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Alouette 2 satellite ionogram loop shaped traces resulting from oblique radio waves at edge of large scale horizontal depressions of electron density
The low speed aerodynamic characteristics of a large-scale model intended to represent advanced fixed-wing fighters have been investigated in the Ames 40 by 80 foot wind tunnel. The model possessed positive static longitudinal stability to nearly 28 deg angle of attack, the maximum tested, both with and without leading-edge flaps deflected. Lateral control with differentially deflected ailerons and a right wing spoiler simultaneously deployed as combined controls was only slightly greater than that with the differentially deflected ailerons deployed as a separate control without the spoiler. Measured lift and drag were in close agreement with that predicted by theory to about 14 deg angle of attack, including the prediction of lift due to 30 deg of trailing edge flap deflection. Estimated takeoff performance of an aircraft 4/3 the scale of the test model showed takeoff distances of less than 2000 ft.
A large scale, variable-geometry inlet system with a design Mach number of 3.0 was tested at Mach numbers from 0.6 to 1.28. Variable features for off-design operation are an adjustable-height ramp system and a translating cowl. Experimental results are presented for transonic ramp and cowl positions showing the effect of throat boundary layer bleed and vortex generators on engine-face performance. Detailed pressure and force-balance data are used to evaluate transonic drag characteristics.
An investigation has been conducted to determine the aerodynamic characteristics of a large-scale subsonic jet transport model with an upper surface blowing flap system that would augment lift. The model had a 25 deg swept wing of aspect ratio 7.89 and two turbofan engines with the engine centerline located at 0.256 of the wing semispan. The lift of the flap system was augmented by turbofan exhaust impingement on the Coanda surface. Results were obtained for several flap deflections and engine nozzle configurations at jet momentum coefficients from 0 to 4.0. Three-component longitudinal data are presented with two engines operating. Limited longitudinal and lateral data are presented with an engine out. In addition, limited exhaust and flap pressure data are presented.
A study was conducted to determine the causes of aircraft noise in large jet aircraft. It was determined that jet noise varies strongly with velocity and that significant pure tones are generated by rotor-stator interaction in the jet engines. An objective method for deducing the large eddy structure in a large jet is described. The provisions of lighthill's theory are analyzed and applied to investigating the nature of jet noise. There is considerable evidence that a large scale coherent structure exists in a jet and that this structure can play a major role in sound radiation. Mathematical models are developed to define the parameters of orthogonal decomposition, finite extent velocity field, homogeneous fields, and periodic velocity fields.
An ejector design concept for V/STOL aircraft, featuring a double-delta configuration with two large chordwise ejector slots adjacent to the fuselage side and a tailplane or canard for longitudinal control is examined. Large scale model tests of the concept have shown that ejector systems are capable of significant thrust augmentation at realistic supply pressures and temperatures, so that power plant size and weight can be reduced accordingly. A thrust augmentation of at least 1.75 can be achieved for the isolated ejector, not making allowance for duct and nozzle losses. Substantial reductions in velocity, temperature and noise of the lifting jet are assured due to mixing within the ejector - this lessens the severity of ground erosion and the thrust loss associated with reingestion. Consideration is also given to the effect of ground proximity, longitudinal aerodynamic characteristics, transition performance, and lateral stability.
The optical, seeding, and data reduction procedures which have been used in the successful application of laser velocimetry to large-scale, unsteady, transonic wind-tunnel testing are described. Flowfield measurements obtained at several facilities are presented. These results include vortex flow measurements and ensemble-averaged data obtained under conditions of vortex-shedding, dynamic stall airfoil oscillation, oscillating trailing-edge control flaps, and helicopter rotor flow fields.
A simple heat-tagging technique was used to isolate and analyze the large-scale coherent structures present in the two-dimensional wake of a flat plate. The results indicate the presence of these coherent structures even at 250 momentum thicknesses downstream of the trailing edge. These structures have a vortexlike topology and carry a significant amount of the total shear stress. The present results for the flat-plate wake seem to be in general agreement with those that have been obtained in cylinder wakes by other comtemporary investigators using more complex techniques of eduction and signal enhancement.
An investigation of the static longitudinal aerodynamic characteristics of a large-scale semispan model with an unswept wing and an upper-surface blown jet flap for lift augmentation was conducted in the Langley full-scale tunnel. The wing had an aspect ratio of 7.8 (3.9 for the semispan) and a simulated turbofan engine mounted ahead of and above the wing in a nacelle with a rectangular-exit nozzle. The flap system had three spanwise flap segments: (1) an inboard plain flap located behind the engine and having a large radius of curvature to provide a smooth upper surface to enhance the turning of the jet sheet, (2) a double-slotted midspan flap, and (3) a drooped aileron equipped with blowing boundary-layer control. The wing was also equipped with a full-span leading-edge Krueger flap with blowing boundary-layer control. In addition to the aerodynamic measurements, noise measurements were also included in the investigation for positions above and below the wing.
The analysis of lunar orbital and sample data combined with laboratory measurements of impact-produced plasmas suggest that large-scale impacts on planetary surfaces may have had significant magnetic effects. These effects may potentially explain part of all lunar crustal magnetization and, by extension, may be responsible for producing paleomagnetism on other airless silicate bodies in the solar system. Theoretical studies are presented of the magnetic field and remanent magnetization effects of basin-scale impacts on the Moon. The specific case of a Moon exposed to the solar wind plasma flow and its embedded magnetic field is investigated. It is shown that maximum compressed field amplitudes occur antipodal to the impact point in agreement with the observed tendency for orbital magnetic anomalies to be concentrated antipodal to young large lunar basins. Generalization of these results to include magnetic effects of impacts on other airless or nearly airless bodies in the solar system is presented.
Sunlight-driven water splitting allows renewable hydrogen to be produced from abundant and environmentally benign water. Large-scale societal implementation of this green fuel production technology within energy generation systems is essential for the establishment of sustainable future societies. Among various technologies, photocatalytic water splitting using particulate semiconductors has attracted increasing attention as a method to produce large amounts of green fuels at low cost. The key to making this technology practical is the development of photocatalysts capable of splitting water with high solar-to-fuel energy conversion efficiency. Furthermore, advances that enable the deployment of water-splitting photocatalysts over large areas are necessary, as is the ability to recover hydrogen safely and efficiently from the produced oxyhydrogen gas. This lead article describes the key discoveries and recent research trends in photosynthesis using particulate semiconductors and photocatalyst sheets for overall water splitting, via one-step excitation and two-step excitation (Z-scheme reactions), as well as for direct conversion of carbon dioxide into renewable fuels using water as an electron donor. We describe the latest advances in solar water-splitting and carbon dioxide reduction systems and pathways to improve their future performance, together with challenges and solutions in their practical application and scalability, including the fixation of particulate photocatalysts, hydrogen recovery, safety design of reactor systems, and approaches to separately generate hydrogen and oxygen from water.
This paper will briefly review previous work in wind tunnel Magnetic Suspension and Balance Systems (MSBS) and will examine the handful of systems around the world currently known to be in operational condition or undergoing recommissioning. Technical developments emerging from research programs at NASA and elsewhere will be reviewed briefly, where there is potential impact on large-scale MSBSS. The likely aerodynamic applications for large MSBSs will be addressed, since these applications should properly drive system designs. A recently proposed application to ultra-high Reynolds number testing will then be addressed in some detail. Finally, some opinions on the technical feasibility and usefulness of a large MSBS will be given.
Winds derived from analyzed geopotential height fields are used to study quasi-horizontal mixing by the large-scale flow in the lower stratosphere during austral spring. This is the period when the Antarctic ozone hole appears and disappears. Trajectories are computed for large ensembles of particles initially inside and outside the main polar vortex. Mixing and transport are diagnosed through estimates of finite time Lyapunov exponents and Lagrangian dispersion statistics of the tracer trajectories. At 450 K and above prior to the vortex breakdown: Lyapunov exponents are a factor of 2 smaller inside the vortex than outside; diffusion coefficients are an order of magnitude smaller inside than outside the vortex; and the trajectories reveal little exchange of air across the vortex boundary. At lower levels (425 and 400 K) mixing is greater, and there is substantial exchange of air across the vortex boundary. In some years there are large wave events that expel small amounts of vortex air into the mid-latitudes. At the end of the spring season during the vortex breakdown there is rapid mixing of air across the vortex boundary, which is evident in the mixing diagnostics and the tracer trajectories.
Here, the large-scale production of 88 Y with proton-induced reactions has been investigated from the perspective of new generation 70 MeV H – cyclotrons. Tandem target configurations are presented for both the direct production of 88 Y as well as for producing 88 Zr/ 88 Y generators. Based on the relevant excitation functions, physical yields have been derived for 88 Y production with Y 2 O 3 /SrCO 3 tandem targets and 88 Zr production with Zr/Y 2 O 3 tandem targets. Yields are presented for optimized targets (i.e. optimum yield) as well as for balanced thermal loads on the individual targets. Liquid 88 Zr/ 88 Y generators have been produced using both natural Zr and Nb target materials, the former for dedicated productions and the latter as a byproduct by processing spent irradiated Nb capsules which normally would constitute radioactive waste. These stock solutions, which contain both the target material and 88 Zr precursor, are retained virtually unchanged after processing except for the removal of 88 Y on AG MP-50 macroporous cation-exchange resin. Methods are presented for the preparation of Nb stock solutions in hydrofluoric acid and Zr stock solutions in sulfuric acid. It is shown that multi-Ci productions of 88 Y are feasible at a 70 MeV cyclotron facility, suitable for the needs of fracking applications. In addition, 88 Zr/ 88 Y generators can provide 88 Y with very high specific activity, suitable for labelling of biomolecules.
Wind tunnel tests of subsonic aerodynamic characteristics of large scale tip turbine cruise fan with 1.075 pressure ratio at angle of attack
In investigations concerned with obtaining an understanding of the general circulation of the atmosphere, the determination of the role of the large-scale eddies presents a special problem. In the present study,attention is given to a theory which, in some ways, provides an extension of the Eliassen-Palm flux concept so that it can be applied in particular to the time-averaged three space dimension problem. Particular emphasis is given to the understanding of the feedback of the eddies onto the mean flow. However, the behavior of the eddies themselves is also discussed. It is shown that, in simple situations, the anisotropic eddy horizontal velocity correlation tensor implies the shape and propagation of eddies and the feedback of the eddies onto the mean flow.
The present study is concerned with the optimization of conditional sampling techniques for eduction of naturally occurring large-scale structures in an axisymmetric mixing layer, and a comparison of the natural structure with that induced by means of controlled excitation. Questions regarding the sensitivity of the educed structure to the excitation amplitude are also explored. Aspects regarding the eduction with the high-speed-side reference signal are considered, taking into account structure identification, the smearing effect and a comparison with the structure under excitation, the effects of the threshold level, and the effect of a trigger-level window. Attention is given to structure characteristics and their dependence on Reynolds number and initial condition.
Using high resolution time sequence photographs of solar granulation from the SOUP experiment on Spacelab 2, large scale horizontal flows were observed in the solar surface. The measurement method is based upon a local spatial cross correlation analysis. The horizontal motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of granulation from a sunspot penumbra into surrounding photosphere is a striking new discovery. Both the supergranulation pattern and cellular structures having the scale of mesogranulation are seen. The vertical flows that are inferred by continuity of mass from these observed horizontal flows have larger upflow amplitudes in cell centers than downflow amplitudes at cell boundaries.