NASA Scientific and Technical Aerospace Reports

calibration including the point of symmetry for distortion computation should be considered.
Author
Calibrating; Zoom Lenses; Wind Tunnel Apparatus; Distortion
20040111436 NASA Langley Research Center, Hampton, VA, USA
Interferometric Tomographic Measurement of an Instataneous Flow Field Under Adverse Environments
Yu, En-Xi; Cha, Soyoung Stephen; Burner, Alpheus W.; Optical Techniques in Fluid, Thermal and Combustion Flow; [1995];
Volume 2546; 12 pp.; In English; Optical Techniques in Fluid, Thermal and Combustion Flow, 10-13 Jul. 1995, San Diego,
CA, USA
Contract(s)/Grant(s): NAG1-1594; No Copyright; Avail: CASI; A03, Hardcopy
Measurement of an instantaneous flow field by interferometric tomography, that is, reconstruction of a three-dimensional
refractive-index field from multi-directional projection data, has been conducted. In order to simulate the expected
experimental arrangement at a wind tunnel, reconstructions are made from a restricted view angle less than 40 degrees and
incomplete projections. In addition, appreciable ambient air and experimental setup disturbances are present. A new
phase-stepping technique, based on a generalized phase-stepping approach of a four-bucket model, is applied for expeditious
and accurate phase information extraction from projection interferograms under the harsh environments. Phase errors caused
by the various disturbances, which can include ambient refractive-index change, optical component disturbance, hologram
repositioning error, etc., are partially compensated with a linear corrective model. A new computational tomographic technique
based on a series expansion approach was also utilized to efficiently deal with arbitrary boundary shapes and the continuous
flow fields in reconstruction. The results of the preliminary investigation are encouraging; however, the technique needs to be
further developed in the future through refinement of the approaches reported here and through hybridization with previously
developed techniques. Keywords: interferometry, tomography, phase stepping
Author
Flow Distribution; Flow Measurement; Interferometry; Tomography
20040120956 NASA Langley Research Center, Hampton, VA, USA
Free-Stream Turbulence Intensity in the Langley 14- by 22-Foot Subsonic Tunnel
Neuhart, Dan H.; McGinley, Catherine B.; August 2004; 65 pp.; In English
Contract(s)/Grant(s): 762-20-11-80
Report No.(s): NASA/TP-2004-213247; L-18336; No Copyright; Avail: CASI; A04, Hardcopy
An investigation was conducted using hot-wire anemometry to determine the turbulence intensity levels in the test section
of the Langley 14- by 22-Foot Subsonic Tunnel in the closed or walls-down configuration. This study was one component of
the three-dimensional High-Lift Flow Physics experiment designed to provide code validation data. Turbulence intensities
were measured during two stages of the study. In the first stage, the free-stream turbulence levels were measured before and
after a change was made to the floor suction surface of the wind tunnel s boundary layer removal system. The results indicated
that the new suction surface at the entrance to the test section had little impact on the turbulence intensities. The second stage
was an overall flow quality survey of the empty tunnel including measurements of the turbulence levels at several vertical and
streamwise locations. Results indicated that the turbulence intensity is a function of tunnel dynamic pressure and the location
in the test section. The general shape of the frequency spectrum is fairly consistent throughout the wind tunnel, changing
mostly in amplitude (also slightly with frequency) with change in condition and location.
Author
Subsonic Wind Tunnels; Turbulence; Free Flow
20040120958 NASA Langley Research Center, Hampton, VA, USA
1998 Calibration of the Mach 4.7 and Mach 6 Arc-Heated Scramjet Test Facility Nozzles
Witte, David W.; Irby, Richard G.; Auslender, Aaron H.; Rock, Kenneth E.; August 2004; 155 pp.; In English; Original
contains color illustrations
Contract(s)/Grant(s): WU 23-745-30-10
Report No.(s): NASA/TM-2004-213250; L-19037; No Copyright; Avail: CASI; A08, Hardcopy
A calibration of the Arc-Heated Scramjet Test Facility (AHSTF) Mach 4.7 and Mach 6 nozzles was performed in 1998.
For each nozzle, three different typical facility operating test points were selected for calibration. Each survey consisted of
measurements, at 340 separate locations across the 11 inch square nozzle exit plane, of pitot pressure, static pressure, and total
temperature. Measurement density was higher (4/inch) in the boundary layer near the nozzle wall than in the core nozzle flow
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