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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Alinement tolerant Schlieren system

Simplified system allows effective viewing of gas flows with relaxed optical-precision requirements. Conventional optical path is folded at its center.

Gunter, W. D., Jr.↗
NASA NTRS1977

Wide-field schlieren system

System uses diffraction grating and wire grid to replace conventional mirror and knife edge, producing larger photographs at reduced costs for fluid flow applications.

Parthasarathy, S. P.↗
NASA NTRS1980

Analysis of localized fringes in the holographic optical Schlieren system

The relation between localization of interference fringes in classical and holographic interferometry is reviewed and an application of holographic interferometry is considered for which the object is a transparent medium with nonhomogeneous refractive index. The technique is based on the analysis of the optical path length change of the object wave as it propagates through a transparent medium. Phase shifts due to variations of the speed of light within the medium give rise to an interference pattern. The resulting interferogram can be used to determine the physical properties of the medium or transparent object. Such properties include the mass density of fluids, electron densities of plasmas, the temperature of fluids, the chemical species concentration of fluids, and the state of stress in solids. The optical wave used can be either a simple plane or spherical wave, or it may be a complicated spatial wave scattered by a diffusing screen. The mathematical theory on the formation and analysis of localized fringes, the general theoretical concepts used, and a computer code for analysis are included along with the inversion of fringe order data.

Kurtz, R. L.↗
NASA NTRS1985

Laser Schlieren and ultraviolet diagnostics of rocket combustion

A low pressure oxygen/hydrogen turbine drive combustor hot-fire test series was conducted on the Turbine Drive Combustor Technology Program. The first objective was to gather data on an axisymmetric combustion system to support anchoring of a new combustion/fluid dynamics computer code under development on the same contract. The second objective was to gain insight into low mixture ratio combustion characteristics of coaxial injector elements.

Fisher, S. C.↗
NASA NTRS1987

Laser schlieren crystal monitor

A system and method for monitoring the state of a crystal which is suspended in a solution is described which includes providing a light source for emitting a beam of light along an optical axis. A collimating lens is arranged along the optical axis for collimating the emitted beam to provide a first collimated light beam consisting of parallel light rays. By passing the first collimated light beam through a transparent container, a number of the parallel light rays are deflected off the surfaces of said crystal being monitored according to the refractive index gradient to provide a deflected beam of deflected light rays. A focusing lens is arranged along optical axis for focusing the deflected rays towards a desired focal point. A knife edge is arranged in a predetermined orientation at the focal point; and a screen is provided. A portion of the deflected beam is blocked with the knife edge to project only a portion of the deflected beam. A band is created at one edge of the image of the crystal which indicates the state of change of the surface of the crystal being monitored.

Owen, Robert B.↗
NASA NTRS1960

Investigation by Schlieren Technique of Methods of Fixing Fully Turbulent Flow on Models at Supersonic Speeds

An investigation has been made of the effectiveness of two-dimensional wire and three-dimensional grandular-type roughnesses for fixing transition on a 27 deg cone at a free-stream Mach number of 2.20. One height of each type of roughness was investigated over a free-stream Reynolds number per foot range of about 1.0 x 10 (exp 6) to 7.0 x 10 (exp 6). The tests were made at an angle of attack of 0 deg and with essentially zero heat transfer. The results indicate that, within the Reynolds number per foot range investigated, both two-dimensional wire and three-dimensional granular types of roughness caused large forward movements of transition at constant Reynolds number per foot; however, the forward movement with increase in Reynolds number per foot was very slow for the two-dimensional wire roughness and transition never reached the roughness location as it did with the three-dimensional granular roughness. An extrapolated value of the roughness Reynolds number (based on roughness height and flow conditions at the outer edge of the roughness) for the first appearance of forward movement from the smooth-cone case for the three-dimensional granular roughness was in good agreement with the value of about 600 for the first appearance of turbulent bursts obtained on a similar cone by the hot-wire technique. The range of values of roughness Reynolds number for which a fully turbulent boundary layer existed in the vicinity of the roughness element was about 4,500 to 6,500.

Jackson, Mary W.↗
NASA NTRS1995

Schlieren System and method for moving objects

A system and method are provided for recording density changes in a flow field surrounding a moving object. A mask having an aperture for regulating the passage of images is placed in front of an image recording medium. An optical system is placed in front of the mask. A transition having a light field-of-view and a dark field-of-view is located beyond the test object. The optical system focuses an image of the transition at the mask such that the aperture causes a band of light to be defined on the image recording medium. The optical system further focuses an image of the object through the aperture of the mask so that the image of the object appears on the image recording medium. Relative motion is minimized between the mask and the transition. Relative motion is also minimized between the image recording medium and the image of the object. In this way, the image of the object and density changes in a flow field surrounding the object are recorded on the image recording medium when the object crosses the transition in front of the optical system.

Weinstein, Leonard M.↗
NASA NTRS1958

Schlieren Movies of the 8-Inch Diameter Rigid Parachute Model of the Cook Research Laboratory Taken During the Fourth Phase of Testing in the Langley Unitary Plan Wind Tunnel

Canopy Model IV was tested in four different configuration series. Shroud lines were used in the first three series of tests; none were used in the fourth series. Other variables were Mach number (1.77, 2.17, 2.76), dynamic pressure (290, 250, 155 lb per sq ft), camera speed, and attitude.

[Tunnel] Unitary Plan Wind Tunnel↗
NASA NTRS1996

Schlieren system and method for moving objects

A system and method are provided for recording density changes in a flow field surrounding a moving object. A mask having an aperture for regulating the passage of images therethrough is placed in front of an image recording medium. An optical system is placed in front of the mask. A transition having a light field-of-view and a dark field-of-view is located beyond the test object. The optical system focuses an image of the transition at the mask such that the aperture causes a band of light to be defined on the image recording medium. The optical system further focuses an image of the object through the aperture of the mask so that the image of the object appears on the image recording medium. Relative motion is minimized between the mask and the transition. Relative motion is also minimized between the image recording medium and the image of the object. In this way, the image of the object and density changes in a flow field surrounding the object are recorded on the image recording medium when the object crosses the transition in front of the optical system.

Weinstein, Leonard M.↗
NASA NTRS2017

Background Oriented Schlieren Using Celestial Objects

The present invention is a system and method of visualizing fluid flow around an object, such as an aircraft or wind turbine, by aligning the object between an imaging system and a celestial object having a speckled background, taking images, and comparing those images to obtain fluid flow visualization.

Haering, Edward, A., Jr.↗