14,162 research outputs found

    The operational processing of wind estimates from cloud motions: Past, present and future

    Get PDF
    Current NESS winds operations provide approximately 1800 high quality wind estimates per day to about twenty domestic and foreign users. This marked improvement in NESS winds operations was the result of computer techniques development which began in 1969 to streamline and improve operational procedures. In addition, the launch of the SMS-1 satellite in 1974, the first in the second generation of geostationary spacecraft, provided an improved source of visible and infrared scanner data for the extraction of wind estimates. Currently, operational winds processing at NESS is accomplished by the automated and manual analyses of infrared data from two geostationary spacecraft. This system uses data from SMS-2 and GOES-1 to produce wind estimates valid for 00Z, 12Z and 18Z synoptic times

    Laser velocimetry in highly three-dimensional and vortical flows

    Get PDF
    The need for experimentally determined 3-D velocity information is crucial to the understanding of highly 3-dimensional and vortical flow fields. In addition to gaining an understanding of the physics of flow fields, a correlation of velocity data is needed for advanced computational modelling. A double pass method for acquiring 3-D flow field information using a 2-D laser velocimeter (LV) is described. The design and implementation of a 3-D LV with expanded capabilities to acquire real-time 3-D flow field information are also described. Finally, the use of such an instrument in a wind tunnel study of a generic fighter configuration is described. The results of the wind tunnel study highlight the complexities of 3-D flow fields, particularly when the vortex behavior is examined over a range of angles of attack

    Design, Fabrication and Test of Multi-Fiber Laminates

    Get PDF
    Unidirectional and angleply multifiber laminates were tested for improved impact strength and other mechanical properties. The effects of several variables on the mechanical properties of epoxy matrix materials were described. These include fiber type (HMS and AS graphites, glass, and Kevlar 49), ratio of primary to hybridizing fiber and hybrid configuration. It is demonstrated that AS graphite/S glass in an intraply configuration results in the best combination of static and Charpy impact properties as well as superior ballistic impact resistance. Pendulum impact tests which were conducted on thin specimens are shown to produce different ranking of materials than tests conducted on standard thickness Charpy specimens. It is shown that the thin specimen results are in better agreement with the ballistic impact data. Additional static test data are reported as a function of temperature for the seven best hybrid configurations having epoxy, polyimide (PMR-15) and polyphenylquinoxaline resins as the matrix

    Measuremants in the wake of an infinite swept airfoil

    Get PDF
    This is a report of the measurements in the trailing edge region as well as in the report of the developing wake behind a swept NACA 0012 airfoil at zero incidence and a sweep angle of 30 degrees. The measurements include both the mean and turbulent flow properties. The mean flow velocities, flow inclination and static pressure are measured using a calibrated three-hole yaw probe. The measurements of all the relevant Reynolds stress components in the wake are made using a tri-axial hot-wire probe and a digital data processing technique developed by the authors. The development of the three dimensional near-wake into a nearly two dimensional far-wake is discussed in the light of the experimental data. A complete set of wake data along with the data on the initial boundary layer in the trailing edge region of the airfoil are tabulated in an appendix to the report

    Development of low modulus material for use in ceramic gas path seal applications

    Get PDF
    Three candidate materials were examined: Brunsbond (R) Pad; plasma sprayed porous NiCrAlY; and plasma sprayed low modulus microcracked zirconia. Evaluation consisted of mechanical, thermophysical, and oxidation resistance testing along with optical microscopy and a feasibility demonstration of attaching the material to a suitable substrate. The goals of the program were the following: feasibility of fastening or depositing the low modulus system onto a broad range of substrate alloys; feasibility of depositing or forming the low modulus system to a thickness of 0.19 cm to 0.38 cm; potential to attain a modulus of elasticity in the range of 3.4 to 6.9 GPa (0.5 to 1.0 MSI), and an ultimate strength of 17.2 MPa (2.5 ksi); suitable thermal conductivity; and static oxidation life of at least 1000 hours at 1311 K. The results of the program indicate that all three systems offer attractive properties as a strain isolator material

    Migration and Final Location of Hot Super Earths in the Presence of Gas Giants

    Full text link
    Based on the conventional sequential-accretion paradigm, we have proposed that, during the migration of first-born gas giants outside the orbits of planetary embryos, super Earth planets will form inside the 2:1 resonance location by sweeping of mean motion resonances (Zhou et al. 2005). In this paper, we study the subsequent evolution of a super Earth (m_1) under the effects of tidal dissipation and perturbation from a first-born gas giant (m_2) in an outside orbit. Secular perturbation and mean motion resonances (especially 2:1 and 5:2 resonances) between m_1 and m_2 excite the eccentricity of m_1, which causes the migration of m_1 and results in a hot super Earth. The calculated final location of the hot super Earth is independent of the tidal energy dissipation factor Q'. The study of migration history of a Hot Super Earth is useful to reveal its Q' value and to predict its final location in the presence of one or more hot gas giants. When this investigation is applied to the GJ876 system, it correctly reproduces the observed location of GJ876d around 0.02AU.Comment: 7 pages, 4 figure

    Investigation of a bearingless helicopter rotor concept having a composite primary structure

    Get PDF
    Experimental and analytical investigations were conducted to evaluate a bearingless helicopter rotor concept (CBR) made possible through the use of the specialized nonisotropic properties of composite materials. The investigation was focused on four principal areas which were expected to answer important questions regarding the feasibility of this concept. First, an examination of material properties was made to establish moduli, ultimate strength, and fatigue characteristics of unidirectional graphite/epoxy, the composite material selected for this application. The results confirmed the high bending modulus and strengths and low shear modulus expected of this material, and demonstrated fatigue properties in torsion which make this material ideally suited for the CBR application. Second, a dynamically scaled model was fabricated and tested in the low speed wind tunnel to explore the aeroelastic characteristics of the CBR and to explore various concepts relative to the method of blade pitch control. Two basic control configurations were tested, one in which pitch flap coupling could occur and another which eliminated all coupling. It was found that both systems could be operated successfully at simulated speeds of 180 knots; however, the configuration with coupling present revealed a potential for undesirable aeroelastic response. The uncoupled configuration behaved generally as a conventional hingeless rotor and was stable for all conditions tested

    Pourable and Destroyable Cosmic Ray Radiation Shield for Spacecraft

    Full text link
    Historically, materials such as lead, tungsten, and iron have been used in spacecraft to shield scientific detectors from Cosmic Rays. These materials work well when reentry to Earth is not an issue. The typical strategy is to have a controlled descent of the spacecraft or to have extremely limited shielding, if any, due to the NASA requirement that all impacting parts must impact with no greater than 15J of energy. Given the nature of this mission neither a controlled descent nor having no shielding was not an option. This is the issue Wichita State University nuSOL team is facing for its 3U CubeSat demonstrator. The CubeSat will be equipped with scientific equipment with the purpose of detecting solar neutrinos, and the less background noise from Cosmic Rays the better the study will be. Through simulations, density tests, and burn tests, WSU was able to develop an epoxy based shield doped with either iron or tungsten powder. The simulations were conducted by firing electrons, protons, alpha particles, and oxygen and iron nuclei into the shield material with energies ranging from 1MeV until consistent failure rate using Geant4. The standards for these simulations are the base epoxy at 1.15g per cc to solid steel at 8g per cc . Mixing tests have determined for iron, a density of 4g per cc is achievable, which is 53 percent iron by volume. Tungsten epoxy with a density of 7.5g per cc is more easily achieved, and results in 40 percent tungsten by volume. These ratios are concrete in texture, pourable, and homogeneous.Comment: Manuscript presented at the International Astronautical Congress, IAC 2022, Paris, France, 18-22 September. Copyright by IA
    • …