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  • FLUID MECHANICS AND HEAT TRANSFER
  • GENERAL
  • 1980-1984  (227)
  • 1975-1979  (194)
  • 1955-1959  (17)
  • 1
    Publication Date: 2011-08-17
    Description: Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computers and Fluids; 6; June 197
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  • 2
    Publication Date: 2016-06-07
    Description: Advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost-effective analysis of combustors, turbine blades, and vanes are being developed. The approach is to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities. Progress in each area is reported.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 3 p
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  • 3
    Publication Date: 2019-06-27
    Description: Results of engineering analyses assessing the conceptual feasibility of a large capacity heat pump for enhancing active cooling of hypersonic aircraft structure are presented. A unique heat pump arrangement which permits cooling the structure of a Mach 6 transport to aluminum temperatures without the aid of thermal shielding is described. The selected concept is compatible with the use of conventional refrigerants, with Freon R-11 selected as the preferred refrigerant. Condenser temperatures were limited to levels compatible with the use of conventional refrigerants by incorporating a unique multipass condenser design, which extracts mechanical energy from the hydrogen fuel, prior to each subsequent pass through the condenser. Results show that it is technically feasible to use a large capacity heat pump in lieu of external shielding. Additional analyses are required to optimally apply this concept.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-145301
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  • 4
    Publication Date: 2019-06-27
    Description: A combined experimental and computational research program is described for testing and guiding turbulence modeling within regions of separation induced by shock waves incident in turbulent boundary layers. Specifically, studies are made of the separated flow the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include highfrequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-X-73157 , A-6690
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  • 5
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 22; 1810-181
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  • 6
    Publication Date: 2011-08-16
    Keywords: GENERAL
    Type: NACA Conf. on Aerodyn. of High Speed Aircraft; p 93-103
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  • 7
    Publication Date: 2011-08-16
    Description: Preliminary compliant wall skin friction test results obtained in a low-turbulence pressure tunnel are reported. Compliant surface skins consisted of 0.0025 cm thick mylar, stretched under tension and area-bonded or longitudinally strip-bonded with silicone rubber adhesive to polyurethane foam. Mean velocity and fluctuating survey data were obtained with a single slanted hot wire. Mean velocity profiles for the area-bonded mylar surface skins indicated up to a 20% reduction in boundary-layer thickness (and lower momentum thickness) over rigid surfaces. This reduction in boundary-layer thickness indicates that a drag reduction occurred. In addition, a 16% reduction in wall shear was evident for the mylar/compressor foam compliant surface.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 13; July 197
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  • 8
    Publication Date: 2011-08-18
    Description: Transonic viscous-inviscid interaction is considered using the Euler and inverse compressible turbulent boundary-layer equations. Certain improvements in the inverse boundary-layer method are mentioned, along with experiences in using various Runge-Kutta schemes to solve the Euler equations. Numerical conditions imposed on the Euler equations at a surface for viscous-inviscid interaction using the method of equivalent sources are developed, and numerical solutions are presented and compared with experimental data to illustrate essential points. Previously announced in STAR N83-17829
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 9
    Publication Date: 2011-08-18
    Description: An alternating direction implicit (ADI) method has been applied to a staggered grid for the computation of convection in a highly stratified fluid. Since artificial viscosity is not needed, subtle effects like the onset of convection can be studied. These computations compare well with the 2-D results by Graham (1975) and also agree with standard Boussinesq results when taken to that limit. Good efficiency has been achieved with a time step hundreds of times larger than the stability limit imposed by the explicit treatment of diffusion and the Courant number is not restricted to be below 1. The Navier-Stokes equation contains cross spatial derivatives which are treated explicitly in most ADI schemes. The destabilizing effect of such a practice on a 2-D model system with second-order spatial derivative terms only was analyzed and found to be not excessive.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 47; July 198
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  • 10
    Publication Date: 2016-06-07
    Description: A structural performance and resizing finite element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle. Two typical wing cross sections and a midfuselage cross section were selected for the analysis. The surface heat inputs to the thermal models were obtained from aerodynamic heating analyses, which assumed a purely turbulent boundary layer, a purely laminar boundary layer, separated flow, and transition from laminar to turbulent flow. The effect of internal radiation was found to be quite significant. With the effect of the internal radiation considered, the wing lower skin temperature became about 39 C (70 F) lower. The results were compared with fight data for space transportation system, trajectory 1. The calculated and measured temperatures compared well for the wing if laminar flow was assumed for the lower surface and bay one upper surface and if separated flow was assumed for the upper surfaces of bays other than bay one. For the fuselage, good agreement between the calculated and measured data was obtained if laminar flow was assumed for the bottom surface. The structural temperatures were found to reach their peak values shortly before touchdown. In addition, the finite element solutions were compared with those obtained from the conventional finite difference solutions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 295-325
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