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  • Polymer and Materials Science  (3.965)
  • Cell & Developmental Biology  (1.145)
  • Inorganic Chemistry  (693)
  • FLUID MECHANICS AND HEAT TRANSFER  (633)
  • METEOROLOGY AND CLIMATOLOGY  (623)
  • Biochemistry and Biotechnology  (603)
  • 1990-1994  (7.662)
  • 1950-1954
  • 1990  (7.662)
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  • 1990-1994  (7.662)
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  • 1
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    An error analysis of least-squares finite element method of velocity-pressure-vorticity formulation for Stokes problem (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: A theoretical proof of the optimal rate of convergence for the least-squares method is developed for the Stokes problem based on the velocity-pressure-vorticity formula. The 2D Stokes problem is analyzed to define the product space and its inner product, and the a priori estimates are derived to give the finite-element approximation. The least-squares method is found to converge at the optimal rate for equal-order interpolation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 84; 3, De
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  • 2
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    Evolution of tropical circulation anomalies associated with 30-60 day oscillation of globally averaged angular momentum during northern summer (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Lag correlation statistics was used to study intraseasonal variations of upper and lower-level zonal winds, outgoing longwave radiation, and globally averaged angular momentum (GAM) for northern summers of 1977-1984. The temporal and spatial distribution of surface wind stress in the tropics and its relationship with zonal wind anomalies were studied to assess the impact of surface frictional drag on the atmospheric angular momentum. The 30-60 day GAM fluctuation is shown to be accompanied by zonal propagation of convection and 850 mb zonal wind anomalies in the tropical belt. The climatological zonal wind in the tropics affects the magnitude of wind stress anomalies. It is suggested that momentum exchange between the lower and upper troposphere may occur in regions of active convection via vertical momentum transport. The tropical central Pacific is considered to play a key role in linking the atmosphere and the earth through angular momentum exchange on intraseasonal time scales.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Meteorological Society of Japan, Journal (ISSN 0026-1165); 68; 237-249
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  • 3
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    Tropical Rainfall Measuring Mission (TRMM) project. III - Japan-U.S. collaborative rain observation experiment using an airborne rain radar (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: A collaborative rain-observation experiment using an airborne rain radar was conducted between Communications Research Laboratory (CRL) and Goddard Space Flight Center (GSFC)/NASA. CRL provided an airborne rain-radar/radiometer system and GSFC/NASA provided a NASA P3-A aircraft. Airborne or spaceborne rain-radar echoes have large sea or land-surface echoes. These surface echoes yield rain-estimation algorithms using rain attenuation. The experiment demonstrated the potential of the rain-estimation techniques using rain attenuation.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Communications Research Laboratory, Review (ISSN 0914-9279); 36; 11, J; 35-44
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  • 4
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    Experimental and computational surface and flow-field results for an all-body hypersonic aircraft (1990)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-04
    Beschreibung: Personnel from NASA Ames Research Center presented a paper on establishing a benchmark experimental data base for generic hypersonic vehicle shape for validation and/or calibration of advanced computational fluid dynamics computer codes. The need for this capability is based on a requirement for extensive hypersonic data to fully validate CFD codes to be used for NASP and other hypersonic vehicles. The use of wind tunnel models in the Ames 3.5-ft Hypersonic Wind Tunnel to obtain pertinent surface and flow-field data over a broad range of test conditions is described.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, 2nd NASA CFD Validation Workshop; p 126-161
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  • 5
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    NASA. Lewis Research Center/IFMD inlet duct and nozzle high speed validation experiments (1990)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-04
    Beschreibung: Personnel from NASA Lewis Research Center spoke on the subject of inlet duct and nozzle high speed validation experiments to include crossing shocks and boundary layer interaction, unsteady shock/boundary layer interactions, and vortex generators. Attention was also paid to the subjects of high speed mixing and transition ducts. Specific application was made to the NASP hypermixing concepts.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: 2nd NASA CFD Validation Workshop; p 197-231
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  • 6
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    Summary of NASA. Lewis Research Center validation efforts (1990)
    In:  CASI
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    Publikationsdatum: 2004-12-04
    Beschreibung: NASA Lewis Research Center personnel presented a summary of LeRC validation experiments. The subjects discussed included: iced wing, linear transonic cascade, transition duct aerodynamics, transition duct heat transfer, low speed centrifugal compressor, turbomachinery blade row interactions, and three dimensional fluid mechanics.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: 2nd NASA CFD Validation Workshop; p 100-125
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  • 7
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    NASA. Langley Research Center CFD code validation program overview (1990)
    In:  CASI
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    Publikationsdatum: 2004-12-04
    Beschreibung: A presentation by Langley Research Center covered subjects of: LaRC approach to CFD code validation, experimental CFD perceptions, CFD code validation program experiment, and highlights of the experiment. The objective of the validation program and the approach taken are discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, 2nd NASA CFD Validation Workshop; p 1-21
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  • 8
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    NASA low speed centrifugal compressor (1990)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-04
    Beschreibung: The flow characteristics of a low speed centrifugal compressor were examined at NASA Lewis Research Center to improve understanding of the flow in centrifugal compressors, to provide models of various flow phenomena, and to acquire benchmark data for three dimensional viscous flow code validation. The paper describes the objectives, test facilities' instrumentation, and experiment preliminary comparisons.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: 2nd NASA CFD Validation Workshop; p 232-256
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  • 9
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    Flow over a rearward facing step (1990)
    In:  CASI
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    Publikationsdatum: 2004-12-04
    Beschreibung: The characteristics of flow over a rearward facing step is discussed in a paper presented by NASA Lewis Research Center personnel. The objective is to obtain data which will be used for validation of Direct Numerical Simulations being developed at NASA Langley and Ames. Two phases of the work are identified as a study of large scale structures in the flow using hot-wire/cold wire techniques and the development of a statistical data base for using three-component laser velocimetry.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, 2nd NASA CFD Validation Workshop; p 182-196
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  • 10
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    Overview of CFD flow modeling and validation: NASA. Ames Research Center (1990)
    In:  CASI
    Details
    Publikationsdatum: 2004-12-04
    Beschreibung: NASA Ames Center personnel presented data on stages of code development and corresponding experiments in the application of computational fluid dynamics for aeronautical investigations. Specific subjects included algorithms, grid generation, facilities, instrumentation, and data acquisition. Numerical simulation and flow modelling were described to show the procedure for calibration and validation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, 2nd NASA CFD Validation Workshop; p 45-69
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  • 11
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    Status of NASA. Marshall Space Flight Center CFD application and validation activities (1990)
    In:  CASI
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    Publikationsdatum: 2004-12-04
    Beschreibung: NASA Marshall Space Flight Center personnel presented a paper on the status of MSFC computational fluid dynamics application and validation activities. Subjects discussed included the Space Shuttle Main Engine studies, unsteady multistage turbine loads, fuel pump discharge volutes, and injector LOX inlet results based on fundamental flows, subcomponents, and interactive components/systems.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, 2nd NASA CFD Validation Workshop; p 70-99
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  • 12
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    Fluid management in the optimization of space construction (1990)
    In:  CASI
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    Publikationsdatum: 2004-10-02
    Beschreibung: Fluid management impacts strongly on the optimization of space construction. Large quantities of liquids are needed for propellants and life support. The mass of propellant liquids is comparable to that required for the structures. There may be a strong dynamic interaction between the stored liquids and the space structure unless the design minimizes the interaction. The constraints of cost and time required optimization of the supply/resupply strategy. The proper selection and design of the fluid management methods for: slosh control; stratification control; acquisition; transfer; gauging; venting; dumping; contamination control; selection of tank configuration and size; the storage state and the control system can improve the entire system performance substantially. Our effort consists of building mathematical/computer models of the various fluid management methods and testing them against the available experimental data. The results of the models are used as inputs to the system operations studies. During the past year, the emphasis has been on modeling: the transfer of cryogens; sloshing and the storage configuration. The work has been intermeshed with ongoing NASA design and development studies to leverage the funds provided by the Center.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Second Annual Symposium; p 412-433
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  • 13
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    Unstructured finite element mesh generation and adaptive procedures for CFD (1990)
    In:  CASI
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    Publikationsdatum: 2011-10-14
    Beschreibung: A method is described for generating unstructured meshes of triangles or tetrahedra for computational domains of complex geometrical shape. To illustrate the power of the approach, it is applied to the solution of flows past several complete aircraft configurations. The advocated approach allows for the natural incorporation of mesh adaptivity and this is demonstrated for both inviscid and viscous computations in two and three dimensions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AGARD, Applications of Mesh Generation to Complex 3-D Configurations; 12 p
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  • 14
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    Applications of algebraic grid generation (1990)
    In:  CASI
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    Publikationsdatum: 2011-10-14
    Beschreibung: Techniques and applications of algebraic grid generation are described. The techniques are univariate interpolations and transfinite assemblies of univariate interpolations. Because algebraic grid generation is computationally efficient, the use of interactive graphics in conjunction with the techniques is advocated. A flexible approach, which works extremely well in an interactive environment, called the control point form of algebraic grid generation is described. The applications discussed are three-dimensional grids constructed about airplane and submarine configurations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AGARD, Applications of Mesh Generation to Complex 3-D Configurations; 12 p
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  • 15
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    A defect stream function formulation for compressible turbulent boundary layers (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Progress to date on the development of a method for turbulent, wall-bounded flow which uses the defect stream function formulation in the outer layer and an analytic law of the wall and wake formulation in the inner region is reviewed. This two-formulation approach avoids the need to computationally resolve the high-gradient inner layer. One of the most appealing recent developments is the transformation of the compressible governing equation for the defect stream function into a linear, second-order differential equation which has analytic solutions for many problems of practical interest. Numerical and analytic results for incompressible and compressible flows are shown to be in excellent agreement with experimental results. In this paper the two-formulation approach is applied to primitive-variable computations. Excellent comparisons with experiment are presented for two compressible flat plate flows.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 16
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    Tropical Rainfall Measuring Mission (TRMM) project. V - Scientific background and goals of TRMM (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The scientific goals of TRMM are described. TRMM provides quantitative measurements of tropical rain which can improve the understanding of the global climate. TRMM can also help to improve techniques for measuring rainfall from space.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Communications Research Laboratory, Review (ISSN 0914-9279); 36; 11, J; 57-70
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  • 17
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    Quasi-coherent structures in the turbulent boundary layer. II - Verification and new information from a numerically simulated flat-plate layer (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 18
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    Velocity and pressure fields associated with near-wall turbulence structures (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Computer generated databases containing velocity and pressure fields in three-dimensional space at a sequence of time-steps, were used for the investigation of near-wall turbulence structures, their space-time evolution, and their associated pressure fields. The main body of the results were obtained from simulation data for turbulent channel flow at a Reynolds number of 180 (based on half-channel height and friction velocity) with a grid of 128 x 129 x and 128 points. The flow was followed over a total time of 141 viscous time units. Spanwise centering of the detected structures was found to be essential in order to obtain a correct magnitude of the associated Reynolds stress contribution. A positive wall-pressure peak is found immediately beneath the center of the structure. The maximum amplitude of the pressure pattern was, however, found in the buffer region at the center of the shear-layer. It was also found that these flow structures often reach a maximum strength in connection with an asymmetric spanwise motion, which motivated the construction of a conditional sampling scheme that preserved this asymmetry.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 19
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    Quasi-coherent structures in the turbulent boundary layer. I - Status report on a community-wide summary of the data (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A review is presented of the approach, motivation and early results of a reevaluation of the knowledge collected by the research community during thirty years of research on the structure of turbulent boundary layers. Four distinctions or criteria concerning the need to improve the practices in this field are discussed: data versus inferences, possible versus actual versus significant events, one structure versus many, and one or two flows versus the totality of data. Attention given to the known quasi-coherent structures show that three factors significantly reduce the information available from laboratory data as a basis for forming a complete model of the quasi-coherent structure in the turbulent boundary layer: (1) the necessity to ensemble average probe output with resulting loss of phase information, (2) the inability to see more than one or two of the various types of structures simultaneously, and (3) the inability to see the spatial relations between the various quasi-coherent structures resulting from (1) and (2).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 20
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    Statistical analysis of near-wall structures in turbulent channel flow (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The two-point correlation tensor is used to analyze near-wall structures in turbulent channel flow. Simulation results have been utilized to obtain the correlation tensor with sufficient spatial resolution to permit accurate differentiation for computing the vorticity correlation, and the resolution of sharp features such as the shear layer and its corresponding region of spanwise vorticity. Proper orthogonal decomposition and stochastic estimation were observed to yield similar results when appropriate conditions were employed for the estimation. Resulting structures were such that they would be detected by standard conditional sampling methods. The results of decomposing the vorticity field and the velocity field were significantly different, indicating that if a coherent structure is found that dominates the velocity fields, the curl of that velocity structure will not dominate the vorticity field.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 21
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    Similarity of organized structures in turbulent shear flows (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent analysis of databases generated by direct numerical simulations of homogeneous turbulent shear flows have revealed the presence of coherent structures similar to those in turbulent boundary layers. In this paper these findings and tentative conclusions on their significance are discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 22
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    Remote sensing of surface turbulence heat flux (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The determination of latent heat-flux variability using spaceborne sensors is discussed. Particular attention is given to the microwave sensors which have all weather capability. The retrieval of surface layer humidity, of wind speed and interfacial humidity, and of sensible heat flux are discussed. Both the indirect retrieval and direct retrieval of latent heat flux are considered.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
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  • 23
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    Unsteady viscous flow around a circular cylinder found by the hopscotch scheme on a vector processing machine (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The hopscotch scheme is examined to see whether it can compete effectively with implicit schemes for the integration of the Navier-Stokes equations on a vector processing machine. This scheme is stable as long as the Courant number is less than or equal to one and it does not underestimate viscous effects. The accuracy of the scheme is tested on one- and two-dimensional problems whose exact solutions are known. The scheme is then used to simulate flows around a circular cylinder with Reynolds numbers 200, 500 and 1000.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Applied Numerical Mathematics (ISSN 0168-9274); 6; 195-208
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  • 24
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    Interfacial dynamics of two liquids under an oscillating gravitational field (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The evolution of two miscible liquids meeting at an initially sharp interface inside a cavity under microgravity g-jitter conditions is studied numerically. The response of the interface and kinematics of the flowfield to various g-jitter accelerations and aspect ratio variations is shown. The interface region acts like a vortex source sheet, and it can be unstable to Kelvin-Helmholtz and Rayleigh-Taylor instabilities. The vortices produced along the interface can serve as a stirring mechanism to promote local mixing. Below the critical Stokes-Reynolds number, the destabilization of the interface results in deformation into wavy structures. In some parameter regions, these structures oscillate in time; in others, they are quasi-steady. Above the critical Stokes-Reynolds number, 'chaotic' instability results, and the interface breaks into concentration pockets. The morphology of the initial breakup is similar to observed Rayleigh-Taylor instability. Subsequent mixing of the two fluids after the breakup of the interface is then very rapid.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 28; 1933-194
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  • 25
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    Stability of an oscillated fluid with a uniform density gradient (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Instabilities in a fluid with a constant density gradient that is subject to arbitrarily oriented oscillatory accelerations are considered. With the Boussinesq approximation and for the case of an unbounded fluid, transformation to Lagrangian coordinates allows the reduction of the problem to an ordinary differential equation for each three-dimensional wavenumber. The problem has three parameters: the nondimensional amplitude R of the base-state oscillation, the nondimensional level of background steady acceleration, which for some cases can be represented in terms of a local (in time) Richardson number Ri, and the Prandtl number Pr. Some general bounds on stability are derived. For Pr = 1 closed-form solutions are found for impulse (delta function) accelerations and a general asymptotic solution is constructed for large R and general imposed accelerations. The asymptotic solution takes advantage of the fact that at large R wave growth is concentrated at 'zero points'. These are times when the effective vertical wavenumber passes through zero. Kelvin-Helmholtz instabilities are found to dominate at low R, while Rayleigh-Taylor instabilities dominate at high R. At high R, the uniform shear of the Kelvin-Helmholtz case tends to distort and weaken instability waves. With unsteady flows, Ri = 1/4 is no longer an instability limit. Significant instabilities have been found for sinusoidal forcing for Ri up to 0.6.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 219; 449-468
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  • 26
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    Evolution of tropical plumes in VAS water vapor imagery (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Synoptic scale tropical plumes are analyzed using satellite data and outgoing longwave radiation data. The evolution of plumes is described and their precursor signals are examined. The horizontal moisture patterns of the plumes are compared with nonplume climatology, and the predictability of plumes based solely on satellite imagery is assessed. The results show that a plume evolves as a stationary, tropical, dry or moist dipole, separated by an exceptionally strong cloud or moisture gradient. Tropical plume evolution is accompanied by a systematic drying of the tropical eastern Pacific atmosphere before development, and moistening and increased cloudiness with development.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Monthly Weather Review (ISSN 0027-0644); 118; 1758-176
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  • 27
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    Riblets (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: In addition to characterizing the various concepts reported in the literature on longitudinally-ribbed surface for aerodynamic surface drag reduction, the present development status evaluation of this technology correlates all available experimental data. An analysis of these data is then conducted to ascertain the parameters most directly involved in drag reduction, and to evaluate the effects which have thus far been exerted on turbulent boundary layer structures. Such advanced riblet techniques as compound and three-dimensional riblets, riblets in combination with large-eddy breakup devices, and riblets with suction/blowing, are also discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 28
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    Active wave control of boundary-layer transition (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The physical processes involved in the boundary layer instability-generation and transition process seem to pose basic restrictions on the implementation of active, wave-based transition-control methods. While suppression short of elimination is possible by these means for primary disturbances, wave-interaction instabilities demand that the control be implemented almost immediately after the appearance of primary disturbances; even slight delays can negate the intended beneficial effects, and this basic problem is exacerbated at the higher Reynolds numbers typical of aircraft in cruising flight. Three-dimensional disturbances are noted to be important in this context, together with the continuous regeneration of TS waves.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 29
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    Satellite observations of instability in the middle atmosphere (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Data from the Limb Infrared Monitor of the Stratosphere (LIMS) have been used to define zonally averaged basic-state temperature and zonal wind fields in the middle atmosphere for several periods during the winter of 1978-79. This basic state has been used to calculate the phase speeds, growth rates, and spatial structures of unstable modes using a linear, quasigeostrophic model. These results have been compared with temperature and ozone variance amplitudes from a spectral analysis of the same LIMS data. The comparison indicates that there is a close match between phase speeds for the most rapidly growing modes predicted by the model and phase speeds for statistically significant temperature and ozone variances. Both calculated and observed modes tend to be limited in latitudinal extent to a few tens of degrees and in vertical extent to about 10 km. These modes also tend to be nondispersive. Examples are given for the Southern Hemisphere near 0.25 mb (60 km) and for low latitudes of the Northern Hemisphere near 15 mb (30 km).
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 1065-107
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    Recent advances, trends and new perspectives via enthalpy-based finite element formulations for applications to solidification problems (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The present paper describes recent advances and trends in finite element developments and applications for solidification problems. In particular, in comparison to traditional methods of approach, new enthalpy-based architectures based on a generalized trapezoidal family of representations are presented which provide different perspectives, physical interpretation and solution architectures for effective numerical simulation of phase change processes encountered in solidification problems. Various numerical test models are presented and the results support the proposition for employing such formulations for general phase change applications.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 30; 803-820
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  • 31
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    Inviscid flux-splitting algorithms for real gases with non-equilibrium chemistry (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Formulations of inviscid flux splitting algorithms for chemical nonequilibrium gases are presented. A chemical system for air dissociation and recombination is described. Numerical results for one-dimensional shock tube and nozzle flows of air in chemical nonequilibrium are examined.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 90; 371-395
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  • 32
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    Ternary baroeffect with a nondiffusing component (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A systematic analysis is developed which describes the isothermal counterdiffusion of two gases in the presence of a third nondiffusing gas. Four distinct regimes are identified for diffusive slip. The nondiffusing gas reduces the pressure drop in all cases, whether it raises or lowers the mean density. The gas leads to nonzero diffusive slip even in the limit of very disparate masses for the diffusing gases. The implications of these findings for controlling concentration creep in crystal growth are discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physical Review Letters (ISSN 0031-9007); 65; 1587-159
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  • 33
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    Diagonally inverted lower-upper factored implicit multigrid scheme for the three-dimensional Navier-Stokes equations (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 28; 1642-164
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    Solitons induced by boundary conditions from the Boussinesq equation (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The behavior of solitons induced by boundary excitation is investigated at various time-dependent conditions and different unperturbed water depths, using the Korteweg-de Vries (KdV) equation. Then, solitons induced from Boussinesq equations under similar conditions were studied, making it possible to remove the restriction in the KdV equation and to treat soliton head-on collisions (as well as overtaking collisions) and reflections. It is found that the results obtained from the KdV and the Boussinesq equations are in good agreement.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 1574-158
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  • 35
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    Hopf bifurcation in the driven cavity (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The algorithm employed in the present incompressible two-dimensional calculations of an impulsively-started lid-driven cavity has its basis in the time-dependent stream-function equation. While a Crank-Nicholson differencing scheme is used for the diffusion terms, the Adams-Bashforth scheme is used for the convection terms. The periodic asymptotic solutions obtained for Reynolds numbers of 5000 and 10,000 are found to be precisely periodic; it is demonstrated that they have reached asymptotic states. The indicators of that achievement are discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 90; 219-261
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  • 36
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    Sun and dust versus greenhouse gases - An assessment of their relative roles in global climate change (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Many mechanisms, including variations in solar radiation and atmospheric aerosol concentrations, compete with anthropogenic greenhouse gases as causes of global climate change. Comparisons of available data show that solar variability will not counteract greenhouse warming and that future observations will need to be made to quantify the role of tropospheric aerosols, for example.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Nature (ISSN 0028-0836); 346; 713-719
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    Containments for liquids at zero gravity (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A theory proposed by Concus and Finn (1974) and recently developed by Finn (1983 and 1984) yields explicit geometrical criteria for the position of the free surface of a liquid at zero gravity in a cylindrical container of specified cross section. These criteria were applied by Concus and Finn to three container geometries: the bathtub, the trapezoid, and the keyhole. It is possible to find geometrical criteria that promise a liquid interface of finite height, with the base still covered with liquid, or a liquid interface of infinite height, with the liquid wetting a well defined portion of the wall. In the present work, calculations are presented for a fourth geometry, the non-concentric cylinders. In addition, the earlier calculations of Concus and Finn are extended, and a unified graphical presentation of all four geometries is given that can be used directly for the design of containments for liquids at zero gravity.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Microgravity Science and Technology (ISSN 0938-0108); 3; 13-23
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  • 38
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    A spectrum model for weakly anisotropic turbulence (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A simple model, parameterized by the Reynolds stress anisotropy, is proposed for the spectrum of weakly anisotropic turbulence. It contains a model constant that affects its region of realizability. This spectrum model is used to derive a one-point closure to the rapid pressure-strain term. The derived pressure-strain model is linear in the Reynolds stress anisotropy and is of the same form as the closure model of Launder et al. (1975). The spectrum model becomes unrealizable in some regions of wave space for sufficiently large anisotropy of the Reynolds stress, and this is used to infer the region of validity of the linear closure model. It is found that the extent of the valid region is very small when the model constant is set to match rapid distortion theory, and largest for a model-constant set close to the value suggested by LRR. However, even the largest valid domain does not extend very far from isotropy, suggesting inherent weakness in the linear pressure-strain models.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 1500-150
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  • 39
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    A technique for measurement of instantaneous heat transfer in steady-flow ambient-temperature facilities (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experimental technique is described for obtaining time-resolved heat flux measurements with high-frequency response (up to 100 kHz) in a steady-flow ambient-temperature facility. The heat transfer test object is preheated and suddenly injected into an established steady flow. Thin-film gages deposited on the test surface detect the unsteady substrate surface temperature. Analog circuitry designed for use in short-duration facilities and based on one-dimensional semiinfinite heat conduction is used to perform the temperature/heat flux transformation. A detailed description of substrate properties, instrumentation, experimental procedure, and data reduction is given, along with representative results obtained in the stagnation region of a circular cylinder subjected to a wake-dominated unsteady flow. An in-depth discussion of related work is also provided.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Experimental Thermal and Fluid Science (ISSN 0894-1777); 3; 416-430
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  • 40
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    Transitions from Hadley to Rossby flows in internally forced rotating spherical systems (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The possibility of global-scale transitions between the Hadley and Rossby atmospheric regimes is investiated using a simple three-dimensional rotating spherical model without a boundary layer structure, bottom topography, or cumulus friction, and the expected occurrence of the Hadley to Rossby transition is demonstrated. It is shown that a transition from Hadley flow to wavenumber-5 Rossby flow is preferred, in agreement with standard baroclinic instability results. This result gives a reasonable Rossby wave bifurcation from the Hadley solution. For the cases examined, it was found that the upper symmetric Hadley regime does not exist and that the Hadley to Rossby transition depends on the values of the eddy viscosities.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 1041-105
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  • 41
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    Near-wall turbulence model and its application to fully developed turbulent channel and pipe flows (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A near-wall turbulence model and its incorporation into a multiple-timescale turbulence model are presented. The near-wall turbulence model is obtained from a k-equation turbulence model and a near-wall analysis. In the method, the equations for the conservation of mass, momentum, and turbulent kinetic energy are integrated up to the wall, and the energy transfer and the dissipation rates inside the near-wall layer are obtained from algebraic equations. Fully developed turbulent channel and pipe flows are solved using a finite element method. The computational results compare favorably with experimental data. It is also shown that the turbulence model can resolve the overshoot phenomena of the turbulent kinetic energy and the dissipation rate in the region very close to the wall.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Numerical Heat Transfer, Part B: Fundamentals (ISSN 1040-7790); 17; 101-122
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  • 42
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    Implicit flux-split schemes for the Euler equations (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 28; 973
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  • 43
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    A numerical study of the onset of baroclinic instabilities in spherical geometry (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The onset of instabilities in a fluid contained in a rotating hemispherical shell, driven by thermal gradients imposed upon the hemispherical boundaries and by a spherically symmetric radial body force, is numerically studied. Computations are presented for a range of Taylor and thermal Rossby numbers. The analysis indicates the presence of an instability dependent upon the spherically radial gravity alone when the warmest temperatures are at the pole and an additional centrifugal buoyant instability for weak imposed gravity and fast rotation when the temperature decreases poleward.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Geophysical and Astrophysical Fluid Dynamics (ISSN 0309-1929); 52; 25-43
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    A simple two-system-parameter model for surface-effected warming of the planetary boundary layer (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The transabsorptivity concept which specifies the heat input into the PBL resulting from surface-atmosphere interactions is discussed. This concept is examined in terms of governing equations, and transabsorptivity is defined as the product of the surface absorptivity and the transfer efficiency. It is proposed that the climatic effects of surface changes be formulated in terms of changes in the transabsorptivity. A diagram of the surface-atmosphere interactions is provided.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Boundary-Layer Meteorology (ISSN 0006-8314); 51; 3, Ma; 213-227
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    Numerical simulations of soft and hard turbulence - Preliminary results for two-dimensional convection (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Results on the transition from soft to hard turbulence in simulations of two-dimensional Boussinesq convection are reported. The computed probability densities for temperature fluctuations are exponential in form in both soft and hard turbulence, unlike what is observed in experiments. In contrast, a change is obtained in the Nusselt number scaling on Rayleigh number in good agreement with the three-dimensional experiments.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physical Review Letters (ISSN 0031-9007); 64; 2370-237
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    Modeling of confined turbulent fluid-particle flows using Eulerian and Lagrangian schemes (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Two important aspects of fluid-particulate interaction in dilute gas-particle turbulent flows (the turbulent particle dispersion and the turbulence modulation effects) are addressed, using the Eulerian and Lagrangian modeling approaches to describe the particulate phase. Gradient-diffusion approximations are employed in the Eulerian formulation, while a stochastic procedure is utilized to simulate turbulent dispersion in the Lagrangina formulation. The k-epsilon turbulence model is used to characterize the time and length scales of the continuous phase turbulence. Models proposed for both schemes are used to predict turbulent fully-developed gas-solid vertical pipe flow with reasonable accuracy.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 33; 691-701
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  • 47
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    The vibrating ribbon problem revisited (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A revised formal solution of the vibrating ribbon problem of hydrodynamic stability is presented. The initial formulation of Gaster (1965) is modified by application of the Briggs method and a careful treatment of the complex double Fourier transform inversions. Expressions are obtained in a natural way for the discrete spectrum as well as for the four branches of the continuous spectra. These correspond to discrete and branch-cut singularities in the complex wavenumber plane. The solutions from the continuous spectra decay both upsteam and downstream of the ribbon, with the decay in the upstream direction being much more rapid than that in the downstream direction. Comments and clarification of related prior work are made.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 213; 531-547
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  • 48
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    Numerical analysis of three-dimensional viscous internal flows (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 28; 798-806
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    Suggestions for the measurement and derivation of fluxes and flux divergences from a satellite (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Consideration is given to the determination of the optimal bands for measuring and deriving the total outgoing longwave radiation (OLR), surface downward flux (SDF), and cooling rates (CRs) using linear regression. The optimal bands are determined from scatter plots of total fluxes and cooling rates associated with the various bands. It is found that the best band for OLR is between 800 and 1200/cm, while the best band for SDF is between 500 and 660/cm or between 660 and 800/cm. For CRs, it is shown that the best band is also between 660 and 800/cm. It is noted that the AVHRR OLR is damped compared with the Nimbus-7 earth radiation budget (ERB) OLR derived from the broadband, narrow FOV ERB instrument.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 5257-527
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    Variable specific heat and thermal relaxation parameter in hyperbolic heat conduction (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 4; 252-255
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    A comparison of Solar Mesosphere Explorer and Stratosphere Aerosol and Gas Experiment II ozone densities near the stratopause (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Ozone measurements made by the SME UV Spectrometer and the Stratosphere Aerosol and Gas Experiment II (SAGE II) spectometer are compared at 1.0 mbar for the time period from October 1984 to December 1986, using a model of the diurnal variation of ozone to correct for the difference in local times of the two measurements. The absolute values of the ozone mixing ratio measured by the two spectrometers were found to agree to better than 5 percent, with no significant divergence between the instruments. It is concluded that, since the SAGE II data are not dependent on the absolute calibration of the instrument, these data can be used as time-dependent 'ground truth' measurements for comparisons with other instruments.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 3533-353
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    Implicit methods for the Navier-Stokes equations (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Numerical solutions of the Navier-Stokes equations using explicit schemes can be obtained at the expense of efficiency. Conventional implicit methods which often achieve fast convergence rates suffer high cost per iteration. A new implicit scheme based on lower-upper factorization and symmetric Gauss-Seidel relaxation offers very low cost per iteration as well as fast convergence. High efficiency is achieved by accomplishing the complete vectorizability of the algorithm on oblique planes of sweep in three dimensions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Computing Systems in Engineering (ISSN 0956-0521); 1; 2-4,
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    Visualization of fluid dynamics at NASA Ames (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Some of the hardware and software tools and techniques in use at NASA's numerical aerodynamic simulation facility for the analysis of computational fluid dynamics are described. The visualization process can be illustrated by video tapes and stereo pictures. Although these visualization tools have dramatically improved the ability to conduct research in fluid dynamics, a comparison of the current environment for analysis with an 'ideal' environment illustrates that there are still major improvements that should be made. The most time-consuming task in future analyses of the increasingly complex computer simulations will be the extraction and clear display of the key features. In addition, the interface between the workstation and the scientist should be improved significantly. Current research on techniques for creating these improvements is described.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Computing Systems in Engineering (ISSN 0956-0521); 1; 2-4,
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    Deep optically thin cirrus clouds in the polar regions. I - Infrared extinction characteristics (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The spectral data obtained by the infrared interferometer Spectrometer (IRIS) flown on Nimbus 4 satellite in 1970 indicated the existence of optically thin ice clouds in the upper troposphere that probably extended into lower stratosphere, in the polar regions, during winter and early spring. The spectral features of these clouds differ somewhat from that of the optically thin cirrus clouds in the tropics. From theoretical simulation of the infrared spectra in the 8-25 micron region, it is inferred that these polar clouds have a vertical stratification in particle size, with larger particles (about 12 microns) in the bottom of the cloud and smaller ones (less than 1 micron) aloft. Radiative transfer calculations also suggest that the equivalent ice-water content of these polar clouds is of the order of 1 mg/sq cm.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Applied Meteorology (ISSN 0894-8763); 29; 1313-132
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    Cirrus structure and radiative parameters from airborne lidar and spectral radiometer observations - The 28 October 1986 FIRE study (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A description is presented of cirrus based on results from a FIRE observation flight in central Wisconsin on October 28, 1986. Cirrus structure and radiative parameters as determined by the ER-2 lidar and imaging spectral radiometers are presented. From the lidar observations a complex structure was shown with differing cloud layers extending over six kilometers of altitude range. Both thin and dense cirrus layers were present and mixed phase clouds were found at lower altitudes. As indicated by the cloud structure, precipitation of crystals from high, but vertically thin, layers produces a significant fraction of the lower cirrus. Multiple layers should be considered as normal for cirrus formations. It is noted that the cloud height is an important factor for satellite cloud retrievals and cloud climatology.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Monthly Weather Review (ISSN 0027-0644); 118; 2329-234
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    An increase of early rains in southern Israel following land-use change? (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Rains at the onset of the October-April rainy season in southern Israel have steeply increased in the last 25 years relative to the previous 20 years, and are accompanied by an appreciable general increase of rainy-season rainfall. This increase in precipitation is specifically attributable to an intensification of the convection and advection processes due to afforestation and increased cultivation-induced enhancement of the daytime sensible heat flux from the generally dry surface; the enhancement proceeds from both the reduced surface albedo and the reduced soil heat flux in October, when insolation is strong. Greater daytime convection can lead to penetration of inversions capping the planetary boundary layer, while strengthened advection can furnish moist air from the Mediterranean.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Boundary-Layer Meteorology (ISSN 0006-8314); 53; 333-351
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    Nonlinear phase-space diffusion approach to turbulent organized structures (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The study deals with the approximation of the effect of all velocity-increment moments on the spatial evolution of the pdf for maximally correlated structures by the effect of the second moment alone by assuming independence of separated length scales. The dependence of the two-point velocity statistics on length-scale or separation is found to be governed by the gradients of the stress, rather than of the velocity. This may provide a new approach for predicting the domain patterns observed in turbulent flows and a new means of characterizing or classifying different structures, namely, by their nonlinear diffusion coefficient.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Canadian Journal of Physics (ISSN 0008-4204); 68; 723-725
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    Estimation of synoptic fields of middle atmosphere parameters from Nimbus-7 LIMS profile data (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The most widely used version of the Nimbus-7 middle atmosphere dataset is the set of high quality, daily, and zonal Fourier coefficients that resolve information out to six wavenumbers at 12 UTC. A Kalman filter algorithm was applied to the original profile data in order to generate those fields for the data archive or LAMAT product. The characteristics and implementation of the algorithm are described in some detail, along with examples of the output for each of the LIMS parameters.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 7; 689-705
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  • 59
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    Vertical structure and characteristics of 23-60 day (zonal) oscillations over the tropical latitudes during the winter months of 1986 - Results of equatorial wave campaign-II (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Results are presented of the equatorial wave campaign-II, a meteorological rocket study which was part of the Indian Middle Atmosphere Program. The equatorial wave campaign-II was conducted from Shar, India (13.7 deg N, 80.2 deg E) from January 15-February 28, 1986. By means of high altitude balloon and the RH-200 meteorological rocket, winds were measured from ground level up to 60 km altitude once each day during the 45-day period. The oscillation frequencies of the deviations in the east-west component of the winds from their mean at each 1-km height interval are obtained by the maximum entropy method. The phases and amplitudes of these frequencies are determined by use of the least squares method on the wind variation time series. Enhanced wave activity is shown to take place in the troposphere and lower mesosphere. The tropospheric waves observed suggest themselves to be Rossby waves of extratropical origin penetrating to tropical latitudes. The observed stratospheric/mesospheric waves appear to emanate from a source around the stratopause.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: (ISSN 0253-4126); 99; 413-423
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  • 60
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    Parameterization of eddy sensible heat transports in a zonally averaged dynamic model of the atmosphere (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A Charney-Branscome based parameterization has been tested as a way of representing the eddy sensible heat transports missing in a zonally averaged dynamic model (ZADM) of the atmosphere. The ZADM used is a zonally averaged version of a general circulation model (GCM). The parameterized transports in the ZADM are gaged against the corresponding fluxes explicitly simulated in the GCM, using the same zonally averaged boundary conditions in both models. The Charney-Branscome approach neglects stationary eddies and transient barotropic disturbances and relies on a set of simplifying assumptions, including the linear appoximation, to describe growing transient baroclinic eddies. Nevertheless, fairly satisfactory results are obtained when the parameterization is performed interactively with the model. Compared with noninteractive tests, a very efficient restoring feedback effect between the modeled zonal-mean climate and the parameterized meridional eddy transport is identified.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 2475-248
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  • 61
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    Behavior of deep convective clouds in the tropical Pacific deduced from ISCCP radiances (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The characteristic features, the diurnal cycle, and the spatial distribution of deep convection over the equatorial Pacific and the relationship of deep convection to SST and surface-wind convergence were examined using a combined visible-IR (VS-IR) threshold method and an IR-only threshold method for diagnosing deep convection clouds (DCCs). Results suggest that deep convection is latitudinally confined to a much smaller spatial scale than that suggested by maps of outgoing long-wave radiation. The results suggested that there are two types of relationships between deep convection, SST, and surface-wind convergence: the west Pacific type and the east Pacific type. The latter relationship is observed in the east Pacific only when SST is not abnormally warm.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Climate (ISSN 0894-8755); 3; 1129-115
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  • 62
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    Global atmospheric temperature monitoring with satellite microwave measurements - Method and results 1979-84 (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper describes a method for determining global atmospheric-temperature anomalies by means of satellite microwave radiometry. It is shown that microwave measurements of molecular oxygen thermal emission by the Microwave Sounding Units (MSUs) flying aboard the NOAA-6 and NOAA-7 can be used to monitor tropospheric temperature anomalies on global basis to a high level of precision. Comparisons between monthly MSU-derived hemispheric temperature anomalies with those computed from surface thermometer data show a very good agreement over the United States, although not for the hemispheres, especially the Southern Hemisphere. In this latter case, the poor agreement is ascribed to weaker thermal coupling between the ocean and the deep troposphere than that over the U.S. Annual anomalies for the hemispheres exhibit better correlations than do monthly anomalies.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Climate (ISSN 0894-8755); 3; 1111-112
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  • 63
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    Effect of metallic coatings on the thermal contact conductance of turned surfaces (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experimental investigation was conducted to determine the degree to which the thermal contact conductance at the interface of contacting Aluminum 6061 T6 surfaces could be enhanced through the use of vapor-deposited metallic coatings. Three different coating materials (lead, tin, and indium) were evaluated using four different thicknesses for each coating material. The results verified the existence of an optimum coating thickness, shown to be in the range of 2.0 to 3.0 microns for indium, 1.5 to 2.5 microns for lead, and 0.2 to 0.5 microns for tin. The enhancement factors for thermal contact conductance were found to be on the order of 700, 400, and 50 percent, respectively. Based upon the experimental data, the hardness of the coating materials appears to be the most significant parameter in ranking the substrate and coating material combinations; however, additional experimental data are needed to substantiate this hypothesis. Finally, it was apparent that the thermal contact conductance enhancement effect was greatest at low contact pressures and decreased significantly with increases in the contact pressure.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 112; 864-871
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  • 64
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    Determination of cloud liquid water content using the SSM/I (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: As part of a calibration/validation effort for the special sensor microwave/imager (SSM/I), coincident observations of SSM/I brightness temperatures and surface-based observations of cloud liquid water were obtained. These observations were used to validate initial algorithms and to derive an improved algorithm. The initial algorithms were divided into latitudinal-, seasonal-, and surface-type zones. It was found that these initial algorithms, which were of the D-matrix type, did not yield sufficiently accurate results. The surface-based measurements of channels were investigated; however, the 85V channel was excluded because of excessive noise. It was found that there is no significant correlation between the SSM/I brightness temperatures and the surface-based cloud liquid water determination when the background surface is land or snow. A high correlation was found between brightness temperatures and ground-based measurements over the ocean.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 28; 817-822
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  • 65
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    Seasonal variation of cloud radiative forcing derived from the Earth Radiation Budget Experiment (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The impact of clouds on the earth's radiation balance is assessed in terms of longwave, shortwave, and net cloud forcing by using monthly averaged clear-sky and cloudy-sky flux data derived from the NASA Earth Radiation Budget Experiment (ERBE). Emphasis is placed on regional measurements, regional cloud forcing, zonal cloud forcing, and snow and ice contributions. It is shown that the global mean cooling varied from 14 to 21 W/sq m between April 1985 and January 1986; hemispherically, the longwave and shortwave cloud forcing nearly cancel each other in the winter hemisphere, while in the summer the negative shortwave cloud forcing is significantly lower than the longwave cloud forcing, producing a strong cooling. The ERBE data reveal that globally, hemispherically, and zonally, clouds have a significant effect on the radiative heating gradients.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 18687-18
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  • 66
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    Influence of geometric features on the performance of pressure-swirl atomizers (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The spray characteristics of several different simplex pressure-swirl nozzles are examined using water as the working fluid. Measurements of mean drop size, drop-size distribution, effective spray cone angle, and circumferential liquid distribution are carried out over wide ranges of injection pressure. Eight different nozzles are employed in order to achieve a wide variation in the length/diameter ratio of the final discharge orifice. Generally, it is found that an increase in discharge orifice length/diameter ratio, l(o)/d(o), increases the mean drop size in the spray and reduces the spray cone angle. The circumferential liquid distribution is most uniform when l(o)/d(o) = 2. If l(o)/d(o) is raised above or lowered below this optimum value, the circumferential uniformity of the liquid distribution is impaired. The observed effects of l(o)/d(o) on spray characteristics are generally the same regardless of whether the change in l(o)/d(o) is accomplished by varying l(o) or d(o).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Engineering for Gas Turbines and Power (ISSN 0022-0825); 112; 579-584
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  • 67
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    Direct numerical simulation of a three-dimensional turbulent boundary layer (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The effects of transverse strain on an initially two-dimensional turbulent boundary layer are studied in a direct numerical simulation of a planar channel flow with impulsively started transverse pressure gradient. Consistent with experiments in three-dimensional boundary layers, the simulation shows a decrease in the Reynolds shear stress with increasing transverse strain. Also, the directions of the Reynolds shear stress vector and the mean velocity gradient vector were found to differ. In addition, the simulation shows a drop in the turbulent kinetic energy. Terms in the Reynolds stress transport equations were computed. The balances indicate that the decrease in turbulent kinetic energy is a result of a decrease in turbulence production, along with an increase in turbulent dissipation. Intuitive reasoning and current turbulence models would predict an increase in kinetic energy along with increases in production and dissipation rates as a result of increased mean-flow strain rate. Later in the evolution of the flow, both turbulence production and dissipation increase.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 1846-185
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  • 68
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    Airborne flux measurements and budget estimates of trace species over the Amazon Basin during the GTE/ABLE 2B expedition (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In situ airborne measurements of turbulent heat, moisture, momentum, ozone, and carbon monoxide fluxes in a convective boundary layer were obtained over a tropical rain forest between 1100 and 1630 LT on May 4, 1987. The aircraft flight path was chosen so as to fly over the tower site at the Ducke Forest Reserve near Manaus, Amazonas, Brazil. Both turbulence statistics and mean quantities were used to study the budgets of heat, water vapor, ozone, and carbon monoxide. The ozone budget study shows an accumulation rate in the boundary layer of 0.3 + or - 0.2 ppbv/h. The surface resistance to ozone during this flight was determined to be 0.06 + or - 0.03 s/cm, while the aerodynamic resistance was 0.14-0.17 s/cm. Results from the CO budget analysis show a midday accumulation rate of 0.6 + or - 0.3 ppbv/h in the Amazonian boundary layer. The evidence suggests production of CO in the PBL. A source of CO may exist below the lowest flight level (about 150 m), although it was not possible to determine what part of the flux at flight level was due to chemical production and what part may be due to surface emission.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 16875-16
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  • 69
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    Time-dependent boundary conditions for hyperbolic systems. II (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A general boundary condition formalism is developed for all types of boundary conditions to which hyperbolic systems are subject; the formalism makes possible a 'cookbook' approach to boundary conditions, by means of which novel boundary 'recipes' may be derived and previously devised ones may be consulted as required. Numerous useful conditions are derived for such CFD problems as subsonic and supersonic inflows and outflows, nonreflecting boundaries, force-free boundaries, constant pressure boundaries, and constant mass flux. Attention is given to the computation and integration of time derivatives.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 89; 439-461
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  • 70
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    Determination of atmospheric optical properties during the First International Satellite Land Surface Climatology Project Field Experiment (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 27; 373-379
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  • 71
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    Origin of low frequency (intraseasonal) oscillations in the tropical atmosphere. III - Monsoon dynamics (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The issue of the interaction of the monsoon large-scale circulation and intraseasonal oscillations is addressed, showing that, as a result of the interaction of the large scale monsoon flow with the near-equatorial intraseasonal oscillation, unstable baroclinic disturbances are generated over the monsoon region. From a linear stability analysis of quasi-geostrophic motion in a two-level model, it is shown that the westward propagating disturbances generated over the monsoon region are the manifestation of heat-induced unstable Rossby waves. The instability is favored in the region with large vertical wind shear and reduced effective static stability. The monsoon large scale circulation over India and southeast Asia and the plentiful supply of moisture in the region appear to be favorable for the development of these unstable waves.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 1443-146
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  • 72
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    Meteorological conditions during the summer 1986 CITE 2 flight series (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An overview of meteorological conditions during the NASA Global Tropospheric Experiment/Chemical Instrumentation Testing and Evaluation (GTE/CITE 2) summer 1986 flight series is presented. Computer-generated isentropic trajectories are used to trace the history of air masses encountered along each aircraft flight path. The synoptic-scale wind fields are depicted based on Montgomery stream function analyses. Time series of aircraft-measured temperature, dew point, ozone, and altitude are shown to depict air mass variability. Observed differences between maritime tropical and maritime polar air masses are discussed.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 10055-10
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  • 73
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    Potential evapotranspiration and the likelihood of future drought (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The possibility that the greenhouse warming predicted by the GISS general-circulation model and other GCMs could lead to severe droughts is investigated by means of numerical simulations, with a focus on the role of potential evapotranspiration E(P). The relationships between precipitation (P), E(P), soil moisture, and vegetation changes in GCMs are discussed; the empirically derived Palmer drought-intensity index and a new supply-demand index (SDDI) based on changes in P - E(P) are described; and simulation results for the period 1960-2060 are presented in extensive tables, graphs, and computer-generated color maps. Simulations with both drought indices predict increasing drought frequency for the U.S., with effects already apparent in the 1990s and a 50-percent frequency of severe droughts by the 2050s. Analyses of arid periods during the Mesozoic and Cenozoic are shown to support the use of the SDDI in GCM drought prediction.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 9983-100
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  • 74
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    Aircraft microwave observations and simulations of deep convection from 18 to 183 GHz. II - Model results (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 7; 392-410
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  • 75
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    Long-wave morphological instabilities in the directional solidification of a dilute binary mixture (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Long-wave instabilities in a directionally-solidified binary mixture may occur in several limits. Sivashinsky (1983) identified a small-segregation-coefficient limit and obtained a weakly nonlinear evolution equation governing subcritical two-dimensional bifurcation. Brattkus and Davis (1988) identified a near-absolute-stability limit and obtained a strongly nonlinear evolution equation governing supercritical two-dimensional bifurcation. The present investigation identifies a third strongly nonlinear evolution equation, arising in the small-segregation-coefficient, large-surface-energy limit. This equation links both of the former and describes the change from the sub- to super-critical bifurcations. This study sets the previous long-wave analyses into a logical framework.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: SIAM Journal on Applied Mathematics (ISSN 0036-1399); 50; 420-436
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    On the Lagrangian description of unsteady boundary-layer separation. II - The spinning sphere (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A theory to explain the initial stages of unsteady separation was proposed by Van Dommelen and Cowley (1989). This theory is verified for the separation process that occurs at the equatorial plane of a sphere or a spheroid which is impulsively spun around an axis of symmetry. A Lagrangian numerical scheme is developed which gives results in good agreement with Eulerian computations, but which is significantly more accurate. This increased accuracy, and a simpler structure to the solution, also allows verification of the Eulerian structure, including the presence of logarithmic terms. Further, while the Eulerian computations broke down at the first occurrence of separation, it is found that the Lagrangian computation can be continued. It is argued that this separated solution does provide useful insight into the further evolution of the separated flow. A remarkable conclusion is that an unseparated vorticity layer at the wall, a familiar feature in unsteady separation processes, disappears in finite time.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 210; 627-645
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  • 77
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    Small-scale transition in a plane mixing layer (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experimental study was conducted to investigate the generation process of random small-scale turbulence in an originally laminar mixing layer. The evolutions of the two types of deterministic structures, the spanwise and streamwise vortices, were first clarified in order to determine their roles in the transition process. A scaling rule for the streamwise distance from the trailing edge of the splitter plate to the vortex merging position was found for various velocity ratios. After this stremwise lengthscale was determined, it became clear that the spanwise wavelength of the streamwise vortices doubled after the merging of the spanwise structures which nominally doubled streamwise wavelengths. The most interesting finding was that the random small-scale eddies were produced by the interactions between the merging spanwise structures and the streamwise vortices.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 210; 475-500
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  • 78
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    On the Lagrangian description of unsteady boundary-layer separation. I - General theory (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Although unsteady, high-Reynolds number, laminar boundary layers have conventionally been studied in terms of Eulerian coordinates, a Lagrangian approach may have significant analytical and computational advantages. In Lagrangian coordinates the classical boundary layer equations decouple into a momentum equation for the motion parallel to the boundary, and a hyperbolic continuity equation (essentially a conserved Jacobian) for the motion normal to the boundary. The momentum equations, plus the energy equation if the flow is compressible, can be solved independently of the continuity equation. Unsteady separation occurs when the continuity equation becomes singular as a result of touching characteristics, the condition for which can be expressed in terms of the solution of the momentum equations. The solutions to the momentum and energy equations remain regular. Asymptotic structures for a number of unsteady 3-D separating flows follow and depend on the symmetry properties of the flow. In the absence of any symmetry, the singularity structure just prior to separation is found to be quasi 2-D with a displacement thickness in the form of a crescent shaped ridge. Physically the singularities can be understood in terms of the behavior of a fluid element inside the boundary layer which contracts in a direction parallel to the boundary and expands normal to it, thus forcing the fluid above it to be ejected from the boundary layer.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 210; 593-626
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  • 79
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    On the sensitivity of a residual circulation model to differences in input temperature data (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The residual mean circulation (RMC) formulation of zonally averaged transport in the middle atmosphere produces a circulation which depends on the distributions of net diabatic heating and temperature. Such circulations are from two temperature data sets, using the same radiative transfer code (Rosenfield et al. 1987). These circulations are then used to transport N2O in a photochemical model. The circulations and the resulting N2O distributions are notably different during the Northern Hemisphere winter, with that based on the NMC temperatures producing too much upward transport in the tropical stratosphere, as judged by comparison with the stratospheric and mesoscale sounder data. The experiment demonstrates that model calculations, in general, and perturbation assessments, in particular, are likely to be quite sensitive to the choice of input temperature data (where this is not computed self-consistently). It also reveals what appears to be a seasonally dependent bias in NMC zonally averaged temperatures with respect to those obtained from the LIMS instrument during 1978/1979.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 873-882
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  • 80
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    Multiple paths to subharmonic laminar breakdown in a boundary layer (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Numerical simulations demonstrate that laminar breakdown in a boundary layer induced by the secondary instability of two-dimensional Tollmien-Schlichting waves to three-dimensional subharmonic disturbancews need not take the conventional lambda vortex/high-shear layer path.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physical Review Letters (ISSN 0031-9007); 64; 641-644
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  • 81
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    Time-accurate simulations of a shear layer forced at a single frequency (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 28; 267-275
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  • 82
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    Analysis of stability of a planar solid-liquid interface in a dilute binary alloy (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper reconsiders the question of stability of a planar solid-liquid interface in an undercooled alloy melt without making the restrictive assumption of no heat flow in the solid (i.e., Gs = 0). The results of this analysis indicate that, provided the thermal gradient on the solid side of the interface, Gs, is positive, stability can be achieved in an undercooled alloy melt for growth rates R greater than Ra (where Ra is the absolute stability limit of Mullins and Sekerka, 1964). Thus, the absolute stability criterion for steady-state planar growth in an undercooled alloy melt is the same as derived earlier by Mullins and Sekerka for directional solidification. Relaxing the restrictive assumption of Gs = 0 also reveals that there is a regime of stability for low growth rates and low supercoolings.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Materials Research (ISSN 0884-2914); 5; 223-228
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    An analysis of the threshold method for measuring area-average rainfall (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Experimental evidence shows that the area-average rain rate and the fractional area covered by rain rate exceeding a fixed threshold are highly correlated; that is, are highly linearly related. A precise theoretical explanation of this fact is given. The explanation is based on the observation that rain rate has a mixed distribution, one that is a mixture of a discrete distribution and a continuous distribution. Under a homogeneity assumption, the slope of the linear relationship depends only on the continuous part of the distribution and as such is found to be markedly immune to parameter changes. This is illustrated by certain slope surfaces obtained from three specific distributions. The threshold level can be chosen in an optimal way by minimizing a certain distance function defined over the threshold range. In general, the threshold level should be not too far from the mean rain rate conditional on rain. The so-called threshold method advocates measuring rainfall from fractional area exploiting the observed linear relationship of the later with the area average rain rate. The method is potentially useful for the estimation of rainfall from space via satellites.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Applied Meteorology (ISSN 0894-8763); 29; 3-20
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  • 84
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    Multiple vortex ring model of the DFW microburst (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Aircraft (ISSN 0021-8669); 27; 163-168
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  • 85
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    Analysis of extreme wind shear (1990)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 27; 21-24
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  • 86
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    Climate change and the middle atmosphere. I - The doubled CO2 climate (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The effect of doubling the atmospheric content of CO2 on the middle-atmosphere climate is investigated using the GISS global climate model. In the standard experiment, the CO2 concentration is doubled both in the stratosphere and troposphere, and the SSTs are increased to match those of the doubled CO2 run of the GISS model. Results show that the doubling of CO2 leads to higher temperatures in the troposphere, and lower temperatures in the stratosphere, with a net result being a decrease of static stability for the atmosphere as a whole. The middle atmosphere dynamical differences found were on the order of 10-20 percent of the model values for the current climate. These differences, along with the calculated temperature differences of up to about 10 C, may have a significant impact on the chemistry of the future atmosphere, including that of stratospheric ozone, the polar ozone 'hole', and basic atmospheric composition.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 475-494
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  • 87
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    Numerical experiments in supersonic boundary-layer stability (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The three-dimensional (3-D) time-dependent compressible Navier-Stokes equations are numerically solved by a Fourier-Chebyshev collocation method to study the stability of supersonic flows over a flat plate. Several direct simulations carried out in this study suggest the existence of a secondary instability that might provide a route to transition. The interaction of the modes involved in the secondary instability is possibly amenable to a Floquet-type analysis. Pertinent differences between this instability and the analogous incompressible K-type secondary instability are pointed out. Some preliminary results of a 2-D direct simulation of the nonlinear evolution of a second mode perturbation wave are also discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 94-104
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  • 88
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    On the three-dimensional instability of strained vortices (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The three-dimensional (3-D) instability of a two-dimensional (2-D) flow with elliptical streamlines has been proposed as a generic mechanism for the breakdown of many 2-D flows. A physical interpretation for the mechanism is presented together with an analytical treatment of the problem. It is shown that the stability of an elliptical flow is governed by an Ince equation. An analytical representation for a localized solution is given and establishes a direct link with previous computations and experiments.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 76-80
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  • 89
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    Unsteady heat transfer on turbine blades (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 4; 47-52
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  • 90
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    Two-dimensional convection and radiation with scattering from a Poiseuille flow (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Two-dimensional combined convection and radiation heat transfer from a gray scattering fluid in a reflecting channel is considered. The model, represented by a set of simultaneous nonlinear integro-partial differential equations, is solved numerically. The effects of aspect ratio, conduction-radiation parameter, scattering albedo, and wall emissivity, are systematically investigated. It is found that these parameters have a significant influence on the temperature field and alter the radiative and convective fluxes at the hot and cold walls. In particular, when radiation effects are considerable, the heat-transfer characteristics of the fluid at the hot and cold walls are very different.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 4; 98-105
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  • 91
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    Climatologically tuned reflectivity-rain rate relations and links to area-time integrals (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An effort is made to determine relationships between reflectivity (Z) and rain rate (R) which are tuned to the local climatology. The development of such relations was motivated by the need to understand the role of precipitation in controlling general circulation and in affecting such phenomena as ENSO. Attention is given to methods of deriving such relations and how they are linked to area integral rainfall measurements. In essence, the relation is tuned so that the probability distribution of reflectivity, P(Z), replicates that of R over some predetermined space-time climatic domain. Thus, the accurate measurement of the average R over any smaller domain depends on how closely the sampled P(Z) approximates the climatic P(Z). The probability matching method used is a modification of the approach of Calheiros and Zawadzki (1987) and Rosenfeld (1980). The technique is applied to data from Germany and the eastern tropical Atlantic (GATE).
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Applied Meteorology (ISSN 0894-8763); 29; 1120-113
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  • 92
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    Elimination of spurious eigenvalues in the Chebyshev tau spectral method (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A very simple modification is presented for the Chebyshev tau method which can eliminate spurious eigenvalues, proceeding from a consideration of the vorticity-streamfunction reformulation of the Chebyshev tau method and the Chebyshev-Galerkin method, which have no spurious modes. Consideration of a model problem indicates that these two approaches are equivalent, and that they reduce to the present modification of the tau method. This modified tau method also eliminates spurious eigenvalues from the Orr-Sommerfeld equation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 91; 228-239
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  • 93
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    Stabilization of Taylor-Couette flow due to time-periodic outer cylinder oscillation (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The linear stability of circular Couette flow between concentric infinite cylinders is considered for the case when the inner cylinder is rotated at a constant angular velocity and the outer cylinder is driven sinusoidally in time with zero mean rotation. This configuration was studied experimentally by Walsh and Donnelly. The critical Reynolds numbers calculated from linear stability theory agree well with the experimental values, except at large modulation amplitudes and small frequencies. The theoretical values are obtained using Floquet theory implemented in two distinct approaches: a truncated Fourier series representation in time, and a fundamental solution matrix based on a Chebyshev pseudospectral representation in space. For large amplitude, low frequency modulation, the linear eigenfunctions are temporally complex, consisting of a quiescent region followed by rapid change in the perturbed flow velocities.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 2147-215
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  • 94
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    The migration of a compound drop due to thermocapillarity (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The quasistatic thermocapillary motion of a compound drop in an unbounded fluid possessing a uniform temperature gradient is analyzed. For completeness, gravitational effects are included in the treatment. The general model is formulated, and the equations for the concentric case are solved using spherical polar coordinates, while the eccentric case is handled using bispherical coordinates. Results are given for the velocity of the drop as well as that of the droplet with respect to the drop, along with useful approximations. Illustrative results are presented graphically for the thermocapillary migration of a compound drop in the special case when the droplet is a gas bubble. In addition to the velocities of the drop and the bubble, representative isotherms and streamlines also are presented which display interesting qualitative features.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids A (ISSN 0899-8213); 2; 2119-213
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  • 95
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    Clear air turbulence as a response to meso- and synoptic-scale dynamic processes (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The paper presents both the Roach equation for the rate of energy dissipation due to clear air turbulence and Richardson number tendencies in isentropic coordinates and examines the implications of these formulations to determine whether there is a dynamic interdependence between Ri and the nonturbulent deformation processes. The equation representing the ln(Ri) tendency is applied diagnostically to grids from an isentropic analysis of archived soundings. The evolution of the Richardson number fields over 12-hour time periods is examined using a mechanistic model. It is suggested that the application of the Roach equation for the turbulent dissipation rate should have a more restricted use. Analyses of the meso-alpha scale Richardson number and of the Richardson number tendency fields reveal a phase relationship consistent with the theoretical predictions.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Monthly Weather Review (ISSN 0027-0644); 118; 2228-224
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  • 96
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    Precipitable water estimation from high-resolution split window radiance measurements (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A technique that uses the spatial variance of image brightness temperature to derive total column precipitable water is applied to high-resolution multispectral aircraft scanner data for the June 19, 1986 COHMEX day. The technique has several advantages over other approaches in that it requires only relative calibration accuracy, is less susceptible to instrument error, and does not directly use a priori information. Results indicate significant horizontal variability of precipitable water at the mesoscale. Precipitable water gradients of 6 mm per 10 km are not uncommon. The results verify well against special rawinsonde measurements and the ensuing cloud field development. While only applied to this specialized aircraft data, the applicability of the technique to operational AVHRR and VAS data is discussed.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Applied Meteorology (ISSN 0894-8763); 29; 863-877
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  • 97
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    In defense of Ertel's potential vorticity and its general applicability as a meteorological tracer (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A potential vorticity theorem and its two summary statements published by Haynes and McIntyre are challenged conceptually by equations, discussions and examples. The apparent simplification proposed by the authors to convert from a mass to volume integral, i.e., by cancelling density against the specific volume in the potential vorticity, changes the physical significance of the integrand. It no longer is the potential vorticity. The resulting mean for either a bulk Eulerian or Lagrangian system is then not analogous to a mixing ratio and therefore not independent of the broad spectrum of internal waves, the independence that makes Ertel's potential vorticity so valuable either as a stratospheric tracer or as a predictive or diagnostic, large scale, meteorological variable.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 2013-202
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  • 98
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    Adaptive mesh generation for viscous flows using Delaunay triangulation (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A method for generating an unstructured triangular mesh in two dimensions, suitable for computing high Reynolds number flows over arbitrary configurations is presented. The method is based on a Delaunay triangulation, which is performed in a locally stretched space, in order to obtain very high aspect ratio triangles in the boundary layer and the wake regions. It is shown how the method can be coupled with an unstructured Navier-Stokes solver to produce a solution adaptive mesh generation procedure for viscous flows.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 90; 271-291
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  • 99
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    Cloud draft structure and trace gas transport (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 95; 17015-17
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    A Poisson equation formulation for pressure calculations in penalty finite element models for viscous incompressible flows (1990)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The calculation of pressures when the penalty-function approximation is used in finite-element solutions of laminar incompressible flows is addressed. A Poisson equation for the pressure is formulated that involves third derivatives of the velocity field. The second derivatives appearing in the weak formulation of the Poisson equation are calculated from the C0 velocity approximation using a least-squares method. The present scheme is shown to be efficient, free of spurious oscillations, and accurate. Examples of applications are given and compared with results obtained using mixed formulations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 30; 349-361
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