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Results for “Flow 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.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Optical tomography for flow visualization of the density field around a revolving helicopter rotor blade

In this paper, a tomographic procedure for reconstructing the density field around a helicopter rotor blade tip from remote optical line-of-sight measurements is discussed. Numerical model studies have been carried out to investigate the influence of the number of available views, limited width viewing, and ray bending on the reconstruction. Performance is measured in terms of the mean-square error. It is found that very good reconstructions can be obtained using only a small number of views even when the width of view is smaller than the spatial extent of the object. An iterative procedure is used to correct for ray bending due to refraction associated with the sharp density gradients (shocks).

Snyder, R.↗
NASA NTRS1985

Flow visualization in the Space Shuttle's main engine

The analysis and design of the Space Shuttle's main engine (SSME) power head involved extended finite difference computations conducted on a supercomputer. Certain problems arise, however, in connection with such a computer, and it is pointed out that the massive output from such analyses can actually inhibit insight into physical behavior. It is, therefore, also important to develop effective techniques for computer-user data transfer which match the computer's computational speed. In order to satisfy such requirements, powerful engineering workstations and three-dimensional color computer graphics codes were employed in the computational fluid dynamics (CFD) analyses of the Shuttle's engine. Consequently, the complex physical characteristics of the SSME's hot-gas manifold could be quickly visualized, interpreted, and compared with alternative designs.

Belie, G.↗
NASA NTRS1985

Visualizing flow in the Space Shuttle Main Engine

Ongoing work is described aimed at applying advanced post-processing techniques to interpret and understand the complex flow behavior of the Space Shuttle Main Engine. The use of color graphics and powerful new engineering work stations to effectively present massive amounts of numerical data is emphasized. This combination of tools can result in better designs, faster turnaround, and more complete understanding of complex engineering systems like the Shuttle. Furthermore, it allows engineers access to the massive amounts of data generated by supercomputers and provides a more efficient coupling of man and supercomputer.

Belie, R. G.↗
NASA NTRS1987

Flow visualization of acoustic levitation experiment

Acoustic levitation experiments for space applications were performed. Holographic interferometry is being used to study the heat transfer rates on a heated rod enclosed in a 6 cu in chamber. Acoustic waves at levels up to 150 db increased the heating rates to the rod by factors of three to four. High speed real time holographic interferometry was used to measure the boundary layer on the heated rod. Data reduction and digitization of the interferograms are being implemented.

Baroth, ED↗
NASA NTRS1986

Liquid crystals for high-altitude in-flight boundary layer flow visualization

A novel method for visualization of laminar to turbulent boundary layer transition in flight is presented, in which liquid crystal coatings are used to indicate the transition by a change of color (in response to the changes in the wall shear and the temperature). The liquid crystals applied to the wing surfaces were either cholesteric crystals formulated to be active between temperatures of 30 and 100 F or a sample of chiral nematic liquid crystals formulated to be active between -18 and -22 F. Liquid crystal coatings were shown to provide visualization data at flight altitudes and temperatures at which data could not be obtained previously. Flight evaluations were successfully conducted on a T-34C and a Learjet research aircraft at Mach numbers of up to 0.8 and altitudes of up to 50,000 ft. The time response during oscillating sideslip tests was very rapid. In wind tunnel tests, a hysteresislike behavior was observed in the liquid crystal coatings, possibly because of the lower dynamic pressures in wind tunnels as compared to flight.

Gall, P. D.↗
NASA NTRS1987

Flow visualization studies of transverse fuel injection patterns in a nonreacting Mach 2 combustor

Planar visualization images are recorded of transverse jet mixing in a supersonic combustor flowfield, without chemical reaction, using laser-induced fluorescence from iodine molecules. Digital image processing and three-dimensional display enable complete representations of fuel penetration boundary and shock surfaces corresponding to several injection geometries and pressures.

Mcdaniel, J. C.↗
NASA NTRS1989

Flow visualization studies of the Mach number effects on the dynamic stall of an oscillating airfoil

Compressibility effects on the dynamic stall of a NACA 0012 airfoil undergoing sinusoidal oscillatory motion were studied using a stroboscopic schlieren system. Schlieren pictures and some quantitative data derived from them are presented and show the influence of free-stream Mach number and reduced frequency on the dynamic-stall vortex. This study shows that a dynamic stall vortex always forms near the leading edge and convects on the airfoil upper surface at approximately 0.3 times the free stream velocity for all cases studied. The results also demonstrate that initiation of the dynamic stall vortex is delayed to higher angles of attack with increased reduced frequency, but that dynamic stall occurs at lower angles of incidence with increasing Mach numbers.

Chandrasekhara, M. S.↗
NASA NTRS1990

Interactive numerical flow visualization using stream surfaces

Particle traces and ribbons are often used to depict the structure of three-dimensional flowfields, but images produced using these models can be ambiguous. Stream surfaces offer a more visually intuitive method for the depiction of flowfields, but interactive response is needed to allow the user to place surfaces which reveal the essential features of a given flowfield. FLORA, a software package which supports the interactive calculation and display of stream surfaces on silicon graphics workstations, is described. Alternative methods for the integration of particle traces are examined, and calculation through computational space is found to provide rapid results with accuracy adequate for most purposes. Rapid calculation of traces is teamed with progressive refinement of appoximated surfaces. An initial approximation provides immediate user feedback, and subsequent improvement of the surface ensures that the final image is an accurate representation of the flowfield.

Hultquist, J. P. M.↗
NASA NTRS1953

Low-speed Aileron Effectiveness as Determined by Force Tests and Visual-flow Observations on a 52 Degree Sweptback Wing with and Without Chord-extensions

The results of an investigation of the effects of leading-edge chord-extensions and extensible leading-edge flaps on the low-speed aileron characteristics of a 52 degrees sweptback wing with circular-arc airfoil sections are presented. A description and illustrations of the vortex flow as it passes over the wing are included. The investigation was conducted at Reynolds numbers of 5.5 times 10(exp 6) and 1.3 times 10(exp 6) and corresponding Mach numbers of 0.11 and 0.065 for an angle-of-attack range of 0 degrees through stall.

CONTROLS, FLAP-TYPE - COMPLETE WINGS↗