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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Flow visualization study of a two-dimensional representation of the Space Shuttle launch pad configuration

The loss of the Space Shuttle Challenger was caused by the failure of the aft joint O-ring seals in its right solid rocket booster. It has been suggested by several sources that wind conditions through a reduction in temperature of the right solid rocket booster caused by the wind blowing across the cold external tank, played a role in the O-ring failure. To check the plausibility of the wind theory, an experiment was carried out in a water towing tank to visualize the flow past a two-dimensional model representing a cross section of the Space Shuttle launch configuration. The periodic formation of vortices was found to characterize the wake generated by the model. It is suggested that this organized motion in the flow is the dominant mechanism that accomplishes heat transfer from the external tank to the right solid rocket booster. Flow visualization results consisting of photographs that show instantaneous streamline patterns of the flow are presented.

Mclachland, B. G.↗
NASA NTRS1987

A study of the laminar separation bubble on an airfoil at low Reynolds numbers using flow visualization techniques

The use of flow visualization to study separation bubbles is evaluated. The wind tunnel, two NACA 66(3)-018 airfoil models, and kerosene vapor, titanium tetrachloride, and surface flow visualizations techniques are described. The application of the three visualization techniques to the two airfoil models reveals that the smoke and vapor techniques provide data on the location of laminar separation and the onset of transition, and the surface method produces information about the location of turbulent boundary layer separation. The data obtained with the three flow visualization techniques are compared to pressure distribution data and good correlation is detected. It is noted that flow visualization is an effective technique for examining separation bubbles.

Schmidt, Gordon S.↗
NASA NTRS1987

Flow visualization model of the leeside flows over conically cambered delta wings at supersonic speeds

Surface pressure, flow visualization, and force-and-moment data have been obtained for four, variously conically-cambered delta wing models in a range of flow conditions, with a view to leeside flow mechanisms. The influences exerted by Mach number, angle-of-attack, and camber are determined. An analysis of photographic data leads to the analysis of 12 distinctive leeside flow types, which are further categorizable into two groups respectively possessing either one or two dominant features in the leeside flow field: in the former, either the leading edge or hinge line are the originators of the dominant feature; in the latter, both the leading edge and hinge line are generators.

Wood, Richard M.↗
NASA NTRS2019

Laser Light Sheet Flow Visualization of the Space Launch System Booster Separation Test

Planar flow visualizations were obtained in a wind tunnel test in the NASA Langley Research Center’s Unitary Plan Wind Tunnel using the laser-light-sheet method. This method uses a laser to illuminate fine particles generated in the wind tunnel to visualize flow structures. The test article was designed to simulate the separation of the two solid rocket boosters (SRBs) from the core stage of the NASA Space Launch System (SLS) at Mach 4 using a scale model. The test was run on of the SLS Block 1B Cargo (27005) configuration and the SLS Block 1B Crew (28005) configuration. Planar flow visualization was obtained only on the crew configuration. Air at pressures up to 1500 psi was used to simulate plumes from the booster separation motors (BSMs) located at the nose, and aft skirt of the two boosters. The facility free stream was seeded with water vapor, which condensed and froze into small ice crystals in the tunnel nozzle expansion. A continuous wave green (532 nm) laser sheet was used to illuminate the ice crystals, and the resulting Mie-scattered light was collected with a camera. The resulting images clearly identify shock waves and other flow features including BSM plume shapes. Measurements were acquired for different BSM pressures and booster separation locations.

Danehy, Paul M.↗
NASA NTRS1991

A water tunnel flow visualization study of the vortex flow structures on the F/A-18 aircraft

The vortex flow structures occurring on the F/A-18 aircraft at high angles of attack were studied. A water tunnel was used to gather flow visualization data on the forebody vortex and the wing leading edge extension vortex. The longitudinal location of breakdown of the leading edge vortex was found to be consistently dependent on the angle of attack. Other parameters such as Reynolds number, model scale, and model fidelity had little influence on the overall behavior of the flow structures studied. The lateral location of the forebody vortex system was greatly influenced by changes in the angle of sideslip. Strong interactions can occur between the leading edge extension vortex and the forebody vortex. Close attention was paid to vortex induced flows on various airframe components of the F/A-18. Reynolds number and angle of attack greatly affected the swirling intensity, and therefore the strength of the studied vortices. Water tunnel results on the F/A-18 correlated well with those obtained in similar studies at both full and sub scale levels. The water tunnel can provide, under certain conditions, good simulations of realistic flows in full scale configurations.

Sandlin, Doral R.↗
NASA NTRS2005

Holographic Flow Visualization at NASA Langley

Holographic flow visualization systems at two NASA Langley facilities, a hypersonic blow-down tunnel using CF4 gas and an expansion tube with very short test time, are described. A pulsed ruby laser is used at a CF4 tunnel for single pulse holography, double pulse with several minutes between exposures, and dual plate holographic interferometry. Shadow-graph, schlieren, and interferograms are reconstructed from the holograms in a separate reconstruction lab. At the expansion tube the short run time of 200 microseconds requires precise triggering of its double pulsed ruby laser. With pulse separation, one pulse can occur before and one after flow is established to obtain fringe free background interferograms (perfect infinite fringe) or both pulses can occur during flow in order to study flow instabilities. Holograms are reconstructed at the expansion tube with an in-place setup which makes use of a high power CW Argon laser and common optics for both recording and reconstructing the holograms. The holographic systems at the CF4 tunnel and expansion tube are operated routinely for flow visualization by tunnel technicians. Typical flow visualization photographs from both facilities are presented.

Burner, A. W.↗
NASA NTRS1982

Propeller flow visualization techniques

Propeller flow visualization techniques were tested. The actual operating blade shape as it determines the actual propeller performance and noise was established. The ability to photographically determine the advanced propeller blade tip deflections, local flow field conditions, and gain insight into aeroelastic instability is demonstrated. The analytical prediction methods which are being developed can be compared with experimental data. These comparisons contribute to the verification of these improved methods and give improved capability for designing future advanced propellers with enhanced performance and noise characteristics.

Stefko, G. L.↗
NASA NTRS1979

Holographic flow visualization at NASA Langley

Holographic flow visualization systems at two NASA Langley facilities, a hypersonic blow-down tunnel using CF4 gas and an expansion tube with very short test time, are described. A pulsed ruby laser is used at a CF4 tunnel for single pulse holography, double pulse with several minutes between exposures, and dual plate holographic interferometry. Shadowgraph, schlieren, and interferograms are reconstructed from the holograms in a separate reconstruction lab. At the expansion tube the short run time of 200 microseconds requires precise triggering of its double pulsed ruby laser. With double pulse capability of 20 to 1200 microseconds pulse separation, one pulse can occur before and one later after flow is established to obtain fringe free background interferograms (perfect infinite fringe) or both pulses can occur during flow in order to study flow instabilities. Holograms are reconstructed at the expansion tube with an in-place setup which makes use of a high power CW Argon laser and common optics for both recording and reconstructing the holograms. The holographic systems at the CF4 tunnel and expansion tube are operated routinely for flow visualization by tunnel technicians. Typical flow visualization photographs from both facilities are presented.

Burner, A. W.↗
NASA NTRS1995

NASA Dryden flow visualization facility

This report describes the Flow Visualization Facility at NASA Dryden Flight Research Center, Edwards, California. This water tunnel facility is used primarily for visualizing and analyzing vortical flows on aircraft models and other shapes at high-incidence angles. The tunnel is used extensively as a low-cost, diagnostic tool to help engineers understand complex flows over aircraft and other full-scale vehicles. The facility consists primarily of a closed-circuit water tunnel with a 16- x 24-in. vertical test section. Velocity of the flow through the test section can be varied from 0 to 10 in/sec; however, 3 in/sec provides optimum velocity for the majority of flow visualization applications. This velocity corresponds to a unit Reynolds number of 23,000/ft and a turbulence level over the majority of the test section below 0.5 percent. Flow visualization techniques described here include the dye tracer, laser light sheet, and shadowgraph. Limited correlation to full-scale flight data is shown.

Delfrate, John H.↗
NASA NTRS1993

Flight validation of a pulsed smoke flow visualization system

A flow visualization scheme, designed to measure vortex fluid dynamics on research aircraft, was validated in flight. Strake vortex trajectories and axial core velocities were determined using pulsed smoke, high-speed video images, and semiautomated image edge detection hardware and software. Smoke was pulsed by using a fast-acting three-way valve. After being redesigned because of repeatedly jamming in flight, the valve shuttle operated flawlessly during the last two tests. A 25-percent scale, Gothic strake was used to generate vortex over the wing of a GA-7 Cougar and was operated at a local angle of attack of 22 degrees and Reynolds number of approximately 7.8 x 10(exp 5)/ft. Maximum axial velocities measured in the vortex core were between 1.75 and 1.95 times the freestream velocity. Analysis of the pulsed smoke system's affect on forebody vortices indicates that the system may reorient the forebody vortex system; however, blowing momentum coefficients normally used will have no appreciable affect on the leading-edge extension vortex system. It is recommended that a similar pulsed smoke system be installed on the F/A-18 High Angle Research Vehicle and that this approach be used to analyze vortex core dynamics during the remainder of its high-angle-of-attack research flights.

Ward, Donald T.↗
NASA NTRS1959

The Fluorescent-Oil Film Method and Other Techniques for Boundary-Layer Flow Visualization

A flow-visualization technique, known as the fluorescent-oil film method, has been developed which appears to be generally simpler and to require less experience and development of technique than previously published methods. The method is especially adapted to use in the large high-powered wind tunnels which require considerable time to reach the desired test conditions. The method consists of smearing a film of fluorescent oil over a surface and observing where the thickness is affected by the shearing action of the boundary layer. These films are detected and identified, and their relative thicknesses are determined by use of ultraviolet light. Examples are given of the use of this technique. Other methods that show promise in the study of boundary-layer conditions are described. These methods include the use of a temperature-sensitive fluorescent paint and the use of a radiometer that is sensitive to the heat radiation from a surface. Some attention is also given to methods that can be used with a spray apparatus in front of the test model.

Loving, Donald L.↗
NASA NTRS1982

Surface flow visualization using indicators

Surface flow visualization using indicators in the cryogenic wind tunnel which requires a fresh look at materials and procedures to accommodate the new test conditions is described. Potential liquid and gaseous indicators are identified. The particular materials illustrate the various requirements an indicator must fulfill. The indicator must respond properly to the flow phenomenon of interest and must be observable. Boundary layer transition is the most important phenomenon for which flow visualization indicators may be employed. The visibility of a particular indicator depends on utilizing various optical or chemical reactions. Gaseous indicators are more difficult to utilize, but because of their diversity may present unusual and useful opportunities. Factors to be considered in selecting an indicator include handling safety, toxicity, potential for contamination of the tunnel, and cost.

Crowder, J. P.↗
NASA NTRS1988

Flow Visualization Techniques for Flight Research

In-flight flow visualization techniques used at the Dryden Flight Research Facility of NASA Ames Research Center (Ames-Dryden) and its predecessor organizations are described. Results from flight tests which visualized surface flows using flow cones, tufts, oil flows, liquid crystals, sublimating chemicals, and emitted fluids have been obtained. Off-surface flow visualization of vortical flow has been obtained from natural condensation and two methods using smoke generator systems. Recent results from flight tests at NASA Langley Research Center using a propylene glycol smoker and an infrared imager are also included. Results from photo-chase aircraft, onboard and postflight photography are presented.

Fisher, David F.↗
NASA NTRS1989

Flow visualization techniques for flight research

In-flight flow visualization techniques used at the Dryden Flight Research Facility of NASA Ames Research Center (Ames-Dryden) and its predecessor organizations are described. Results from flight tests which visualized surface flows using flow cones, tufts, oil flows, liquid crystals, sublimating chemicals, and emitted fluids were obtained. Off-surface flow visualization of vortical flow was obtained from natural condensation and two methods using smoke generator systems. Recent results from flight tests at NASA Langley Research Center using a propylene glycol smoker and an infrared imager are also included. Results from photo-chase aircraft, onboard and postflight photography are presented.

Fisher, David F.↗
NASA NTRS1991

Development of image processing techniques for applications in flow visualization and analysis

A comparison between two flow visualization studies of an axi-symmetric circular jet issuing into still fluid, using two different experimental techniques, is described. In the first case laser induced fluorescence is used to visualize the flow structure, whilst smoke is utilized in the second. Quantitative information was obtained from these visualized flow regimes using two different digital imaging systems. Results are presented of the rate at which the jet expands in the downstream direction and these compare favorably with the more established data.

Disimile, Peter J.↗