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  • Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory  (130)
  • English  (130)
  • Japanese
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  • 2000-2004
  • 1980-1984  (130)
  • 1
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    Computer modeling of time-dependent rime icing in the atmosphere (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/2
    In: CRREL Report, 83-2
    Description / Table of Contents: A numerical model of rime ice accretion on an arbitrary two-dimensional airfoil is presented. The physics of the model are described and results are presented that demonstrate, by comparison with other theoretical data and experimental data, that the model predictions are believable. Results are also presented that illustrate the capability of the model to handle time-dependent rime ice accretion, taking into account the feedback between the ice accretion and the airflow and droplet trajectory fields.
    Type of Medium: Series available for loan
    Pages: vi, 81 Seiten , Illustrationen
    Series Statement: CRREL Report 83-2
    URL: https://apps.dtic.mil/docs/citations/ADA126404
    URL: https://hdl.handle.net/11681/9309
    Language: English
    Note: CONTENTS Abstract Preface Nomenclature Introduction Methodology Potential flow around an arbitrary airfoil Incompressible velocity field Droplet trajectory equation Computational procedure for trajectories Determining the point of impact Calculation of collision efficiencies Accreting an ice layer Determining the accuracy of the flow field Determining the accuracy of the trajectories Results and discussion Comparing results with and without the history term Collision efficiency of NACA 0015 airfoil at 8° attack angle Time-dependent accretion on NACA 0015 airfoil at 8° attack angle Time-dependent accretion on NACA 0015 airfoil at 0° attack angle Conclusions and recommendations Literature cited Appendix A : Sample input Appendix B: Sample output Appendix C : Program listing
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  • 2
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    Analysis of roof snow load case studies : uniform loads (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/1
    In: CRREL Report, 83-1
    Description / Table of Contents: Roof snow load case studies gathered throughout the United States over a three-year period are analyzed. The objective of the analysis is to determine a relationship between the snow load on the ground and the corresponding uniform snow load on flat and sloped roofs. The main parameters considered are the thermal characteristics of the roof, the roof slope and the exposure of the structure. Exposure has the strongest effect on the ratio of ground to roof snow loads. Comparisons are made with existing and proposed building codes and standards.
    Type of Medium: Series available for loan
    Pages: iv, 47 Seiten , Illustrationen
    Series Statement: CRREL Report 83-1
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a126330.pdf
    URL: https://hdl.handle.net/11681/9329
    Language: English
    Note: CONTENTS Abstract Preface Metric conversion table Introduction Data base Conversion factor Ground load effects Exposure effects Thermal effects Slope effects Expected value relationship Comparison with existing codes and standards Comparison with relationships proposed in new ANSI standard Summary and conclusions Literature cited Appendix A. Roof snow load case history reports Appendix B. Roofs in the snow load case study data base Appendix C. Ground and roof snow load data Appendix D. Conversion factors from the 1982 ANSI standard
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  • 3
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    Computer models for two-dimensional transient heat conduction (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/12
    In: CRREL Report, 83-12
    Description / Table of Contents: This paper documents the development and verification of two finite difference models that solve the general two-dimensional form of the heat conduction equation, using the alternative-direction implicit method. Both can handle convective, constant flux, specified temperature and semi-infinite boundaries. The conducting medium may be composed of many materials. The first program, ADI, solves for the case where no change of state occurs. ADIPC solves for case where a freeze/thaw change of phase may occur, using the apparent heat capacity method. Both models are verified by comparison to analytical results.
    Type of Medium: Series available for loan
    Pages: 74 Seiten , Illustrationen
    Series Statement: CRREL Report 83-12
    URL: https://apps.dtic.mil/docs/citations/ADA134893
    URL: https://hdl.handle.net/11681/9334
    Language: English
    Note: CONTENTS Abstract Preface Introduction Finite differences applied to heat transfer Heat conduction equation Boundary conditions Phase change Computer program ADDATA, the data subroutine TRIDIG, the matrix solver ISOTHM, the isotherm finider ADI, main program ADEPC, main program Verification of ADI Comparison of ADI with analytical results Comparison of ADI with experimental results Verification of ADIPC Comparison of ADIPC with analytical results-the Neumann solution Comparison of ADIPC with analytical results-two-dimensional phase change verification User instruction for ADI User instruction for ADIPC Conclusions Literature cited Appendix A. Program INFSUM and sample input and output for program ADI Appendix B. Program ADIPC and sample input and output
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  • 4
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    A study on the tensile strength of ice as a function of grain size (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/14
    In: CRREL Report, 83-14
    Description / Table of Contents: An analysis of ice fracture that incorporates dislocation mechanics and linear elastic fracture mechanics is discussed. The derived relationships predict a brittle to ductile transition in polycrystalline ice under tension with a Hall-Petch type dependence of brittle fracture strength on grain size. A uniaxial tensile testing technique, including specimen preparation and loading system design was developed and employed to verify the model. The tensile strength of ice in purely brittle fracture was found to vary with the square root of the reciprocal of grain size, supporting the relationship that the theory suggests. The inherent strength of the ice lattice and the Hall-Petch slope are evaluated and findings discussed in relation to previous results. Monitoring of acoustic emissions was incorporated in the tests, providing insights into the process of microfracture during ice deformation.
    Type of Medium: Series available for loan
    Pages: 43 Seiten , Illustrationen
    Series Statement: CRREL Report 83-14
    URL: https://apps.dtic.mil/docs/citations/ADA134889
    URL: https://hdl.handle.net/11681/9340
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Development of testing technique Test specimens Tensile testing Compression testing Experimental results Tensile tests Compression tests Discussion Conclusions Suggestions for further work Literature cited Appendix A: Additional information on seed grains Appendix B: Thin-sectioning procedure Appendix C: Displacement transducer calibration
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  • 5
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    Developing a model for predicting snowpack parameters affecting vehicle mobility (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/16
    In: CRREL Report, 83-16
    Description / Table of Contents: The presence of snow on the ground can impose limitations on the mobility of wheeled and tracked vehicles. Snow depth and density are the two most easily measured snow properties that can be related to mobility over snow. Existing models of snowpack accumulation and ablation processes and models of internal snowpack structure were examined to determine if a model of the snowpack can be developed for use in predicting the snow parameters that affect mobility. Simple models, such as temperature index models, do not provide sufficient snowpack details, and the more detailed models require too many measured inputs. Components of the various models were selected from a basis of a snowpack model for predicting snow properties related to mobility over snow. Methods of obtaining the input data from some components are suggested, and areas where more development is needed are described.
    Type of Medium: Series available for loan
    Pages: 34 Seiten , Illustrationen
    Series Statement: CRREL Report 83-16
    URL: https://apps.dtic.mil/docs/citations/ADA134878
    URL: https://hdl.handle.net/11681/9338
    Language: English
    Note: CONTENTS Abstract Preface Nomenclature Conversion of metric units Introduction Review of existing models Accumulation models Ablation models Using existing models for studying mobility Proposed snowpack model for mobility studies Model components Implementation of the model Developing input data Conclusions Literature cited
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  • 6
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    Radar profiling of buried reflectors and the groundwater table (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/11
    In: CRREL Report, 83-11
    Description / Table of Contents: Investigations of ground radar performance over thawed and seasonally frozen silts, and sands and gravels containing artificial and natural reflectors were carried out in Alaska. The radar emitted 5-10 ns pulses, the center frequency of which was approximately 150 MHz. The artificial reflectors were metal sheets and discs and the natural reflectors were the groundwater table and interfaces between frozen and thawed material. The water table was profiled at three sites where the subsurface material was coarse-grained alluvium. Dielectric constants of 16 to 18 were measured for the thawed silts, 6 to 7 for the frozen silts and 3 to 9 for the sands and gravels. Signal penetration in the thawed high moisture content silts may be achieved only by use of a lower frequency radar, whereas in the sands and gravels greater depths may be detected with more sophisticated signal processing.
    Type of Medium: Series available for loan
    Pages: 16 Seiten , Illustrationen
    Series Statement: CRREL Report 83-11
    URL: https://apps.dtic.mil/docs/citations/ADA130225
    URL: https://hdl.handle.net/11681/9337
    Language: English
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  • 7
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    Forecasting water temperature decline and freeze-up in rivers (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/19
    In: CRREL Report, 84-19
    Description / Table of Contents: In this study a method for making long-range forecasts of freeze-up dates in rivers is developed. The method requires the initial water temperature at an upstream station, the long-range air temperature forecast, the predicted mean flow velocity in the river reach, and water temperature response parameters. The water temperature response parameters can be either estimated from the surface heat exchange coefficient and the average flow depth or determined empirically from recorded air and water temperature data. The method is applied to the St. Lawrence River between Kingston, Ontario, and Massena, New York, and is shown to be capable of accurately forecasting freeze-up. Originator-supplied keywords include: Ice formation, and River ice.
    Type of Medium: Series available for loan
    Pages: iii, 22 Seiten , Illustrationen
    Series Statement: CRREL Report 84-19
    URL: https://apps.dtic.mil/docs/citations/ADA147068
    URL: https://hdl.handle.net/11681/9544
    Language: English
    Note: CONTENTS Abstract Preface Introduction Problem formulation Analytical treatment Application to the upper St. Lawrence River Summary Literature cited Appendix A: Basic program for St. Lawrence River freeze-up forecast
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  • 8
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    Crystalline structure of urea ice sheets used in modeling experiments in the CRREL test basin (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/24
    In: CRREL Report, 84-24
    Description / Table of Contents: This report describes the growth characteristics and crystalline textures of urea ice sheets which are now used extensively in the Cold Regions Research and Engineering Lab. (CRREL) test basin for modeling sea ice. The aims of the report are to describe the different kinds of crystalline texture encountered in urea ice sheets and to show that even small variations in texture can drastically influence the mechanical behavior of urea ice sheets. Standard petrographic techniques for studying microstructure in thin sections were used on 24 urea ice sheets. These investigations entailed observations of the crystalline texture of the ice (including details of the subgrain structure), grain size measurements, and studies of the nature and extent of urea entrapment and drainage patterns in the ice. Increased knowledge of the factors controlling the crystalline characteristics of urea ice sheets has progressed to the point where test basin researchers at CRREL are now able to fabricate ice sheets with prescribed structures leading to predictable mechanical properties. Originators supplied keywords include: Sea ice, and Mechanical properties.
    Type of Medium: Series available for loan
    Pages: iv, 55 Seiten , Illustrationen
    Series Statement: CRREL Report 84-24
    URL: https://apps.dtic.mil/docs/citations/ADA148434
    URL: https://hdl.handle.net/11681/9553
    Language: English
    Note: Contents: Abstract Preface Introduction Objectives Analytical techniques Procedures for growing urea ice sheets Analysis of the crystalline structure of urea ice Characteristics of urea ice Results and discussion Ice sheet no. 1 Ice sheet no. 2 Ice sheet no. 3 Ice sheet no. 4 Ice sheet no. 5 Ice sheet no. 6 Ice sheet no. 7 Ice sheet no. 8 Ice sheet no. 9 Ice sheet no. 10 Ice sheet no. 11 Ice sheet no. 12 Ice sheet no. 13 Ice sheet no. 14 Ice sheet no. 15 Ice sheet no. 16 Ice sheet no. 17 Ice sheet no. 18 Ice sheet no. 19 Ice sheet no. 20 Ice sheet no. 21 Ice sheet no. 22 Ice sheet no. 23 Ice sheet no. 24 Urea concentrations in test tank solution and ice Discussion and conclusions E/σf ratio Thickness of incubation layer Crystal properties Literature cited Appendix A: Thin sections of urea ice sheets
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  • 9
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    Pulse transmission through frozen silt (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/17
    In: CRREL Report, 84-17
    Description / Table of Contents: VHF-band radiowave short pulses were transmitted within the permafrost tunnel at Fox, Alaska, over distances between 2.2 and 10.5 m. The propagation medium was a frozen silt containing both disseminated and massive ice with temperatures varying from -7°C near the transmitter to probably -2 C near the center of the tunnel overburden. The short pulses underwent practically no dispersion in the coldest zones but did disperse and refract through the warmer overburden, as suggested by calculations of the effective dielectric constant. Most significantly the measured frequency content decreased as the effective dielectric constant increased. The results indicate that deep, cross-borehole pulse transmissions over distances greater than 10 m might be possible, especially when the ground is no warmer than -4°C. The information thus pined could be used for identifying major subsurface variations, including ground ice features.
    Type of Medium: Series available for loan
    Pages: ii, 14 Seiten , Illustrationen
    Series Statement: CRREL Report 84-17
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a147108.pdf
    URL: https://hdl.handle.net/11681/9519
    Language: English
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  • 10
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    Frazil ice formation (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/18
    In: CRREL Report, 84-18
    Description / Table of Contents: This report investigates the influences of turbulence and water temperature on frazil ice formation. The rate and thequantity of frazil ice formed in a specified volume of supercooled water increase with both increasing turbulence inten-sitv and decreasing water temperature. The influence of turbulence intensity on the rate of frazil ice formation, how-ever. is more pronounced for larger initial supercooling. The turbulence characteristics of a flow affect the rate offrazil ice formation by governing the temperature to which the flow can be supercooled, by influencing heat transferfrom the frazil ice to surrounding water, and by promoting collision nucleation, particle and floc rupture and increasingthe number of nucleation sites. larger frazil ice particles formed in water supercooled to lower temperatures. The par-ticles usually were disks, with diameters several orders greater than their thickness. Particle size generally decreased with increasing turbulence intensity. This report develops an analytical model, in which the rate of frazil ice formation isrelated to temperature rise of a turbulent volume of water from the release of latent heat of fusion of liquid water toice. Experiments conducted in a turbulence jar with a heated, vertically oscillating grid served both to guide and tocalibrate thanalytical'model as well as to afford insights into frazil ice formation. The formation of frazil ice wasstudied for Vemperatures of supercooled water ranging from -0.9° to -0.050°C.
    Type of Medium: Series available for loan
    Pages: vi, 50 Seiten , Illustrationen
    Series Statement: CRREL Report 84-18
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a147425.pdf
    URL: https://hdl.handle.net/11681/9547
    Language: English
    Note: CONTENTS Abstract Preface Nomenclature Introduction Background Scope of study Literature review Introduction Incipient formation of frazil ice Particle size and evolution of frazil ice Influences of turbulence and water temperature on the rate of frazil ice formation Conclusions Analytical model Introduction Elements of heat transfer Elements of turbulence Experimentation Experimental apparatus Experimental procedure Results Introduction Nucleation of frazil ice Influences of turbulence on frazil ice formation Water temperature Influences of water temperature and turbulence on the concentration of frazil ice Frazil ice particle shape and size Conclusions Literature cited Appendix A: Preliminary frazil ice experiments Flume experiments Couette-flow Appendix B: Listing of computer program for calculation of frazil ice formation Appendix C: Water temperature rise attributable to frazil ice formation as computed usingthe analytical model .
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