Search NASA⌕ Search

SEARCH · Search NASA

Results for “visualization technique”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Experiments on identification and control of inflow disturbances in contracting streams

Vorticity from all surfaces and isolated objects in the vicinity of the fan intake, including the outside surfaces of the fan housing, were identified as the major sources for disturbances leading to blade passing frequency noise. The previously proposed mechanism based on atmospheric turbulence is refuted. Flow visualization and hot wire techniques were used in three different facilities to document the evolution of various types of disturbances, including the details of the mean flow and turbulence characteristics. The results suggest that special attention must be devoted to the design of the inlet and that geometric modeling may not lead to adequate simulation of the in flight characteristics. While honeycomb type flow manipulators appear to be effective in reducing some of the disturbances, higher pressure drop devices that generate adequate turbulence, for mixing of isolated nonuniformities, may be necessary to suppress the remaining disturbances. The results are also applicable to the design of inlets of open return wind tunnels and similar flow facilities.

Lee, A. H.↗
NASA NTRS1985

Image processing of aerodynamic data

The use of digital image processing techniques in analyzing and evaluating aerodynamic data is discussed. An image processing system that converts images derived from digital data or from transparent film into black and white, full color, or false color pictures is described. Applications to black and white images of a model wing with a NACA 64-210 section in simulated rain and to computed low properties for transonic flow past a NACA 0012 airfoil are presented. Image processing techniques are used to visualize the variations of water film thicknesses on the wing model and to illustrate the contours of computed Mach numbers for the flow past the NACA 0012 airfoil. Since the computed data for the NACA 0012 airfoil are available only at discrete spatial locations, an interpolation method is used to provide values of the Mach number over the entire field.

Faulcon, N. D.↗
NASA NTRS1986

Disturbance functions of the Goertler instability on an airfoil

Goertler vortices arise in boundary layers along concave surfaces due to centrifugal effects. This paper presents some results of an experiment conducted to study the development of these vortices on an airfoil with a pressure gradient in the concave region where an attached laminar boundary layer was insured with suction through a perforated panel. A sublimating chemical technique was used to visualize Goertler vortices and the velocity field was measured by laser velocimetry. Experimental disturbance functions are compared with those predicted by the linear stability theory. The trend of vortex amplification in the concave zone and damping in the following convex region is shown to essentially follow the theoretical predictions.

Dagenhart, J. R.↗
NASA NTRS1986

Analysis of crew functions as an aid in Space Station interior layout

The Space Station must be designed to facilitate all of the functions that its crew will perform, both on-duty and off-duty, as efficiently and comfortably as possible. This paper examines the functions to be performed by the Space Station crew in order to make inferences about the design of an interior layout that optimizes crew productivity. Twenty-seven crew functions were defined, as well as five criteria for assessing relationships among all pairs of those functions. Hierarchical clustering and multidimensional scaling techniques were used to visually summarize the relationships. A key result was the identification of two dimensions for describing the configuration of crew functions: 'Private-Public' and 'Group-Individual'. Seven specific recommendations for Space Station interior layout were derived from the analyses.

Steinberg, A. L.↗
NASA NTRS1985

The Goertler instability on an airfoil

Goertler vortices arise in boundary layers along concave surfaces due to centrifugal effects. This paper presents some results of an experiment conducted to study the development of these vortices on an airfoil with a pressure gradient in the concave region where an attached laminar boundary layer was insured with suction through a perforated panel. The sublimating chemical technique was used to visualize Goertler vortices and the velocity field was measured by laser velocimetry. The vortex wavelength clearly varied with Goertler number as predicted by linear theory. Both flow visualization and velocity measurements indicated vortex damping in the convex zone. Secondary instability was observed at the higher Goertler numbers.

Mangalam, S. M.↗
NASA NTRS1990

Supercomputer applications in gas turbine flowfield simulation

The numerical simulation of the unsteady three-dimensional viscous flow in a gas turbine stage is considered. Results from a three-dimensional time-accurate Navier-Stokes simulation of rotor-stator interaction in an axial turbine stage are presented. The present study uses a fine grid in the spanwise direction to better resolve the complex three-dimensional flowfield, and complements earlier reported coarse-grid calculations. Several different features of the flowfield are analyzed and compared to earlier calculations and to experimental data whenever possible. Computer animation techniques are used to visualize various unsteady three-dimensional features of the flow. The results demonstrate the capabilities of current computing hardware in obtaining accurate simulations of unsteady flows in turbomachines.

Madavan, Nateri K.↗
NASA NTRS1990

Drop coalescence studies

The objective of this experimental study is to understand the detailed mechanics of the coalescence of liquid drops. The experiments are being conducted in an immiscible acoustic levitator with degassed water as the host medium. Typically, a quasineutrally buoyant drop of silicon oil mixed with bromobenzene is levitated close to the velocity node of the levitator. A second drop of the same liquid is introduced, and as it slowly seeks levitation position, the drops coalesce. Coalescence is delayed until the host film between drops is completely drained. Following coalescence, the excess surface energy in the coalesced drop is dissipated through shape oscillations. The final events of film rupture followed by drop coalescence are rapid and are photographically studied with high-speed video (1000 fps). The laser-induced fluorescence technique is used to visualize the dynamics of host film drainage. The details of the coalescence mechanics are presented.

Anikumar, A. V.↗
NASA NTRS1992

Characteristics of two adjacent rectangular jets

Rectangular supersonic (Design Mach number 1.8), single and twin free jets were tested in a Mach number range of 1.2 to 2.4. The objective was to study the interaction between the jets and the effect of the interaction on the spreading rate of the jets. Nozzle spacing in the range of one to four equivalent exit diameters, and jet Mach number were the parameters investigated. The experimental techniques used were Schlieren visualization and direct mixing (gas sampling) measurements from which jet spreading can be readily obtained. At the design Mach number of the nozzles and above the twin jets interact but the interaction does not affect the spreading rate of the jets. At lower Mach numbers, a moderate increase in the twin jets' spread compared to the single jet's spread was observed. The greater increase was observed for nozzle spacing of two equivalent exit diameters. Similar conclusions are drawn from both visualization and direct mixing results.

Zeierman, S.↗
NASA NTRS1991

A study of rotor wake development and wake/body interactions in hover

Experiments were conducted to document the wake geometry and interactional effects between a hovering rotor and a body representing a simplified helicopter fuselage. The wide-field shadowgraph technique was used to visualize the rotor wake vortices and to obtain quantitative information on the wake trajectories, with and without the presence of the body. Particular attention was paid to visualizing and quantifying the wake geometry during the direct impingement of tip vortices on the body surface. The rotor performance with and without the fuselage is also discussed.

Bagai, A.↗
NASA NTRS1988

Providing structural modules with self-integrity monitoring

With the advent of complex space structures (i.e., U.S. Space Station), the need for methods for remotely detecting structural damage will become greater. Some of these structures will have hundreds of individual structural elements (i.e., strut members). Should some of them become damaged, it could be virtually impossible to detect it using visual or similar inspection techniques. The damage of only a few individual members may or may not be a serious problem. However, should a significant number of the members be damaged, a significant problem could be created. The implementation of an appropriate remote damage detection scheme would greatly reduce the likelihood of a serious problem related to structural damage ever occurring. This report presents the results of the research conducted on remote structural damage detection approaches and the related mathematical algorithms. The research was conducted for the Small Business Innovation and Research (SBIR) Phase 2 National Aeronautics and Space Administration (NASA) Contract NAS7-961.

Walton, W. B.↗
NASA NTRS1993

Wave packet motion in harmonic potential and computer visualization

Wave packet motions of a single electron in harmonic potentials or a magnetic field are obtained analytically. The phase of the wave function which depends on both time and space is also presented explicitly. The probability density of the electron changes its width and central position periodically. These results are visualized using computer animation techniques.

Tsuru, Hideo↗
NASA NTRS1992

Experimental study of rotor wake/body interactions in hover

Experiments were conducted to document the tip vortex geometries and interactional effects betwen a hovering rotor and a body representing a simplified helicopter fuselage. The wide-field shadowgraph technique was used to visualize the rotor tip vortices and to obtain quantitative information on the trajectories, with and without the presence of the body. It was found that the effects of the body caused significant changes to both the radial contraction and axial displacements of the tip vortices compared to the isolated case. Direct impingement of the tip vortices on the body surface was also observed, and found to cause large local wake deformations. The rotor performance was significantly affected by the body, producing a higher figure of merit relative to the isolated case.

Bagai, A.↗
NASA NTRS1994

Dynamics and statics of nonaxisymmetric liquid bridges

We finished the construction of the experimental apparatus and the design and testing of some of the visualization and data acquisition techniques. Experimental work focused on three areas: force measurements, loss of stability to nonaxisymmetric bridges, and vibration behavior. The experimental work is summarized in section 2. Selected results from our force measurement experiments are outlined in section 3. In addition we worked on the theory of the dynamic stability of axisymmetric bridges and undertook numerical simulation of the effects of inclined gravity vectors on the minimum volume stability limit for static bridges. The results and status of our theoretical work and numerical simulation are described in section 4. Papers published and in preparation, conference presentations, etc., are described in section 5. Work planned for the third year is discussed in section 6. References cited in the report are listed in section 7.

Alexander, J. Iwan D.↗
NASA NTRS1997

An Experimental Study of Characteristic Combustion-Driven Flow for CFD Validation

A series of uni-element rocket injector studies were completed to provide benchmark quality data needed to validate computational fluid dynamic models. A shear coaxial injector geometry was selected as the primary injector for study using gaseous hydrogen/oxygen and gaseous hydrogen/liquid oxygen propellants. Emphasis was placed on the use of nonintrusive diagnostic techniques to characterize the flowfields inside an optically-accessible rocket chamber. Measurements of the velocity and species fields were obtained using laser velocimetry and Raman spectroscopy, respectively. Qualitative flame shape information was also obtained using laser-induced fluorescence excited from OH radicals and laser light scattering studies of aluminum oxide particle seeded combusting flows. The gaseous hydrogen/liquid oxygen propellant studies for the shear coaxial injector focused on breakup mechanisms associated with the liquid oxygen jet under subcritical pressure conditions. Laser sheet illumination techniques were used to visualize the core region of the jet and a Phase Doppler Particle Analyzer was utilized for drop velocity, size and size distribution characterization. The results of these studies indicated that the shear coaxial geometry configuration was a relatively poor injector in terms of mixing. The oxygen core was observed to extend well downstream of the injector and a significant fraction of the mixing occurred in the near nozzle region where measurements were not possible to obtain. Detailed velocity and species measurements were obtained to allow CFD model validation and this set of benchmark data represents the most comprehensive data set available to date. As an extension of the investigation, a series of gas/gas injector studies were conducted in support of the X-33 Reusable Launch Vehicle program. A Gas/Gas Injector Technology team was formed consisting of the Marshall Space Flight Center, the NASA Lewis Research Center, Rocketdyne and Penn State. Injector geometries studied under this task included shear and swirl coaxial configurations as well as an impinging jet injector.

Santoro, Robert J.↗
NASA NTRS1997

An Experimental Study of Characteristic Combustion-Driven Flow for CFD Validation

A series of uni-element rocket injector studies were completed to provide benchmark quality data needed to validate computational fluid dynamic models. A shear coaxial injector geometry was selected as the primary injector for study using gaseous hydrogen/oxygen and gaseous hydrogen/liquid oxygen propellants. Emphasis was placed on the use of non-intrusive diagnostic techniques to characterize the flowfields inside an optically-accessible rocket chamber. Measurements of the velocity and species fields were obtained using laser velocimetry and Raman spectroscopy, respectively Qualitative flame shape information was also obtained using laser-induced fluorescence excited from OH radicals and laser light scattering studies of aluminum oxide particle seeded combusting flows. The gaseous hydrogen/liquid oxygen propellant studies for the shear coaxial injector focused on breakup mechanisms associated with the liquid oxygen jet under sub-critical pressure conditions. Laser sheet illumination techniques were used to visualize the core region of the jet and a Phase Doppler Particle Analyzer was utilized for drop velocity, size and size distribution characterization. The results of these studies indicated that the shear coaxial geometry configuration was a relatively poor injector in terms of mixing. The oxygen core was observed to extend well downstream of the injector and a significant fraction of the mixing occurred in the near nozzle region where measurements were not possible to obtain Detailed velocity and species measurements were obtained to allow CFD model validation and this set of benchmark data represents the most comprehensive data set available to date As an extension of the investigation, a series of gas/gas injector studies were conducted in support of the X-33 Reusable Launch Vehicle program. A Gas/Gas Injector Technology team was formed consisting of the Marshall Space Flight Center, the NASA Lewis Research Center, Rocketdyne and Penn State. Injector geometries studied under this task included shear and swirl coaxial configurations as well as an impinging jet injector.

Santoro, Robert J.↗
NASA NTRS2000

Visually Lossless Data Compression for Real-Time Frame/Pushbroom Space Science Imagers

A visually lossless data compression technique is currently being developed for space science applications under the requirement of high-speed push-broom scanning. The technique is also applicable to frame based imaging and is error-resilient in that error propagation is contained within a few scan lines. The algorithm is based on a block transform of a hybrid of modulated lapped transform (MLT) and discrete cosine transform (DCT), or a 2-dimensional lapped transform, followed by bit-plane encoding; this combination results in an embedded bit string with exactly the desirable compression rate as desired by the user. The approach requires no unique table to maximize its performance. The compression scheme performs well on a suite of test images typical of images from spacecraft instruments. Flight qualified hardware implementations are in development; a functional chip set is expected by the end of 2001. The chip set is being designed to compress data in excess of 20 Msamples/sec and support quantizations from 2 to 16 bits.

Yeh, Pen-Shu↗
NASA NTRS1993

Virtual Reality: You Are There

Telepresence or "virtual reality," allows a person, with assistance from advanced technology devices, to figuratively project himself into another environment. This technology is marketed by several companies, among them Fakespace, Inc., a former Ames Research Center contractor. Fakespace developed a teleoperational motion platform for transmitting sounds and images from remote locations. The "Molly" matches the user's head motion and, when coupled with a stereo viewing device and appropriate software, creates the telepresence experience. Its companion piece is the BOOM-the user's viewing device that provides the sense of involvement in the virtual environment. Either system may be used alone. Because suits, gloves, headphones, etc. are not needed, a whole range of commercial applications is possible, including computer-aided design techniques and virtual reality visualizations. Customers include Sandia National Laboratories, Stanford Research Institute and Mattel Toys.

Source record↗
NASA NTRS1985

The Goertler Instability on an Airfoil

Goertler vortices arise in boundary layers along concave surfaces due to centrifugal effects. This paper presents some results of an experiment conducted to study the development of these vortices on an airfoil with a pressure gradient in the concave region where an attached laminar boundary layer was insured with suction through a perforated panel. The sublimating chemical technique was used to visualize Goertler vortices and the velocity field was measured by laser velocimetry. The vortex wavelength clearly varied with Goertler number as predicted by linear theory. Both flow visualization and velocity measurements indicated vortex damping in the convex zone. Secondary instability was observed at the higher Goertler numbers.

Mangalam, S. M.↗