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All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Vapor-screen flow-visualization experiments in the NASA Langley 0.3-m transonic cryogenic tunnel

The vortical flow on the leeward side of a delta-wing model has been visualized at several different tunnel conditions in the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel using a vapor-screen flow-visualization technique. Vapor-screen photographs of the subject flow field are presented and interpreted relative to phenomenological implications. Results indicate that the use of nitrogen fog in conjunction with the vapor-screen technique is feasibile.

Selby, G. V.↗
NASA NTRS1986

Dynamic measurement of total temperature, pressure and velocity in the Langley 0.3-meter transonic cryogenic tunnel

There is theoretical and experimental evidence which indicates that a sudden or step change in the rate at which the liquid nitrogen is injected into the circuit of a cryogenic wind tunnel can cause a temperature front in the flow for several tunnel circuit times. A temperature front, which occurs at intervals equal to the circuit time, is a sudden increase or decrease in the temperature of the flow followed by a nearly constant temperature. Since these fronts can have an effect on the control of the tunnel as well as the time required to establish steady flow conditions in the test section of cryogenic wind tunnel, tests were conducted in the settling chamber in the Langley 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT) in which high response instrumentation was used to measure the possible existence of these temperature fronts. Three different techniques were used to suddenly change the rate of liquid nitrogen being injected into the tunnel and the results from these three types of tests showed that temperature fronts do not appear to be present in the 0.3-m TCT. Also included are the velocity and pressure fluctuations measured in the settling chamber downstream of the screens and the associated power spectra.

Johnson, C. B.↗
NASA NTRS1986

Tables for correcting airfoil data obtained in the Langley 0.3-meter transonic cryogenic tunnel for sidewall boundary-layer effects

Tables for correcting airfoil data taken in the Langley 0.3-meter Transonic Cryogenic Tunnel for the presence of sidewall boundary layer are presented. The corrected Mach number and the correction factor are minutely altered by a 20 percent change in the boundary layer virtual origin distance. The sidewall boundary layer displacement thicknesses measured for perforated sidewall inserts and without boundary layer removal agree with the values calculated for solid sidewalls.

Jenkins, R. V.↗
NASA NTRS1986

Operating envelope charts for the Langley 0.3-meter transonic cryogenic wind tunnel

To take full advantage of the unique Reynolds number capabilities of the 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT) at the NASA Langley Research Center, it was designed to accommodate test sections other than the original, octagonal, three-dimensional test section. A 20- by 60-cm two-dimensional test section was installed in 1976 and was extensively used, primarily for airfoil testing, through the fall of 1984. The tunnel was inactive during 1985 so that a new test section and improved high speed diffuser could be installed in the tunnel circuit. The new test section has solid adaptive top and bottom walls to reduce or eliminate wall interference for two-dimensional testing. The test section is 33- by 33-cm in cross section at the entrance and is 142 cm long. In the planning and running of past airfoil tests in the 0.3-m TCT, the use of operating envelope charts have proven very useful. These charts give the variation of total temperature and pressure with Mach number and Reynolds number. The operating total temperature range of the 0.3-m TCT is from about 78 K to 327 K with total pressures ranging from about 17.5 psia to 88 psia. This report presents the operating envelope charts for the 0.3-m TCT with the adaptive wall tes t section installed. They were all generated based on a 1-foot chord model. The Mach numbers vary from 0.1 to 0.95.

Rallo, R. A.↗
NASA NTRS1984

Aeroelastic model helicopter rotor testing in the Langley TDT

Wind-tunel testing of a properly scaled aeroelastic model helicopter rotor is considered a necessary phase in the design development of new or existing rotor systems. For this reason, extensive testing of aeroelastically scaled model rotors is done in the Transonic Dynamics Tunnel (TDT) located at the NASA Langley Research Center. A unique capability of this facility, which enables proper dynamic scaling, is the use of Freon as a test medium. A description of the TDT and a discussion of the benefits of using Freon as a test medium are presented. A description of the model test bed used, the Aeroelastic Rotor Experimental System (ARES), is also provided and examples of recent rotor tests are cited to illustrate the advantages and capabilities of aeroelastic model rotor testing in the TDT. The importance of proper dynamic scaling in identifying and solving rotorcraft aeroelastic problems, and the importance of aeroelastic testing of model rotor systems in the design of advanced rotor systems are demonstrated.

Mantay, W. R.↗
NASA NTRS1984

Modification to the NASA Langley 4- by 7-meter tunnel for improved rotorcraft aerodynamics and acoustics

Investigations have been conducted with the aim of improving circuit mean flow characteristics and test section turbulence intensity in the NASA Langley 4 x 7-m wind tunnel. Flow deflectors were instaled to displace the airstream and provide more symmetrical velocity distributions. The periodic flow pulsations of the open test section configuration were addressed by modifications of either the test section entrance, using triangular vanes, or the test section exit, using an alternative flow collector geometry; the latter proved more effective.

Applin, Z. T.↗
NASA NTRS1986

The Langley Research Center's Low-Turbulence Pressure Tunnel

The Low-Turbulence Pressure Tunnel (LTPT), located at the Langley Research Center, is a relatively old wind tunnel which was recently rehabilitated and which has several unique capabilities. A brief history of the LTPT will be presented along with its present operating characteristics. Its unique capabilities will be described and data will be presented to demonstrate these capabilities. Finally, a suggestion will be made for the construction of a new improved facility incorporating and extending the capabilities of the present LTPT.

Stainback, P. C.↗
NASA NTRS1986

Design requirements for the NASA Langley supersonic low-disturbance wind tunnel

The high intensity, high frequency acoustic disturbances that cause large adverse boundary layer transition effects on test models in conventional supersonic wind tunnels consist of finite length wavelets radiating from eddies in the turbulent boundary layers of the wind tunnel walls. NASA Langley has undertaken 'quiet' supersonic tunnel research that demonstrates the ability to maintain laminarity at high unit Reynolds numbers on limited upstream regions of the nozzle wall boundary layers in small, Mach 3.0, 3.5, and 5.0 pilot tunnels. The high level acoustic disturbances are then eliminated, and the transition Reynolds numbers measured on cones approach those for atmospheric flight. Attention is presently given to the design requirements that can be extrapolated from these results for a large wind tunnel facility; high quality air filtering, noise attenuation, nozzle coordinate accuracy, and surface finish, are quantified with pilot tunnel data.

Beckwith, I. E.↗
NASA NTRS1986

The NASA-Langley 20-inch supersonic wind tunnel

NASA Langley's new 20-inch supersonic wind tunnel is in the process of reassembly, following extensive modifications. These will result in its incorporation of such features as a 'quiet' flow control valve, thick sintered screens with very large pressure drops, special farings in the contraction section, an instantaneous relief hatch in the test section, and a switching exhaust system that permits flow into a vacuum sphere during startup and shutdown and to the atmosphere during data acquisition. Attention is given to the expected operating map of the new tunnel.

Dillon, J. L.↗
NASA NTRS1985

Selected topics in experimental aeroelasticity at the NASA Langley Research Center

The results of selected studies that have been conducted by the NASA Langley Research Center in the last three years are presented. The topics presented focus primarily on the ever-important transonic flight regime and include the following: body-freedom flutter of a forward-swept-wing configuration with and without relaxed static stability; instabilities associated with a new tilt-rotor vehicle; effects of winglets, supercritical airfoils, and spanwise curvature on wing flutter; wind-tunnel investigation of a flutter-like oscillation on a high-aspect-ratio flight research wing; results of wing-tunnel demonstration of the NASA decoupler pylon concept for passive suppression of wing/store flutter; and, new flutter testing methods which include testing at cryogenic temperatures for full scale Reynolds number simulation, subcritical response techniques for predicting onset of flutter, and a two-degree-of-freedom mount system for testing side-wall-mounted models.

Ricketts, R. H.↗
NASA NTRS1986

Langley hypersonic facilities complex - Description and application

The Langley Hypersonic Facilities Complex (HFC) consists of hypersonic, blowdown wind tunnels developed and put into operation between the late 1950's and early 1970's. These facilities complement one another to presently provide ranges of Mach number from 6 to 22, unit Reynolds number from 0.1 to 15 million per foot, and normal shock density ratio from 4 to 12. Descriptions of these facilities are presented along with the testing techniques routinely used. Examples of the application of the HFC to generate data bases for proposed entry vehicles and for the verification of computer codes are given. Plans to upgrade the facilities to improve flow quality, productivity, capability and reliability are discussed.

Miller, C. G.↗
NASA NTRS1986

Acoustic reflection contamination measurements in the 16-foot NASA Langley Transonic Wind Tunnel

The Propfan Test Assessment (PTA) contract, awarded recently to Lockheed by the NASA-Lewis Research Center, required a comprehesive series of near field acoustic measurements. These were to use transducers mounted on the surfaces on a one-ninth scale model of the Gulfstream G-II aircraft, modified to the PTA single propfan testbed configuration. The 16-foot Transonic Wind Tunnel at the NASA Langley Research Center was chosen as the facility to be used for these model acoustic tests. Since the tunnel was hard-walled, it is not clear to what extent the propfan noise signals, reaching the various transducers, might be contaminated by reflections from the walls. A Multidriver Acoustic Source was built, and using an impulse and time domain averaging technique, the reflection contaminations in the wind tunnel were measured at selected microphone locations. Results of the investigations of near field measurements exists, due to reflections from the hard walls of the wind tunnnel.

Burrin, R. H.↗
NASA NTRS1987

A simplified fourwall interference assessment procedure for airfoil data obtained in the Langley 0.3-meter transonic cryogenic tunnel

A simplified fourwall interference assessment method has been described, and a computer program developed to facilitate correction of the airfoil data obtained in the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The procedure adopted is to first apply a blockage correction due to sidewall boundary-layer effects by various methods. The sidewall boundary-layer corrected data are then used to calculate the top and bottom wall interference effects by the method of Capallier, Chevallier and Bouinol, using the measured wall pressure distribution and the model force coefficients. The interference corrections obtained by the present method have been compared with other methods and found to give good agreement for the experimental data obtained in the TCT with slotted top and bottom walls.

Murthy, A. V.↗
NASA NTRS1987

Compendium of NASA Langley reports on hypersonic aerodynamics

Reference is made to papers published by the Langley Research Center in various areas of hypersonic aerodynamics for the period 1950 to 1986. The research work was performed either in-house by the Center staff or by other personnel supported entirely or in part by grants or contracts. Abstracts have been included with the references when available. The references are listed chronologically and are grouped under the following general headings: (1) Aerodynamic Measurements - Single Shapes; (2) Aerodynamic Measurements - Configurations; (3) Aero-Heating; (4) Configuration Studies; (5) Propulsion Integration Experiment; (6) Propulsion Integration - Study; (7) Analysis Methods; (8) Test Techniques; and (9) Airframe Active Cooling Systems.

Sabo, Frances E.↗
NASA NTRS1987

Calculation of sidewall boundary-layer parameters from rake measurements for the Langley 0.3-meter transonic cryogenic tunnel

Correction of airfoil data for sidewall boundary-layer effects requires a knowledge of the boundary-layer displacement thickness and the shape factor with the tunnel empty. To facilitate calculation of these quantities under various test conditions for the Langley 0.3 m Transonic Cryogenic Tunnel, a computer program was written. This program reads the various tunnel parameters and the boundary-layer rake total head pressure measurements directly from the Engineering Unit tapes to calculate the required sidewall boundary-layer parameters. Details of the method along with the results for a sample case are presented.

Murthy, A. V.↗
NASA NTRS1987

Scientific and technical information output of the Langley Research Center for calendar year 1986

This document is a compilation of the scientific and technical information that the Langley Research Center has produced during the calendar year 1986. Included are citations for Formal Reports, Quick-Release Technical Memorandums, Contractor Reports, Journal Articles and Other Publications, Meeting Presentations, Techncial Talks, Computer Programs, Tech Briefs, and Patents.

Source record↗
NASA NTRS1987

Aerothermal evaluation of a spherically blunted body with a trapezoidal cross section in the Langley 8-foot high-temperature tunnel

A model to be used in the flow studies and curved Thermal Protection System (TPS) evaluations was tested in the Langley 8 Foot High-Temperature Tunnel at a nominal Mach number of 6.8. The purpose of the study was to define the surface pressure and heating rates at high angles of attack (in support of curved metallic TPS studies) and to determine the conditions for which the model would be suitable as a test bed for aerothermal load studies. The present study was conducted at a nominal total temperature of 2400 and 3300 R, dynamic pressures from 2.3 to 10.9 psia, and free-stream Reynolds numbers from 4000,000 to 1,700,000/ft. The measurements consisted primarily of surface pressure and cold-wall (530 R) heating rates. Qualitative comparisons between predictions and data show that for this configuration, aerothermal tests should be limited to angles of attack between 10 and -10 degrees. Outside this range, the effects of free-stream flow nonuniformity appear in the data, as a result of the long length of the model. However, for TPS testing, this is not a concern and tests can be performed at angles of attack ranging from 20 to -20 degrees. Laminar and naturally turbulent boundary layers are available over limited ranges of conditions.

Albertson, Cindy W.↗
NASA NTRS1987

NASA Langley Research Center tethered balloon systems

The NASA Langley Research Center tethered balloon system operations are covered in this report for the period of 1979 through 1983. Meteorological data, ozone concentrations, and other data were obtained from in situ measurements. The large tethered balloon had a lifting capability of 30 kilograms to 2500 meters. The report includes descriptions of the various components of the balloon systems such as the balloons, the sensors, the electronics, and the hardware. Several photographs of the system are included as well as a list of projects including the types of data gathered.

Owens, Thomas L.↗