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  • FLUID MECHANICS AND HEAT TRANSFER  (703)
  • 1985-1989  (703)
  • 1
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    Unsteady heat transfer and direct comparison to steady-state measurements in a rotor-wake experiment (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Circumferentially local and time-resolved heat transfer measurements were obtained for a circular cylinder in crossflow located downstream of a rotating spoked wheel wake generator in a steady flow tunnel. The unsteady heat transfer effects were obtained by developing an extension of a thin film gauge technique employed to date exclusively in short-duration facilities. The time-average thin film results and conventional steady-state heat transfer measurements were compared. Time-averaged wake-induced stagnation heat transfer enhancement levels above the nowake case were about 10 percent for the four cylinder Reynolds numbers. This enhancement level was nearly independent of bar passing frequency and was related directly to the time integral of the heat transfer spikes observed at the bar passing frequency. It is observed that the wake-induced heat transfer spikes have peak magnitudes averaging 30 to 40 percent above the interwake heat transfer level.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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    NASA TECHNICAL REPORTS
  • 2
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    Rotational effects on impingement cooling (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The present consideration of rotation effects on heat transfer in a radially exhausted, impingement-cooled turbine blade model gives attention to experimental results for Reynolds and Rossby numbers and blade/coolant temperature ratio values that are representative of small gas turbine engines. On the basis of a model that encompasses the effects of Coriolis force and buoyancy on heat transfer, bouyancy is identified as the cause of an average Nusselt number that is 20-30 percent lower than expected from previous nonrotating data. A heuristic model is proposed which predicts that the impingement jets nearest the blade roots should deflect inward, due to a centripetal force generated by their tangential velocity counter to the blade motion. Potentially serious thermal stresses must be anticipated from rotation effects in the course of blade design.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 3
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    Fuel-injector/air-swirl characterization (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objectives of this program are to establish an experimental data base documenting the behavior of gas turbine engine fuel injector sprays as the spray interacts with the swirling gas flow existing in the combustor dome, and to conduct an assessment of the validity of current analytical techniques for predicting fuel spray behavior. Emphasis is placed on the acquisition of data using injector/swirler components which closely resemble components currently in use in advanced aircraft gas turbine engines, conducting tests under conditions that closely simulate or closely approximate those developed in actual combustors, and conducting a well-controlled experimental effort which will comprise using a combination of low-risk experiments and experiments requiring the use of state-of-the-art diagnostic instrumentation. Analysis of the data is to be conducted using an existing, TEACH-type code which employs a stochastic analysis of the motion of the dispersed phase in the turbulent continuum flow field.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Turbine Engine Hot Section Technology, 1985; p 109-117
    Format: application/pdf
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  • 4
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    Numerical simulation of the flow field and fuel sprays in an IC engine (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A two-dimensional model for axisymmetric piston-cylinder configurations is developed to study the flow field in two-stroke direct-injection Diesel engines under motored conditions. The model accounts for turbulence by a two-equation model for the turbulence kinetic energy and its rate of dissipation. A discrete droplet model is used to simulate the fuel spray, and the effects of the gas phase turbulence on the droplets is considered. It is shown that a fluctuating velocity can be added to the mean droplet velocity every time step if the step is small enough. Good agreement with experimental data is found for a range of ambient pressures in Diesel engine-type microenvironments. The effects of the intake swirl angle in the spray penetration, vaporization, and mixing in a uniflow-scavenged two-stroke Diesel engine are analyzed. It is found that the swirl increases the gas phase turbulence levels and the rates of vaporization.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: SAE PAPER 870599
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  • 5
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    Mean velocity and turbulence measurements in a 90 deg curved duct with thin inlet boundary layer (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The experimental database established by this investigation of the flow in a large rectangular turning duct is of benchmark quality. The experimental Reynolds numbers, Deans numbers and boundary layer characteristics are significantly different from previous benchmark curved-duct experimental parameters. This investigation extends the experimental database to higher Reynolds number and thinner entrance boundary layers. The 5% to 10% thick boundary layers, based on duct half-width, results in a large region of near-potential flow in the duct core surrounded by developing boundary layers with large crossflows. The turbulent entrance boundary layer case at R sub ed = 328,000 provides an incompressible flowfield which approaches real turbine blade cascade characteristics. The results of this investigation provide a challenging benchmark database for computational fluid dynamics code development.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-174811 , NAS 1.26:174811 , UTSI/85-08
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  • 6
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    Unsteady heat transfer and direct comparison to steady-state measurements in a rotor-wake experiment (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Circumferentially local and time-resolved heat transfer measurements were obtained for a circular cylinder in crossflow located downstream of a rotating spoked wheel wake generator in a steady flow tunnel. The unsteady heat transfer effects were obtained by developing an extension of a thin film gauge technique employed to date exclusively in short-duration facilities. The time-average thin film results and conventional steady-state heat transfer measurements were compared. Time-averaged wake-induced stagnation heat transfer enhancement levels above the nowake case were about 10% for the four cylinder Reynolds numbers. This enhancement level was nearly independent of bar passing frequency and was related directly to the time integral of the heat transfer spikes observed at the bar passing frequency. It is observed that the wake-induced heat transfer spikes have peak magnitudes averaging 30 to 40% above the interwake heat transfer level.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87220 , E-2757 , NAS 1.15:87220 , International Heat Transfer Conference; Aug 17, 1986 - Aug 22, 1986; San Francisco, CA; United States
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  • 7
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    The structure and dynamics of reacting plane mixing layers (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Experimental studies of the combusting mixing layers formed over a rearward facing step and between two parallel streams are reported. The steady behavior of the mean properties of the reacting flows is similar to that of nonreacting flows except for the global effects of thermodynamic property changes. Vortices form by the two-dimensional K-H instability and grow by subharmonic combination until the layer begins to interact with the walls. Unsteady behavior occurs when there are resonator interactions with the K-H instability or the instability associated with the recirculation vortex in the rearward facing step flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Experiments in Fluids (ISSN 0723-4864); 6; 1 19; 33-43
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  • 8
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    A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A wide range of recent work on compressible turbulent boundary layers is described. Special attention was paid to flows with rapid changes in pressure including flows with shock waves, curved walls, and expansions. The application of rapid distortion theory to flows transversing expansion and shock waves is reviewed. This is followed by an account of experiments aimed at elucidating the large scale structures present in supersonic boundary layers. The current status of laser-Doppler and hot-wire anemometry in supersonic flow is discussed, and a new interferometric technique for the determination of wall-stress is described. The use of small pressure transducers to deduce information about the structure of zero pressure-gradient and severely perturbed boundary layers is investigated. Finally, there is an extension of the data presentation of AGARDographs 223, 253 and 263 to cover rapidly distorted boundary layers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD-AG-315 , AD-A211107 , NONP-NASA-SUPPL-DK-89-223860
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  • 9
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    A new approach for solving the three-dimensional steady Euler equations. I - General theory (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The present iterative procedure combines the Clebsch potentials and the Munk-Prim (1947) substitution principle with an extension of a semidirect Cauchy-Riemann solver to three dimensions, in order to solve steady, inviscid three-dimensional rotational flow problems in either subsonic or incompressible flow regimes. This solution procedure can be used, upon discretization, to obtain inviscid subsonic flow solutions in a 180-deg turning channel. In addition to accurately predicting the behavior of weak secondary flows, the algorithm can generate solutions for strong secondary flows and will yield acceptable flow solutions after only 10-20 outer loop iterations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 60; 23-61
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  • 10
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    Numerical simulation and comparison with experiment for self-excited oscillations in a diffuser flow (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 25; 936-943
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