Engineering topics

Burner, Alpheus W.

Publications and source records attributed to Burner, Alpheus W..

26 records · Page 2

NASA NTRS1998

Summary Report of the First International Symposium on Strain Gauge Balances and Workshop on AoA/Model Deformation Measurement Techniques

The first International Symposium on Strain Gauge Balances was sponsored under the auspices of the NASA Langley Research Center (LaRC), Hampton, Virginia. Held at the LaRC Reid Conference Center, the Symposium provided an open international forum for presentation, discussion, and exchange of technical information among wind tunnel test technique specialists and strain gauge balance designers. The Symposium also served to initiate organized professional activities among the participating and relevant international technical communities. The program included a panel discussion, technical paper sessions, tours of local facilities, and vendor exhibits. Over 130 delegates were in attendance from 15 countries. A steering committee was formed to plan a second international balance symposium tentatively scheduled to be hosted in the United Kingdom in 1998 or 1999. The Balance Symposium was followed bv the half-day, Workshop on Angle of Attack and Model Deformation on the afternoon of October 25. The thrust of the Workshop was to assess the state of the art in angle of attack (AoA) and model deformation measurement techniques and to discuss future developments.

Tripp, John S.↗

NASA NTRS1997

Static Aeroelastic Analysis of Transonic Wind Tunnel Models Using Finite Element Methods

A computational method for accurately predicting the static aeroelastic deformations of typical transonic transport wind tunnel models is described. The method utilizes a finite element method (FEM) for predicting the deformations. Extensive calibration/validation of this method was carried out using a novel wind-off wind tunnel model static loading experiment and wind-on optical wing twist measurements obtained during a recent wind tunnel test in the National Transonic Facility (NTF) at NASA LaRC. Further validations were carried out using a Navier-Stokes computational fluid dynamics (CFD) flow solver to calculate wing pressure distributions about several aeroelastically deformed wings and comparing these predictions with NTF experimental data. Results from this aeroelastic deformation method are in good overall agreement with experimentally measured values. Including the predicted deformations significantly improves the correlation between CFD predicted and experimentally measured wing & pressures.

Hooker, John R.↗

NASA NTRS1996

Wing Twist Measurements at the National Transonic Facility

A technique for measuring wing twist currently in use at the National Transonic Facility is described. The technique is based upon a single camera photogrammetric determination of two dimensional coordinates with a fixed (and known) third dimensional coordinate. The wing twist is found from a conformal transformation between wind-on and wind-off 2-D coordinates in the plane of rotation. The advantages and limitations of the technique as well as the rationale for selection of this particular technique are discussed. Examples are presented to illustrate run-to-run and test-to-test repeatability of the technique in air mode. Examples of wing twist in cryogenic nitrogen mode are also presented.

Burner, Alpheus W.↗

NASA NTRS1995

Interferometric Tomographic Measurement of an Instataneous Flow Field Under Adverse Environments

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

Yu, En-Xi↗

NASA NTRS1989

Digital Video Measurements Of Wing Deflections In A Wind Tunnel

Solid-state cameras and computer-controlled image-acquisition system measure deformations of wind-tunnel models. Digital video model-deformation (VMD) system includes solid-state-array cameras and digital image-acquisition system controlled by personal computer. Eliminates both vibration-induced distortion associated with tube cameras and manual processing of video hardcopy images necessary in earlier version. AT-class personal computer controls two commercially available image-capture boards ganged to capture simultaneously two video images, each 752 picture elements wide and 480 picture elements high, in one-thirtieth of second. Video images digitized into 256 gray levels. Figure block diagram of system.

Burner, Alpheus W.↗

NASA NTRS1989

Photogrammetric technique for in-flight ranging of trailing vortices using entrained balloons

A method for experimentally determining the radial distance of a probe aircraft from a trailing vortex is described. The method relies on photogrammetric triangulation of targets entrained in the vortex core. The theory and preliminary testing were described using laboratory mock-ups. Solid state video cameras were to provide data at 300 Hz rates. Practical methods for seeding the vortex are under separate investigation and are not addressed.

Snow, Walter L.↗

NASA NTRS1987

Recent flow visualization studies in the 0.3-m TCT

Light beams are altered by refractive index changes; flow induced refractive index changes provide the impetus for conventional visualization techniques such as schlieren and shadowgraph. Unfortunately effects related to the flow can be masked by refractive index inhomogeneities external to the test section. A simple shadowgraph scheme was used to assess the flow quality of the Langley 0.3 meter Transonic Cryogenic Tunnel. When the penetration tubes were evacuated the quality of the shadowgraph improved dramatically.

Snow, Walter L.↗

NASA NTRS1972

A Holographic Interferometer System for Measuring Density Profiles in High-Velocity Flows

This paper describes a holographic interferometric technique for obtaining density measurements across a test gas that is traveling at a velocity of over 5500 meters per second in an expansion tube facility. Interferometric data describing the flow in the test section are obtained using a long coherence length cw argon laser in a holographic system and a rotating drum camera recorder. The object beam, which passes through the test section, intersects the reference beam at a small angle (5 degrees) to form an interference pattern of about 170 lines per millimeter, and is recorded as a hologram. Before a test, this hologram is placed in its original position and rotated slightly so that an interference pattern is generated by the intersection of the reconstructed and real-time object beams. This interference pattern is adjusted to a series of bright, horizontal fringes having a spatial frequency of about 5 fringes per centimeter. During the few milliseconds it takes the test gas to pass through the test section, variations in the gas density across the 8.4-centimeter test section produce phase variations in the object beam and result in a varying interference pattern. A rotating drum camera with a 0.15-millimeter slit aligned perpendicular to the fringes is used to record the varying fringe shifts with a time resolution of about 3 microseconds. The average gas density across the test section is determined by measuring these fringe shifts.

Burner, Alpheus W.↗