, and 8 degrees angle of attack and a freestream Mach Number of 0.17. Instantaneous velocities obtained from PIV images are used to obtain mean and fluctuating components of velocity and vorticity. The data show the recirculation in the cove, reattachment of the shear layer on the slat lower surface, and discrete vortical structures within the shear layer emanating from the slat cusp and slat trailing edge. Detailed measurements are used to examine the shear layer formation at the slat cusp, vortex shedding at the slat trailing edge, and convection of vortical structures through the slat gap. Selected results are discussed and compared with unsteady, Reynolds-Averaged Navier-Stokes (URANS) computations for the same configuration in a companion paper by Khorrami, Choudhari, and Jenkins (2004). The experimental dataset provides essential flow-field information for the validation of near-field inputs to noise prediction tools.

Jenkins, Luther N.; Khorrami, Mehdi R.; Choudhari, Meelan

2004-01-01

198

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

199

Dual modes of motility at the leading edge of migrating epithelial cell sheets  

PubMed Central

Purse-string healing is driven by contraction of actin/myosin cables that span cells at wound edges, and it is the predominant mode of closing small round wounds in embryonic and some adult epithelia. Wounds can also heal by cell crawling, and my colleagues and I have shown previously that the presence of unconstrained, straight edges in sheets of epithelial cells is a sufficient signal to induce healing by crawling. Here, it is reported that the presence of highly concave edges, which are free or physically constrained by an inert material (agarose), is sufficient to induce formation of purse strings. It was determined that neither of the two types of healing required cell damage or other potential stimuli by using the particularly gentle procedure of introducing gaps by digesting agarose blocks imbedded in the cell sheets. Movement by crawling depends on signaling by the EGF receptor (EGFR); however, this was not required for purse-string contraction. A migrating epithelial cell sheet usually produces finger-like projections of crawling cells. The cells between fingers contain continuous actin cables, which were also determined to contain myosin IIA and exhibit additional characteristics of purse strings. When crawling was blocked by inhibition of EGFR signaling, the concave regions continued to move, suggesting that both mechanisms contribute to propel the sheets forward. Wounding epithelial cell sheets causes activation of the EGFR, which triggers movement by crawling. The EGFR was found to be activated only at straight and convex edges, which explains how both types of movement can coexist at leading epithelial edges.

Klarlund, Jes K.

2012-01-01

200

Lift Augmentation on a Delta Wing via Leading Edge Fences and the Gurney Flap  

NASA Technical Reports Server (NTRS)

Wind tunnel tests have been conducted on two devices for the purpose of lift augmentation on a 60 deg delta wing at low speed. Lift, drag, pitching moment, and surface pressures were measured. Detailed flow visualization was also obtained. Both the leading edge fence and the Gurney flap are shown to increase lift. The fences and flap shift the lift curve by as much as 5 deg and 10 deg, respectively. The fences aid in trapping vortices on the upper surface, thereby increasing suction. The Gurney flap improves circulation at the trailing edge. The individual influences of both devices are roughly additive, creating high lift gain. However, the lower lift to drag ratio and the precipitation of vortex burst caused by the fences, and the nose down pitching moment created by the flap are also significant factors.

Buchholz, Mark D.; Tso, Jin

1993-01-01

201

An experimental investigation of convective heat transfer at the leading edge of a gas turbine airfoil  

NASA Astrophysics Data System (ADS)

This paper describes the experimental methods used to determine the surface temperatures and heat-transfer coefficients at the leading edge, and elsewhere over the surface, of a specially designed double-edge wedge shell specimen subjected to cyclic heating in a high velocity hot gas stream generated by a burner rig. The methods included temperature measurements with thermocouples (embedded below the surface) as well as surface temperature measurements by optical pyrometry. The experiments were carried out at gas temperatures between 806 to 1323 C and velocities in the range from Mach 0.32 to Mach 0.39. The calibration procedures for each method, the various testing conditions to which the airfoil-like specimen was exposed and the results pertaining to the determination of the surface temperatures and heat-transfer coefficients are described and discussed.

Gendron, S.; Marchand, N. J.; Korn, C.; Immarigeon, J. P.; Kacprzynski, J. J.

1992-06-01

202

Flow visualization of vortices locked by spanwise blowing over wings featuring a unique leading and trailing-edge flap system  

NASA Technical Reports Server (NTRS)

Flow visualization studies were conducted to qualitatively determine the effects of active generation and augmentation of vortex flow over wings by blowing a discrete jet in a spanwise direction in the channel formed by extension of upper surface leading- and trailing-edge flaps. Spanwise blowing from a reflection plane over a rectangular wing was found to generate and lock a dual corotating vortex system within the channel and, at sufficient blowing rates, cause the separated flow off the upper end of the leading-edge flap to reattach to the trailing-edge flap. Test parameters included wing angle of attack, jet momentum coefficient, leading- and trailing-edge flap deflection angle, and jet location above the wing surface. Effects due to removal of the leading- and trailing-edge flap were also investigated.

Erickson, G. E.; Campbell, J. F.

1975-01-01

203

An improved Woodward's panel method for calculating leading-edge and side-edge suction forces at subsonic and supersonic speeds  

NASA Technical Reports Server (NTRS)

Woodward's panel method for subsonic and supersonic flow was improved by employing control points determined by exactly matching two-dimensional pressure at a finite number of points. The results show great improvement in the predicted pressure distribution of a flapped airfoil. With the paneling scheme of cosine law in both chordwise and spanwise directions, the method is shown to accurately predict leading edge and side edge suction forces of various configurations in subsonic and supersonic flow.

Lan, C. E.; Mehrotra, S. C.

1979-01-01

204

Modeling the Nonlinear, Strain Rate Dependent Deformation of Shuttle Leading Edge Materials with Hydrostatic Stress Effects Included  

NASA Technical Reports Server (NTRS)

An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.

Goldberg, Robert K.; Carney, Kelly S.

2004-01-01

205

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

206

Leading Edge Receptivity to Sound at Incidence Angles on Parabolic Bodies at Mean Angles of Attack.  

NASA Astrophysics Data System (ADS)

The leading edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier-Stokes equations in vorticity/stream function form in parabolic 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(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. We primarily investigated the effect of the angle of incidence (-180^circ <= ?1 <= 180^circ) of the acoustic waves on the leading edge receptivity of parabolic bodies at mean angles of attack (0^circ <= ?2 <= 7^circ). The results at ?_1=?_2=0^circ quantitatively agree with those of Haddad & Corke, which showed an increase in the receptivity coefficient with increasing angle of attack. Of special interest is an asymmetry in the receptivity coefficient when determined by extrapolation to the leading from the lower or upper sides of the body, which is produced when the sound incidence angles and angles of attack are large.

Corke, T. C.; Erturk, E.

1999-11-01

207

How differential deflection of the inboard and outboard leading-edge flaps affected the handling qua  

NASA Technical Reports Server (NTRS)

How differential deflection of the inboard and outboard leading-edge flaps affected the handling qualities of this modified F/A-18A was evaluated during the first check flight in the Active Aeroelastic Wing program at NASA's Dryden Flight Research Center. The Active Aeroelastic Wing program at NASA's Dryden Flight Research Center seeks to determine the advantages of twisting flexible wings for primary maneuvering roll control at transonic and supersonic speeds, with traditional control surfaces such as ailerons and leading-edge flaps used to aerodynamically induce the twist. From flight test and simulation data, the program intends to develop structural modeling techniques and tools to help design lighter, more flexible high aspect-ratio wings for future high-performance aircraft, which could translate to more economical operation or greater payload capability. AAW flight tests began in November, 2002 with checkout and parameter-identification flights. Based on data obtained during the first flight series, new flight control software will be developed and a second series of research flights will then evaluate the AAW concept in a real-world environment. The program uses wings that were modified to the flexibility of the original pre-production F-18 wing. Other modifications include a new actuator to operate the outboard leading edge flap over a greater range and rate, and a research flight control system to host the aeroelastic wing control laws. The Active Aeroelastic Wing Program is jointly funded and managed by the Air Force Research Laboratory and NASA Dryden Flight Research Center, with Boeing's Phantom Works as prime contractor for wing modifications and flight control software development. The F/A-18A aircraft was provided by the Naval Aviation Systems Test Team and modified for its research role by NASA Dryden technicians.

2002-01-01

208

Redetermination of lead isotopic composition in Canyon Diablo troilite  

Microsoft Academic Search

Redetermination of the lead isotopic composition in Canyon Diablo ; troilite shows that the original analysis was overcorrected for analytical ; fractionation. The new analysis indicates that the lead in nodule CDN-1 is a ; mixture of primordial lead plus a small amount of common lead. (auth)

V OVERSBY

1973-01-01

209

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. 18 figs.

Powell, H.T.; Wolfe, C.A.; Campbell, J.H.; Murray, J.E.; Riley, M.O.; Lyon, R.E.; Jessop, E.S.

1987-11-02

210

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

211

Compressible Navier-Stokes equations: A study of leading edge effects  

NASA Technical Reports Server (NTRS)

A computational method is developed that allows numerical calculations of the time dependent compressible Navier-Stokes equations.The current results concern a study of flow past a semi-infinite flat plate.Flow develops from given inflow conditions upstream and passes over the flat plate to leave the computational domain without reflecting at the downstream boundary. Leading edge effects are included in this paper. In addition, specification of a heated region which gets convected with the flow is considered. The time history of this convection is obtained, and it exhibits a wave phenomena.

Hariharan, S. I.; Karbhari, P. R.

1987-01-01

212

Design and testing of a piezostack-actuated leading-edge flap  

NASA Astrophysics Data System (ADS)

This paper presents the design and preliminary test results of a piezoelectric stack (piezostack) driven leading-edge flap actuator. The actuator uses six commercially available piezostacks with a curved contact tip for force and stroke profile tailoring. Force requirements were calculated using a quasi-steady aerodynamic model. Stroke amplification is achieved through a single lever. Initial results show that the current prototype is not ready to achieve the desired stroke output, but potential problems are identified and action is being take to rectify these problems.

Shaner, Mark C.; Chopra, Inderjit

1999-06-01

213

Influence of a heated leading edge on boundary layer growth, stability, and transition  

NASA Astrophysics Data System (ADS)

This paper presents the results of a combined theoretical and experimental study of the influence of a heated leading edge on the growth, stability, and transition of a two-dimensional boundary layer. The findings are directly applicable to aircraft wings and nacelles that use surface heating for anti-icing protection. The potential effects of the non-adiabatic condition are particularly important for laminar-flow sections where even small perturbations can result in significantly degraded aerodynamic performance. The results of the study give new insight to the fundamental coupling between streamwise pressure gradient and surface heat flux in laminar and transitional boundary layers.

Landrum, D. B.; Macha, J. M.

1987-06-01

214

Influence of a heated leading edge on boundary layer growth, stability and transition  

NASA Astrophysics Data System (ADS)

This paper presents the results of a combined theoretical and experimental study of the influence of a heated leading edge on the growth, stability, and transition of a two-dimensional boundary layer. The findings are directly applicable to aircraft wings and nacelles that use surface heating for anti-icing protection. The potential effects of the non-adiabatic condition are particularly important for laminar-flow sections where even small perturbations can result in significantly degraded aerodynamic performance. The results of the study give new insight to the fundamental coupling between streamwise pressure gradient and surface heat flux in laminar and transitional boundary layers.

Landrum, D. B.; Macha, J. M.

1987-04-01

215

The Leading Edge 250: Oblique wing aircraft configuration project, volume 4  

NASA Technical Reports Server (NTRS)

The design of a high speed transport aircraft using the oblique wing concept as a part of the High Speed Civil Transport (HSCT) aircraft study is the Leading Edge 250 capable of travelling at Mach 4 with 250 passengers and has a 6,500 nautical mile range. Its innovation lies within its use of the unconventional oblique wing to provide efficient flight at any Mach number. Wave drag is kept to a minimum at high speed, while high lift is attained during critical takeoff and landing maneuvers by varying the sweep of the wing.

Schmidt, Andre; Moore, Peri; Nguyen, Dan; Oganesyan, Petros; Palmer, Charles

1988-01-01

216

Subsonic balance and pressure investigation of a 60-deg delta wing with leading-edge devices (data report)  

NASA Technical Reports Server (NTRS)

The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.

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

1981-01-01

217

Localized deformation zones in the offshore leading edge of the Yakutat microplate, Gulf of Alaska  

NASA Astrophysics Data System (ADS)

The Gulf of Alaska margin is dominated by the collision and subduction of the Yakutat microplate as it travels northwest with respect to North America at near Pacific Plate velocities (\\~45 mm/yr). The oblique Yakutat block collision with North America is in transition between convergence to the west and translation along the Queen Charlotte-Fairweather-Denali Fault system to the east and north. Industry seismic reflection and high- resolution seismic reflection data collected by the R/V Maurice Ewing (2004) provides insight into how the Yakutat-North America collision is accommodated by active offshore structures near the leading edge of the Yakutat microplate. A \\~200 km wide area bounded by the Ten Fathom Fault, the offshore N. America-Yakutat contact, to the west and the eastern edge of the Pamplona Zone (PZ) to the east has previously been mapped as a continuous deformation zone consisting of NE-SW trending imbricate thrusts and folds. Though this mapping corroborates onshore measurements of active deformation west of the Bering Glacier in the Yakutat block, the relationship between current onshore deformation and the observed offshore structures remains unclear. Our observations indicate that neotectonic deformation is accommodated offshore by highly localized, asynchronous thrusts that, when analyzed in an accretionary context, may be connected by a sub-horizontal decollement. Data from the eastern edge of the PZ, the proposed deformation front, shows surface deformation caused by east-verging thrust faults. Seismic reflection profiles in the western PZ and the Bering Trough show no evidence of active tectonic deformation and up to \\~200 m of undisturbed sediments indicating that faulting in this part of the Yakutat block has been inactive since the Last Glacial Maximum or earlier. Farther west, above the Kayak Island fault zone, directly east of the Ten Fathom Fault, the presence of up to \\~50 m of undeformed sediments suggests a recent (ca. 14 ka) transition in deformation style, including a possible eastward jump of the deformation front to the eastern PZ. In addition, images of the Khitrov fault zone south of Kayak Island show possible transpressional faulting and associated surface deformation that may indicate a shift in tectonic style in this corner of the microplate as Yakutat material is constricted west of the PZ. Collision in the leading edge of the Yakutat block therefore appears to be accommodated by deformation along localized fault structures as opposed to a broad zone of deformation. These localized deformation zones correlate with the edges of the large temperate glaciers that are the dominant erosional force in the St. Elias orogeny.

Lowe, L. A.; Gulick, S. P.; Pavlis, T.; Bruhn, R. L.; Mann, P.

2006-12-01

218

Lead isotopic heterogeneities within alkali feldspars: Implications for the determination of initial lead isotopic compositions  

SciTech Connect

The mobility of uranium during metamorphism and alteration places constraints on the use of lead isotopic compositions as petrogenetic tracers in older rocks. The problem of uranium mobility may be partially circumvented by analysis of alkali feldspar which, because of its low U:Pb ratio, should have a lead isotopic composition similar to the initial lead isotopic composition of the rock. Previous leaching and volatilization experiments, however, have demonstrated that alkali feldspars contain radiogenic lead which can be removed preferentially to nonradiogenic lead. This paper reports on the results of progressive acid leaching of a single alkali feldspar phenocryst and on albitic perthites separated from the phenocryst. This experiment suggests that a number of distinct lead isotopic reservoirs are present within the alkali feldspar, including a nonradiogenic reservoir approximating the initial lead isotopic composition of the system, a radiogenic reservoir corresponding to albitic exsolution lamellae within the alkali feldspar, loosely bound labile lead presumably associated with uranium and thorium occupying fractures, and finally a radiogenic component corresponding to unidentified uranium-thorium-rich phases. The results of this experiment confirm that initial lead isotopic compositions may be estimated from alkali feldspars through severe acid leaching; however, this experiment also illustrates the complexity of the lead isotopic systematics of alkali feldspars. The determination of the initial lead isotopic composition of an alkali feldspar requires experimental procedures which recognize and compensate for the presence of multipe lead reservoirs within typical alkali feldspars.

Housh, T.; Bowring, S.A. (Washington Univ., St. Louis, MO (United States))

1991-08-01

219

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

220

Low-order phenomenological modeling of leading-edge vortex formation  

NASA Astrophysics Data System (ADS)

A low-order point vortex model for the two-dimensional unsteady aerodynamics of a flat plate wing section is developed. A vortex is released from both the trailing and leading edges of the flat plate, and the strength of each is determined by enforcing the Kutta condition at the edges. The strength of a vortex is frozen when it reaches an extremum, and a new vortex is released from the corresponding edge. The motion of variable-strength vortices is computed in one of two ways. In the first approach, the Brown-Michael equation is used in order to ensure that no spurious force is generated by the branch cut associated with each vortex. In the second approach, we propose a new evolution equation for a vortex by equating the rate of change of its impulse with that of an equivalent surrogate vortex with identical properties but constant strength. This impulse matching approach leads to a model that admits more general criteria for shedding, since the variable-strength vortex can be exchanged for its constant-strength surrogate at any instant. We show that the results of the new model, when applied to a pitching or perching plate, agree better with experiments and high-fidelity simulations than the Brown-Michael model, using fewer than ten degrees of freedom. We also assess the model performance on the impulsive start of a flat plate at various angles of attack. Current limitations of the model and extensions to more general unsteady aerodynamic problems are discussed.

Wang, Chengjie; Eldredge, Jeff D.

2013-09-01

221

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

222

Leading-edge receptivity to a vortical freestream disturbance: A numerical analysis  

NASA Technical Reports Server (NTRS)

The receptivity to freestream vorticity of the boundary layer over a flat plate with an elliptic leading edge is investigated numerically. The flow is simulated by solving the incompressible Navier-Stokes system in general curvilinear coordinates with the vorticity and stream function as dependent variables. A finite-difference scheme which is second-order accurate in both space and time is used. As a first step, the steady basic-state solution is computed. Then a small amplitude vortical disturbance is introduced at the upstream boundary and the governing equations are solved time-accurately to evaluate the spatial and temporal growth of the perturbations leading to instability waves (Tollmien-Schlichting waves) inside the boundary layer. Preliminary results for a symmetric, 2-D disturbance reveal the presence of Tollmien-Schlichting waves aft of the flat-plate/ellipse juncture.

Buter, Thomas A.; Reed, Helen L.

1991-01-01

223

Leading edge film cooling enhancement for an inlet guide vane with fan-shaped holes  

NASA Astrophysics Data System (ADS)

This paper describes the improvement of leading edge film cooling effectiveness for a turbine inlet guide vane by using fan-shaped film cooling holes. The modification details are presented in comparison with the base-line configuration of cylindrical holes. Numerical simulations were carried out for the base-line and modified configurations by using CFX, in which the ?-? turbulence model and scalable wall function were chosen. Contours of adiabatic film cooling effectiveness on the blade surfaces and span-wise distributions of film cooling effectiveness downstream the rows of cooling holes interested for the different cooling configurations were compared and discussed. It is showed that with the use of fan-shaped cooling holes around the leading edge, the adiabatic film cooling effectiveness can be enhanced considerably. In comparison with the cylindrical film cooling holes, up to 40% coolant mass flow can be saved by using fan-shaped cooling holes to obtain the comparable film cooling effectiveness for the studied inlet guide vane.

Liu, Jian-Jun; An, Bai-Tao; Liu, Jie; Zhan, W.

2010-12-01

224

Leading edge vortex dynamics on a pitching delta wing. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The leading edge flow structure was investigated on a 70 deg flat plate delta wing which was pitched about its 1/2 chord position, to increase understanding of the high angle of attack aerodynamics on an unsteady delta wing. The wing was sinusoidally pitched at reduced frequencies ranging from k being identical with 2pi fc/u = 0.05 to 0.30 at chord Reynolds numbers between 90,000 and 350,000, for angle of attack ranges of alpha = 29 to 39 deg and alpha = 0 to 45 deg. The wing was also impulsively pitched at an approximate rate of 0.7 rad/s. During these dynamic motions, visualization of the leading edge vorticies was obtained by entraining titanium tetrachloride into the flow at the model apex. The location of vortex breakdown was recorded using 16mm high speed motion picture photography. When the wing was sinusoidally pitched, a hysteresis was observed in the location of breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing, and the phase lag between model motion and breakdown location were also determined. When the wing was impulsively pitched, several convective times were required for the vortex flow to reach a steady state. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases.

Lemay, Scott P.

1988-01-01

225

Experimental Study of Shock Wave Interference Heating on a Cylindrical Leading Edge. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

An experimental study of shock wave interference heating on a cylindrical leading edge representative of the cowl of a rectangular hypersonic engine inlet at Mach numbers of 6.3, 6.5, and 8.0 is presented. Stream Reynolds numbers ranged from 0.5 x 106 to 4.9 x 106 per ft. and stream total temperature ranged from 2100 to 3400 R. The model consisted of a 3" dia. cylinder and a shock generation wedge articulated to angles of 10, 12.5, and 15 deg. A fundamental understanding was obtained of the fluid mechanics of shock wave interference induced flow impingement on a cylindrical leading edge and the attendant surface pressure and heat flux distributions. The first detailed heat transfer rate and pressure distributions for two dimensional shock wave interference on a cylinder was provided along with insight into the effects of specific heat variation with temperature on the phenomena. Results show that the flow around a body in hypersonic flow is altered significantly by the shock wave interference pattern that is created by an oblique shock wave from an external source intersecting the bow shock wave produced in front of the body.

Wieting, Allan R.

1987-01-01

226

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

227

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

228

Navier-Stokes analysis of airfoils with leading edge ice accretions  

NASA Technical Reports Server (NTRS)

A numerical analysis of the flowfield characteristics and the performance degradation of an airfoil with leading edge ice accretions was performed. The important fluid dynamic processes were identified and calculated. Among these were the leading edge separation bubble at low angles of attack, complete separation on the low pressure surface resulting in premature shell, drag rise due to the ice shape, and the effects of angle of attack on the separated flow field. Comparisons to experimental results were conducted to confirm these calculations. A computer code which solves the Navier-Stokes equations in two dimensions, ARC2D, was used to perform the calculations. A Modified Mixing Length turbulence model was developed to produce grids for several ice shape and airfoil combinations. Results indicate that the ability to predict overall performance characteristics, such as lift and drag, at low angles of attack is excellent. Transition location is important for accurately determining separation bubble shape. Details of the flowfield in and downstream of the separated regions requires some modifications. Calculations for the stalled airfoil indicate periodic shedding of vorticity that was generated aft of the ice accretion. Time averaged pressure values produce results which compare favorably with experimental information. A turbulence model which accounts for the history effects in the flow may be justified.

Potapczuk, Mark G.

1993-01-01

229

Noise development in transonic flows at the impact of vortices on a profile leading edge  

NASA Astrophysics Data System (ADS)

The production of noise in the interaction of a vortex with the leading edge of a profile in a transonic flow was investigated. The occurring phenomena are detected in the far field as noise (blade-vortex interaction noise). The vortex was produced as a von Karman vortex street in the wake of a rectangular cylinder. The interferograms show a strong shock-like pressure wave in a broad parameter range after the passing of the leading edge by the vortex; this is probably the most important mechanism of the down stream pulse noise as, e.g., observed for helicopters and can thus easily be simulated in experiments. The development of weaker shocks at the profile were also observed downstream; this phenomenon does not seem to be important for the noise production. The measurement of the pressure distribution in the unsteady potential flow shows similarities with the theory with respect to the dipole-like noise radiation characteristic; however there are significant differences in the details, probably due to the neglect of compressibility and friction.

Lent, H. M.

1986-05-01

230

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

231

Space Shuttle Orbiter Wing-Leading-Edge Panel Thermo-Mechanical Analysis for Entry Conditions  

NASA Technical Reports Server (NTRS)

Linear elastic, thermo-mechanical stress analyses of the Space Shuttle Orbiter wing-leading-edge panels is presented for entry heating conditions. The wing-leading-edge panels are made from reinforced carbon-carbon and serve as a part of the overall thermal protection system. Three-dimensional finite element models are described for three configurations: integrated configuration, an independent single-panel configuration, and a local lower-apex joggle segment. Entry temperature conditions are imposed and the through-the-thickness response is examined. From the integrated model, it was concluded that individual panels can be analyzed independently since minimal interaction between adjacent components occurred. From the independent single-panel model, it was concluded that increased through-the-thickness stress levels developed all along the chord of a panel s slip-side joggle region, and hence isolated local joggle sections will exhibit the same trend. From the local joggle models, it was concluded that two-dimensional plane-strain models can be used to study the influence of subsurface defects along the slip-side joggle region of these panels.

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

2010-01-01

232

Flow Field Characteristics of Finite-span Hydrofoils with Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

Past work has shown that humpback whale-like leading edge protuberances can significantly alter the load characteristics of both 2D and finite-span hydrofoils. To understand the mechanisms responsible for observed performance changes, the flow field characteristics of a baseline hydrofoil and models with leading edge protuberances were examined using the Stereo Particle Image Velocimetry (SPIV) technique. The near surface flow field on the hydrofoils was measured along with the tip vortex flow field on finite-span hydrofoils. Angles of attack ranging from 6 to 24 degrees were examined at freestream velocities of 1.8 m/s and 4.5 m/s, corresponding to Reynolds numbers of 180 and 450 thousand, respectively. While Reynolds number does not play a major role in establishing the flow field trends, both the protuberance geometry and spatial proximity to protuberances affect the velocity and vorticity characteristics near the foil surface, and in the wake and tip vortex. Near surface measurements reveal counter-rotating vortices on protuberance shoulders, while tip vortex measurements show that streamwise vorticity can be strongly affected by the presence of protuberances. The observed flow field characteristics will be presented.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2011-11-01

233

Boundary layer leading-edge receptivity to sound at incidence angles  

NASA Astrophysics Data System (ADS)

The leading-edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier Stokes equations in vorticity/streamfunction form in parabolic 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 linearized perturbation flow are solved separately. We primarily investigated the effect of frequency and angle of incidence ([minus sign]180° [less-than-or-eq, slant] [alpha]2 [less-than-or-eq, slant] 180°) of the acoustic waves on the leading-edge receptivity. The results at [alpha]2 = 0° were found to be in quantitative agreement with those of Haddad & Corke (1998), and substantiated the Strouhal number scaling based on the nose radius. The results with sound waves at angles of incidence agreed qualitatively with the analysis of Hammerton & Kerschen (1996). These included a maximum receptivity at [alpha]2 = 90°, and an asymmetric variation in the receptivity with sound incidence angle, with minima at angles which were slightly less than [alpha]2 = 0° and [alpha]2 = 180°.

Erturk, Ercan; Corke, Thomas C.

2001-10-01

234

Experimental Study of Wing Leading-Edge Devices for Improved Maneuver Performance of a Supercritical Maneuvering Fighter Configuration.  

National Technical Information Service (NTIS)

Wind tunnel tests were conducted to examine the use of wing leading-edge devices for improved subsonic and transonic maneuver performance. These devices were tested on a fighter configuration which utilized supercritical-wing technology. The configuration...

M. J. Mann J. K. Huffman C. H. Fox R. L. Campbell

1983-01-01

235

Directly deposited fluxless lead-indium-gold composite solder  

Microsoft Academic Search

Lead-indium-gold multilayer composite solder has been developed for bonding electronic devices without the use of flux. The composite is deposited directly on GaAs wafers in high vacuum to inhibit indium oxidation. The gold layer on the composite further protects the indium layer from oxidation in atmosphere. Using the composite solder without flux, GaAs dies have been successfully bonded to alumina

Chen Y. Wang; Yi C. Chen; Chin C. Lee

1993-01-01

236

Investigation of leading-edge flap performance on delta and double-delta wings at supersonic speeds  

NASA Technical Reports Server (NTRS)

An investigation of the aerodynamic performance of leading-edge flaps on three clipped delta and three clipped double-delta wing planforms with aspect ratios of 1.75, 2.11, and 2.50 was conducted in the Langley Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.90, and 2.16. A primary set of fullspan leading-edge flaps with similar root and tip chords were investigated on each wing, and several alternate flap planforms were investigated on the aspect-ratio-1.75 wings. All leading-edge flap geometries were effective in reducing the drag at lifting conditions over the range of wing aspect ratios and Mach numbers tested. Application of a primary flap resulted in better flap performance with the double-delta planform than with the delta planform. The primary flap geometry generally yielded better performance than the alternate flap geometries tested. Trim drag due to flap-induced pitching moments was found to reduce the leading-edge flap performance more for the delta planform than for the double-delta planform. Flow-visualization techniques showed that leading-edge flap deflection reduces crossflow shock-induced separation effects. Finally, it was found that modified linear theory consistently predicts only the effects of leading-edge flap deflection as related to pitching moment and lift trends.

Covell, Peter F.; Wood, Richard M.; Miller, David S.

1987-01-01

237

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

238

Fracture resistance of microhybrid composite, nano composite and fibre-reinforced composite used for incisal edge restoration.  

PubMed

Traumatized anterior teeth need quick, aesthetic and functional repair. Along with aesthetics, the physical properties of restorative material should also be considered for long-lasting restoration. Fibre reinforcement has been tried as a newer technique to improve the physical properties of composite materials. Hence, this study was carried out to evaluate the fracture resistance of microhybrid composite, nano composite and fibre-reinforced composite used for restoration of incisal edge of fractured maxillary central incisors. Extracted permanent maxillary central incisors were randomly divided into four groups of 10 samples each: control group with intact teeth (Group A), microhybrid composite (Esthet X; Dentsply/Caulk, Milford, DE, USA) (group B), nano composite (Ceram X; Dentsply/Caulk) (group C) and microhybrid composite reinforced with polyethylene fibre - flowable composite unit [(Ribbond THM; Ribbond Inc., Seattle, WA, USA; Esthet X flow; Dentsply/Caulk)] (group D). The fracture resistance was measured under universal testing machine at a speed of 1mmmin(-1) with the loading tip of 2mm diameter. The samples were further evaluated for mode of fracture under stereomicroscope at 3.5× magnification. The data were analysed using one-way anova and Tukey's test for fracture resistance. Group A and group D exhibited significantly higher fracture resistance than group B and group C. No significant difference was found between group B and group C as well as between group A and group D. Fisher's exact test for the mode of fracture revealed no statistical significance. It was concluded that fibre reinforcement of composite could be an alternative technique for restoration of fractured anterior teeth for better aesthetics and longevity of the restoration. PMID:21564519

Badakar, Chandrashekhar M; Shashibhushan, Kukkalli Kamalaksharappa; Naik, N Sathyajith; Reddy, Vulavala Venkata Subba

2011-06-01

239

Measurement of the temperature field downstream of simulated leading-edge film-cooling holes  

NASA Astrophysics Data System (ADS)

Experiments to measure the temperature field downstream of simulated leading-edge-region film-cooling holes were performed in an 11 m/s wind tunnel flow. Heated air was passed to a hollow 140 mm diameter cylinder in which three 10.5 mm diameter, spanwise-inclined, film-cooling holes had been machined. A fine nylon mesh, coated with encapsulated thermochromic liquid crystals, was used to measure temperature contours downstream of the holes by moving the mesh relative to the holes and adjusting the power to the air heater. The measurements indicate the extent of the lateral spreading of the coolant gas and show the influence of hole location and coolant mass flow rate on film trajectory and spreading.

Mee, D. J.; Ireland, P. T.; Bather, S.

240

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

241

Application of finite element and remeshing technique to shock interference on a cylindrical leading edge  

NASA Technical Reports Server (NTRS)

The problem of planar oblique shock impingement on a cylindrical leading edge in hypersonic flow is modeled using a Galerkin-Runge Kutta finite element method. The method utilizes a four stage Runge-Kutta time stepping scheme to solve the compressible Euler equations. Freestream Mach numbers of 6.5, 8.0 and 16.0 are studied. The computed surface pressure distributions consistently agree well with available experimental data. The peak pressure amplification ranges from 5.45 at M = 6.5 to approximately 17.0 at M = 16.0. Stagnation point heat transfer rate amplifications are calculated from the inviscid solution using the method of Fay and Riddell. The value and wall location of the peak pressure and heat transfer rate amplifications are extremely sensitive to the location of the impinging shock/bow shock intersection point.

Stewart, James R.; Thareja, Rajiv R.; Wieting, Allan R.; Morgan, Ken

1988-01-01

242

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

243

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

244

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

245

Lead isotopic heterogeneities within alkali feldspars: Implications for the determination of initial lead isotopic compositions  

NASA Astrophysics Data System (ADS)

The mobility of uranium during metamorphism and alteration places constraints on the use of lead isotopic compositions as petrogenetic tracers in older rocks. The problem of uranium mobility may be partially circumvented by analysis of alkali feldspar which, because of its low U:Pb ratio, should have a lead isotopic composition similar to the initial lead isotopic composition of the rock. Previous leaching and volatilization experiments, however, have demonstrated that alkali feldspars contain radio-genic lead which can be removed preferentially to nonradiogenic lead. This paper reports on the results of progressive acid leaching of a single alkali feldspar phenocryst and on albitic perthites separated from the phenocryst. This experiment suggests that a number of distinct lead isotopic reservoirs are present within the alkali feldspar, including a nonradiogenic reservoir approximating the initial lead isotopic composition of the system, a radiogenic reservoir corresponding to albitic exsolution lamellae within the alkali feldspar, loosely bound labile lead presumably associated with uranium and thorium occupying fractures, and finally a radiogenic component corresponding to unidentified uranium-thorium rich phases. The commonly observed decrease in radiogenicity with progressive leaching of alkali feldspars is interpreted to be largely the result of preferential leaching of the albitic perthites relative to the host alkali feldspar containing the nonradiogenic reservoir. The results of this experiment confirm that initial lead isotopic compositions may be estimated from alkali feldspars through severe acid leaching; however, this experiment also illustrates the complexity of the lead isotopic systematics of alkali feldspars. The determination of the initial lead isotopic composition of an alkali feldspar requires experimental procedures which recognize and compensate for the presence of multiple lead reservoirs within typical alkali feldspars.

Housh, Todd; Bowring, Samuel A.

1991-08-01

246

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

247

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

248

Directly deposited lead-indium-gold composite solder  

Microsoft Academic Search

Lead-indium-gold multilayer composite solder has been developed for bonding electronic devices. The composite is deposited directly on GaAs wafers in high vacuum to prevent indium oxidation. The gold layer on the composite further protects the indium layer from oxidation in the atmosphere. The GaAs dies are bonded to a gold-coated alumina substrate at a process temperature of 250°C. Nearly perfect

Yi-Chia Chen; Chen Y. Wang; Chin C. Lee

1993-01-01

249

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

250

Design of a smart leading edge device for low speed wind tunnel tests in the European project SADE  

Microsoft Academic Search

Purpose – The purpose of this paper is to describe the pre-design and sizing of a smart leading edge section which is developed in the project SADE (Smart High Lift Devices for Next Generation Wings), which is part of the seventh framework program of the EU. Design\\/methodology\\/approach – The development of morphing technologies in SADE concentrates on the leading and

Markus Kintscher; Martin Wiedemann; Hans Peter Monner; Olaf Heintze; Timo Kühn

2011-01-01

251

A Mesh Refinement Study on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation  

NASA Technical Reports Server (NTRS)

A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. During the study, nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. In addition, the element nominal edge-length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0-in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms of simulation time. Contour plots of resultant panel displacement and effective stress in the foam were compared at four discrete time intervals. Also, time-history responses of internal and kinetic energy of the panel, kinetic and hourglass energy of the foam, and resultant contact force were plotted to determine the influence of mesh density.

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

2006-01-01

252

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

PubMed

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. PMID:21415476

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

2011-04-01

253

Isotopic composition of primeval lead of the earth  

Microsoft Academic Search

Based upon the variation of isotopic composition of lead ores from the same site, the age of the earth is estimated to be 4.55 billion years ( b . y . = 10 9 years ). By assuming a fixed heterogeneity of two radioactive elements, thorium and uranium, we can obtain a self-consistent primeval lead with 204 Pb : 206

Akimasa Masuda

1958-01-01

254

NanoComposite Lead-Free Interconnect and Reliability  

Microsoft Academic Search

Lead free solder bumping requirements have challenged researchers to develop new technologies to achieve fine pitch interconnects. ITRS has predicts that by 2017 the industry will require 70 micron pitch area array lead free interconnects for flip chips. This paper describes bumping, assembly and reliability evaluation of a new nano composite 20 micron pitch interconnect technology. Nanoparticles are the most

Ravi Doraiswami; Rao Tummala

2005-01-01

255

Design approaches for edge delamination resistance in laminated composites  

SciTech Connect

This paper reviews the material and structural approaches to increase resistance of delamination initiation and growth. In the material approach, it was found that currently available toughened thermosets and thermoplastic composites can significantly improve delamination resistance for static, but not fatigue, loading. In the structural approach, it was concluded that stitching and interleafing are effective ways to resist delamination as a result of impact. However, terminating and discretizing the critical ply, as well as selective interleafing, are the most effective ways to increase delamination resistance for both static and fatigue in-plane loadings. 25 refs.

Chan, W.S. (Texas, University, Arlington (USA))

1991-01-01

256

Kinematic analysis of a large-scale leading edge fold, Lost River Range, Idaho  

NASA Astrophysics Data System (ADS)

The Mahogany Creek-Buck Creek structure within the Lost River Range, Idaho, is a large-scale, leading edge fold which developed in late Paleozoic outer shelf stratigraphy during the Sevier orogeny. Incremental strain histories determined from antitaxial fibrous pressure shadows are used to quantify temporal variations in the magnitude and orientation of elongation as a function of structural position around the leading edge of this northward and eastward propagating blind thrust. Plane strain is indicated by coaxial, up-dip extension on cleavage planes. On the backlimb of the structure, the Bluebird Mountain Formation, a calcareous sandstone, has deformed by flexural-flow whereas the forelimb of the structure records spin through a fixed steeply plunging incremental extension direction. The flat limb ahead of the anticline exhibits top-to-the foreland simple shear. In contrast, the underlying Surrett Canyon Formation, a thick-bedded limestone, has experienced flexural-flow localized within thin zones on both limbs of the anticline. Samples from the anticlinal hinge zone suggests kinematic partitioning with pin lines which were variably distributed within each unit and which were temporally transient. Finite elongations are greatest in the hinge and above the foreland flat in the Bluebird Mountain Formation but are negligible in the Surrett Canyon Formation, except within the mechanically active interbeds of the hanging wall and within the footwall adjacent to the fault along the northernmost exposures. Strain histories in the hanging wall do not vary significantly along strike, while the footwall varies from undeformed in the south to penetratively deformed in the north. Thus, the strain data are consistent with self similar along-strike fold development in the hanging wall during strike-parallel ramp propagation. Forward thrust propagation may have been blunted by a combination of fold-accommodated shortening and footwall deformation to the north. Once the fold had tightened and fold shortening required greater differential stress, forward fault propagation resumed, transporting the anticline onto the upper flat with little change in hanging wall fold geometry or strain distribution.

Fisher, Donald M.; Anastasio, David J.

1994-03-01

257

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

258

Preservation of wing leading edge suction at the plane of symmetry as a factor in wing-fuselage design  

NASA Technical Reports Server (NTRS)

Most fuselage geometries cover a portion of the wing leading edge near the plane of symmetry, and it seems reasonable to expect that a large fraction of the leading edge suction which would be developed by the covered wing at high angles of attack is not developed on the fuselage. This is one of the reasons that the Oswald span efficiency factor for the wing body combination fails to approach the value predicted by lifting line theory for the isolated wing. Some traditional and recent literature on wing-body interference is discussed and high Reynolds number data on wing-body-nacelle drag are reviewed. An exposed central leading edge geometry has been developed for a sailplane configuration. Low Reynolds number tests have not validated the design concept.

Larrabee, E. E.

1975-01-01

259

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

260

Influence of high mainstream turbulence on leading edge film cooling heat transfer - Effect of film hole spacing  

NASA Astrophysics Data System (ADS)

The effect of injection hole geometry on the leading edge heat transfer coefficient and film cooling effectiveness, under high mainstream turbulence condition, was experimentally studied for an incident mainstream Reynolds number of 100,000. Data were obtained for three blowing ratios of 0.4, 0.8, and 1.2 through two rows of film holes located at +/- 15 and +/- 40 deg for two injection geometries: (1) film holes spaced four hole diameters apart, and (2) film holes spaced three hole diameters apart, in the spanwise direction. The results show that the leading edge heat transfer coefficient increases and the film effectiveness decreases with increasing mainstream turbulence; however, the effect reduces with increasing blowing ratio. The leading edge heat transfer with coolant injection (heat load) for the three hole diameters case is lower than that for the four hole diameters case at low mainstream turbulence, but the difference reduces at higher mainstream turbulence.

Mehendale, A. B.; Han, J. C.

1992-10-01

261

Mass loss of TEOS-coated RCC subjected to the environment at the shuttle wing leading edge  

NASA Technical Reports Server (NTRS)

Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the Space Shuttle. The mass loss characteristics of RCC specimens coated with tetra-ethyl-ortho-silicate (TEOS) were determined for conditions which simulated the entry environment expected at the stagnation area of the wing leading edge. Maximum specimen temperature was 1632 K. Specimens were exposed for up to 100 missions. Stress levels up to 8.274 MPa caused an average increase in oxidation of 6 percent over unstressed specimens. Experimentally determined mass losses were compared with those predicted by an existing empirical analysis.

Stroud, C. W.; Rummler, D. R.

1981-01-01

262

Dkk-1 Inhibits Intestinal Epithelial Cell Migration by Attenuating Directional Polarization of Leading Edge Cells  

PubMed Central

Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating cells, which coincided with a displacement of the polarity protein Par6 from the leading edge. Consequently, the relocation of the microtubule organizing center and the Golgi apparatus in the direction of migration was significantly and persistently inhibited in the presence of Dkk-1. Small interfering RNA-induced down-regulation of Dkk-1 confirmed that extracellular exposure to Dkk-1 was required for this effect. Together, these data demonstrate a novel role of Dkk-1 in the regulation of directional polarization of migrating intestinal epithelial cells, which contributes to the effect of Dkk-1 on wound closure in vivo.

Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B.; Parkos, Charles A.

2009-01-01

263

Development of Detectability Limits for On-Orbit Inspection of Space Shuttle Wing Leading Edge  

NASA Technical Reports Server (NTRS)

At the conclusion of the Columbia Accident Investigation, one of the recommendations of the Columbia Accident Investigation Board (CAIB) was that NASA develop and implement an inspection plan for the Reinforced Carbon-Carbon (RCC) system components of the Space Shuttle. To address these issues, a group of scientists and engineers at NASA Langley Research Center proposed the use of an IR camera to inspect the RCC. Any crack in an RCC panel changes the thermal resistance of the material in the direction perpendicular to the crack. The change in thermal resistance can be made visible by introducing a heat flow across the crack and using an IR camera to image the resulting surface temperature distribution. The temperature difference across the crack depends on the change in the thermal resistance, the length of the crack, the local thermal gradient, and the rate of radiation exchange with the environment. This paper describes how the authors derived the minimum thermal gradient detectability limits for a through crack in an RCC panel. This paper will also show, through the use of a transient, 3-dimensional, finite element model, that these minimum gradients naturally exist on-orbit. The results from the finite element model confirm that there are sufficient thermal gradient to detect a crack on 96% of the RCC leading edge.

Stephan, Ryan A.; Johnson, David G.; Mastropietro, A. J.; Ancarrow, Walt C.

2005-01-01

264

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

265

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

266

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

267

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

268

Performance of laminar-flow leading-edge test articles in cloud encounters  

NASA Technical Reports Server (NTRS)

An extensive data bank of concurrent measurements of laminar flow (LF), particle concentration, and aircraft charging state was gathered for the first time. From this data bank, 13 flights in the simulated airline service (SAS) portion were analyzed to date. A total of 6.86 hours of data at one-second resolution were analyzed. An extensive statistical analysis, for both leading-edge test articles, shows that there is a significant effect of cloud and haze particles on the extent of laminar flow obtained. Approximately 93 percent of data points simulating LFC flight were obtained in clear air conditions; approximately 7 percent were obtained in cloud and haze. These percentages are consistent with earlier USAF and NASA estimates and results. The Hall laminar flow loss criteria was verified qualitatively. Larger particles and higher particle concentrations have a more marked effect on LF than do small particles. A particle spectrometer of a charging patch are both acceptable as diagnostic indicators of the presence of particles detrimental to laminar flow.

Davis, Richard E.; Maddalon, Dal V.; Wagner, Richard D.

1987-01-01

269

Prediction and Assessment of Reynolds Number Sensitivities Associated with Wing Leading-Edge Radius Variations  

NASA Technical Reports Server (NTRS)

The primary objectives of this study were to expand the data base showing the effects of LE radius distribution and corresponding sensitivity to Rn at subsonic and transonic conditions, and to assess the predictive capability of CFD for these effects. Several key elements led to the initiation of this project: 1) the necessity of meeting multipoint design requirements to enable a viable HSCT, 2) the demonstration that blunt supersonic leading-edges can be associated with performance gain at supersonic speeds , and 3) limited data. A test of a modified Reference H model with the TCA planform and 2 LE radius distributions was performed in the NTF, in addition to Navier-Stokes analysis for an additional 3 LE radius distributions. Results indicate that there is a tremendous potential to improve high-lift performance through the use of a blunt LE across the span given an integrated, fully optimized design, and that low Rn data alone is probably not sufficient to demonstrate the benefit.

Wahls, Richard A.; Rivers, Melissa B.; Owens, Lewis R., Jr.

1999-01-01

270

Optimal acceleration of ions by laser pulses with a sharp leading edge  

NASA Astrophysics Data System (ADS)

We consider acceleration of ions through the interaction of a laser pulse with a sharp leading edge with nanofilms. At sufficiently large amplitude of the pulse, all the electrons can be expelled from the film, which provides an effective regime of ion acceleration. Limiting the maximum energy of ions can result from the longitudinal reverse motion of electrons to the initial position and by the transverse motion of electrons along the nanofilm surface, which causes the ion charge compensation. The characteristic parameters of the dynamics of ions and electrons in the system are analytically evaluated, which agree well with the results of twodimensional numerical simulations by the particle-in-cell method. Optimisation of the acceleration process by using the analytical estimates makes it possible to select the optimal parameters of the laser pulse and nanofilm. Numerical simulation of ion acceleration at these parameters shows that the maximum energy of ions can be substantially increased. Reported at the Conference 'Laser Optics', Russia, St. Petersburg, June 2010.

Kulagin, V. V.; Kornienko, V. N.; Cherepenin, Vladimir A.; Suk, Hyyong

2012-01-01

271

Development of detectability limits for on-orbit inspection of space shuttle wing leading edge  

NASA Astrophysics Data System (ADS)

At the conclusion of the Columbia Accident Investigation, one of the recommendations of the Columbia Accident Investigation Board (CAIB) was that NASA develop and implement an inspection plan for the Reinforced Carbon-Carbon (RCC) system components. To address these issues, a group of scientists and engineers at NASA Langley Research Center proposed the use of an IR camera to inspect the RCC. Any crack in an RCC panel changes the thermal resistance of the material in the direction perpendicular to the crack. The change in thermal resistance can be made visible by introducing a heat flow across the crack and using an IR camera to image the resulting surface temperature distribution. The temperature difference across the crack depends on the change in the thermal resistance, the length of the crack, the local thermal gradient, and the rate of radiation exchange with the environment. The current paper describes how the authors derived the minimum thermal gradient detectability limits for a through crack in an RCC panel. This paper will also show, through the use of a transient, 3-dimensional, finite element model, that these minimum gradients naturally exist on-orbit. The results from the finite element model showed that there exists sufficient thermal gradient to detect a crack on 96% of the RCC leading edge.

Stephan, Ryan A.; Johnson, David G.; Mastropietro, A. J.

2005-03-01

272

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

273

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

274

Flow adjustment at the leading edge of a submerged aquatic canopy  

NASA Astrophysics Data System (ADS)

This paper describes the transition from open channel flow to flow over submerged vegetation using velocity measurements collected with acoustic Doppler velocimetry (ADV) and particle-image velocimetry (PIV). Submerged canopies were constructed from arrays of rigid circular cylinders of height h in water of depth H. Both the canopy density, described by the frontal area per volume (a), and degree of submergence (H/h) were varied. Flow adjustment occurs in three stages. First, velocity begins to decelerate upstream of the canopy, due to a high-pressure region generated at the canopy leading edge, and continues to decelerate within the canopy, due to canopy drag. Rapid flow deceleration within the canopy creates strong vertical flux out through the top of the canopy that extends over a length proportional to the canopy drag length scale, (CDa)-1, with CD being the canopy drag coefficient. Second, a mixing layer develops at the canopy interface, with the stress at the top of the canopy initially increasing, but eventually reaching a constant value. At this point, the flow within the canopy is fully developed. The length scale for mixing-layer development is related to canopy drag (CDa) and the depth ratio (H/h). In the third stage, the boundary layer above the mixing layer adjusts to the channel boundary conditions. A model is developed to predict the adjustment of vertically averaged velocity within the canopy. Measurements confirm that the flow adjustment is not dependent on canopy length.

Chen, Zhengbing; Jiang, Chunbo; Nepf, Heidi

2013-09-01

275

Interlaminar strains at the free edge of a hole in laminated composites: An experimental study  

SciTech Connect

Free-edge effects in laminated composite materials were studied experimentally using high-sensitivity moire interferometry. Six laminates from two material systems were tested in uniaxial compression on an electro-mechanical testing machine. Interlaminar deformations were measured on a ply-by-ply basis at the straight free-edge and, for the first time, on the cylindrical surface of a hole. Strain distributions were determined with high fidelity for the hole surface and the straight free edge of the thick composite panels. Comparisons were made on a ply-by-ply basis for the transverse and tangential strains at the horizontal centerline of the hole (90{degree} location) and the corresponding plies at the straight boundaries.

Boeman, R.G. [Oak Ridge National Lab., TN (United States). Engineering Technology Div.

1993-12-31

276

Repeatable On-the-Machine Cutting-Edge-Forming Technology Applying Composite Electroplating and Anodic Electrolysis  

Microsoft Academic Search

If a cutting tool could be repeatedly formed without removal from a machine utilized in a cutting process, it would be highly beneficial in that it could reduce not only any positioning error due to a tool exchange, but also the consumption of scarce tool materials and energy. Composite electroplating to build up the cutting edge and anodic electrolysis to

K. Kurahashi; K. Yanagihara; Y. Tani; H. Sato

2004-01-01

277

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

278

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

279

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

280

Design fabrication, testing, and delivery of shuttle heat pipe leading edge test modules. Volume 1: Executive summary  

NASA Technical Reports Server (NTRS)

The construction of two test modules is presented for a feasibility demonstration of a concept for reusable space shuttle wing leading edge surfaces. In this leading edge concept high temperature heat pipes were incorporated into the structure to cool the stagnation region, allowing the use of super-alloys in place of refractory metal, ablator protected, or carbon-carbon structures. The program included the analysis and design of the heat pipes, their integration into the test module structure, heat pipe development testing, construction of the test modules and a facility adapter, and formulation of recommended testing conditions. The results of the heat pipe and leading edge module thermal analyses indicate the test modules will meet the design goal; reducing the leading edge temperature at the stagnation line from 1315 C (2400 F) to less than 1010 C (1850 F). The development tests demonstrated that the module assembly could be brazed with active heat pipes, as was borne out by the subsequent successful brazing of both modules with active heat pipes loaded with sodium.

1973-01-01

281

The Effect of Leading-Edge Sweep and Surface Inclination on the Hypersonic Flow Field Over a Blunt Flat Plate  

NASA Technical Reports Server (NTRS)

An investigation of the effects of variation of leading-edge sweep and surface inclination on the flow over blunt flat plates was conducted at Mach numbers of 4 and 5.7 at free-stream Reynolds numbers per inch of 6,600 and 20,000, respectively. Surface pressures were measured on a flat plate blunted by a semicylindrical leading edge over a range of sweep angles from 0 deg to 60 deg and a range of surface inclinations from -10 deg to +10 deg. The surface pressures were predicted within an average error of +/- 8 percent by a combination of blast-wave and boundary-layer theory extended herein to include effects of sweep and surface inclination. This combination applied equally well to similar data of other investigations. The local Reynolds number per inch was found to be lower than the free-stream Reynolds number per inch. The reduction in local Reynolds number was mitigated by increasing the sweep of the leading edge. Boundary-layer thickness and shock-wave shape were changed little by the sweep of the leading edge.

Creager, Marcus O.

1959-01-01

282

An Improved Panel Method for the Solution of Three-Dimensional Leading-Edge Vortex Flows. Volume 1: Theory Document.  

National Technical Information Service (NTIS)

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 ...

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

1980-01-01

283

Heat transfer and material temperature conditions in the leading edge area of impingement-cooled turbine vanes  

NASA Astrophysics Data System (ADS)

The resultant effects on the cooling effectiveness at the leading edge area of an impingement-cooled turbine vane by varying certain geometrical parameters is described with reference to local internal heat transfer coefficients determined from experiment and temperature calculations. The local heat transfer on the cooling-air side is determined experimentally with the aid of the analogy between heat- and mass transfer. The impingement cooling is provided from an inserted sheet-metal containing a single row of holes. The Reynolds Number and several of the cooling geometry parameters were varied. The results demonstrate the high local resolution of the method of measurement, which allows improved analytical treatment of the leading-edge cooling configuration. These experiments also point to the necessity of not always performing model tests under idealized conditions. This becomes very clear in the case of the tests performed on an application-oriented impingement-cooling configuration like that often encountered in engine manufacture. In conclusion, as an example, temperature calculations are employed to demonstrate the effect on the cooling effectiveness of varying the distances between insert and inner surface of the leading edge. It shows how the effectiveness of the leading edge cooling can be increased by simple geometrical measures, which results in a considerable improvement in service life.

Berg, H. P.; Pfaff, K.; Hennecke, D. K.

284

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.

285

Mask blank material optimization impact on leading-edge ArF lithography  

NASA Astrophysics Data System (ADS)

In this study, we investigate what kind of mask blank material is optimum for the resolution enhancement techniques (RET) of leading-edge ArF lithography. The source mask optimization (SMO) is one of the promising RET in 2Xnm-node and it optimizes mask pattern and illumination intensity distribution simultaneously. We combine SMO with the blank material optimization and explore the truly optimized SMO. This study consists of three phases. In the first phase, we evaluate maximum exposure latitude (Max.E.L.) and mask error enhancement factor (MEEF) of fictitious materials that have typical real (n) and imaginary (k) value of refractive index by 3D rigorous simulator as the basic analysis. The simulation result shows that there are two high lithographic performance combinations of n and k values; one is low-n/high-k and the other is high-n/low-k. In the second phase, we select actual blank material that has similar optical parameters with the result of the previous phase. The lithographic performance of the selected material is investigated more precisely. We find that the candidate material has good lithographic performance at the semi-dense pitch. In the final phase, we create a test mask of this candidate blank material and verify simulation result by experimental assessment. The exposures are performed on NA1.30 immersion scanner (Nikon NSR-S610C). The experimental result shows the improvement of Max.E.L. in head to head type pattern. This study will discuss the potential of blank material tuning for the ArF lithography extension.

Mesuda, Kei; Watanabe, Hiroshi; Hayano, Katsuya; Tsujimoto, Eiji; Takamizawa, Hideyoshi; Ohhashi, Toshio; Sakasai, Naruo; Kudo, Shintaro; Matsuyama, Tomoyuki

2011-04-01

286

Free vibration analysis of laminated composite plates with elastically restrained edges using FEM  

NASA Astrophysics Data System (ADS)

The application of FEM is shown for free vibration analysis of moderately thick laminated composite plates with edges elastically restrained against translation and rotation. The governing equations employed are based on the first order shear deformation theory including the effects of rotary inertia. Several combinations of translational and rotational elastic edge constraints are considered. Convergence study with respect to the number of nodes has been carried out and the results are compared with those from past investigations available only for simpler problems. Angle-ply and cross-ply laminates with different thickness-to-length ratios are examined. Comparisons are made with results for thin as well as moderately thick laminated plates.

Sharma, Avadesh K.; Mittal, N. D.

2013-06-01

287

Isotopic Composition of Lead in the Sediments Near Japan Trench.  

National Technical Information Service (NTIS)

The isotopic composition of lead in the sediments near the Japan Trench was determined. The values are: (206) PB/204PB=18.45; (207)PB/(204) PB=15.63; and (208)PB/(204)PB=38.68. The mu and kappa values of the source material are also calculated to be 8.8 a...

T. J. Chow M. Tatsumoto

1964-01-01

288

The Influence of Mesh Density on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation  

NASA Technical Reports Server (NTRS)

A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. During the study, nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. In addition, the element nominal edge-length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0- in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA version 960 for 6 ms of simulation time. Contour plots of resultant panel displacement and effective stress in the foam were compared at five discrete time intervals. Also, time-history responses of internal and kinetic energy of the panel, kinetic and hourglass energy of the foam, and resultant contact force were plotted to determine the influence of mesh density. As a final comparison, the model with a fine panel and fine foam mesh was executed with slightly different material properties for the RCC. For this model, the average degraded properties of the RCC were replaced with the maximum degraded properties. Similar comparisons of panel and foam responses were made for the average and maximum degraded models.

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

2004-01-01

289

Application of the leading edge suction analogy to prediction of longitudinal load distribution and pitching moments for sharp edged delta wings  

NASA Technical Reports Server (NTRS)

The leading-edge-suction analogy of Polhamus has been used to develop the longitudinal load distribution of the vortex lift for delta wings. This distribution is shown to be similar in shape to that of the potential-flow longitudinal loading for delta wings having aspect ratios of 2 or less. The totals of the two theoretical distributions for delta wings with an aspect ratio near 1 are in good agreement with the experimentally determined loadings over the angle-of-attack range from 0 to 30 deg. The corresponding predicted pitching moments show slightly more stability than those measured, because of loss of lift near the wing tips.

Snyder, M. H., Jr.; Lamar, J. E.

1972-01-01

290

Kinetic Study of Lead Adsorption to Composite Biopolymer Adsorbent.  

PubMed

A kinetic study of lead adsorption to composite biopolymer adsorbents was carried out. Spherical and membranous adsorbents containing two biopolymers, humic acid and alginic acid, were used for lead adsorption in dilute acidic solutions. The shrinking core model derived by M. G. Rao and A. K. Gupta (Chem. Eng. J. 24, 181, 1982) was applied to describe the rate process of lead adsorption to spherical adsorbents (average radii of 0.12, 0.15, and 0.16 cm). Furthermore, the shrinking core model was modified and adapted for description of the rate process of lead adsorption to membranous adsorbent (average thickness of 0.0216 cm). The adsorption rate process for the both cases was well described and average apparent lead diffusion coefficients of about 6 x 10(-6) and 7 x 10(-6) cm2 s-1 were found for the spherical and membranous adsorbents, respectively. Copyright 1999 Academic Press. PMID:10049553

Seki; Suzuki

1999-03-15

291

Local heat transfer in internally cooled turbine airfoil leading edge regions. I - Impingement cooling without film coolant extraction. II - Impingement cooling with film coolant extraction  

Microsoft Academic Search

The highly localized internal heat transfer characteristics of large-scale models of impingement-cooled turbine blade leading edge regions presently studied derives its cooling from a single line of equally-spaced multiple jets aimed at the leading-edge apex, and exiting the leading-edge region in the opposite or chordwise direction. Detailed two-dimensional local surface Nusselt number distributions have been obtained with temperature-indicating coatings. Results

R. S. Bunker; D. E. Metzger

1988-01-01

292

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

293

Reduction of Free Edge Peeling Stress of Laminated Composites Using Active Piezoelectric Layers  

PubMed Central

An analytical approach is proposed in the reduction of free edge peeling stresses of laminated composites using active piezoelectric layers. The approach is the extended Kantorovich method which is an iterative method. Multiterms of trial function are employed and governing equations are derived by taking the principle of complementary virtual work. The solutions are obtained by solving a generalized eigenvalue problem. By this approach, the stresses automatically satisfy not only the traction-free boundary conditions, but also the free edge boundary conditions. Through the iteration processes, the free edge stresses converge very quickly. It is found that the peeling stresses generated by mechanical loadings are significantly reduced by applying a proper electric field to the piezoelectric actuators.

Huang, Bin; Kim, Heung Soo

2014-01-01

294

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

295

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

NASA Technical Reports Server (NTRS)

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 prematurely and weaken the bond. The three-dimensional, steady state, thermal transport equation is solved by the Green's function method for a tape of finite width being placed on an infinitely wide substrate. The isotherm for the glass transition temperature on the weld interface is used to determine the distance inward from the tape edge that is prematurely cooled, called the cooling incursion Delta a. For the Langley ATP robot, Delta a = 0.4 mm for a unidirectional lay-up of PEEK/carbon fiber composite, and Delta a = 1.2 mm for an isotropic lay-up. A formula for Delta a is developed and applied to a wide range of operating conditions. A surprise finding is that Delta a need not decrease as the Peclet number Pe becomes very large, where Pe is the dimensionless ratio of inertial to diffusive heat transport. Conformable rollers that increase the consolidation length would also increase Delta a, unless other changes are made, such as proportionally increasing the material speed. To compensate for premature edge cooling, the thermal input could be extended past the tape edges by the amount Delta a. This method should help achieve uniform weld strength and crystallinity across the width of the tape.

Costen, Robert C.

2000-01-01

296

Effects of feedrate and chisel edge on delamination in composites drilling  

NASA Astrophysics Data System (ADS)

Delamination occurring during the drilling of composite laminates has been recognized as a major problem. An analytical model is established to predict critical thrust force and critical feedrate at which the delamination crack begins to propagate. For unidirectional composites, the delamination zone is modeled as an elliptical plate, with clamped edges and subjected to a central load. Based on fracture mechanics, laminated plate theory and cutting mechanics, expressions are developed for critical thrusts and critical feedrates at which delamination is initiated at different ply locations. This model has been verified by experiments. A variable feedrate strategy is formulated based on this model, which avoids delamination while drilling in a time-optimal fashion. In addition, the need to modify tool geometry to avoid delamination is highlighted. Chisel edge width has been identified as an important factor contributing to the thrust force and hence delamination.

Jain, Sanjeev; Yang, Daniel C. H.

297

The Leading Edge of the Galapagos Hotspot: Geochemistry and Geochronology of Submarine Glasses Coupled to New Sidescan Sonar Imagery  

NASA Astrophysics Data System (ADS)

Fernandina, the western-most volcano in the Galapagos archipelago, is at the leading edge of the hotspot with respect to plate motion. Recent mapping of the ocean floor west of Fernandina (on R/V Revelle, using the HMRG towed sidescan sonar MR1, and Simrad EM120 multibeam) provides a dramatic new view of the volcanic constructional processes that have created the islands. The western flank of the volcano is characterized by the prominent Northwest, West, and Southwest rift zones, which are constructed of hummocky pillow lavas. Older lava flow terrain is distinguished by weaker acoustic return, whereas extensive younger flows are characterized by strong backscatter patterns with distinctive flow-like margins. MR1 sidescan sonar mapping provides an important new geologic and stratigraphic context for understanding the submarine Galapagos platform, particularly from a geochemical perspective. Fernandina lavas have high 3He/4He ratios, up to 29 times atmospheric, and solar-like neon isotopic compositions, characteristics which suggest they are derived from the deep mantle. The high 3He/4He ratios, and rapid eruption rates at Fernandina also indicate that it lies directly above the center of the Galapagos hotspot. In order to place these geochemical data into a chronological framework, we have determined ages for Fernandina submarine glasses using the Th-U-He crushing/melting disequilibrium method. Preliminary Th-U-He ages (from the 2000 R/V Melville AHA-Nemo expedition), combined with the new MR1 sonar mapping, shows that the rift zones are characterized by extremely young ages (0 to 30 Ka) while older submarine lava flows with lower acoustic backscatter have significantly older ages ( ~ 100 Ka). The geochronological data, and the geological context from the side-scan sonar, provide new evidence for volcano growth rates in oceanic hotspot provinces, and will be used to determine the growth rate of the Galapagos platform.

Kurz, M. D.; Fornari, D. J.; Geist, D. J.; Johnson, P. D.; Curtice, J. M.; Lott, D. E.; Harpp, K.; Saal, A. E.; Peckman, U. G.

2001-12-01

298

Initiation and Growth of Transverse Cracks and Edge Delamination in Composite Laminates Part 2. Experimental Correlation  

Microsoft Academic Search

In part one of this paper, the fracture processes of multiple transverse cracking and free edge delamination in composite laminates have been analyzed by an energy method. Numerical analyses and experimental examination using a series of T300\\/934 graphite epoxy laminates are pre sented in this part two. While part one is presented in a self-contained form, part two must be

F. W. Crossman; W. J. Warren; A. S. D. Wang; G. E. Law

1980-01-01

299

Study of free edge effect on sub-laminar scale for thermoplastic composite laminates  

Microsoft Academic Search

The interlaminar deformation on the free edge surface in thermoplastic composite AS4\\/PEEK laminates under bending loading are studied by means of digital image correlation method (DICM) using a white-light industrial microscopic. During the test, any artificial stochastic spray is not applied to the specimen surface. In laminar scale, the interlaminare displacements of [0\\/90]3s laminate are measured. In sub-laminar scale, the

Min Shen; Huanbao Lu; Jingwei Tong; Yishi Su; Hongqi Li; Yongmin Lv

2008-01-01

300

Plasma-sprayed lead zirconate titanate-glass composites  

SciTech Connect

A plasma-spray process was used to produce piezoelectric lead zirconate titanate (PZT)-glass composite thick films. The films were found to have the same crystal structure as the PZT (Navy-type V) and lead-based glass starting powder mixture. The films showed good adhesion to stainless steel and silver-coated glass slides and poor adhesion to aluminum substrates. The dielectric constant of the films varied between 58 and 20 with dissipations between 0.019 and 0.032. The films were poled, and their piezoelectric charge coefficient, d[sub 33], was 1.1 pC/N.

Sherrit, S.; Savin, C.R.; Wiederick, H.D.; Mukherjee, B.K. (Royal Military Coll. of Canada, Kingston, Ontario (Canada). Dept. of Physics); Prasad, S.E. (Sensor Technology, Ltd., Collingwood, Ontario (Canada))

1994-07-01

301

Two and three-dimensional shock-shock interactions on the blunt leading edges of the hypersonic inlets  

NASA Technical Reports Server (NTRS)

The effect of shock impingement on the blunt leading edges of the top and sidewall compression type inlet of a scramjet engine is studied numerically. The impinging shock is caused by the vehicle forebody. The interaction of this forebody shock with the inlet leading edge shock results in a very complex flowfield containing local regions of high pressure and intense heating. This complex flowfield in calculated by solving the Navier-Stokes equations using a finite volume flux splitting technique due to van Leer. To resolve the finer details of the flow structure as well as to predict the surface heat transfer accurately, adaptive grid technique is used in the analysis. Results of the present numerical study are compared with available experimental results.

Singh, D. J.; Kumar, Ajay; Tiwari, S. N.

1991-01-01

302

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

303

The Leading Edge of the Galapagos Hotspot: Geochemistry and Geochronology of Submarine Glasses Coupled to New Sidescan Sonar Imagery  

Microsoft Academic Search

Fernandina, the western-most volcano in the Galapagos archipelago, is at the leading edge of the hotspot with respect to plate motion. Recent mapping of the ocean floor west of Fernandina (on R\\/V Revelle, using the HMRG towed sidescan sonar MR1, and Simrad EM120 multibeam) provides a dramatic new view of the volcanic constructional processes that have created the islands. The

M. D. Kurz; D. J. Fornari; D. J. Geist; P. D. Johnson; J. M. Curtice; D. E. Lott; K. Harpp; A. E. Saal; U. G. Peckman

2001-01-01

304

Cease-fire at the leading edge: new perspectives on actin filament branching, debranching and cross-linking  

PubMed Central

Membrane protrusion at the leading edge of migrating cells is driven by the polymerization of actin. Recent studies using advanced imaging techniques raised a lively controversy about the morphology of these filaments; however, common ground between the two sides now appears to have been found. Here we discuss how the controversy has led to a deeper consideration of the architecture of actin networks underlying cell migration, and has helped define new challenges that lie ahead.

Ydenberg, Casey A.; Smith, Benjamin A.; Breitsprecher, Dennis; Gelles, Jeff; Goode, Bruce L.

2011-01-01

305

Wind-Tunnel Tests on Various Types of Dive Brakes Mounted in Proximity of the Leading Edge of the Wing  

NASA Technical Reports Server (NTRS)

The present report is concerned with a series of tests on a model airplane fitted with four types of dive flaps of various shapes, positions, and incidence located near the leading edge of the wing (from 5 to 20 percent of the wing chord). Tests were also made on a stub airfoil fitted with a ventral dive (located at 8 percent of the wing chord). The hinge moments of the dive flaps were measured.

Lattanzi, Bernardino; Bellante, Erno

1949-01-01

306

Sequential activation of Rap1 and Rac1 small G proteins by PDGF locally at leading edges of NIH3T3 cells.  

PubMed

Moving cells form protrusions, such as filopodia and lamellipodia, and focal complexes at leading edges, which eventually enhance cell movement. The Rho family small G proteins, Rac1, Cdc42 and RhoA, are involved in the formation of these leading edge structures. We investigated the role of another small G protein Rap1 in the platelet-derived growth factor (PDGF)-induced formation of leading edge structures and cell movement. Upon stimulation of NIH3T3 cells by PDGF, leading edge structures were formed and Necl-5, integrin alpha(V)beta(3), and PDGF receptor were accumulated at leading edges. Rap1, upstream regulators of Rap1 such as Crk and C3G, and a downstream effector RalGDS, were accumulated at peripheral ruffles over lamellipodia. Over-expression of Rap1GAP, which inactivates Rap1, and knockdown of Rap1 inhibited the PDGF-induced formation of leading edge structures, accumulation of these molecules, and cell movement. In addition, Rap1 activation subsequently induced accumulation of Rac1, Vav2 and PAK at peripheral ruffles, which was inhibited by Rap1GAP and knockdown of Rap1. These results indicate that Rap1, activated by PDGF, is recruited to leading edges and that Rac1 is thereby activated locally at peripheral ruffles. This process is pivotal for the PDGF-induced formation of leading edge structures and cell movement. PMID:18422604

Takahashi, Motonori; Rikitake, Yoshiyuki; Nagamatsu, Yuichi; Hara, Tetsuya; Ikeda, Wataru; Hirata, Ken-ichi; Takai, Yoshimi

2008-06-01

307

Electrostriction of lead zirconate titanate/polyurethane composites  

SciTech Connect

Electrostriction of a ferroelectric inclusion/nonferroelectric matrix composite system was studied. The samples were prepared by blending the lead zirconate titanate (PZT) particles with the thermoplastic polyurethane through extrusion and subsequently by hot pressing. Quasistatic cyclic electric fields were applied across the samples while strains and currents were monitored simultaneously. It was found that the electrostriction of the composites depended on the applied electric field in a hysteretic manner. In particular at the high-field regime, the samples exhibited a reversal in the electrostrictive strain. This switching effect occurred at a critical field which was inversely proportional to the PZT content. An associated increase in the displacement current with the critical field was also observed. It indicates that the switching in strain of the composites was mainly due to the flipping of the PZT dipoles in the nonferroelectric polymer matrix. A model was developed for describing the electrostriction behavior of this composite system and the calculated results are comparable to the experimental curves. The success of this theoretical model encourages its application further to the ferroelectric-ferroelectric composite systems.

Lam, K.S.; Zhou, Y.; Wong, Y.W.; Shin, F.G. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)

2005-05-15

308

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.

309

Numerical Simulation of Fluctuations Leading to Noise in a Flap-Edge Flowfield  

NASA Technical Reports Server (NTRS)

In this paper we develop an approximate computational framework for simulation of the fluctuating flowfield associated with the complex vortex system seen at the side edge of a flap in a multi-element high-lift airfoil system. The eventual goal of these simulations is to provide an estimate of the spectral content of these fluctuations, in order that the spectrum of the noise generated by such flowfields may be estimated. Results from simulations utilizing this computational framework are shown.

Streett, C. L.

1998-01-01

310

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

311

A composite view on Windenburg's problem: Buckling and minimum stiffness requirements of compressively loaded orthotropic plates with edge reinforcements  

Microsoft Academic Search

This paper discusses the buckling behaviour of orthotropic composite plates under uniform uniaxial compression with one free reinforced unloaded edge. A typical application example for use of such a mechanical model is the web of stiffeners and frames attached to the fuselage skin of an aircraft. The considered plates are rectangular and simply supported at the loaded transverse edges. One

Christian Mittelstedt; Martin Schagerl

2010-01-01

312

Plasma-surface interaction at sharp edges and corners during ion-assisted physical vapor deposition. Part I: Edge-related effects and their influence on coating morphology and composition  

NASA Astrophysics Data System (ADS)

Ion-assisted physical vapor deposition (PVD) is a common industrial method for growing thin coatings of various interstitial nitride alloys. The interaction between the ions and three-dimensional nonflat samples during the deposition can, however, lead to unwanted local changes in the properties of the coating and thus its performance. We analyze the characteristics of the ion bombardment during ion-assisted PVD on sharp convex substrates and their effect on the growing coating. We show that the magnitude and the spatial extent of the edge-related changes are directly related to the characteristics of the plasma sheath around the biased edges. We examine the influence of the edge geometry and the deposition conditions. The edge-related effects are studied on the example of wedge-shaped samples coated with TiAlN/VN by closed-field unbalanced magnetron deposition process using high-flux low-energy Ar+-ion irradiation (Ji/Jme~4, Ei=75-150 eV). The samples are analyzed by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Significant changes in the morphology, thickness, and composition of the coatings are found in the edge region. In order to account for the changes, we apply a self-consistent model of the plasma sheath around wedge-shaped samples proposed by Watterson [J. Phys. D 22, 1300 (1989)], to our conditions. For a 30° wedge coated at -150 V, the resputtering rate in the edge region is found to be increased by up to ten times as compared to flat substrate areas. The effect is due to the combined action of an increased ion flux and increased sputtering yield as a result of the nonperpendicular angle of incidence of ions in the edge region. The situation at sharp corners, where even more severe effects are observed, is analyzed and modeled in the companion article E. B. Macak et al., J. Appl. Phys. (2003) (Part II).

Macak, E. B.; Münz, W.-D.; Rodenburg, J. M.

2003-09-01

313

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

314

Lift augmentation on a delta wing via leading edge fences and the Gurney flap. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Wind tunnel tests were conducted on two devices for the purpose of lift augmentation on a 60 deg delta wing at low speed. Lift, drag, pitching moment, and surface pressures were measured. Detailed flow visualization was also obtained. Both the leading edge fence and the Gurney flap are shown to increase lift. The fences and flap shift the lift curve as much as 5 deg and 10 deg, respectively. The fences aid in trapping vortices on the upper surface, thereby increasing suction. The Gurney flap improves circulation at the trailing edge. The individual influences of both devices are roughly additive, creating high lift gain. However, the lower lift to drag ratio and the precipitation of vortex burst caused by the fences, and the nose down pitching moment created by the flap are also significant factors.

Buchholz, Mark D.

1992-01-01

315

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

316

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

NASA Technical Reports Server (NTRS)

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 survivability in a hostile environment. These analyses show a mixture of results from one configuration to the next. Results for each configuration are presented and discussed. Combinations of enhanced internal film coefficients and high material thermal conductivity of copper and tungsten are predicted to maintain the maximum wall temperature for each concept within acceptable operating limits. The exception is the TD nickel material which is predicted to melt for most cases. The wide range of internal impingement film coefficients (based on correlations) for these conditions can lead to a significant uncertainty in expected leading-edge wall temperatures. The equivalent plastic strain, inherent in each configuration which results from the high thermal gradients, indicates a need for further cyclic analysis to determine component life.

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

1990-01-01

317

Experimental study of flow separation control on a low- Re airfoil using leading-edge protuberance method  

NASA Astrophysics Data System (ADS)

An experimental study of flow separation control on a low- Re c airfoil was presently investigated using a newly developed leading-edge protuberance method, motivated by the improvement in the hydrodynamics of the giant humpback whale through its pectoral flippers. Deploying this method, the control effectiveness of the airfoil aerodynamics was fully evaluated using a three-component force balance, leading to an effectively impaired stall phenomenon and great improvement in the performances within the wide post-stall angle range (22°-80°). To understand the flow physics behind, the vorticity field, velocity field and boundary layer flow field over the airfoil suction side were examined using a particle image velocimetry and an oil-flow surface visualization system. It was found that the leading-edge protuberance method, more like low-profile vortex generator, effectively modified the flow pattern of the airfoil boundary layer through the chordwise and spanwise evolutions of the interacting streamwise vortices generated by protuberances, where the separation of the turbulent boundary layer dominated within the stall region and the rather strong attachment of the laminar boundary layer still existed within the post-stall region. The characteristics to manipulate the flow separation mode of the original airfoil indicated the possibility to further optimize the control performance by reasonably designing the layout of the protuberances.

Zhang, M. M.; Wang, G. F.; Xu, J. Z.

2014-04-01

318

Effects of Wing Leading Edge Penetration with Venting and Exhaust Flow from Wheel Well at Mach 24 in Flight  

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: (1) holes through the leading edge into a vented cavity; and (2) a scarfed, conical nozzle directed toward the centerline of the vehicle from the forward, inboard corner of the landing gear door. The simulations were generated relatively quickly and early in the investigation because simplifications were made to the leading edge cavity geometry and an existing utility to merge scarfed nozzle grid domains with structured baseline external domains was implemented. These simplifications in the breach simulations enabled: (1) a very quick grid generation procedure; and (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 two-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 six-inch diameter breach the boundary layer is fully ingested. The intent of externally directed jet simulations in the second scenario was to approximately model aerodynamic effects of a relatively large internal wing pressure, fueled by combusting aluminum, which deforms the corner of the landing gear door and directs a jet across the windside surface. These jet interactions, in and of themselves, were not sufficiently large to explain observed aerodynamic behavior.

Gnoffo, Peter A.

2003-01-01

319

Effects of Mach Number, Leading-Edge Bluntness, and Sweep on Boundary-Layer Transition on a Flat Plate  

NASA Technical Reports Server (NTRS)

The effects of leading-edge bluntness and sweep on boundary-layer transition on flat plate models were investigated at Mach numbers of 2.00, 2.50, 3.00, and 4.00. The effect of sweep on transition was also determined on a flat plate model equipped with an elliptical nose at a Mach number of 0.27. Models used for the supersonic investigation had leading-edge radii varying from 0.0005 to 0.040 inch. The free-stream unit Reynolds number was held constant at 15 million per foot for the supersonic tests and the angle of attack was 0 deg. Surface flow conditions were determined by visual observation and recorded photographically. The sublimation technique was used to indicate transition, and the fluorescent-oil technique was used to indicate flow separation. Measured Mach number and sweep effects on transition are compared with those predicted from shock-loss considerations as described in NACA Rep. 1312. For the models with the blunter leading edges, the transition Reynolds number (based on free-stream flow conditions) was approximately doubled by an increase in Mach number from 2.50 to 4.00; and nearly the same result was predicted from shock-loss considerations. At all super- sonic Mach numbers, increases in sweep reduced the transition Reynolds number and the amount of reduction increased with increases in bluntness. The shock-loss method considerably underestimated- the sweep effects, possibly because of the existence of crossflow instability associated with swept wings. At a Mach number of 0.27, no reduction in the transition Reynolds number with sweep was measured (as would be expected with no shock loss) until the sweep angle was attained where crossflow instability appeared.

Jillie, Don W.; Hopkins, Edward J.

1961-01-01

320

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

321

A Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings  

NASA Technical Reports Server (NTRS)

A survey is presented of factors affecting blunt leading-edge separation for swept and semi-slender wings. This class of separation often results in the onset and progression of separation-induced vortical flow over a slender or semi-slender wing. The term semi-slender is used to distinguish wings with moderate sweeps and aspect ratios from the more traditional highly-swept, low-aspect-ratio slender wing. Emphasis is divided between a selection of results obtained through literature survey a section of results from some recent research projects primarily being coordinated through NATO s Research and Technology Organization (RTO). An aircraft context to these studies is included.

Luckring, James M.

2010-01-01

322

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

323

Interlaminar fracture toughness of composites. II - Refinement of the edge delamination test and application to thermoplastics  

NASA Technical Reports Server (NTRS)

The mixed mode interlaminar fracture toughness, G(c), is obtained for the two thermoplastic matrices UDEL P1700 polysulfone and ULTEM polyetherimide by means of edge delamination tensile (EDT) tests on unnotched, eleven-ply graphite fiber reinforced composite specimens. A novel method is used to obtain the stiffness parameter employed in the closed form equation for the calculation of G(c), decreasing the number of stiffness measurements required and simplifying the calculations. The G(Ic) values from double cantilever beam (DCB) measurements on composites of the two thermoplastics were similar to each other, but slightly higher than the G(c) data obtained by EDT. Interfacial resin/fiber failures predominated in both the EDT and DCB tests.

Johnston, N. J.; Obrien, T. K.; Morris, D. H.; Simonds, R. A.

1983-01-01

324

Visco-elastic properties and edge stress relaxation of laminated composite materials  

SciTech Connect

Applicability of the Schapery single-integral nonlinear visco-elastic constitutive model to describe time-dependent mechanical behavior of laminated composite materials containing two visco-elastic phases was explored. Procedures to measure all five visco-elastic material properties necessary to describe visco-elastic behavior of a transversely isotropic continuous-fiber unidirectional lamina were implemented. Measurement of the through-the-thickness or interlaminar shear visco-elastic response required development of a new test methodology. The losipescu shear test method was selected for this purpose. The visco-elastic response of unidirectional DuPont Kevlar KV49/Hercules 3501-6 epoxy was measured. An automated data-reduction scheme was developed to facilitate description of visco-elastic properties using the Schapery single-integral approach. The basis for this data-reduction scheme differs from similar approaches used by other investigators in that time-superposition features of linear visco-elasticity are preserved. Finally, measured visco-elastic properties of KV49/3501-6 were used to model the interlaminar shear-stress relaxation that occurs near free edges in symmetric angle-ply laminated composite materials loaded by uniform axial extension. Interlaminar stresses induced near free edges were shown to be time-dependent for KV49/3501-6.

Walrath, D.E.

1986-01-01

325

Convergence of strain energy release rate components for edge-delaminated composite laminates  

NASA Technical Reports Server (NTRS)

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strain was studied. The individual components of the strain energy release rates did not show convergence as the delamination tip elements were made smaller. In contrast, the total strain energy release rate converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes.

Raju, I. S.; Crews, J. H., Jr.; Aminpour, M. A.

1987-01-01

326

Convergence of strain energy release rate components for edge-delaminated composite laminates  

NASA Technical Reports Server (NTRS)

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strain was studied. The individual components of the strain energy release rates did not show convergence as the delamination tip elements were made smaller. In contrast, the total strain energy release rate converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes.

Raju, I. S.; Crews, J. H., Jr.; Aminpour, M. A.

1988-01-01

327

Edge delamination of composite laminates subject to combined tension and torsional loading  

NASA Technical Reports Server (NTRS)

Delamination is a common failure mode of laminated composite materials. Edge delamination is important since it results in reduced stiffness and strength of the laminate. The tension/torsion load condition is of particular significance to the structural integrity of composite helicopter rotor systems. Material coupons can easily be tested under this type of loading in servo-hydraulic tension/torsion test stands using techniques very similar to those used for the Edge Delamination Tensile Test (EDT) delamination specimen. Edge delamination of specimens loaded in tension was successfully analyzed by several investigators using both classical laminate theory and quasi-three dimensional (Q3D) finite element techniques. The former analysis technique can be used to predict the total strain energy release rate, while the latter technique enables the calculation of the mixed-mode strain energy release rates. The Q3D analysis is very efficient since it produces a three-dimensional solution to a two-dimensional domain. A computer program was developed which generates PATRAN commands to generate the finite element model. PATRAN is a pre- and post-processor which is commonly used with a variety of finite element programs such as MCS/NASTRAN. The program creates a sufficiently dense mesh at the delamination crack tips to support a mixed-mode fracture mechanics analysis. The program creates a coarse mesh in those regions where the gradients in the stress field are low (away from the delamination regions). A transition mesh is defined between these regions. This program is capable of generating a mesh for an arbitrarily oriented matrix crack. This program significantly reduces the modeling time required to generate these finite element meshes, thus providing a realistic tool with which to investigate the tension torsion problem.

Hooper, Steven J.

1990-01-01

328

AMELIA CESTOL Test: Acoustic Characteristics of Circulation Control Wing with Leading- and Trailing-Edge Slot Blowing  

NASA Technical Reports Server (NTRS)

The AMELIA Cruise-Efficient Short Take-off and Landing (CESTOL) configuration concept was developed to meet future requirements of reduced field length, noise, and fuel burn by researchers at Cal Poly, San Luis Obispo and Georgia Tech Research Institute under sponsorship by the NASA Fundamental Aeronautics Program (FAP), Subsonic Fixed Wing Project. The novel configuration includes leading- and trailing-edge circulation control wing (CCW), over-wing podded turbine propulsion simulation (TPS). Extensive aerodynamic measurements of forces, surfaces pressures, and wing surface skin friction measurements were recently measured over a wide range of test conditions in the Arnold Engineering Development Center(AEDC) National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Ft Wind Tunnel. Acoustic measurements of the model were also acquired for each configuration with 7 fixed microphones on a line under the left wing, and with a 48-element, 40-inch diameter phased microphone array under the right wing. This presentation will discuss acoustic characteristics of the CCW system for a variety of tunnel speeds (0 to 120 kts), model configurations (leading edge(LE) and/or trailing-edge(TE) slot blowing, and orientations (incidence and yaw) based on acoustic measurements acquired concurrently with the aerodynamic measurements. The flow coefficient, Cmu= mVSLOT/qSW varied from 0 to 0.88 at 40 kts, and from 0 to 0.15 at 120 kts. Here m is the slot mass flow rate, VSLOT is the slot exit velocity, q is dynamic pressure, and SW is wing surface area. Directivities at selected 1/3 octave bands will be compared with comparable measurements of a 2-D wing at GTRI, as will as microphone array near-field measurements of the right wing at maximum flow rate. The presentation will include discussion of acoustic sensor calibrations as well as characterization of the wind tunnel background noise environment.

Horne, William C.; Burnside, Nathan J.

2013-01-01

329

The Influence of Projectile Trajectory Angle on the Simulated Impact Response of a Shuttle Leading Edge Wing Panel  

NASA Technical Reports Server (NTRS)

In support of recommendations by the Columbia Accident Investigation Board, a team has been studying the effect of debris impacting the reinforced carbon-carbon panels of the shuttle leading edge. The objective of this study was to examine the effect of varying parameters of the debris trajectory on the damage tolerance. Impacts at the upper and lower surface and the apex of the leading edge were examined. For each location, trajectory variances included both the alpha and beta directions. The results of the analysis indicated in all cases the beta sweep decreased the amount of damage to the panel. The increases in alpha resulted in a significant increase in damage to the RCC panel. In particular, for the lower surface, where the alpha can increase by 10 degrees, there was a nearly 40% increase in the impulse. As a result, it is recommended that for future analyses, a 10 degree offset in alpha from the nominal trajectory is included for impacts on the lower surface. It is also recommended to assume a straight aft, or zero beta, trajectory for a more conservative analysis.

Spellman, Regina L.; Jones, Lisa E.; Lyle, Karen H.; Jackson, Karen E.; Fasanella, Edwin L.

2005-01-01

330

Explanation of the effects of leading-edge tubercles on the aerodynamics of airfoils and finite wings  

NASA Astrophysics Data System (ADS)

A computational study was conducted to explain the aerodynamic effect of leading edge tubercles on maximum lift coefficient, stall angle of attack (AoA), drag, and post stall characteristics for airfoils as well as finite wings. Past experiments demonstrated airfoils with leading edge tubercles do not improve Clmax, drag, or stall AoA but smoothen post stall characteristics to a great degree. In contrast to airfoils, finite wings with L.E. tubercles improved all aerodynamic characteristics. We explain the stall mechanism of the tubercled wing by considering each L.E. tubercle as a combination of a swept forward and a swept backward wing.There are 3 mechanisms (streamline curvature, accelerated stall, and upwash) that cause Clmax of airfoils with L.E. tubercles always be lower than that of smooth airfoils. We also identify two additional mechanisms which are responsible for improved post-stall characteristics of airfoils with L.E. tubercles. Finally, we discuss why finite wings with L.E. tubercles have higher Clmax and lower drag than their smooth L.E. counterparts by studying effects of wing tip, sweep, and taper ratio.

Saadat, Mehdi; Haj-Hariri, Hossein; Fish, Frank

2010-11-01

331

Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells  

PubMed Central

Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells.

Howes, Mark T.; Kirkham, Matthew; Riches, James; Cortese, Katia; Walser, Piers J.; Simpson, Fiona; Hill, Michelle M.; Jones, Alun; Lundmark, Richard; Lindsay, Margaret R.; Hernandez-Deviez, Delia J.; Hadzic, Gordana; McCluskey, Adam; Bashir, Rumasia; Liu, Libin; Pilch, Paul; McMahon, Harvey; Robinson, Phillip J.; Hancock, John F.; Mayor, Satyajit

2010-01-01

332

Program for Computing the Pressure Distribution and Aerodynamic Coefficients for Cambered Thin Supersonic Wings of Arbitrary Planform with Subsonic Leading Edges.  

National Technical Information Service (NTIS)

The computer solution to the linearized potential flow equations which gives a reasonably accurate description of the pressure distribution for thin cambered supersonic wings with subsonic leading edges is presented. The program will compute the aerodynam...

B. L. Van Buren

1973-01-01

333

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

334

Leading Edge Flame Detachment: Effect on Burning Rate of Ammonium Perchlorate Propellants  

NASA Technical Reports Server (NTRS)

Inner details of the transition from premixed to diffusion controlled burning are examined by considering the transition at the individual particle flamelet level. These considerations lead to prediction of observable singular burning rate behavior of bimodal AP formulations. Burning rate measurements verify the predictions, supporting the view that particle flamelets become detached and retreat to more remote premixed locations at definite (particles size dependent) pressures, revealed by the burning rate tests.

Price, E. W.; Chakravarthy, S. R.; Sambamurthi, J. K.; Sigman, R. K.

1997-01-01

335

Application of an aerodynamic analysis method including attainable thrust estimates to low speed leading-edge flap design for supersonic cruise vehicles  

NASA Technical Reports Server (NTRS)

A study of low speed leading-edge flap design for supersonic cruise vehicle was conducted. Wings with flaps were analyzed with the aid of a newly developed subsonic wing program which provides estimates of attainable leading-edge thrust. Results indicate that the thrust actually attainable can have a significant influence on the design and that the resultant flaps can be smaller and simpler than those resulting from more conventional approaches.

Carlson, H. W.

1982-01-01

336

A study of the effect of the temperature factor on pressure losses in the cooling system of the leading edge of a deflector vane  

NASA Astrophysics Data System (ADS)

Reference is made to several earlier studies in which pressure losses associated with the use of single-row and multiple-row jet cooling of the leading edge of nozzle vanes of gas turbine engines have been estimated using independent models of the leading edge. Here, experiments are carried out on a specially designed high-temperature gasdynamic test bench in order to verify the validity of the earlier results and also to determine the effect of process nonisothermality on pressure losses.

Arkhipov, A. I.; Limanskii, A. S.; Rumiantsev, V. V.; Khasbiullin, M. M.

337

Space Shuttle Orbiter - Leading edge structural design/analysis and material allowables  

NASA Technical Reports Server (NTRS)

Reinforced Carbon-Carbon (RCC), a structural composite whose development was targeted for the high temperature reentry environments of reusable space vehicles, has successfully demonstrated that capability on the Space Shuttle Orbiter. Unique mechanical properties, particularly at elevated temperatures up to 3000 F, make this material ideally suited for the 'hot' regions of multimission space vehicles. Design allowable characterization testing, full-scale development and qualification testing, and structural analysis techniques will be presented herein that briefly chart the history of the RCC material from infancy to eventual multimission certification for the Orbiter. Included are discussions pertaining to the development of the design allowable data base, manipulation of the test data into usable forms, and the analytical verification process.

Johnson, D. W.; Curry, D. M.; Kelly, R. E.

1986-01-01

338

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

339

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

NASA Astrophysics Data System (ADS)

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 edge'' of the North American continent. Fundamental concepts and observations progress from global patterns, to regional context, and then to local applications. For example, earthquakes are concentrated near tectonic plate boundaries such as the Cascadia subduction zone between the Juan de Fuca and North American plates. Earthquake hazards include liquefaction and landslides that are affected by regional and local geology. And relative earthquake hazard maps provide comparisons of hazards on county, city, and neighborhood scales. Inquiry-based field investigation of coastal ghost forests and Cascadia tsunami geology stimulates learning about Cascadia great earthquakes and tsunamis and provides a case study of scientific discovery. Field studies of volcanic mudflow (lahar) deposits from Mt Hood and Mt Rainier highlight volcanic hazards to rapidly increasing populations that live near recently active Cascade volcanoes. We emphasize the importance of infrastructure engineering and emergency preparedness in preventing geologic hazards damage, injuries, and deaths in order to: (1) demonstrate how Geoscience research leads to improved engineering designs that mitigate hazards; (2) align lessons with national and state K-12 science education standards that focus on science, technology, and societal connections; and (3) avoid fatalism and develop a culture of geologic hazards awareness among future citizens of the Pacific Northwest.

Butler, Robert

2010-03-01

340

Why specific mixed solvent composition leads to appropriate film formation of composite during spin coating?  

NASA Astrophysics Data System (ADS)

In this paper, we explain why specific mixed solvent composition leads to appropriate film formation of composite (polymer: inorganic nanoparticle) during spin coating. As a typical case, P3HT:TiO2 film formation has been discussed by taking chloroform as good solvent for P3HT while ethanol, methanol, and 2-propanol are used as co-solvents for dispersing TiO2. Mixed solvent evaporation dynamics during film drying has been simulated to explain the experimental results. Present study can be immensely useful for selecting proper solvents and their initial ratio for blend film formation of a particular phase separation.

Ghosh, S. S.; Zerwal, A. P.; Bisen, G. G.; Lonkar, G. S.; Sali, J. V.; Waman, V. S.; Jadkar, S. R.

2013-02-01

341

Equations and charts for the rapid estimation of hinge-moment and effectiveness parameters for trailing-edge controls having leading and trailing edges swept ahead of the Mach lines  

NASA Technical Reports Server (NTRS)

Existing conical-flow solutions have been used to calculate the hinge-moments and effectiveness parameters of trailing-edge controls having leading and trailing edges swept ahead of the Mach lines and having streamwise root and tip chords. Equations and detailed charts are presented for the rapid estimation of these parameters. Also included is an approximate method by which these parameters may be corrected for airfoil-section thickness.

Goin, Kennith L

1951-01-01

342

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

343

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

344

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

345

Effects of wing leading-edge radius and Reynolds number on longitudinal aerodynamic characteristics of highly swept wing-body configurations at subsonic speeds  

NASA Technical Reports Server (NTRS)

An investigation was conducted in the Langley low turbulence pressure tunnel to determine the effects of wing leading edge radius and Reynolds number on the longitudinal aerodynamic characteristics of a series of highly swept wing-body configurations. The tests were conducted at Mach numbers below 0.30, angles of attack up to 16 deg, and Reynolds numbers per meter from 6.57 million to 43.27 million. The wings under study in this investigation had leading edge sweep angles of 61.7 deg, 64.61 deg, and 67.01 deg in combination with trailing edge sweep angles of 0 deg and 40.6 deg. The leading edge radii of each wing planform could be varied from sharp to nearly round.

Henderson, W. P.

1976-01-01

346

AMELIA CESTOL Test: Acoustic Characteristics of Circulation Control Wing with Leading-and Trailing-Edge Slot Blowing  

NASA Technical Reports Server (NTRS)

Aeroacoustic measurements of the 11 % scale full-span AMELIA CESTOL model with leading- and trailing-edge slot blowing circulation control (CCW) wing were obtained during a recent test in the Arnold Engineering Development Center 40- by 80-Ft. Wind Tunnel at NASA Ames Research Center, Sound levels and spectra were acquired with seven in-flow microphones and a 48-element phased microphone array for a variety of vehicle configurations, CCW slot flow rates, and forward speeds, Corrections to the measurements and processing are in progress, however the data from selected configurations presented in this report confirm good measurement quality and dynamic range over the test conditions, Array beamform maps at 40 kts tunnel speed show that the trailing edge flap source is dominant for most frequencies at flap angles of 0deg and 60deg, The overall sound level for the 60deg flap was similar to the 0deg flap for most slot blowing rates forward of 90deg incidence, but was louder by up to 6 dB for downstream angles, At 100 kts, the in-flow microphone levels were louder than the sensor self-noise for the higher blowing rates, while passive and active background noise suppression methods for the microphone array revealed source levels as much as 20 dB lower than observed with the in-flow microphones,

Horne, Clifton; Burnside, Nathan J.

2013-01-01

347

Recent advances in the solution of three-dimensional flow over wings with leading edge vortex separation  

NASA Technical Reports Server (NTRS)

Recent advances in a panel method for the solution of three-dimensional flow about wing and wing-body combinations with leading-edge vortex separation are presented. These advances were achieved as part of an ultimately successful assault on two shortcomings of the method, namely convergence failures in seemingly random cases, and overprediction of lift coefficient for high aspect-ratio wings. Advances include the implementation of improved panel numerics for the purpose of eliminating the highly non-linear effects of ring vortices around doublet panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A variety of cases generated by the computer program implementing the method are presented. These cases are of two types. The first type consists of numerical studies, which verify the underlying mathematical assumptions of the method and moreover show that the results are strongly invariant with respect to such user dependent input as wing panel layout, initial sheet shape, sheet rollup, etc. The second type consists of cases run for the purpose of comparing computed results with experimental data, and these comparisons verify the underlying physical assumptions made by the method.

Johnson, F. T.; Tinoco, E. N.; Lu, P.; Epton, M. A.

1979-01-01

348

Air forces and moments on triangular and related wings with subsonic leading edges oscillating in supersonic potential flow  

NASA Technical Reports Server (NTRS)

This analysis treats the air forces and moments in supersonic potential flow on oscillating triangular wings and a series of sweptback and arrow wings with subsonic leading edges and supersonic trailing edges. For the wings undergoing sinusoidal torsional oscillations simultaneously with vertical translations, the linearized velocity potential is derived in the form of a power series in terms of a frequency parameter. This method can be useful for treatment of similar problems for other plan forms and for wings undergoing other sinusoidal motions. For triangular wings, as many terms of such a series expansion as may be derived can be determined; however, the terms after the first few become very cumbersome. Closed expressions that include the reduced frequency to the fifth power, an order which is sufficient for a large class of practical application, are given for the velocity potential and for the components of chordwise section force and moment coefficients. These wings are found to exhibit the possibility of undamped torsional oscillations for certain ranges of Mach number and locations of the axis of rotation. The ranges of these parameters are delineated for triangular wings.

Watkins, Charles E; Berman, Julian N

1952-01-01

349

Predictive process simulation of cryogenic implants for leading edge transistor design  

SciTech Connect

Two cryogenic implant TCAD-modules have been developed: (i) A continuum-based compact model targeted towards a TCAD production environment calibrated against an extensive data-set for all common dopants. Ion-specific calibration parameters related to damage generation and dynamic annealing were used and resulted in excellent fits to the calibration data-set. (ii) A Kinetic Monte Carlo (kMC) model including the full time dependence of ion-exposure that a particular spot on the wafer experiences, as well as the resulting temperature vs. time profile of this spot. It was calibrated by adjusting damage generation and dynamic annealing parameters. The kMC simulations clearly demonstrate the importance of the time-structure of the beam for the amorphization process: Assuming an average dose-rate does not capture all of the physics and may lead to incorrect conclusions. The model enables optimization of the amorphization process through tool parameters such as scan speed or beam height.

Gossmann, Hans-Joachim; Zographos, Nikolas; Park, Hugh; Colombeau, Benjamin; Parrill, Thomas; Khasgiwale, Niranjan; Borges, Ricardo; Gull, Ronald; Erokhin, Yuri [Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States); Synopsys Switzerland LLC, Thurgauerstrasse 40, 8050 Zuerich (Switzerland); Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States); Synopsys Inc., 1101 Slater Road, Durham, NC 27703 (United States); Synopsys Switzerland LLC, Thurgauerstrasse 40, 8050 Zuerich (Switzerland); Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States)

2012-11-06

350

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

351

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.  

National Technical Information Service (NTIS)

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 appare...

W. A. Newsom D. R. Satran J. L. Johnson

1982-01-01

352

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

353

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

354

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

355

Syk-Mediated Translocation of PI3K? to the Leading Edge Controls Lamellipodium Formation and Migration of Leukocytes  

PubMed Central

The non-receptor tyrosine kinase Syk is mainly expressed in the hematopoietic system and plays an essential role in ?2 integrin-mediated leukocyte activation. To elucidate the signaling pathway downstream of Syk during ?2 integrin (CD11/CD18)-mediated migration and extravasation of polymorphonuclear neutrophils (PMN), we generated neutrophil-like differentiated HL-60 (dHL-60) cells expressing a fluorescently tagged Syk mutant lacking the tyrosine residue at the position 323 (Syk-Tyr323) that is known to be required for the binding of the regulatory subunit p85 of the phosphatidylinositol 3-kinase (PI3K) class IA. Syk-Tyr323 was found to be critical for the enrichment of the catalytic subunit p110? of PI3K class IA as well as for the generation of PI3K products at the leading edge of the majority of polarized cells. In accordance, the translocation of PI3K p110? to the leading edge was diminished in Syk deficient murine PMN. Moreover, the expression of EGFP-Syk Y323F interfered with proper cell polarization and it impaired efficient migration of dHL-60 cells. In agreement with a major role of ?2 integrins in the recruitment of phagocytic cells to sites of lesion, mice with a Syk-deficient hematopoietic system demonstrated impaired PMN infiltration into the wounded tissue that was associated with prolonged cutaneous wound healing. These data imply a novel role of Syk via PI3K p110? signaling for ?2 integrin-mediated migration which is a prerequisite for efficient PMN recruitment in vivo.

Sindrilaru, Anca; Gerstl, Ronald; Jakus, Zoltan; Tybulewicz, Victor L. J.; Scharffetter-Kochanek, Karin; Walzog, Barbara

2007-01-01

356

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

SciTech Connect

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-{sup 3}H)diaminopimelic acid (({sup 3}H)Dap). The second method was autoradiography of cells pulse-labeled with ({sup 3}H)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 ({sup 3}H)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 ({sup 3}H)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.

Wientjes, F.B.; Nanninga, N. (Univ. of Amsterdam (Netherlands))

1989-06-01

357

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

358

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

359

Effects of Outboard Thickened and Blunted Leading Edges on the Wave Drag of a 45 Degree Swept-Wing and Body Combination  

NASA Technical Reports Server (NTRS)

An investigation to evaluate the effects of thickened and blunted leading-edge modifications on the wave drag of a swept wing has been made at Mach numbers from 0.65 to 2.20 and at a Reynolds number of 2,580,000 based on the mean aerodynamic chord of the basic wing. Two leading-edge designs were investigated and they are referred to as the thickened and the blunted modifications although both sections had equally large leading-edge radii. The thickened leading edge was formed by increasing the thickness over the forward 40 percent of the basic wing section. The blunted modification was formed by reducing the wing chords about 1 percent and by increasing the section thickness slightly over the forward 6 percent of the basic section in a manner to keep the wing sweep and volume essentially equal to the respective values for the basic wing. The basic wing had an aspect ratio of 3, a leading-edge sweep of 45 deg., a taper ratio of 0.4, and NACA 64AO06 sections perpendicular to a line swept back 39.45 deg., the quarter-chord line of these sections. Test results indicated that the thickened modification resulted in an increase in zero-lift drag coefficient of from 0.0040 to 0.0060 over values for the basic model at Mach numbers at which the wing leading edge was sonic or supersonic. Although drag coefficients of both the basic and thickened models were reduced at all test Mach numbers by body indentations designed for the range of Mach numbers from 1.00 to 2.00, the greater drag of the thickened model relative to that of the basic model was not reduced. The blunted model, however, had less than one quarter of the drag penalty of the thickened model relative to the basic model at supersonic leading-edge conditions (M greater or equal to root-2).

Holdaway, George H.; Lazzeroni, Frank A.; Hatfield, Elaine W.

1959-01-01

360

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

361

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

362

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

363

Na Kika: Secure Service Execution and Composition in an Open Edge-Side Computing Network  

Microsoft Academic Search

Making the internet's edge easily extensible fosters col- laboration and innovation on web-based applications, but also raises the problem of how to secure the execution platform. This paper presents Na Kika, an edge-side computing network, that addresses this tension between extensibility and security; it safely opens the internet's edge to all content producers and consumers. First, Na Kika expresses services

Robert Grimm; Guy Lichtman; Nikolaos Michalakis; Amos Elliston; Adam Kravetz; Jonathan Miller; Sajid Raza

2006-01-01

364

Initiation and Growth of Transverse Cracks and Edge Delamination in Composite Laminates Part 1. An Energy Method  

Microsoft Academic Search

This paper is concerned with the basic fracture mechanisms involved in matrix-dominated failures in fibrous composite laminates, Specifically, interlaminar fracture in the form of free-edge ply delamination and intra- laminar fracture in the form of multiple transverse cracks are investigated. In each case, a theory is formulated based on the classical linear fracture mechanics concept of strain energy release rate

A. S. D. Wang; F. W. Crossman

1980-01-01

365

PIP3-independent activation of TorC2 and PKB at the cell's leading edge mediates chemotaxis  

PubMed Central

Summary Background Studies show that high phosphotidylinositol 3,4,5 tris phosphate (PIP3) promotes cytoskeletal rearrangements and alters cell motility and chemotaxis, possibly through activation of PKBs. However, chemotaxis can still occur in the absence of PIP3 and the identities of the PIP3 independent pathways remain unknown. Results Here, we outline a PIP3-independent pathway linking temporal and spatial activation of PKBs by Tor complex 2 (TorC2) to the chemotactic response. Within seconds of stimulating Dictyostelium cells with chemoattractant, two PKB homologs, PKBA and PKBR1, mediate transient phosphorylation of at least eight proteins, including Talin, PI4P 5-kinase, two RasGefs, and a RhoGap. Surprisingly, all of the substrates are phosphorylated with normal kinetics in cells lacking PI 3-kinase activity. Cells deficient in TorC2 or PKB activity show reduced phosphorylation of the endogenous substrates and are impaired in chemotaxis. The PKBs are activated through phosphorylation of their hydrophobic motifs via TorC2 and subsequent phosphorylation of their activation loops. These chemoattractant-inducible events restricted to the cell’s leading edge even in the absence of PIP3. Activation of TorC2 depends on heterotrimeric G-protein function and intermediate G-proteins, including Ras GTPases. Conclusions The data lead to a model where cytosolic TorC2, encountering locally activated small G-protein(s) at the leading of the cell, becomes activated and phosphorylates PKBs. These in turn phosphorylate a series of signaling and cytoskeletal proteins, thereby regulating directed migration.

Kamimura, Yoichiro; Xiong, Yuan; Iglesias, Pablo A.; Hoeller, Oliver; Bolourani, Parvin; Devreotes, Peter N.

2008-01-01

366

A Textbook Argument: Definitions of Argument in Leading Composition Textbooks  

ERIC Educational Resources Information Center

This essay examines the definitions and practices of argument perpetuated by popular composition textbooks, illustrating how even those texts that appear to forward expansive notions of argument ultimately limit it to an intent to persuade. In doing so, they help perpetuate constricted practices of argument within undergraduate composition

Knoblauch, A. Abby

2011-01-01

367

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

SciTech Connect

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 well as experimental analyses, such cavities can be simplified in shape by a four-sided polygon with one curved side similar to the leading edge curvature, a rectangle with one semicircular side (often the smaller side) or a trapezoid, the smaller base of which is replaced by a semicircle. Furthermore, to enhance the heat transfer coefficient in these cavities, they are mostly roughened on three sides with ribs of different geometries. Experimental data on friction factors and heat transfer coefficients in such cavities are rare if not nonexistent. A liquid crystal technique was used in this experimental investigation to measure heat transfer coefficients in six test sections representing the leading-edge cooling cavities. Both straight and tapered ribs were configured on the two opposite sidewalls in a staggered arrangement with angles of attack to the mainstream flow, {alpha}, of 60 and 90 deg. The ribs on the curved surface were of constant cross section with an angle of attack 90 deg to the flow. Heat transfer measurements were performed on the straight sidewalls, as well as on the round surface adjacent to the blade leading edge. Effects such as rib angle of attack to the mainstream flow and constant versus tapered rib cross-sectional areas were also investigated. Nusselt numbers, friction factors, and thermal performances are reported for nine rib geometries in six test sections.

Taslim, M.E.; Li, T. [Northeastern Univ., Boston, MA (United States). Dept. of Mechanical Engineering; Spring, S.D. [GE Aircraft Engines, Lynn, MA (United States)

1997-07-01

368

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

369

Effects of wing leading-edge deflection on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration  

NASA Technical Reports Server (NTRS)

Wing leading-edge deflection effects on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration were determined. Static force tests were conducted in a V/STOL tunnel at a Reynolds number of about 2.5 x 1 million for an angle-of-attack range from -10 deg to 17 deg and an angle-of-sideslip range from -5 deg to 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.

1978-01-01

370

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

371

A numerical investigation of new film cooling hole configuration at the leading edge of asymmetrical turbine blade: part A  

NASA Astrophysics Data System (ADS)

The focus of the first part of this numerical study is to investigate the effects of two new configurations: (1) slot with cylindrical end and (2) slot with median cylindrical hole, generated by the combination between two film cooling configurations: cylindrical hole and uniform slot. Computational results are presented for a row of coolant injection holes on each side of an asymmetrical turbine blade model near the leading edge. For each configuration, three values of the radius are taken: R = 0.4, R = 0.8 and R = 1.2. The six cases simulations, thus obtained, are conducted for the same density ratio of 1.0 and the same inlet plenum pressure. A new parameter, Rc, is defined to measure the rate of blade coverage by the film cooling. Results show that, at the pressure side; for the two new configurations, the six studied cases exceed the case baseline in cooling effectiveness term with the best result obtained for R = 0.8 (case 2). For the suction side, only configurations with R = 0.4 (cases 1 and 4) provide an increase of film effectiveness compared to the case baseline. The following configuration: Cases 1 or 4 at the suction side and case 2 at the pressure side, gets the best thermal protection because of their higher coverage and strong cooling effectiveness.

Benabed, Mustapha

2013-04-01

372

Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing.  

PubMed

Following the identification and confirmation of the substructures of the leading-edge vortex (LEV) system on flapping wings, it is apparent that the actual LEV structures could be more complex than had been estimated in previous investigations. In this experimental study, we reveal for the first time the detailed three-dimensional (3-D) flow structures and evolution of the LEVs on a flapping wing in the hovering condition at high Reynolds number (Re=1624). This was accomplished by utilizing an electromechanical model dragonfly wing flapping in a water tank (mid-stroke angle of attack=60 degrees) and applying phase-lock based multi-slice digital stereoscopic particle image velocimetry (DSPIV) to measure the target flow fields at three typical stroke phases: at 0.125 T (T=stroke period), when the wing was accelerating; at 0.25 T, when the wing had maximum speed; and at 0.375 T, when the wing was decelerating. The result shows that the LEV system is a collection of four vortical elements: one primary vortex and three minor vortices, instead of a single conical or tube-like vortex as reported or hypothesized in previous studies. These vortical elements are highly time-dependent in structure and show distinct ;stay properties' at different spanwise sections. The spanwise flows are also time-dependent, not only in the velocity magnitude but also in direction. PMID:18375846

Lu, Yuan; Shen, Gong Xin

2008-04-01

373

Do rapid 'superbug' tests pay off? Balance the costs and benefits of leading-edge technology. Interview by Alan Joch.  

PubMed

As hospitals become increasingly sensitive to the health and financial consequences of health care-associated infections (HAIs), a new generation of molecular-based testing technologies promises to significantly shorten the time required to identify "superbugs" and other bacterial infections. The leading-edge techniques promise to reduce costs by helping hospitals quickly determine which patients to isolate because they carry active methicillin-resistant Staphylococcus aureus (MRSA) infections, for example, or which ones to release from prophylactic isolation because they ultimately tested negative for a dangerous infection. But diagnostic speed comes at a price--the costs to perform molecular tests are significantly higher than conventional methods. This challenges hospitals to balance health care expenses with medical efficacy, says molecular testing veteran Margie Morgan, Ph.D., scientific director at Cedars-Sinai Medical Center, Los Angeles. "The rapid methods can be extreme time savers and possibly help a great deal with the isolation of patients. But some of the tests may cost five times what manual methods might be, so there is a price for seeing so much of a reduction in time," she says. PMID:19288674

Morgan, Margie Ann

2009-02-01

374

Confinement Effects on Flows Past an In-Duct Rectangular Bluff Body with Semi-Circular Leading Edge  

NASA Astrophysics Data System (ADS)

This paper reports a numerical study of a two-dimensional time-dependent viscous flow past a rectangular bluff body with a Reynolds number Re = 6 073 based on bluff body height installed in a flow duct. The leading edge of the bluff body takes a semi-circular profile. The governing equations of the flow are solved with large-eddy simulation (LES) using a commercial computational fluid dynamics software FLUENT. The focus of the present study is to explore the effects of the ratio of the height of the bluff body H and the separation D between the bluff body and the duct wall surface. The numerical simulations are validated with the results obtained from a separate wind-tunnel experiment. Numerical simulations with various D/H are carried out. The numerical results show that the mean and instantaneous flow quantities are strongly dependent on the ratio D/H. The suppression effects of vortex shedding by the neighboring duct wall are highlighted by comparing the unsteady flow structure topology, dominant Strouhal number, lift and drag forces, etc. The mechanism for the suppression of vortex shedding suppression and its variation with D/H are analyzed, and its relevance to generation of flow inducing noise by a bluff body in a flow duct is discussed.

Yu, K. F.; Leung, R. C. K.; Lu, Z. B.; Cheng, L.; Chan, H. Y. H.

2011-09-01

375

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

376

Experimental Observations on the Deformation and Breakup of Water Droplets Near the Leading Edge of an Airfoil  

NASA Technical Reports Server (NTRS)

This work presents the 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. An airfoil model placed at the end of the rotating arm was moved at speeds of 50 to 90 m/sec. A monosize droplet generator was employed to produce droplets that were allowed to fall from above, perpendicular to the path of the airfoil at a given location. High speed imaging was employed to observe the interaction between the droplets and the airfoil. The high speed imaging allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. A tracking software program was used to measure from the high speed movies the horizontal and vertical displacement of the droplet against time. The velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of a given droplet from beginning of deformation to breakup and/or hitting the airfoil. Results are presented for droplets with a diameter of 490 micrometers at airfoil speeds of 50, 60, 70, 80 and 90 m/sec

Vargas, Mario; Feo, Alex

2011-01-01

377

Gene Expression Profiling of the Leading Edge of Cutaneous Squamous Cell Carcinoma: IL-24-Driven MMP-7.  

PubMed

The precise mechanisms governing invasion at the leading edge of squamous cell carcinoma (SCC) and its subsequent metastasis are not fully understood. We aimed to define the cancer-related molecular changes that distinguish noninvasive tumor from invasive SCC. To this end, we combined laser capture microdissection with complementary DNA (cDNA) microarray analysis. We defined invasion-associated genes as those differentially regulated only in invasive SCC nests, but not in actinic keratosis or in situ SCC, compared with normal epidermis. There were 383 upregulated and 354 downregulated genes in the "invasion set." SCC invasion was characterized by aberrant expression of various proteolytic molecules. We noted increased expression of MMP7 and IL-24 in invasive SCC. IL-24 induced the expression of matrix metallopeptidase 7 (MMP7) in SCC cells in culture. In addition, blocking of MMP7 by a specific antibody significantly delayed the migration of SCC cells in culture. These results suggest a possible contribution of IL-24 to SCC invasion via enhancing focal expression of MMP7, although IL-24 has been suggested to have antitumor growth effects in other cancer types. Identification of regional molecular changes that regulate cancer invasion may facilitate the development of new targeted treatments for aggressive cancer. PMID:24270662

Mitsui, Hiroshi; Suárez-Farińas, Mayte; Gulati, Nicholas; Shah, Kejal R; Cannizzaro, Maria V; Coats, Israel; Felsen, Diane; Krueger, James G; Carucci, John A

2014-05-01

378

Prediction of leading-edge transition and relaminarization phenomena on a subsonic multi-element high-lift system  

NASA Technical Reports Server (NTRS)

Boundary-layer transition and relaminarization may have a critical effect on the flow development about multi-element high-lift systems of subsonic transport jets with swept wings. The purpose of the research is to study these transition phenomena in the leading-edge region of the various elements of a high-lift system. The flow phenomena studied include transition to the attachment-line flow, relaminarization, and crossflow instability, and transition. The calculations are based on pressure distributions measured in flight on the NASA Transport Systems Research Vehicle (Boeing 737-100) at a wing station where the flow approximated infinite swept wing conditions. The results indicate that significant regions of laminar flow can exist on all flap elements in flight. In future flight experiments (planned for January-February, 1994) the extent of these regions, the transition mechanisms and the effect of laminar flow on the high-lift characteristics of the multi-element system will be further explored.

Vandam, C. P.

1993-01-01

379

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

380

Theoretical effect of modifications to the upper surface of two NACA airfoils using smooth polynomial additional thickness distributions which emphasize leading edge profile and which vary linearly at the trailing edge  

NASA Technical Reports Server (NTRS)

An investigation was conducted on a CDC 7600 digital computer to determine the effects of additional thickness distributions to the upper surface of airfoils. The additional thickness distribution had the form of a continuous mathematical function which disappears at both the leading edge and the trailing edge. Results were obtained at a Mach number of 0.2 with an angle of attack of 6 deg. All calculations employed the full potential flow equations for two dimensional flow. The relaxation method of Jameson was used for solution of the potential flow equations. It is shown that increasing the thickness and variations in shape increases the lift and the adverse pitching moment coefficients.

Hague, D. S.; Werz, A. W.

1975-01-01

381

Analysis of Composite Wipe Samples for Lead Content.  

National Technical Information Service (NTIS)

The United States government has responded to the existing hazard posed by the presence of lead-based paint in the nation's housing stock by enacting Title X (the Residential Lead-based Paint Hazard Reduction Act, of federal housing legislation). This Act...

N. Friederich K. Bauer

1996-01-01

382

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

383

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

384

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

385

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

386

Stability behaviour of arbitrarily laminated composite plates with free and elastically restrained unloaded edges  

Microsoft Academic Search

In this paper, the initial buckling loads and the corresponding buckling modes of symmetric rectangular laminated plates are investigated. The considered laminates are supposed to have a uniform thickness, are subjected to a linearly distributed inplane compressive normal load N110 and are simply supported at the two loaded edges with one free unloaded plate edge and with one simply supported

Christian Mittelstedt

2007-01-01

387

Lift, Drag, and Pitching Moment of an Aspect-Ratio-2 Triangular Wing with Leading-Edge Flaps Designed to Simulate Conical Camber  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effectiveness of leading-edge flaps in reducing the drag at lifting conditions of a triangular wing of aspect ratio 2.0. The flaps, deflected to simulate conically cambered wings having a wide range of design lift coefficients, were tested over a Mach number range of 0.70 to 2.22 through an angle-of-attack variation from -6 deg to +18 deg at a constant Reynolds number of 3.68 million based on the wing mean aerodynamic chord. A symmetrical wing of the same plan form and aspect ratio was also tested to provide a basis for comparison. The experimental results showed that with the flaps in the undeflected position, a small amount of fixed leading-edge droop incorporated over the outboard 5 percent of the wing semispan was as effective at high subsonic speeds as conical camber in improving the maximum lift-drag ratio above that of the symmetrical wing. At supersonic speeds, the penalty in minimum drag above that of the symmetrical wing was less than that incurred by conical camber. Deflecting the leading-edge flaps about the hinge line through 80 percent of the wing semispan resulted in further improvements of the drag characteristics at lift coefficients above 0.20 throughout the Mach number range investigated. The lift and pitching-moment characteristics were not significantly affected by the leading-edge flaps.

Menees, Gene P.

1958-01-01

388

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

389

An improved panel method for the solution of three-dimensional leading edge vortex flows Volume 2: User's guide and programmer's document  

NASA Technical Reports Server (NTRS)

A computer program developed for solving the subsonic, three dimensional flow over wing-body configurations with leading edge vortex separation is presented. Instructions are given for the proper set up and input of a problem into the computer code. Program input formats and output are described, as well as the overlay structure of the program. The program is written in FORTRAN.

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

1980-01-01

390

Preliminary Investigation in the NACA Low-Turbulence Tunnel of Low-Drag Airfoil Sections Suitable for Admitting Air at the Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation was carried out in the NACA low-turbulence tunnel to develop low-drag airfoil sections suitable for admitting air at the leading edge. A thickness distribution having the desired type of pressure distribution was found from tests of a flexible model. Other airfoil shapes were derived from this original shape by varying the thickness, the camper, the leading-edge radius, and the size of the leading-edge opening. Data are presented giving the characteristics of the airfoil shapes in the range of lift coefficients for high-speed and cruising flight. Shapes have been developed which show no substantial increases in drag over that of the same position along the chord. Many of these shapes appear to have higher critical compressibility speeds than plain airfoils of the same thickness. Low-drag airfoil sections have been developed with openings in the leading edge as large as 41.5 percent of the maximum thickness. The range of lift coefficients for low drag in several cases is nearly as large as that of the corresponding plain airfoil sections. Preliminary measurements of maximum lift characteristics indicate that nose-opening sections of the type herein considered may not produce any marked effects on the maximum lift coefficient.

von Doenhoff, Albert E.; Horton, Elmer A.

1942-01-01

391

Schallentstehungsmechanismen in Transsonischen Stroemungen Beim Auftreffen von Wirbeln Auf Eine Profilvorderkante (Noise Development in Transonic Flows at the Impact of Vortices on a Profile Leading Edge).  

National Technical Information Service (NTIS)

The production of noise in the interaction of a vortex with the leading edge of a profile in a transonic flow was investigated. The occurring phenomena are detected in the far field as noise (blade-vortex interaction noise). The vortex was produced as a v...

H. M. Lent

1986-01-01

392

Upper Cretaceous HP-LT metamorphism along the leading edge of the Mesozoic Bolkardag platform, southern Turkey  

NASA Astrophysics Data System (ADS)

HP/LT metamorphism within the Anatoliodes (Tav?anl? and Afyon zonses) provides key evidence of Late Cretaceous/Paleogene subduction of N the margin of the Tauride microcontinent. HP/LT metamorphism within the Bolkar Da? has long been suspected, but without supporting evidence until now. HP/LT rocks are exposed as disrupted stratiform bodies interbedded with pale-coloured meta-limestones (tens of metres thick in all) around the periphery of Kargöl, 20 km SE of Uluk??la. The outcrops are mapped as lying within the Bokar Da? stratigraphy, separate from lower grade accretionary melange and unmetamorphosed ophiolitic rocks further north. The age of the meta-basic rocks is uncertain but could be either Early Mesozoic or Late Meszoic based on comparison with the Ta?vanl? Zone elsewhere. The protoliths of the HP/LT rock are mostly meta-basic extrusives igneous rocks, including massive lava and lava breccia, mostly converted to amphibolite. The protoliths fall into two groups, alkaline (Nb/Y=1.43-2.05) and tholeiitic (Nb/Y=0.04-0.58). Chondrite-normalized REE patterns, N-MORB normalized multi-element diagrams and tectonic discrimination diagrams suggest that the alkaline amphibolites were derived from the metamorphism of intra-plate basaltic rocks. The tholeiitic amphibolites form two groups, one characterized by slightly LREE-enriched (La/YbN=1,74-2,67) patterns and progressive enrichment in LIL elements; this has a similarity to enriched-mid ocean ridge basalts (E-MORB). The second group of tholeiitic amphibolites is characterized by LREE-depleted (La/YbN=0,57-0,90) rare earth element patterns. Multi-element diagram of this group exhibits strong negative Nb anomalies and flat HFS elements compared to N-MORB, suggesting a subduction influence on magmatism. Petrographic studies of the amphibolites indicate a blueschist facies overprint, represented by glaucophane. 40Ar-39Ar isotopic age determinations performed on amphibole separates yielded ages from 92.29±0.38 Ma to 94.96±0.50 Ma (Turonian), similar to the Tav?anl? zone elsewhere. The oldest rocks unconformably overlying the HP/LT rocks are Upper Paleocene to Middle Eocene sediments. However, detrital glaucophane is present in Maastrichtian sediments which unconformably overlie the accretionary melange further NE. Taken together, the available data suggest the the meta-basic rocks and interbedded meta-carbonate rocks represent part of the northerly, leading edge of the Bolkar continental unit, which subducted at a N-dipping subduction zone during the Late Cretaceous. During the collision of the subduction trench with the passive margin, the leading edge of the Tauride microcontinent was deeply underthrust and metamorphosed under HP-LT conditions.The HP-LT rocks were exhumed by the Maastrichtian. The new evidence supports the existence of a Mesozoic basin directly north of the Bolkar continental unit, known as the Inner Tauride ocean.

Parlak, Osman; Kop, Alican; Robertson, Alastair; Karaoglan, Fatih; Neubauer, Franz; Koepke, Jürgen

2014-05-01

393

Theoretical effect of modifications to the upper surface of two NACA airfoils using smooth polynomial additional thickness distributions which emphasize leading edge profile and which vary quadratically at the trailing edge. [using flow equations and a CDC 7600 computer  

NASA Technical Reports Server (NTRS)

An investigation was conducted on a CDC 7600 digital computer to determine the effects of additional thickness distributions to the upper surface of the NACA 64-206 and 64 sub 1 - 212 airfoils. The additional thickness distribution had the form of a continuous mathematical function which disappears at both the leading edge and the trailing edge. The function behaves as a polynomial of order epsilon sub 1 at the leading edge, and a polynomial of order epsilon sub 2 at the trailing edge. Epsilon sub 2 is a constant and epsilon sub 1 is varied over a range of practical interest. The magnitude of the additional thickness, y, is a second input parameter, and the effect of varying epsilon sub 1 and y on the aerodynamic performance of the airfoil was investigated. Results were obtained at a Mach number of 0.2 with an angle-of-attack of 6 degrees on the basic airfoils, and all calculations employ the full potential flow equations for two dimensional flow. The relaxation method of Jameson was employed for solution of the potential flow equations.

Merz, A. W.; Hague, D. S.

1975-01-01

394

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

395

A closed-form solution for stresses at curved free edges in composite laminates: A variational approach  

Microsoft Academic Search

An analytical method developed for determining the interlaminar stresses at straight free boundaries is extended to predict the free-edge stresses at curved boundaries of symmetric composite laminates under inplane loading. The three-dimensional (3D) stress distribution in laminates with curved boundaries is approximately described on the basis of a zero-order approximation of the boundary-layer theory. The related stress functions are found

Chao Zhang; Larry B. Lessard; James A. Nemes

1997-01-01

396

Asian industrial lead inputs to the North Pacific evidenced by lead concentrations and isotopic compositions in surface waters and aerosols.  

PubMed

Recent trends of atmospheric lead deposition to the North Pacific were investigated with analyses of lead in aerosols and surface waters collected on the fourth Intergovernmental Oceanographic Commission Contaminant Baseline Survey from May to June, 2002. Lead concentrations of the aerosols varied by 2 orders of magnitude (0.1-26.4 pmol/m(3)) due in part to variations in dust deposition during the cruise. The ranges in lead aerosol enrichment factors relative to iron (1-119) and aluminum (3-168) were similar, evidencing the transport of Asian industrial lead aerosols across the North Pacific. The oceanic deposition of some of those aerosols was substantiated by the gradient of lead concentrations of North Pacific waters, which varied 3-fold (32.7-103.5 pmol/kg), were highest along with the Asian margin of the basin, and decreased eastward. The hypothesized predominance of Asian industrial lead inputs to the North Pacific was further corroborated by the lead isotopic composition of ocean surface waters ((206)Pb/(207)Pb = 1.157-1.169; (208)Pb/(206)Pb = 2.093-2.118), which fell within the range of isotopic ratios reported in Asian aerosols that are primarily attributed to Chinese industrial lead emissions. PMID:22007971

Gallon, Céline; Ranville, Mara A; Conaway, Christopher H; Landing, William M; Buck, Clifton S; Morton, Peter L; Flegal, A Russell

2011-12-01

397

Stress and strain field singularities, micro-cracks, and their role in failure initiation at the composite laminate free-edge  

NASA Astrophysics Data System (ADS)

A state-of-the-art multi-scale analysis was performed to predict failure initiation at the free-edge of an angle-ply laminate using the Strain Invariant Failure Theory (SIFT), and multiple improvements to this analysis methodology were proposed and implemented. Application of this analysis and theory led to the conclusion that point-wise failure criteria which ignore the singular stress and strain fields from a homogenized analysis and the presence of free-edge damage in the form of micro-cracking, may do so at the expense of failure prediction capability. The main contributions of this work then are made in the study of the laminate free-edge singularity and in the effects of micro-cracking at the composite laminate free-edge. Study of both classical elasticity and finite element solutions of the laminate free-edge stress field based upon the assumption of homogenized lamina properties reveal that the order of the free-edge singularity is sufficiently small such that the domain of dominance of this term away from the laminate free-edge is much smaller than the relevant dimensions of the microstructure. In comparison to a crack-tip field, these free-edge singularities generate stress and strain fields which are half as intense as those at the crack-tip, leading to the conclusion that existing flaws at the free-edge in the form of micro-cracks would be more prone to the initiation of free-edge failure than the existence of a singularity in the free-edge elasticity solutions. A methodical experiment was performed on a family of [±25°/90°] s laminates made of IM7/8552 carbon/epoxy composite, to both characterize micro-cracks present at the laminate free-edge and to study their behavior under the application of a uniform extensional load. The majority of these micro-cracks were of length on the order of a few fiber diameters, though larger micro-cracks as long as 100 fiber diameters were observed in thicker laminates. A strong correlation between the application of vacuum during cure and the presence of micro-cracks was observed. The majority of micro-cracks were located along ply interfaces, even along the interfaces of plies with identical orientation, further implicating processing methods and conditions in the formation of these micro-cracks and suggesting that a region of interphase is present between composite plies. No micro-cracks of length smaller than approximately 36 fiber diameters (180 µm) grew or interacted with the free-edge delamination or damage at ultimate laminate failure, and the median length of micro-cracks which did grow was approximately 50 fiber diameters (250 µm). While the internal depth of these free-edge cracks was unknown, the results of these experiments then suggests a critical free-edge crack-length in the [±25°/90°]s family of laminates of approximately 50 fiber diameters (250 µm, or 1.5 lamina thicknesses). A multi-scale analysis of free-edge micro-cracks using traditional displacement based finite element submodeling and XFEM was used to explain the experimental observation that micro-cracks did not grow unless they were of sufficient length. Analysis of the stress-intensity factors along the micro-crack front revealed that penny shaped micro-cracks in the 90° plies of the [±25°/90°] s family of laminates of length two fiber diameters or longer are under mode I dominated loading conditions when oriented parallel or perpendicular to the laminate loading direction. The maximum observed KI along the crack-front of these modeled micro-cracks was no larger than 26% of the ultimate KIC of the matrix material, under the application of a uniform temperature change (?T=-150°C) and uniform extension equal to the experimentally measured ultimate failure strain of the laminate. This indicates that insufficient energy is supplied to these small micro-cracks to facilitate crack growth, confirming what was experimentally observed. A method for estimating a critical micro-crack length based upon the results of the fracture mechanics analysis was developed, and predictions for this critical

Dustin, Joshua S.

398

Aerodynamic Characteristics of a Large-Scale Unswept Wing-Body-Tail Configuration with Blowing Applied Over the Flap and Wind Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation has been conducted in the Langley full-scale tunnel to determine the effects of a blowing boundary-layer-control lift-augmentation system on the aerodynamic characteristics of a large-scale model of a fighter-type airplane. The wing was unswept at the 70-percent- chord station, had an aspect ratio of 2.86, a taper ratio of 0.40, and 4-percent-thick biconvex airfoil sections parallel to the plane of symmetry. The tests were conducted over a range of angles of attack from approximately -4 deg to 23 deg for a Reynolds number of approximately 5.2 x 10(exp 6) which corresponds to a Mach number of 0.08. Blowing rates were normally restricted to values just sufficient to control air-flow separation. The results of this investigation showed that wing leading-edge blowing in combination with large values of wing leading-edge-flap deflection was a very effective leading-edge flow-control device for wings having highly loaded trailing-edge flaps. With leading-edge blowing there was no hysteresis of the lift, drag, and pitching-moment characteristics upon recovery from stall. End plates were found to improve the lift and drag characteristics of the test configuration in the moderate angle-of-attack range, and blockage to one-quarter of the blowing-slot area was not detrimental to the aerodynamic characteristics. Blowing boundary-layer control resulted in a considerably reduced landing speed and reduced landing and take-off distances. The ailerons were very effective lateral-control devices when used with blowing flaps.

McLemore, H. Clyde; Peterson, John B., Jr.

1960-01-01

399

Thermal and mechanical properties of styrene-butadiene rubber\\/lead oxide composites as gamma-radiation shields  

Microsoft Academic Search

Styrene-butadiene rubber\\/lead oxide composites were prepared as ?-radiation shields. The composites were prepared with three different types of lead oxide, namely lead mono-oxide (PbO), lead dioxide (PbO2) and red lead oxide (Pb3O4). Concentrations of about 87–88 wt% for the three lead oxides were used. The assessment of the linear attenuation coefficient of the SBR\\/lead oxide composites for ?-rays from different

M. M. Abdel-Aziz; S. E. Gwaily

1997-01-01

400

Characterization of noise amplifiers with global singular modes: the case of the leading-edge flat-plate boundary layer  

NASA Astrophysics Data System (ADS)

This article deals with the linear dynamics of a transitional boundary layer subject to two-dimensional Tollmien-Schlichting instabilities. We consider a flat plate including the leading edge, characterized by a Reynolds number based on the length of the plate equal to Re = 6 × 105, inducing a displacement thickness-based Reynolds number of 1,332 at the end of the plate. The global linearized Navier-Stokes equations only display stable eigenvalues, and the associated eigen-vectors are known to poorly represent the dynamics of such open flows. Therefore, we resort to an input-output approach by considering the singular value decomposition of the global resolvent. We then obtain a series of singular values, an associated orthonormal basis representing the forcing (the so-called optimal forcings) as well as an orthonormal basis representing the response (the so-called optimal responses). The objective of this paper is to analyze these spatial structures and to closely relate their spatial downstream evolution to the Orr and Tollmien-Schlichting mechanisms. Analysis of the spatio-frequential diagrams shows that the optimal forcings and responses are respectively localized, for all frequencies, near the upstream neutral point (branch I) and the downstream neutral point (branch II). It is also shown that the spatial growth of the dominant optimal response favorably compares with the e N method in regions where the dominant optimal forcing is small. Moreover, thanks to an energetic input-output approach, it is shown that this spatial growth is solely due to intrinsic amplifying mechanisms related to the Orr and Tollmien-Schlichting mechanisms, while the spatial growth due to the externally supplied power by the dominant optimal forcing is negligible even in regions where the dominant optimal forcing is strong. The energetic input-output approach also yields a general method to assess the strength of the instability in amplifier flows. It is based on a ratio comparing two quantities of same physical dimension, the mean-fluctuating kinetic energy flux of the dominant optimal response across some boundary and the supplied mean external power by the dominant optimal forcing. For the present boundary-layer flow, we have computed this amplification parameter for each frequency and discussed the results with respect to the Orr and Tollmien-Schlichting mechanisms.

Sipp, Denis; Marquet, Olivier

2013-09-01

401

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

402

Borosilicate and lead silicate glass matrix composites containing pyrochlore phases for nuclear waste encapsulation  

NASA Astrophysics Data System (ADS)

Glass matrix composites intended for the immobilisation of plutonium bearing nuclear legacy waste have been manufactured. Two different matrices, a soda borosilicate glass and a lead silicate glass, are proposed for encapsulating lanthanum and gadolinium zirconates having pyrochlore crystalline structure. The fabrication of the composites involves powder mixing followed by cold pressing and pressureless sintering or hot-pressing at relatively low temperatures (<620 °C). The hot-pressing route is found to be the most convenient, since it leads to relatively high densification even with substantial loading of pyrochlore phase (40 vol.%). The absence of microcracks, due to the close matching of thermal expansion coefficients of the composite constituents, together with the strong pyrochlore particle/glass matrix interfacial bonding, suggests that the composites have good mechanical properties. The innovative introduction of gadolinium zirconate in a lead silicate matrix represents an attractive approach, since the composites reach reasonably high densities both by pressureless sintering and hot-pressing.

Boccaccini, A. R.; Bernardo, E.; Blain, L.; Boccaccini, D. N.

2004-05-01

403

Compatability of SiC and SiC Composites with Molten Lead.  

National Technical Information Service (NTIS)

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 ...

H. Tunison

2006-01-01

404

Static force tests of a sharp leading edge delta-wing model at ambient and cryogenic temperatures with a description of the apparatus employed  

NASA Technical Reports Server (NTRS)

A sharp leading edge delta-wing model was tested through an angle-of-attack range at Mach numbers of 0.75, 0.80, and 0.85 at both ambient and cryogenic temperatures in the Langley 1/3-meter transonic cryogenic tunnel. Total pressure was varied with total temperature in order to hold test Reynolds number constant at a given Mach number. Agreement between the aerodynamic data obtained at ambient and cryogenic temperatures indicates that flows with leading-edge vortex effects are duplicated properly at cryogenic temperatures. The test results demonstrate that accurate aerodynamic data can be obtained by using conventional force-testing techniques if suitable measures are taken to minimize temperature gradients across the balance and to keep the balance at ambient (warm) temperatures during cryogenic operation of the tunnel.

Kilgore, R. A.; Davenport, E. E.

1976-01-01

405

Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges  

NASA Technical Reports Server (NTRS)

Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.

Carlson, Harry W.; Darden, Christine M.

1987-01-01

406

A flow visualization study of the leading edge separation bubble on a NACA 0012 airfoil with simulated glaze ice. Final Report M.S. Thesis  

NASA Technical Reports Server (NTRS)

As a part of the ongoing research in aircraft icing, the leading edge separation bubble on the NACA 0012 model with a 5-min simulated glaze ice was investigated. The flow visualization methods used oil, tuft, splitter plate, smoke, and liquid crystals to get reattachment line data for the leading edge separation bubble on both surfaces of the airfoil. On the upper surface, the bubble was found to grow larger with increasing negative angles of attack and reduce in size with increasing angles of attack. The separated flow fails to reattach beyond 6 deg for the upper surface and -5 deg for the lower surface. The results of this study compared well with those of other experiments and computational results.

Khodadoust, Abdollah

1988-01-01

407

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.

408

Comparison of power loss and pad temperature for leading edge groove tilting pad journal bearings and conventional tilting pad journal bearings  

Microsoft Academic Search

A study was undertaken to compare power loss and pad temperature characteristics between LEG (leading edge groove) tilting pad journal bearings and conventional tilting pad journal bearings with and without a seal tooth. All test bearings were double tilting type with six-pad LOP (Load On Pad), 300.6mm inner diameter, and 120.0mm effective length. Pad temperatures and power losses were compared

Kyung-Bo Bang; Jeong-Hun Kim; Yong-Joo Cho

2010-01-01

409

Experimental study of wing leading-edge devices for improved maneuver performance of a supercritical maneuvering fighter configuration. [Langley 7- by 10-ft high speed tunnel tests  

NASA Technical Reports Server (NTRS)

Wind tunnel tests were conducted to examine the use of wing leading-edge devices for improved subsonic and transonic maneuver performance. These