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At least 793 records · Page 44

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NASA NTRS1991

A synthetic environment for visualization and planning of orbital maneuvers

An interactive proximity operations planning system, which allows on-site planning of fuel-efficient, multi-burn maneuvers in a potential multi-space-craft environment has been developed and tested. This display system most directly assists planning by providing visual feedback in a synthetic virtual space that aids visualization of trajectories and their constraints. Its most significant features include (1) an 'inverse dynamics' algorithm that removes control nonlinearities facing the operator and (2) a stack-oriented action-editor that reduces the order of control and creates, through a 'geometric spreadsheet,' the illusion of an inertially stable environment. This synthetic environment provides the user with control of relevant static and dynamic properties of way-points during small orbital changes allowing independent solutions to otherwise coupled problems of orbital maneuvering.

Ellis, Stephen R.↗

NASA NTRS1992

Knowledge-based assistance for science visualization and analysis using large distributed databases

Within this decade, the growth in complexity of exploratory data analysis and the sheer volume of space data require new and innovative approaches to support science investigators in achieving their research objectives. To date, there have been numerous efforts addressing the individual issues involved in inter-disciplinary, multi-instrument investigations. However, while successful in small scale, these efforts have not proven to be open and scaleable. This proposal addresses four areas of significant need: scientific visualization and analysis; science data management; interactions in a distributed, heterogeneous environment; and knowledge-based assistance for these functions. The fundamental innovation embedded within this proposal is the integration of three automation technologies, namely, knowledge-based expert systems, science visualization and science data management. This integration is based on the concept called the Data Hub. With the Data Hub concept, NASA will be able to apply a more complete solution to all nodes of a distributed system. Both computation nodes and interactive nodes will be able to effectively and efficiently use the data services (access, retrieval, update, etc.) with a distributed, interdisciplinary information system in a uniform and standard way. This will allow the science investigators to concentrate on their scientific endeavors, rather than to involve themselves in the intricate technical details of the systems and tools required to accomplish their work. Thus, science investigators need not be programmers. The emphasis will be on the definition and prototyping of system elements with sufficient detail to enable data analysis and interpretation leading to publishable scientific results. In addition, the proposed work includes all the required end-to-end components and interfaces to demonstrate the completed concept.

Handley, Thomas H., Jr.↗

NASA NTRS1992

A distributed system for visualizing and analyzing multivariate and multidisciplinary data

The Linked Windows Interactive Data System (Link Winds) is being developed with NASA support. The objective of this proposal is to adapt and apply that system in a complex network environment containing elements to be found by scientists working multidisciplinary teams on very large scale and distributed data sets. The proposed three year program will develop specific visualization and analysis tools, to be exercised locally and remotely in the Link Winds environment, to demonstrate visual data analysis, interdisciplinary data analysis and cooperative and interactive televisualization and analysis of data by geographically separated science teams. These demonstrations will involve at least two science disciplines with the aim of producing publishable results.

Jacobson, Allan S.↗

NASA NTRS1993

Visualizing the semantic content of large text databases using text maps

A methodology for generating text map representations of the semantic content of text databases is presented. Text maps provide a graphical metaphor for conceptualizing and visualizing the contents and data interrelationships of large text databases. Described are a set of experiments conducted against the TIPSTER corpora of Wall Street Journal articles. These experiments provide an introduction to current work in the representation and visualization of documents by way of their semantic content.

Combs, Nathan↗

NASA NTRS1991

SAVS: A Space Data Analysis and Visualization System

Viewgraphs on a Space Data Analysis and Visualization System (SAVS) are presented. Topics covered include: SAVS - a data acquisition, manipulation, analysis and a visualization system; the SAVS focus; the NASA vision for the coming decade; statement of the problem; needs of the practicing scientist; projecting capabilities; and SAVS near term activities.

Szuszczewicz, Edward↗

NASA NTRS1992

In-Flight Flow Visualization Results From the X-29A Aircraft at High Angles of Attack

Flow visualization techniques were used on the X-29A aircraft at high angles of attack to study the vortical flow off the forebody and the surface flow on the wing and tail. The forebody vortex system was studied because asymmetries in the vortex system were suspected of inducing uncommanded yawing moments at zero sideslip. Smoke enabled visualization of the vortex system and correlation of its orientation with flight yawing moment data. Good agreement was found between vortex system asymmetries and the occurrence of yawing moments. Surface flow on the forward-swept wing of the X-29A was studied using tufts and flow cones. As angle of attack increased, separated flow initiated at the root and spread outboard encompassing the full wing by 30° angle of attack. In general, the progression of the separated flow correlated well with subscale model lift data. Surface flow on the vertical tail was also studied using tufts and flow cones. As angle of attack increased, separated flow initiated at the root and spread upward. The area of separated flow on the vertical tail at angles of attack ≥ 20° correlated well with the marked decrease in aircraft directional stability.

Flight Testing↗

NASA NTRS1992

Fiber optic-based laser vapor screen flow visualization systems for aerodynamic research in larger-scale subsonic and transonic wind tunnels

The design, installation, and application of the NASA laser vapor screen (LVS) flow visualization systems developed by 10-foot high speed tunnel and 8-foot transonic pressure tunnel are discussed. Sufficient quantity of water is injected into the wind tunnel diffuser section to increase the relative humidity and promote condensation of the water vapor in the flow field about the model. Vortex-dominated flows are illuminated with an intense sheet of laser light. Fiber optics are used to deliver the laser beam through the plenum shell that surrounds the test section of each facility and to the light sheet-generating optics positioned in the ceiling window of the test section. Operational experience indicates that fiber optic-based systems are safe, reliable, and capable of proving high-quality off-surface flow visualization in larger scale subsonic and transonic wind tunnels.

Erickson, Gary E.↗

NASA NTRS1991

Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

The results are given of flow visualization studies and inflow velocity field measurements performed on a 1/12 scale model of the XV-15 tilt rotor aircraft in the hover mode. The complex recirculating flow due to the rotor-wake-body interactions characteristic of tilt rotors was studied visually using neutrally buoyant soap bubbles and quantitatively using hot wire anemometry. Still and video photography were used to record the flow patterns. Analysis of the photos and video provided information on the physical dimensions of the recirculating fountain flow and on details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Recirculating flows were also observed along the length of the fuselage. Hot wire anemometry results indicate that the wing under the rotor acts to obstruct the inflow causing a deficit in the inflow velocities over the inboard region of the model. Hot wire anemometry also shows that the turbulence intensities in the inflow are much higher in the recirculating fountain reingestion zone.

Coffen, Charles D.↗

NASA NTRS1992

Information, entropy and fidelity in visual communication

This paper presents an assessment of visual communication that integrates the critical limiting factors of image gathering and display with the digital processing that is used to code and restore images. The approach focuses on two mathematical criteria, information and fidelity, and on their relationships to the entropy of the encoded data and to the visual quality of the restored image.

Huck, Friedrich O.↗

NASA NTRS1993

Visual and somesthetic influences on postural orientation in the median plane

We investigated optic and somesthetic contributions to perceived body orientation in the pitch dimension. In a within-subject factorial design, each of 12 subjects attempted to set his/her body erect or 45 degrees back from erect while restrained in a movable bed surrounded by an adjustable box. The box provided a visual environment consisting of either a grid pattern, two luminous lines, or complete darkness. Both the grid pattern and the luminous lines were effective at biasing settings of body position when the box was pitched; the pitched grid was more effective than the pitched lines. Although the pitch of the box influenced orientation to both goals, the effect was greater for the diagonal goal than for the erect goal. We present a model of postural orientation in the median plane that involves vestibular, somatosensory, and visual inputs.

Nemire, K.↗

NASA NTRS1992

Visual augmentation for night flight over featureless terrain

Visual augmentation technique based on infrared cueing lights which project from the aircraft to the terrain is proposed to mitigate the problems associated with night flight over regions with featureless terrains. A series of simulation studies evaluated the effectiveness of several cueing light configurations. Results indicate that certain relatively low-cost cueing light configurations can be effectively used as pseudo-flight directors without impairing the pilot's use of available natural cues in the scene. Pilots prefer configurations which provide multiple samples of the forward terrain. Providing several 'look-aheads' helps to resolve potential vehicle/terrain state ambiguities. It is concluded that cueing lights are capable of creating visual patterns which are readily interpreted and translated to control commands, thus providing pilots with intuitive, low-workload decision aids.

Kaiser, Mary K.↗

NASA NTRS1992

Engineering a visual system for seeing through fog

We examine the requirements for on-board aircraft sensor systems that would allow pilots to 'see through' poor weather, especially fog, and land and rollout aircraft under conditions that currently cause flight cancellations and airport closures. Three visual aspects of landing and rollout are distinguished: guidance, hazard detection and hazard recognition. The visual features which support the tasks are discussed. Three broad categories of sensor technology are examined: passive millimeter wave (PMMW), imaging radar, and passive infrared (IR). PMMW and imaging radar exhibit good weather penetration, but poor spatial and temporal resolution. Imaging radar exhibits good weather penetration, but typically relies on a flat-earth assumption which can lead to interpretive errors. PMMW systems have a narrow field of view. IR has poorer weather penetration but good spatial resolution. We recommend using both millimeter-wave and infrared sensor systems, blending the images using multiresolution digital-image pyramid-processing technology, and fusing the resulting real-time images with stored database imagery of the same scene.

Larimer, J.↗

NASA NTRS1993

Visualization of internal swirling flows

Flow solutions were analyzed using three visualization tools, FAST, UFAT, and Visual3. The simulation models axisymmetric unsteady flow inside a closed circular cylinder with a rotating lid. The capabilities and limitations of these visualization packages are presented. The versatility of these tools enhances scientific study and presentation of numerical results.

Potter, R.↗

NASA NTRS1993

On the assessment of visual communication by information theory

This assessment of visual communication integrates the optical design of the image-gathering device with the digital processing for image coding and restoration. Results show that informationally optimized image gathering ordinarily can be relied upon to maximize the information efficiency of decorrelated data and the visual quality of optimally restored images.

Huck, Friedrich O.↗

NASA NTRS1992

Flow visualization in a single simulated brush seal

A method to visualize and characterize the complex flow fields in brush seals is presented. A configuration characteristic of the brush seal confined in a two-dimensional tunnel with water as the working fluid was studied. Visualization of the flow field revealed regions that are characteristically jetting, vortical, and crossflow and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion and cylindrical configuration have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in brush seals.

Braun, M. J.↗

NASA NTRS1991

An experimental study of curved mixing layers: Flow visualization using volume rendering

The existence and importance of large-scale spanwise vortical structures for 2-D straight mixing layers has been well documented in the last decade. Computer models and simulations have sought to reproduce these vortical structures associated with the Kelvin-Helmholtz (K-H) instability mode which is due to the shear per se. Secondary streamwise vortical structures for the same flows were also seen experimentally and have recently been given importance in computational efforts. Curved mixing layers can be characterized as stable (the high-speed stream is placed on the outside of the longitudinal bend), leading to a suppression of the Taylor-Gortler (T-G) instability, and unstable (high-speed stream on the inside of the bend), leading to an enhancement of the T-G instability. The T-G instability is associated with the centripetal acceleration that the curvature imparts. Thus, curvature superimposed on 2-D shear layer flows provides a way for studying the importance of streamwise vorticity, its competition with spanwise vorticity, and changes to entrainment and mixing. Furthermore, the outcome of the competition of a relatively enhanced or suppressed T-G instability with the K-H instability offers the possibility of achieving passive mixing enhancement. As a first step in understanding the competition between the K-H and the T-G instabilities and the resulting changes to the structure of the flow, highly resolved visualizations of the flow structure for the stable and the unstable configurations are provided. The straight layer is also visualized for comparison with earlier works.

Karasso, Paris S.↗

NASA NTRS1956

Visualization of Rotor Tip Secondary Flows with Blade Tip Air Discharge and Suction in a Low-speed Turbine

Smoke was used to visualize outer-wall secondary flows in a low-speed turbine utilizing rotor tip air discharge and suction. Photographs as well as visual observations of the effect of tip air discharge and suction were made by independently varying the direction and quantity of the tip air discharge and suction, and varying tip clearance, and main-stream air speed. In addition, the cross-sectional area of the hollow blade discharge opening was varied for the case of tip air discharge.

Kofskey, Milton G↗

NASA NTRS1994

Program Supports Scientific Visualization

Primary purpose of General Visualization System (GVS) computer program is to support scientific visualization of data generated by panel-method computer program PMARC_12 (inventory number ARC-13362) on Silicon Graphics Iris workstation. Enables user to view PMARC geometries and wakes as wire frames or as light shaded objects. GVS is written in C language.

Keith, Stephan↗