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  • 1
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-79/4
    In: CRREL Report, 79-4
    Description / Table of Contents: A computer model is described to compute the amount of ice accretion on an object under a variety of initial conditions. Numerical techniques are best applied to these problems because of time dependent effects governing the amount of ice collected and also the variety of initial conditions that can lead to ice accumulation. The helicopter rotor icing problem adds an additional complexity since the velocity along the rotor blade varies over a wide range strongly affecting the amounts of ice collected at different blade positions. The physics of ice accretion is reviewed and the accounting for time-dependence in the computer model is described. Some model results are presented and indicate the dependence of ice accretion on velocity, droplet sizes, cloud liquid water content, and temperature for a cylindrical object of constant size.
    Type of Medium: Series available for loan
    Pages: iii, 39 Seiten , Illustrationen
    Series Statement: CRREL Report 79-4
    Language: English
    Note: CONTENT Abstract Preface Introduction Ice accretion parameters Physics of ice accretion Interaction between water droplets and flow field Time dependence in droplet trajectories Thermodynamic processes at the surface of the object Time dependence in the thermodynamics Time dependence of lesser order Numerical ice accretion model Major subroutines Options for droplet size variations Option for the helicopter rotor case Results Conclusions and future studies Literature cited Appendix A: Computer program ILLUSTRATIONS Figure Velocity potential 0and stream function around a circular cylinder of radius a em-bedded in a fluid with free stream velocity Air streamlines and droplet trajectories with respect to a right circular cylinder Schematic indicating the five terms used in the heat balance and whether they arecarrying heat toward or away from the freezing surface 64. The fraction of accreted water lost for various temperatures and average radii of accret-ing objects Block diagram of the numerical model for cilculating ice accretion Initial variables input in the run control sequence of the numerical model Subroutines Profile and Ice Den used to calculate the changes in object profile and icedensity from the output of the icing thermodynamics 98. Subroutines controlling computation of the droplet trajectory, collection efficiency and trajectory control, and free stream velocity Based on the ambient conditions, the calculation of mass accreted is completed by in-corporating the thermodynamics at the surface Forms of the Erlang distribution for various values of the parameter (Top) The change in profile dimension at 50-s intervals by ice accretion (Bottom) The surface temperature of the front half cylinder as a function of time Numerical simulation of helicopter rotor blade icing showing the surface temperature,leading edge ice thickness, collection efficiency and fraction accreted as a function ofvelocity for the initial conditions shown Droplet trajectories and ice profile changes for a Gaussian droplet size distribution Accreted Ice thickness and temperature for the ambient conditions indicated Comparison between experimental data and model simulation of the same conditions Magnitude of the individual thermodynamic terms as a function of velocity for the simulation shown in Figure 12
    Location: AWI Archive
    Branch Library: AWI Library
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  • 2
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 1678-1679 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 1439-1441 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 151-153 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Linear polarization of synchrotron radiation is sensitive to position in unfocused beams, to angular acceptance for focused beams, and to the spread of vertical position and direction of the electron orbits. Measurements using a Borrmann filter show the need for attention to these effects and the importance of contemporary measurements at typical beamlines when the degree of polarization is important.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 2 (1995), S. 31-35 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Second-rank tensors describing how the real and imaginary dispersion terms f′ and f′′ depend on photon polarization for Br atoms substituted on a benzene ring have been measured at six energies near the Br K absorption edge in diffraction experiments with synchrotron radiation and crystals of homocubanecarboxylic acid p-bromoanilide. Resonance with a σ antibonding orbital causes f′ to change with polarization as much as 4.3 and f′′′ as much as 7.5. The tensors for two independent Br atoms are equal, uniaxial and aligned with the respective Br—C bond. Absorption spectra show the average effect of two tensors with different orientations. Atomic coordinates from a new refinement of the structure are listed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 17 (1964), S. 933-936 
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 62-67 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Dichroism is observed near the L1 and L3 edges of uranium in X-ray absorption spectra of single-crystal rubidium uranyl nitrate, Rb.UO2.3NO3, recorded with linearly polarized synchrotron radiation. The anomalous X-ray scattering terms f′ and f′′ calculated from these spectra are anisotropic functions of polarization direction at these wavelengths, adding new complexity to diffraction optics. These terms are measured independently in diffraction experiments with sodium uranyl acetate at five wavelengths near L3. The cubic symmetry permits the diffraction effects to be observed without the complications of macroscopic dichroism and birefringence. Both f′ and f′′ change with polarization direction by as much as 2 electrons atom-l. These values agree with those derived from the absorption experiments.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The anomalous scattering terms f′ and f′′ for Gd and Sm near their L3 absorption edges, measured in diffraction experiments with synchrotron radiation more nearly monochromatic than the natural level widths, show even larger effects than earlier measurements with a larger X-ray bandwidth. A test of angular dependence shows f′ for Sm to decrease in magnitude with increasing diffraction angle, while f′′ is essentially constant.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 274-278 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The anomalous scattering terms for trivalent holmium are measured for Cu Kα1, Kα2 and Kβ radiation in diffraction experiments with a crystal of HoNa(edta).8H2O. Intensities at these wavelengths and at Mo Kα are used to calculate amplitudes and the phase difference for the waves scattered by holmium and by the rest of the structure to test the multiple-wavelength method of diffraction phase determination. Relative phases are determined with a mean accuracy of 44° for 759 high-angle reflections. A similar calculation for the analogous Sm crystal using synchrotron radiation data gives the phase difference with an average error of 5°.
    Type of Medium: Electronic Resource
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