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Lee, George

Publications and source records attributed to Lee, George.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

The Joint Agency Commercial Imagery Evaluation (JACIE) Team: Overview and IKONOS Joint Characterization Approach

An overview of the Joint Agency Commercial Imagery Evalation (JACIE) team is presented. JACIE, composed of the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA), and the U.S. Geological Survey (USGS), was formed to leverage government agencies' capabilities for the characterization of commercial remote sensing data. Each JACIE agency purchases, or plans to purchase, commercial imagery to support its research and applications. It is critical that the data be assessed for its accuracy and utility. Through JACIE, NASA, NIMA, and USGS jointly characterized image products from Space Imaging's IKONOS satellite. Each JACIE agency performed an aspect of the characterization based on its expertise. NASA and its university partners performed a system characterization focusing on radiometric calibration, geopositional accuracy, and spatial resolution assessment; NIMA performed image interpretability and feature extraction evaluations; and USGS assessed geopositional accuracy of several IKONOS products. The JACIE team purchased IKONOS imagery of several study sites to perform the assessments and presented results at an industry-government workshop. Future plans for JACIE include the characterization of DigitalGlobe's QuickBird-2 image products.

Zanoni, Vicki↗
NASA NTRS1993

Study of optical techniques for the Ames unitary wind tunnel, part 7

A summary of optical techniques for the Ames Unitary Plan wind tunnels are discussed. Six optical techniques were studied: Schlieren, light sheet and laser vapor screen, angle of attack, model deformation, infrared imagery, and digital image processing. The study includes surveys and reviews of wind tunnel optical techniques, some conceptual designs, and recommendations for use of optical methods in the Ames Unitary Plan wind tunnels. Particular emphasis was placed on searching for systems developed for wind tunnel use and on commercial systems which could be readily adapted for wind tunnels. This final report is to summarize the major results and recommendations.

Lee, George↗
NASA NTRS1993

Study of optical techniques for the Ames unitary wind tunnel: Digital image processing, part 6

A survey of digital image processing techniques and processing systems for aerodynamic images has been conducted. These images covered many types of flows and were generated by many types of flow diagnostics. These include laser vapor screens, infrared cameras, laser holographic interferometry, Schlieren, and luminescent paints. Some general digital image processing systems, imaging networks, optical sensors, and image computing chips were briefly reviewed. Possible digital imaging network systems for the Ames Unitary Wind Tunnel were explored.

Lee, George↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnel. Part 5: Infrared imagery

A survey of infrared thermography for aerodynamics was made. Particular attention was paid to boundary layer transition detection. IR thermography flow visualization of 2-D and 3-D separation was surveyed. Heat transfer measurements and surface temperature measurements were also covered. Comparisons of several commercial IR cameras were made. The use of a recently purchased IR camera in the Ames Unitary Plan Wind Tunnels was studied. Optical access for these facilities and the methods to scan typical models was investigated.

Lee, George↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 4: Model deformation

A survey of systems capable of model deformation measurements was conducted. The survey included stereo-cameras, scanners, and digitizers. Moire, holographic, and heterodyne interferometry techniques were also looked at. Stereo-cameras with passive or active targets are currently being deployed for model deformation measurements at NASA Ames and LaRC, Boeing, and ONERA. Scanners and digitizers are widely used in robotics, motion analysis, medicine, etc., and some of the scanner and digitizers can meet the model deformation requirements. Commercial stereo-cameras, scanners, and digitizers are being improved in accuracy, reliability, and ease of operation. A number of new systems are coming onto the market.

Lee, George↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 3: Angle of attack

A review of optical sensors that are capable of accurate angle of attack measurements in wind tunnels was conducted. These include sensors being used or being developed at NASA Ames and Langley Research Centers, Boeing Airplane Company, McDonald Aircraft Company, Arnold Engineering Development Center, National Aerospace Laboratory of the Netherlands, National Research Council of Canada, and the Royal Aircraft Establishment of England. Some commercial sensors that may be applicable to accurate angle measurements were also reviewed. It was found that the optical sensor systems were based on interferometers, polarized light detector, linear or area photodiode cameras, position sensing photodetectors, and laser scanners. Several of the optical sensors can meet the requirements of the Ames Unitary Plan Wind Tunnel. Two of these, the Boeing interferometer and the Complere lateral effect photodiode sensors are being developed for the Ames Unitary Plan Wind Tunnel.

Lee, George↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 2: Light sheet and vapor screen

Light sheet and vapor screen methods have been studied with particular emphasis on those systems that have been used in large transonic and supersonic wind tunnels. The various fluids and solids used as tracers or light scatters and the methods for tracing generation have been studied. Light sources from high intensity lamps and various lasers have been surveyed. Light sheet generation and projection methods were considered. Detectors and location of detectors were briefly studied. A vapor screen system and a technique for location injection of tracers for the NASA Ames 9 by 7 foot Supersonic Wind Tunnel were proposed.

Lee, George↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 1: Schlieren

Alignment procedures and conceptual designs for the rapid alignment of the Ames Unitary Wind Tunnel schlieren systems were devised. The schlieren systems can be aligned by translating the light source, the mirrors, and the knife edge equal distances. One design for rapid alignment consists of a manual pin locking scheme. The other is a motorized electronic position scheme. A study of two optical concepts which can be used with the schlieren system was made. These are the 'point diffraction interferometers' and the 'focus schlieren'. Effects of vibrations were studied.

Lee, George↗
NASA NTRS1991

Two-dimensional adaptive-wall tests in the NASA Ames two- by two-foot transonic wind tunnel

The first tests conducted in the adaptive-wall test section of the Ames Research Center's 2- by 2-Foot Transonic Wind Tunnel are described. A procedure was demonstrated for reducing wall interference in transonic flow past a two-dimensional airfoil by actively controlling flow through the slotted walls of the test section. Flow through the walls was controlled by adjusting pressures in compartments of plenums above and below the test section. Wall interference was assessed by measuring (with a laser velocimeter) velocity distributions along a contour surrounding the model, and then checking those measurements for their compatibility with free-air far-field boundary conditions. Plenum pressures for minimum wall interference were determined from empirical influence coefficients. An NACA 0012 airfoil was tested at angles of attack of 0 and 2, and at Mach numbers between 0.70 and 0.85. In all cases the wall-setting procedure greatly reduced wall interference. Wall interference, however, was never completely eliminated, primarily because the effect of plenum pressure changes on the velocities along the contour could not be accurately predicted.

Schairer, Edward T.↗
NASA NTRS1989

A two-dimensional adaptive-wall test section with ventilated walls in the Ames 2- by 2-foot transonic wind tunnel

The first tests conducted in the adaptive-wall test section of the Ames Research Center's 2- by 2-Foot Transonic Wind Tunnel are described. A procedure was demonstrated for reducing wall interference in transonic flow past a two-dimensional airfoil by actively controlling flow through the slotted walls of the test section. Flow through the walls was controlled by adjusting pressures in compartments of plenums above and below the test section. Wall interference was assessed by measuring (with a laser velocimeter) velocity distributions along a contour surrounding the model, and then checking those measurements for their compatibility with free-air far-field boundary conditions. Plenum pressures for minimum wall interference were determined from empirical influence coefficients. An NACA 0012 airfoil was tested at angles of attach of 0 and 2, and at Mach numbers between 0.70 and 0.85. In all cases the wall-setting procedure greatly reduced wall interference. Wall interference, however, was never completely eliminated, primarily because the effect of plenum pressure changes on the velocities along the contour could not be accurately predicted.

Schairer, Edward T.↗
NASA NTRS1989

Fast Laser Holographic Interferometry For Wind Tunnels

Proposed system makes holographic interferograms quickly in wind tunnels. Holograms reveal two-dimensional flows around airfoils and provide information on distributions of pressure, structures of wake and boundary layers, and density contours of flow fields. Holograms form quickly in thermoplastic plates in wind tunnel. Plates rigid and left in place so neither vibrations nor photgraphic-development process degrades accuracy of holograms. System processes and analyzes images quickly. Semiautomatic micro-computer-based desktop image-processing unit now undergoing development moves easily to wind tunnel, and its speed and memory adequate for flows about airfoils.

Lee, George↗
NASA NTRS1988

Adaptive-Wall Wind Tunnel

Side vents controlled automatically to compensate for interference by walls. Improved test station for 2- by 2-Foot Adaptive-Wall Wind Tunnel at Ames Research Center equipped for automatic sensing and correction of effects of walls on airflow in vicinity of test model. New facility well suited for advanced research and development. Velocities measured along lines near model used to calculate velocities observed along lines farther from model if model were in free air. Calculated values compared with velocities measured along farther lines.

Morgan, Daniel G.↗
NASA NTRS1987

Real-time laser holographic Interferometry for aerodynamics

Recent developments in thermoplastic recording holograms and advancements in automated image digitalization and analysis make real-time laser holographic interferometry feasible for two-dimensional flows such as airfoil flows. Typical airfoil measurements would include airfoil presssure distributions, wake and boundary layer profiles, and flow field density contours. This paper addresses some of the problems and requirements of a real-time laser holographic interferometer.

Lee, George↗
NASA NTRS1987

Real-time laser holographic interferometry for aerodynamics

Recent developments in thermoplastic recording holograms and advancements in automated image digitalization and analysis make real-time laser holographic interferometry feasible for two-dimensional flows such as airfoil flows. Typical airfoil measurements would include airfoil pressure distributions, wake and boundary layer profiles, and flow field density contours. This paper addresses some of the problems and requirements of a real-time laser holographic interferometer.

Lee, George↗
NASA NTRS1986

Construction of a 2- by 2-foot transonic adaptive-wall test section at the NASA Ames Research Center

The development of a new production-size, two-dimensional, adaptive-wall test section with ventilated walls at the NASA Ames Research Center is described. The new facility incorporates rapid closed-loop operation, computer/sensor integration, and on-line interference assessment and wall corrections. Air flow through the test section is controlled by a series of plenum compartments and three-way slide vales. A fast-scan laser velocimeter was built to measure velocity boundary conditions for the interference assessment scheme. A 15.2-cm- (6.0-in.-) chord NACA 0012 airfoil model will be used in the first experiments during calibration of the facility.

Morgan, Daniel G.↗
NASA NTRS1986

A dual plate thermoplastic recording device for holographic interferometry

The development of a dual plate holographic interferometer using thermoplastic recording devices is described. The operational characteristics of the thermoplastic devices are investigated and optimized for fringe contrast and signal-to-noise ratio. The dual plate device was demonstrated in a transonic wind tunnel at NASA Ames Research Center. The interferograms derived from the thermoplastic device are compared with those derived from conventional photographic emulsions. The fringe contrast achieved with the optimized thermoplastic device is equivalent to the contrast achieved with conventional techniques.

Umstatter, Holly L.↗
NASA NTRS1961

An Investigation of Transonic Flow Fields Surrounding Hot and Cold Sonic Jets

An investigation at free-stream Mach numbers of 0.90 t o 1.10 was made to determine (1) the jet boundaries and the flow fields around hot and cold jets, and (2) whether a cold-gas jet could adequately simulate the boundary and flow field of hot-gas jet. Schlieren photographs and static-pressure surveys were taken in the vacinity of a sonic jet which was operated over a range of jet pressure ratios of 1 to 6, specific heat ratios at the nozzle exit of 1.29 and 1.40, and jet temperatures up to 2600 R.

Lee, George↗