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  • 1
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    Thin-layer composite unimorph ferroelectric driver and sensor properties (1998)
    Elsevier
    Details
    Publication Date: 1998-04-01
    Print ISSN: 0167-577X
    Electronic ISSN: 1873-4979
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Generation of circumferential velocity contours associated with pulsed point suction on a rotating disk (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Numerous experimental studies were conducted on the steady, three-dimensional boundary layer over a disk rotating at constant angular speed in an otherwise undisturbed fluid. The subject flow geometry is of interest because it provides a relatively simple way to study the cross-flow instability phenomenon which occurs in three-dimensional boundary layers, as on swept wings. This flow instability results in the formation of a stationary spiral vortex flow field over the disk, as shown by Wilkinson and Malik. Using a hot-wire probe, the spatial wave pattern of stationary vortices, which filled the entire circumference of the disk was mapped. The subject flow instability caused transition-to-turbulent flow as the periphery of the disk was approached. The effect on receptivity and transition of discrete disturbance modes, such as three-dimensional toughness elements and acoustic excitation was investigated. The present study (an extension of the work of Wilkinson and Malik) is focused on the effect of pulsed point suction on flow instability and transition, and consequently, on the classical stationary vortical flow pattern.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program 1989; NASA(American Societ
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Boundary-layer measurements on a high Reynolds number three-element airfoil (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An experimental investigation is being conducted to evaluate the boundary layer associated with a two-dimensional three-element single-flap airfoil at high Reynolds numbers. The present measurements are being made in the Langley Low-Turbulence (centerline turbulence intensity level is 0.034 percent at a Mach number of 0.2 and a total pressure of 60 psia) Pressure Tunnel (LTPT). The LTPT is a closed-circuit wind tunnel with a test section which is 3 ft wide, 7.5 ft high, and 7.5 ft long. Operating total pressure for the LTPT varies from 10 atmospheres to near-vacuum conditions. Tests are being conducted at a Mach number of 0.2 and Reynolds numbers (based on chord length) of 5, 9, and 16 million. Measurements include boundary-layer velocity surveys at several chordwise locations and surface skin-friction measurements using Preston tubes.
    Keywords: AERODYNAMICS
    Type: Hampton Univ., NASA(American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program 1992 p 171-172 (SEE N93-16760 05-80); Hampton Univ., NASA(
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Non-linear boundary-layer receptivity due to distributed surface roughness (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The process by which a laminar boundary layer internalizes the external disturbances in the form of instability waves is known as boundary-layer receptivity. The objective of the present research was to determine the effect of acoustic excitation on boundary-layer receptivity for a flat plate with distributed variable-amplitude surface roughness through measurements with a hot-wire probe. Tollmien-Schlichting (T-S) mode shapes due to surface-roughness receptivity have also been determined, analyzed, and shown to be in agreement with theory and other experimental work. It has been shown that there is a linear relationship between the surface roughness and receptivity for certain roughness configurations with constant roughness wavelength. In addition, strong nonlinear receptivity effects exist for certain surface roughness configurations over a band where the surface roughness and T-S wavelength are matched. The results from the present experiment follow the trends predicted by theory and other experimental work for linear receptivity. In addition, the results show the existence of nonlinear receptivity effects for certain combinations of surface roughness elements.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-199224 , NAS 1.26:199224
    Format: application/pdf
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  • 5
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    An Experimental Investigation of Wall-Cooling Effects on Hypersonic Boundary-Layer Stability in a Quiet Wind Tunnel (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of continuous spectra data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.
    Keywords: Aerodynamics
    Type: NASA-CR-198287 , NAS 1.26:198287
    Format: application/pdf
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  • 6
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    A quiet tunnel investigation of hypersonic boundary-layer stability over a cooled, flared cone (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A flared-cone model under adiabatic and cooled-wall conditions was placed in a calibrated, low-disturbance Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N = 10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows under low freestream noise conditions was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of spectral data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA-CR-202200 , NAS 1.26:202200
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Thin-Layer Composite Unimorph Ferroelectric Driver Sensor Properties (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Tests were conducted on 13 different configurations of a new class of piezoelectric devices called THUNDER (thin layer composite unimorph ferroelectric driver and sensor). These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25.4 micron thick aluminium as a backing material, with and without a top layer of 25.4 micrometer aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.08 x 3.81 x 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after repoling. The parameters measured included frequency, driving voltage. displacement, capacitance, and radius of curvature. An optic sensor recorded the displacement at a fixed voltage(100 - 400 V peak to peak) over a predetermined frequency range (1 - 1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter alpha was defined which can be used to predict the which configuration will produce the most displacement for a free standing device.
    Keywords: Composite Materials
    Type: Materials Letters (ISSN 0167-577X); 35; 39-49
    Format: text
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  • 8
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    Infrared surface imaging as a flowfield diagnostic tool (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An infrared imaging system supported by a dedicated image processing system was evaluated as a diagnostic tool for aerodynamic research. Results are reported characterizing the system's capability for performing a variety of experimental investigations, such as temperature transients, air velocity distributions, capture of vortices, boundary layer flows, and separated flows over a flat plate with a two-dimensional rearward-facing step.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''87 - International Congress on Instrumentation in Aerospace Simulation Facilities; Jun 22, 1987 - Jun 25, 1987; Williamsburg, VA; United States
    Format: text
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