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  • FLUID MECHANICS AND HEAT TRANSFER  (6)
  • SPACECRAFT PROPULSION AND POWER  (4)
  • Launch Vehicles and Launch Operations
  • 2005-2009
  • 1990-1994  (10)
  • 1991  (10)
Collection
Years
  • 2005-2009
  • 1990-1994  (10)
Year
  • 1
    Publication Date: 2011-08-19
    Description: The linear-stability theory of plane stagnation-point flow against an infinite flat plate is re-examined. Disturbances are generalized from those of Goertler type to include other types of variations along the plate. It is shown that Hiemenz flow is linearly stable and that the Goertler-type modes are those that decay slowest. This work then rationalizes the use of such self-similar disturbances on Hiemenz flow and shows how questions of disturbance structure can be approached on other self-similar flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Quarterly Journal of Mechanics and Applied Mathematics (ISSN 0033-5614); 44; 135-146
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  • 2
    Publication Date: 2019-06-28
    Description: A flow reactor for simulating the interaction in the troposphere is set forth. A first reactant mixed with a carrier gas is delivered from a pump and flows through a duct having louvers therein. The louvers straighten out the flow, reduce turbulence and provide laminar flow discharge from the duct. A second reactant delivered from a source through a pump is input into the flowing stream, the second reactant being diffused through a plurality of small diffusion tubes to avoid disturbing the laminar flow. The commingled first and second reactants in the carrier gas are then directed along an elongated duct where the walls are spaced away from the flow of reactants to avoid wall interference, disturbance or turbulence arising from the walls. A probe connected with a measuring device can be inserted through various sampling ports in the second duct to complete measurements of the first and second reactants and the product of their reaction at selected XYZ locations relative to the flowing system.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 3
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: Instability of boundary-layer over a concave wall and a rotating disk which were thought to be essentially different in instability sources, are compared in order to investigate whether or not a single crossflow parameter can be defined. Using a newly defined crossflow parameter, prediction was attempted on a yawed cylinder boundary-layer transition. By comparing the calculation with experiment, it was found out that this parameter can document fairly well the onset condition of the crossflow instability.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME and JSME Joint Fluids Engineering Conference; Jun 23, 1991 - Jun 27, 1991; Portland, OR; United States
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  • 4
    Publication Date: 2019-07-13
    Description: A sensible heat receiver considered in this study uses a vapor grown carbon fiber-carbon (VGCF/C) composite as the thermal storage media and was designed for a 7 kW Brayton engine. The proposed heat receiver stores the required energy to power the system during eclipse in the VGCF/C composite. The heat receiver thermal analysis was conducted through the Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA) software package. The sensible heat receiver compares well with other latent and advanced sensible heat receivers analyzed in other studies while avoiding the problems associated with latent heat storage salts and liquid metal heat pipes. The concept also satisfies the design requirements for a 7 kW Brayton engine system. The weight and size of the system can be optimized by changes in geometry and technology advances for this new material.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-104393 , E-6208 , NAS 1.15:104393 , Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 5
    Publication Date: 2019-07-13
    Description: Photovoltaic (PV) coverslip material was subjected to Maritan dust storm conditions using basaltic dust flowing through the Martian Surface Wind Tunnel at NASA-Ames. Initially dusted and clear coverslips were held at angles from 0 to 90 deg., and the dust laden wind velocity was varied from 20 to 97 m/s. Blowing dust was found to adhere more to the coverslips as the angle was increased. However, dust was partially cleared from surfaces that were initially dusted at substantially lower velocities in dust laden wind than in clear wind. Thus, an equilibrium amount of dust accumulated which was dependent only upon angle and wind velocity and not upon initial concentration of dust. Abrasion was also evident in the coverslips. It increased with wind velocity and angle of attack. It appears that an initial dust layer may help to protect PV surfaces from abrasion.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-104448 , E-6289 , NAS 1.15:104448 , Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 6
    Publication Date: 2019-07-13
    Description: Glass coverglass and SiO2 covered and uncovered silicon photovoltaic (PV) cells were subjected to conditions simulating a Mars dust storm, using the Martian Surface Wind Tunnel, to assess the effect of particle size on the performance of PV cells in the Martian environment. The dust used was an artificial mineral of the approximate elemental composition of Martian soil, which was sorted into four different size ranges. Samples were tested both initially clean and initially dusted. The samples were exposed to clear and dust laden winds, wind velocities varying from 23 to 116 m/s, and attack angles from 0 to 90 deg. It was found that transmittance through the coverglass approximates the power produced by a dusty PV cell. Occultation by the dust was found to dominate the performance degradation for wind velocities below 50 m/s, whereas abrasion dominates the degradation at wind velocities above 85 m/s. Occultation is most severe at 0 deg (parallel to the wind), is less pronounced from 22.5 to 67.5 deg, and is somewhat larger at 90 deg (perpendicular to the wind). Abrasion is negligible at 0 deg, and increases to a maximum at 90 deg. Occultation is more of a problem with small particles, whereas large particles (unless they are agglomerates) cause more abrasion.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-105232 , E-6556 , NAS 1.15:105232 , International Solar Energy Conference; Apr 04, 1992 - Apr 08, 1992; Maui, HI; United States
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  • 7
    Publication Date: 2019-07-13
    Description: Two new algorithms for solving coupled Navier-Stokes and energy equations are presented. The algorithms are compared with available Navier-Stokes solutions for the model problem of a driven-cavity-flow over a range of Reynolds numbers. It is noted that the algorithms represent two different implementations of the fractional step approach to the solution of the coupled Navier-Stokes and energy equations using the Boussinesq approximation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Computational Fluid Dynamics Conference; Jun 24, 1991 - Jun 27, 1991; Honolulu, HI; United States
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  • 8
    Publication Date: 2019-07-13
    Description: A sensible heat receiver is considered which uses a vapor grown carbon fiber-carbon (VGCF/C) composite as the thermal storage medium and which was designed for a 7-kW Brayton engine. This heat receiver stores the required energy to power the system during eclipse in the VGCF/C composite. The heat receiver thermal analysis was conducted through the Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA) software package. The sensible heat receiver compares well with other latent and advanced sensible heat receivers analyzed in other studies, while avoiding the problems associated with latent heat storage salts and liquid metal heat pipes. The concept also satisfies the design requirements for a 7-kW Brayton engine system. The weight and size of the system can be optimized by changes in geometry and technology advances for this new material.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: IECEC ''91: Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 9
    Publication Date: 2019-07-12
    Description: Quantitative predictions of the collision rate of two spherical drops undergoing Brownian diffusion or gravitational sedimentation are presented. The diffusion equation for relative Brownian motion of two drops is derived, and the relative motion of pairs of drops in gravitational sedimentation is traced via a trajectory analysis in order to develop theoretical models to determine the collision efficiencies, both with and without interparticle forces applied between the drops. It is concluded that finite collision rates between nondeforming fluid drops are possible for Brownian diffusion or gravitational sedimentation in the absence of attractive forces, in stark contrast to the prediction that lubrication forces prevent rigid spheres from contacting each other unless an attractive force that becomes infinite as the separation approaches zero is applied. Collision rates are shown to increase as the viscosity of the drop-phase decreases. In general, hydrodynamic interactions reduce the collision rates more for gravitational collisions than for Brownian collisions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 230; 479-504
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  • 10
    Publication Date: 2019-07-13
    Description: Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper and niobium-1 percent-zirconium samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-103704 , E-5841 , NAS 1.15:103704 , Symposium on Space Nuclear Power Systems; Jan 06, 1991 - Jan 10, 1991; Albuquerque, NM; United States
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