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  • 1
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    Numerical experiments on stability and transition in plane channel flow (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Various secondary and tertiary instabilities in plane channael flow are explored via time-dependent numerical simulations using the incompressible Navier-Stokes equations. Comparisons are made between transitional flows at Reynolds numbers 1500, 5000, and 8000. The lambda vortex, detached shear layer, and inverted vortex regions are identified, and the origin of the latter is explained. The laminar breakdown of the Re = 1500 flow is computed with high resolution, and the nature of its ensuing hairpin eddies is clarified by numerical particle paths. The potential of center-mode, rather than wall-mode transitions is proposed, and the resulting flow structure is described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Theoretical and Computational Fluid Dynamics (ISSN 0935-4964); 1; 1, 19
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  • 2
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    Design of Optimum Ducts Using an Efficient 3-D Viscous Computational Flow Analysis (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Design of fluid dynamically efficient ducts is addressed through the combination of an optimization analysis with a three-dimensional viscous fluid dynamic analysis code. For efficiency, a parabolic fluid dynamic analysis was used. Since each function evaluation in an optimization analysis is a full three-dimensional viscous flow analysis requiring 200,000 grid points, it is important to use both an efficient fluid dynamic analysis and an efficient optimization technique. Three optimization techniques are evaluated on a series of test functions. The Quasi-Newton (BFGS, eta = .9) technique was selected as the preferred technique. A series of basic duct design problems are performed. On a two-parameter optimization problem, the BFGS technique is demonstrated to require half as many function evaluations as a steepest descent technique.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: GRC-E-DAA-TN55806 , Pennsylvania State Univ., The Second International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-2); p 147-166
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  • 3
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    SSME 3-D Turnaround Duct flow analysis - CFD predictions (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: CFD analysis is presently employed to obtain an improved flowfield for an individual flowpath in the case of the Space Shuttle Main Engine's High Pressure Fuel Turbopump Turn-Around Duct (TAD), which conducts the flow exiting from the gas turbines into the fuel bowl. It is demonstrated that the application of CFD to TAD flow analysis, giving attention to the duct's configuration and to the number, shape, and alignment of the diffuser struts, can enhance understanding of flow physics and result in improved duct design and performance.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3006
    Format: text
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  • 4
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    Design, fabrication, and dynamic testing of a V-groove radiator mechanical development unit (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the design, fabrication, and dynamic testing of a V-groove radiator development unit. The intended goal was to survive the dynamic environment of the Mars Observer mission. The development unit was designed to achieve a temperature of 80 K with a heat load of about 80 milliwatts. An analysis was performed to predict the thermal performance of the development unit. The radiator with a mass mockup of a Gamma Ray Spectrometer detector, the most massive of the candidate Mars Observer instrument detectors (1.7 Kg), passed vibration and acoustic testing to the Mars Observer requirements in effect at that time.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-0558
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  • 5
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    The measurement of boundary layers on a compressor blade in cascade. II - Suction surface boundary layers (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional, periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two were taken in the near wake. In this part of the study, the LDV system is described and the suction surface flow field is documented. The suction surface profiles appear to separate both at the leading edge and again somewhat beyond midchord; the leading edge separation apparently reattaches by 2.6 percent chord.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 87-GT-249
    Format: text
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  • 6
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    The measurement of boundary layers on a compressor blade in cascade. I - A unique experimental facility (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A unique cascade facility is described which makes it possible to use LDV for measuring blade boundary layer profiles. Because of the need for a laser access window, the facility cannot rely on continuous blade pack suction to achieve stable flow. Instead, a combination of tailboards and strong suction upstream of the blade pack is used to create a two-dimensional periodic flow field at a chord Reynolds number of 500,000. The distribution of the upstream suction is controlled through a complex baffling system. Details of the inlet and outlet flow are documented using five-hole pressure probes, blade static-pressure measurements, and sublimation flow visualization. Experimental data are presented on the flow field on the suction surface of the blade, the pressure surface, and near-wake flow fields.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 87-GT-248
    Format: text
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  • 7
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    Resolution requirements for numerical simulations of transition (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The resolution requirements for direct numerical simulations of transition to turbulence are investigated. A reliable resolution criterion is determined from the results of several detailed simulations of channel and boundary-layer transition.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181799 , ICASE-89-9 , NAS 1.26:181799
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  • 8
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    The measurement of boundary layers on a compressor blade in cascade. III - Pressure surface boundary layers and the near wake (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two profiles were taken in the near wake. In this part of the study, the detailed LDV studies are described. The measurements indicate that the onset of transition occurs near 60 percent chord. The lack of a logarithmic region in the data measured at 97.9 percent chord indicates that transition is not complete. The thin laminar boundary layers near the leading edge led to some measurement problems, characterized by large turbulence intensities, in using the LDV.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 87-GT-250
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  • 9
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    Nonlinear structures in the later stages of transition (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The transition to turbulence in low-Reynolds-number channel flow and in a boundary-layer flow (under the conditions studied experimentally by Kovasznay et al., 1962) is investigated by means of high-resolution numerical simulations. The results are presented graphically, and breakdown phenomena are characterized in detail, with a focus on artificially suppressed streamwise vortices, channel-center modes, and the important roles of lambda vortices and mean shear. It is shown that shear-layer roll-up is accurately reproduced by both simulations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 87-1204
    Format: text
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  • 10
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    High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-89855 , E-3269 , NAS 1.15:89855 , ASME National Heat Transfer Conference; Aug 09, 1987 - Aug 12, 1987; Pittsburgh, PA; United States
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