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  • Other Sources  (13)
  • Fluid Mechanics and Thermodynamics  (13)
  • 2015-2019  (3)
  • 1995-1999  (9)
  • 1985-1989  (1)
  • 1945-1949
  • 1
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    Oscillation pressure device for dynamic calibration of pressure transducers (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Method and apparatus for obtaining dynamic calibrations of pressure transducers. A calibration head (15), a flexible tubing (23) and a bellows (20) enclose a volume of air at atmospheric pressure with a transducer (11) to be calibrated subject to the pressure inside the volume. All of the other apparatus in the drawing apply oscillations to bellows (20) causing the volume to change thereby applying oscillating pressures to transducer (11) whereby transducer (11) can be calibrated.
    Keywords: Fluid Mechanics and Thermodynamics
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  • 2
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    Experimental and Computational Boundary-Layer Studies In a Supersonic Two-Dimensional Nozzle (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Experiments and computations were carried out on the adiabatic laminar boundary layer developing along the surfaces of a two-dimensional supersonic nozzle, consisting of upper and lower contoured nozzle blocks and flat sidewalls. Two- and three-dimensional Navier-Stokes codes, as well as two-dimensional boundary-layer codes were employed. These codes were adapted to the characteristics of a specific wind tunnel nozzle, so that their numerical results could be directly compared with experimental data obtained in the same nozzle. Such comparisons were made for the boundary-layer growth on the nozzle contoured surfaces, and for the boundary-layer growth, surface streamlines and surface shear on the sidewalls. The three-dimensional Navier-Stokes code was found to be the only one to correctly predict the mean laminar boundary-layer flow on both the sidewalls and the contoured surfaces. Theory and experiment both indicated that the sidewall flow is highly three-dimensional, with non-uniform shear, corner vortices and a boundary layer strongly distorted by cross flows induced by lateral pressure gradients.
    Keywords: Fluid Mechanics and Thermodynamics
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  • 3
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    Interactions Between Klebanoff Modes and TS Waves (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The Harmonic Point Source (HPS) is the simplest possible form of 3D disturbance yet even this case is not fully understood. One of the characteristics of HPS generated Tolmien Schlichting (TS) waves is that the maximum rms amplitude downstream of the source occurs away from the centerline. As the waves fan out in the spanwise direction they can encounter Klebanoff modes (weak streamwise vortices) which may be present as background disturbances within the layer. The vortices originate near the leading edge and they appear to be caused by amplification of almost immeasurably small nonuniformities in the free stream. The vortices can be steady but they often appear as very low frequency background unsteadiness (as observed by Klebanoff). The vortices locally distort the mean flow and therefore (by definition) they are nonlinear phenomena e.g. the growth rate of the TS waves is altered. Kendall (private communication) has demonstrated total suppression of TS waves by deliberately introducing strong vortices generated by a delta wing. For the very weak vortices that are often encountered in experiments, their effect is characterized by a local reduction in the rms TS magnitude. The laminar wake behind a fine wire is used to generate Klebanoff modes and the interactions with HPS generated TS waves are explored in a controlled manner. It is shown that a proportion of the reduction in the observed TS magnitude can be attributed to washout of the phase-averaged signals owing to phase jitter.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 49th Annual Meeting, Division of Fluid Dynamics of the American Physical Society; Nov 24, 1996 - Nov 26, 1996; Syracuse, NY; United States
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  • 4
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    Experimental and Computational Boundary-Layer Studies in a Supersonic Two-Dimensional Nozzle (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Calculations have been carried out on the adiabatic laminar boundary layer developing on the surface of a two-dimensional supersonic nozzle, consisting of contoured nozzle blocks and flat sidewalls. Two- and three-dimensional Navier-Stokes codes, as well as two-dimensional boundary-layer codes have been employed. Thee codes have been adapted to the characteristics of a specific wind tunnel nozzle, so that their numerical results could be directly compared with experimental data obtained in the same nozzle. Such comparisons have been made for the boundary-layer growth on the contoured nozzle, and for the boundary-layer growth, surface streamlines and surface shear on the sidewalls. The three-dimensional Navier-Stokes code was found to be the only one to correctly predict the mean boundary-layer flow on both the sidewalls and the contoured nozzle. Theory and experiment both indicate that the sidewall flow is highly three-dimensional, with non-uniform shear, comer vortices and a boundary layer strongly distorted by cross flows induced by lateral pressure gradients.
    Keywords: Fluid Mechanics and Thermodynamics
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  • 5
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    Boundary Layer Receptivity to Three-Dimensional Freestream Disturbances at Two-Dimensional Roughness (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The receptivity of a laminar boundary layer to an isolated three-dimensional convected disturbance is investigated in a low-speed wind tunnel experiment. The disturbance is created by the short-duration pulsed displacement of a small low-aspect-ratio wing located upstream of a flat plate. The height of the wing is set so that the convected disturbance grazes the edge of the flat-plate boundary layer. A receptivity site is provided by a two-dimensional roughness strip on the surface of the plate. The different propagation speeds of acoustic, convected and instability waves cause the various wave packets from the pulsed displacement to arrive at a downstream measurement station at different times, separating the phenomena and allowing them to be studied independently. Ensemble- averaged measurements are made with and without roughness on the plate. Preliminary analysis of the measurements suggest the presence of a two-dimensional T-S wave packet arising from an interaction between an acoustic wave and the roughness, and a three-dimensional T-S wave packet arising from an interaction between the localized convected disturbance and the roughness strip. The growth rates and spatial characteristics of the disturbances and the instability wave packets are measured as they propagate downstream.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: DFD 1997 Meeting of the American Physical Society; Nov 23, 1997 - Nov 25, 1997; San Francisco, CA; United States
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  • 6
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    Flow Quality and Boundary Layer Transition (1997)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The widely held view is that transition to turbulence in the Blasius boundary layer occurs via amplification and eventual nonlinear breakdown of initially small amplitude instabilities i.e. Tollmien-Schlichting (TS) waves. However this scenario is only observed for low amplitude free-stream turbulence levels, i.e. u/U 〈 0.1%. Bypass of linear TS instability mechanism occurs for higher EST levels, yet considerable differences exist between the few experiments carefully designed to assess the effect of EST on transition. The consensus is that EST leads to longitudinal streaks that form near the leading edge in the boundary layer . These streaks appeal to be regions of concentrated streamwise vorticity and they are often referred to as Klebanoff modes. The importance of mean flow free-stream nonuniformity (FSN) is not as widely appreciated as EST for characterizing wind tunnel flow quality. Here it is shown that, although the v like generated by a d=50micron wire located upstream of the contraction (Re(sub d)=6.6, x/d=45,000) is immeasurably small by the time it interacts with the leading edge in the test section, it is responsible for generation of a pair of weak streamwise vortices in the boundary layer downstream. The characteristics of these wake-induced vortices and their effect on TS waves are demonstrated. Small remnant FSN variations are also shown to exist downstream of a turbulence grid. The question arises Are the adverse effects introduced by the turbulence grid caused by FST or by small remnant FSN variations?
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 50th Annual Meeting Division of Fluid Dynamics, American Physical Society; Nov 23, 1997 - Nov 25, 1997; San Francisco, CA; United States
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  • 7
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    CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave/Boundary-Layer Interaction (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental investigations of specific flow phenomena, e.g., Shock Wave Boundary-Layer Interactions (SWBLI), provide great insight to the flow behavior but often lack the necessary details to be useful as CFD validation experiments. Reasons include: 1.Undefined boundary conditions Inconsistent results 2.Undocumented 3D effects (CL only measurements) 3.Lack of uncertainty analysis While there are a number of good subsonic experimental investigations that are sufficiently documented to be considered test cases for CFD and turbulence model validation, the number of supersonic and hypersonic cases is much less. This was highlighted by Settles and Dodsons [1] comprehensive review of available supersonic and hypersonic experimental studies. In all, several hundred studies were considered for their database.Of these, over a hundred were subjected to rigorous acceptance criteria. Based on their criteria, only 19 (12 supersonic, 7 hypersonic) were considered of sufficient quality to be used for validation purposes. Aeschliman and Oberkampf [2] recognized the need to develop a specific methodology for experimental studies intended specifically for validation purposes.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GRC-E-DAA-TN25302 , 2015 AJK Fluids Engineering Division Summer Meeting; Jul 26, 2015 - Jul 31, 2015; Seoul; Korea, Democratic People''s Republic of
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  • 8
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    CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave Boundary-Layer Interaction (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Preliminary results of an experimental investigation of a Mach 2.5 two-dimensional axisymmetric shock-wave/boundary-layer interaction (SWBLI) are presented. The purpose of the investigation is to create a SWBLI dataset specifically for CFD validation purposes. Presented herein are the details of the facility and preliminary measurements characterizing the facility and interaction region. The results will serve to define the region of interest where more detailed mean and turbulence measurements will be made.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AJK2015-06342 , GRC-E-DAA-TN23733 , 2015 AJK Fluids Engineering Division Summer Meeting; Jul 26, 2015 - Jul 31, 2015; Seoul; Korea, Republic of
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  • 9
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    Directional Solidification of a Binary Alloy into a Cellular Convective Flow: Localized Morphologies (1999)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: A steady, two dimensional cellular convection modifies the morphological instability of a binary alloy that undergoes directional solidification. When the convection wavelength is far longer than that of the morphological cells, the behavior of the moving front is described by a slow, spatial-temporal dynamics obtained through a multiple-scale analysis. The resulting system has a "parametric-excitation" structure in space, with complex parameters characterizing the interactions between flow, solute diffusion, and rejection. The convection stabilizes two dimensional disturbances oriented with the flow, but destabilizes three dimensional disturbances in general. When the flow is weak, the morphological instability behaves incommensurably to the flow wavelength, but becomes quantized and forced to fit into the flow-box as the flow gets stronger. At large flow magnitudes the instability is localized, confined in narrow envelopes with cells traveling with the flow. In this case the solutions are discrete eigenstates in an unbounded space. Their stability boundary and asymptotics are obtained by the WKB analysis.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Proceedings of the Fourth Microgravity Fluid Physics and Transport Phenomena Conference; 228-233; NASA/CP-1999-208526/SUPPL1
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  • 10
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    The Effect of Transition Modeling on the Prediction of Compressible Deep Dynamic Stall (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The importance of transition modeling in the computation of compressible, unsteady separated flows is discussed. The study showed that it is critical to predict the experimentally attained transition point properly in order to obtain good agreement with data it the same Mach number and Reynolds number.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 7th Asian Congress of Fluid Mechanics; Dec 08, 1997 - Dec 12, 1997; Madras; India
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