SEARCH · Engineering Papers

Results for “Geometry Visualization”

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.

SourceResearch connectionFrom yearThrough year

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

At least 163 records · Page 9

All sources NASA NTRS DOE OSTI

NASA NTRS1990

Schlieren System For Flow Studies In Round Glass Pipes

In schlieren system for studying flow of gas in transparent pipe of circular cross section, cylindrical lenses placed on opposite sides of pipe compensate for refraction caused by wall of pipe. Enables direct visualization of such phenomena as laminar or turbulent flow, shock waves, vortexes, and flow separations in systems having inherently cylindrical geometry; potentially unreliable extrapolations from results in flat-sided test cells no longer necessary.

Costen, Robert C.↗

NASA NTRS1976

A differential game solution to the Coplanar tail-chase aerial combat problem

Numerical results obtained in a simplified version of the one on one aerial combat problem are presented. The primary aim of the data is to specify the roles of pursuer and evader as functions of the relative geometry and of the significant physical parameters of the problem. Numerical results are given in a case in which the slower aircraft is more maneuverable than the faster aircraft. A third order dynamic model of the relative motion is described, for which the state variables are relative range, bearing, and heading. The ranges at termination are arbitary in the present version of the problem, so the weapon systems of both aircraft can be visualized as forward firing high velocity weapons, which must be aimed at the tail pipe of the evader. It was found that, for the great majority of the ralative geometries, each aircraft can evade the weapon system of the other.

Merz, A. W.↗

NASA NTRS1994

Geometry and physical conditions in the stellar wind of AG Carinae

AG Carinae is one of the prototypes of the class of Luminous Blue Variables (LBVs). Since 1990 the star has continuously brightened in its visual continuum. We report on a multi-instrument and -wavelength observing campaign to monitor the current activity phase of AG Car. Ground-based photometry, polarimetry, spectroscopy, and space-ultraviolet spectroscopy and spectropolarimetry have been obtained. From the variability of the polarization at ultraviolet and optical wavelengths we detect significant intrinsic polarization. P(sub int) greater than or equal to 0.5% is a large value for a hot, luminous star, suggesting departure from spherical symmetry in the wind of AG Car. The intrinsic polarization is variable on a timescale of 2 months or less. The measured ultraviolet polarization (intrinsic + interstellar) dropped to 0.5% in 1992 May and returned to 1% in 1992 July. The results are interpreted in terms of a variable outflow with a density enhancement in the equatorial plane. A similar model was suggested for the related object R127 in the Large Magellanic Cloud (LMC). This geometry is reminiscent of the large-scale morphology of the gas nebula and dust 'jet' surrounding AG Car. It is therefore likely that physical conditions close to the stellar surface are responsible for the geometry of the spatially resolved circumstellar material around AG Car. Despite the drastic change of the photospheric conditions, the mass-loss rate did not increase. We find no evidence for a positive correlation between wind density and stellar radius. This makes models that explain the radius increase by opacity effects in the outflow unlikely. The mechanism responsible for the temperature and radius variations is still unknown but most likely has its origin in subphotospheric regions.

Leitherer, Claus↗

NASA NTRS1990

Study of two-phase flow in helical and spiral coils

The principal purposes of the present study were to: (1) observe and develop a fundamental understanding of the flow regimes and their transitions occurring in helical and spiral coils; and (2) obtain pressure drop measurements of such flows, and, if possible, develop a method for predicting pressure drop in these flow geometries. Elaborating upon the above, the general intent is to develop criteria (preferably generalized) for establishing the nature of the flow dynamics (e.g. flow patterns) and the magnitude of the pressure drop in such configurations over a range of flow rates and fluid properties. Additionally, the visualization and identification of flow patterns were a fundamental objective of the study. From a practical standpoint, the conditions under which an annular flow pattern exists is of particular practical importance. In the possible practical applications which would implement these geometries, the working fluids are likely to be refrigerant fluids. In the present study the working fluids were an air-water mixture, and refrigerant 113 (R-113). In order to obtain records of flow patterns and their transitions, video photography was employed extensively. Pressure drop measurements were made using pressure differential transducers connected across pressure taps in lines immediately preceding and following the various test sections.

Keshock, Edward G.↗

NASA NTRS1982

Color visualization for fluid flow prediction

High-resolution raster scan color graphics allow variables to be presented as a continuum, in a color-coded picture that is referenced to a geometry such as a flow field grid or a boundary surface. Software is used to map a scalar variable such as pressure or temperature, defined on a two-dimensional slice of a flow field. The geometric shape is preserved in the resulting picture, and the relative magnitude of the variable is color-coded onto the geometric shape. The primary numerical process for color coding is an efficient search along a raster scan line to locate the quadrilteral block in the grid that bounds each pixel on the line. Tension spline interpolation is performed relative to the grid for specific values of the scalar variable, which is then color coded. When all pixels for the field of view are color-defined, a picture is played back from a memory device onto a television screen.

Smith, R. E.↗

NASA NTRS1996

Marching Cubes in Cylindrical and Spherical Coordinates

Isosurface extraction is a common analysis and visualization technique for three-dimensional scalar data. Marching Cubes is the most commonly-used algorithm for finding polygonal representations of isosurfaces in such data. We extend Marching Cubes to produce geometry for data sets that lie in spherical and cylindrical coordinate systems as well as show the steps for derivation of transformations for other coordinate systems.

techniques marching cubes isosurfaces coordinate s↗

NASA NTRS1989

Helicopter hub fairing and pylon interference drag

A wind tunnel test was conducted to study the aerodynamics of helicopter hub and pylon fairings. The test was conducted in the 7-by 10 Foot Subsonic Wind Tunnel (Number 2) at Ames Research Center using a 1/5-scale XH-59A fuselage model. The primary focus of the test was on the rotor hub fairing and pylon mutual interference drag. Parametric studies of pylon and hub fairing geometry were also conducted. This report presents the major findings of the test as well as tabulated force and moment data, flow visualization photographs, and graphical presentations of the drag data. The test results indicate that substantial drag reduction can be attained through the use of a cambered hub fairing with circular arc upper surface and flat lower surface. Furthermore, a considerable portion of the overall drag reduction is attributed to the reduction in the hub-on-pylon interference drag. It is also observed that the lower surface curvature of the fairing has a strong influence on the hub fairing and on pylon interference drag. However, the drag reduction benefit that was obtained by using the cambered hub fairing with a flat lower surface was adversely affected by the clearance between the hub fairing and the pylon.

Graham, D. R.↗

NASA NTRS1999

Use of Boundary Layer Transition Detection to Validate Full-Scale Flight Performance Predictions

Full-scale flight performance predictions can be made using CFD or a combination of CFD and analytical skin-friction predictions. However, no matter what method is used to obtain full-scale flight performance predictions knowledge of the boundary layer state is critical. The implementation of CFD codes solving the Navier-Stokes equations to obtain these predictions is still a time consuming, expensive process. In addition, to ultimately obtain accurate performance predictions the transition location must be fixed in the CFD model. An example, using the M2.4-7A geometry, of the change in Navier-Stokes solution with changes in transition and in turbulence model will be shown. Oil flow visualization using the M2.4-7A 4.0% scale model in the 14'x22' wind tunnel shows that fixing transition at 10% x/c in the CFD model best captures the flow physics of the wing flow field. A less costly method of obtaining full-scale performance predictions is the use of non-linear Euler codes or linear CFD codes, such as panel methods, combined with analytical skin-friction predictions. Again, knowledge of the boundary layer state is critical to the accurate determination of full-scale flight performance. Boundary layer transition detection has been performed at 0.3 and 0.9 Mach numbers over an extensive Reynolds number range using the 2.2% scale Reference H model in the NTF. A temperature sensitive paint system was used to determine the boundary layer state for these conditions. Data was obtained for three configurations: the baseline, undeflected flaps configuration; the transonic cruise configuration; and, the high-lift configuration. It was determined that at low Reynolds number conditions, in the 8 to 10 million Reynolds number range, the baseline configuration has extensive regions of laminar flow, in fact significantly more than analytical skin-friction methods predict. This configuration is fully turbulent at about 30 million Reynolds number for both 0.3 and 0.9, Mach numbers. Both the transonic cruise and the high-lift configurations were fully turbulent aft of the leading-edge flap hingeline at all Reynolds numbers.

Hamner, Marvine↗

NASA NTRS1991

A new method for visualizing data on a sphere

A method for visualizing data on a globe or unit sphere is described. Information that is distributed over a sphere - global oceanographic or geographic measurements, all-sky astronomy observations, or any quantities that are best represented in spherical coordinates - can benefit from this technique. Retaining a better sense of the geometry and information content of the data, 3D graphics can provide an unobstructed view of the entire sphere, without undue deformation of its surface area. A 'parameterized ray trace' produces look-up tables (LUTs) that can be used for all visualizations. The ray-trace result shows one or more spheres with the data as a texture map and three reflecting rectangles that 'mirror' the far sides of the sphere(s) into view. The LUTs need only be created once. No special purpose hardware is required beyond a PC or workstation that supports color. Examples from astronomical and geophysical datasets, which are commonly displayed with an area deforming (2D) projection, are presented.

Hon, David↗

NASA NTRS1993

Animation of multi-flexible body systems and its use in control system design

Animation can greatly assist the structural dynamicist and control system analyst with better understanding of how multi-flexible body systems behave. For multi-flexible body systems, the structural characteristics (mode frequencies, mode shapes, and damping) change, sometimes dramatically with large angles of rotation between bodies. With computer animation, the analyst can visualize these changes and how the system responds to active control forces and torques. A characterization of the type of system we wish to animate is presented. The lack of clear understanding of the above effects was a key element leading to the development of a multi-flexible body animation software package. The resulting animation software is described in some detail here, followed by its application to the control system analyst. Other applications of this software can be determined on an individual need basis. A number of software products are currently available that make the high-speed rendering of rigid body mechanical system simulation possible. However, such options are not available for use in rendering flexible body mechanical system simulations. The desire for a high-speed flexible body visualization tool led to the development of the Flexible Or Rigid Mechanical System (FORMS) software. This software was developed at the Center for Simulation and Design Optimization of Mechanical Systems at the University of Iowa. FORMS provides interactive high-speed rendering of flexible and/or rigid body mechanical system simulations, and combines geometry and motion information to produce animated output. FORMS is designed to be both portable and flexible, and supports a number of different user interfaces and graphical display devices. Additional features have been added to FORMS that allow special visualization results related to the nature of the flexible body geometric representations.

Juengst, Carl↗

NASA NTRS1985

Space Shuttle ice prevention studies

Turbojet engine exhausts are being considered for the prevention of ice formation on the Space Shuttle External Tank (ET) when cryogenic propellants are loaded. The ice could dislodge and damage the Thermal Protection System tiles of the Shuttle Orbiter. An oil flow visualization technique was developed to quickly and inexpensively study the flowfields created by jet exhausts. The procedure can also determine the influence of geometry, jet exhausts, and wind conditions on the size and location of flow regions. A black tempra and kerosene mixture was applied to an ET model; the wind tunnel and jet flow were started; and when they stopped the flow patterns were photographed to determine which parameters had the greatest influence on the flowfields.

Porteiro, J. L. F.↗

NASA NTRS1995

Managing Complexity in Multidisciplinary Visualization

As high performance computing technology progresses, computational simulations are becoming more advanced in their capabilities. In the computational aerosciences domain, single discipline steady-state simulations computed on a single grid are far from the state-of-the-art. In their place are complex, time-dependent multidisciplinary simulations that attempt to model a given geometry more realistically. The product of these multidisciplinary simulations is a massive amount of data stored in different formats, grid topologies, units of measure, etc., as a result of the differences in the simulated physical domains. In addition to the challenges posed by setting up and performing the simulation, additional challenges exist in analyzing computational results. Visualization plays an important role in the advancement of multidisciplinary simulations. To date, visualization has been used to aid in the interpretation of large amounts of simulation data. Because the human visual system is effective in digesting a large amount of information presented graphically, visualization has helped simulation scientists to understand complex simulation results. As these simulations become even more complex, integrating several different physical domains, visualization will be critical to digest the massive amount of information. Another important role for visualization is to provide a common communication medium from which the domain scientists can use to develop, debug, and analyze their work. Multidisciplinary analyses are the next step in simulation technology, not only in computational aerosciences, but in many other areas such as global climate modeling. Visualization researchers must understand and work towards the challenges posed by multidisciplinary simulation scenarios. This paper addresses some of these challenges, describing technologies that must be investigated to create a useful visualization analysis tool for domain scientists.

Miceli, Kristina D.↗

NASA NTRS1989

Experiments in swept-wing transition

Stability and transition experiments are conducted on a 45 degree sweep airfoil in the ASU Unsteady Wind Tunnel. Combined flow-visualization techniques and hot-wire measurements are used in conjuction with stability-code calculations to map out transition behavior for this flow geometry. Both steady and unsteady crossflow vortices are observed and at this time there is no contradiction with the theoretical predictions.

Saric, William S.↗

NASA NTRS2003

Flow Visualization of Low Prandtl Number Fluids using Electrochemical Measurements

It is well established that residual flows exist in contained liquid metal processes. In 1-g processing, buoyancy forces often drive these flows and their magnitudes can be substantial. It is also known that residual flows can exist during microgravity processing, and although greatly reduced in magnitude, they can influence the properties of the processed materials. Unfortunately, there are very few techniques to visualize flows in opaque, high temperature liquid metals, and those available are not easily adapted to flight investigation. In this study, a novel technique is developed that uses liquid tin as the model fluid and solid-state electrochemical cells constructed from Yttria-Stabilized Zirconia (YSZ) to establish and measure dissolved oxygen boundary conditions. The melt serves as a common electrode for each of the electrochemical cells in this design, while independent reference electrodes are maintained at the outside surfaces of the electrolyte. By constructing isolated electrochemical cells at various locations along the container walls, oxygen is introduced or extracted by imposing a known electrical potential or passing a given current between the melt and the reference electrode. This programmed titration then establishes a known oxygen concentration boundary condition at the selected electrolyte-melt interface. Using the other cells, the concentration of oxygen at the electrolyte-melt interface is also monitored by measuring the open-circuit potentials developed between the melt and reference electrodes. Thus the electrochemical cells serve to both establish boundary conditions for the passive tracer and sense its path. Rayleigh-Benard convection was used to validate the electrochemical approach to flow visualization. Thus, a numerical characterization of the second critical Rayleigh numbers in liquid tin was conducted for a variety of Cartesian aspect ratios. The extremely low Prandtl number of tin represents the lowest value studied numerically. Additionally, flow field oscillations are visualized and the effect of tilt on convecting systems is quantified. Experimental studies of the effect of convection in liquid tin are presented. Three geometries are studied: (1) double electrochemical cell with vertical concentration gradients; (2) double cell with horizontal concentration gradients; and (3) multiple cells with vertical temperature gradients. The first critical Rayleigh number transition is detected with geometry (1) and it is concluded that current measurements are not as affected by convection as EMF measurements. The system is compared with numerical simulations in geometry (2), and oscillating convection is detected with geometry (3).

Crunkleton, D.↗

NASA NTRS2006

Planar laser-induced fluorescence (PLIF) investigation of hypersonic flowfields in a Mach 10 wind tunnel

Planar laser-induced fluorescence (PLIF) of nitric oxide (NO) was used to visualize four different hypersonic flowfields in the NASA Langley Research Center 31-Inch Mach 10 Air wind tunnel. The four configurations were: (1) the wake flowfield of a fuselage-only X-33 lifting body, (2) flow over a flat plate containing a rectangular cavity, (3) flow over a 70deg blunted cone with a cylindrical afterbody, formerly studied by an AGARD working group, and (4) an Apollo-geometry entry capsule - relevant to the Crew Exploration Vehicle currently being developed by NASA. In all cases, NO was seeded into the flowfield through tubes inside or attached to the model sting and strut. PLIF was used to visualize the NO in the flowfield. In some cases pure NO was seeded into the flow while in other cases a 5% NO, 95% N2 mix was injected. Several parameters were varied including seeding method and location, seeding mass flow rate, model angle of attack and tunnel stagnation pressure, which varies the unit Reynolds number. The location of the laser sheet was as also varied to provide three dimensional flow information. Virtual Diagnostics Interface (ViDI) technology developed at NASA Langley was used to visualize the data sets in post processing. The measurements demonstrate some of the capabilities of the PLIF method for studying hypersonic flows.

Danehy, Paul M.↗

NASA NTRS1979

Deep photospheric flows in Tau Scorpii

From analysis of weak, unblended, ultraviolet lines observed in Tau Scorpii by Copernicus, the same line widths and the same slightly blue-depressed wings as found in the upper photospheric lines of the visual region are found. In addition, a radial-velocity discrepancy of about 6 km/s between weak and strong lines in the 1000-1300-A region is found. These results are in quantitative agreement with one another and with the results of the visual region. They imply that a flow of material is present even in the deep photosphere of this star. However, one cannot yet specify the geometry of the flow (outward-radial versus temperature-weighted convection columns). At the least, this flow alters the expected radiation-driven flow solution close to the photosphere. At the most, it could provide the heating of a chromosphere or a corona just outside the photosphere, as required by the imperfect flow model.

Smith, M. A.↗

NASA NTRS1986

The exciting star of HH 57

The first spectral classification for the exciting star of HH 57 is provided. The star is an F8 III and suffers about 5 mag of visual extinction, far greater than that toward the HH 57A knot, only a few arcseconds away. This difference supports the previous identification of a flattened geometry for the circumstellar dust around this star. Using IRAS photometry, a distance of 940 pc to HH 57 is determined by bolometrically matching the observed luminosity of the star to those of FU Ori and V1057 Cyg.

Cohen, M.↗

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.↗