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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Background Pressure Profiles for Sonic Boom Vehicle Testing in the NASA Glenn 8- by 6-Foot Supersonic Wind Tunnel

In an effort to identify test facilities that offer sonic boom measurement capabilities, an exploratory test program was initiated using wind tunnels at NASA research centers. The subject of this report is the sonic boom pressure rail data collected in the Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel. The purpose is to summarize the lessons learned based on the test activity, specifically relating to collecting sonic boom data which has a large amount of spatial pressure variation. The wind tunnel background pressure profiles are presented as well as data which demonstrated how both wind tunnel Mach number and model support-strut position affected the wind tunnel background pressure profile. Techniques were developed to mitigate these effects and are presented.

Castner, Raymond↗
NASA NTRS1974

Measurements of V/STOL aircraft noise mechanisms using pressure cross-correlation techniques in a reverberant wind tunnel

A 3.8 cm. model jet was operated in a wind tunnel with cross-flow in order to determine the effect on jet noise radiated characteristics. A method was developed for the determination of noise radiating characteristics of sources within reverberant wind tunnels; cross-correlation measurements were used. The averaging time in the cross-correlation is determined by the amount of background noise within the wind tunnel. It was found that cross-flow increases the radiated noise by 10 db. There was some indication of downstream radiation exceeding the sideline radiation.

Meecham, W. C.↗
NASA NTRS1977

Measurement of model aeroelastic deformations in the wind tunnel at transonic speeds using stereophotogrammetry

A stereophotographic method of determining the aeroelastic deformations of an airplane model under aerodynamic load in the wind tunnel was evaluated. Wind tunnel tests were conducted in the Langley 8 foot transonic pressure tunnel on the wing of a 0.0625 scale model of the TF-8A supercritical wing research airplane to obtain simultaneously the aerodynamic forces and moments, pressure distributions, and stereophotographs. Tests were conducted at Mach numbers of 0.80, 0.95, and 1.20, and at free stream dynamic pressures of 20,349 Pa and 40,698 Pa. Accuracy of the stereophotographic technique in determining wing deflections was within 0.013 cm under static conditions. This value translates to an error in wing twist of 0.10 deg inboard and increases to 0.20 deg outboard. When the model was under aerodynamic load in the wind tunnel, the accuracy of the stereophotographic technique of determining wind deflections increased to 0.052 cm when compared with static wing loadings because of the dynamic motion of the model in the tunnel.

Brooks, J. D.↗
NASA NTRS2009

SMART Rotor Development and Wind-Tunnel Test

Boeing and a team from Air Force, NASA, Army, Massachusetts Institute of Technology, University of California at Los Angeles, and University of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center, figure 1. The SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing-edge flap on each blade. The development effort included design, fabrication, and component testing of the rotor blades, the trailing-edge flaps, the piezoelectric actuators, the switching power amplifiers, the actuator control system, and the data/power system. Development of the smart rotor culminated in a whirl-tower hover test which demonstrated the functionality, robustness, and required authority of the active flap system. The eleven-week wind tunnel test program evaluated the forward flight characteristics of the active-flap rotor, gathered data to validate state-of-the-art codes for rotor noise analysis, and quantified the effects of open- and closed-loop active-flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness and the reliability of the flap actuation system were successfully demonstrated in more than 60 hours of wind-tunnel testing. The data acquired and lessons learned will be instrumental in maturing this technology and transitioning it into production. The development effort, test hardware, wind-tunnel test program, and test results will be presented in the full paper.

Lau, Benton H.↗
NASA NTRS2018

Mitigation of Polystyrene Microsphere Surface Contamination for Wind Tunnel Applications

Polystyrene latex (PSL) microspheres have been utilized as seed material for flow visualization in wind tunnels. However, PSL microspheres have been observed to strongly adhere to wind tunnel and model surfaces. Surface contamination on the cleaning screens that remove vorticity and provide laminar flow in the test section, is particularly problematic. Agglomeration of particles on these screens cause constriction of the airflow through the screen resulting in inconsistent airflow properties in the test section. The adhesion mechanism of PSL microspheres to wind tunnel screens and 316 stainless steel flat plates, were evaluated in a contamination apparatus where small sections of screen material were exposed to PSL-seeded airflow. Using a design of experiments (DOE) methodology airflow seeding parameters were changed to evaluate how these modifications affected the degree of surface contamination. The solution composition, comprised of ethanol and water, was determined to be the most significant factor in particle adhesion. Utilizing image analysis software, data were collected from the contaminated surfaces and incorporated to generate predictive particle contamination models. A relationship was identified between the solvent evaporation rate, and the morphology and magnitude of PSL contaminants on the test surfaces. This analysis can be extended to other solvent mixtures to provide insight into simultaneously improving wind tunnel testing capabilities while diminishing facility contamination.

Wohl, Christopher J.↗
NASA NTRS2002

Accessing Wind Tunnels From NASA's Information Power Grid

The NASA Ames wind tunnel customers are one of the first users of the Information Power Grid (IPG) storage system at the NASA Advanced Supercomputing Division. We wanted to be able to store their data on the IPG so that it could be accessed remotely in a secure but timely fashion. In addition, incorporation into the IPG allows future use of grid computational resources, e.g., for post-processing of data, or to do side-by-side CFD validation. In this paper, we describe the integration of grid data access mechanisms with the existing DARWIN web-based system that is used to access wind tunnel test data. We also show that the combined system has reasonable performance: wind tunnel data may be retrieved at 50Mbits/s over a 100 base T network connected to the IPG storage server.

Becker, Jeff↗
NASA NTRS2014

9-Ft By 7-Ft Supersonic Wind Tunnel Nozzle Improvement Study

Engineers at the Unitary Plan Wind Tunnel at NASA Ames Research Center have recently embarked on a project focused on improving flow quality and tunnel capabilities in the 9-ft by 7-ft supersonic wind tunnel. Collaborating with Jacobs Tech Group, the project has explored potential improvements to the nozzle design using computational fluid dynamics. Preliminary predictions suggest changes to the nozzle design could significantly improve flow quality at the lower operating range (M1.5-1.8), however potential improvements in the upper operating range have yet to be realized.

Wind Tunnel Testing↗
NASA NTRS2006

Investigating Tiltrotor Formation Flight Via 1/48-Scale Wind Tunnel Experiment

This paper describes two small-scale wind tunnel tests conducted in the Army 7- by 10-Foot Wind Tunnel at NASA Ames Research Center. These tests featured two 1/48-scale V-22 models that were operated in a variety of simulated flight conditions including climb, descent, and level flight at various flight speeds and spatial separations. Forces and moments experienced by the trail aircraft were used to deduce the influence of the lead aircraft on the trail aircraft. Particle Image Velocimetry (PIV) data were collected to relate these forces and moments to features in the lead aircraft wake. In general, the roll moment on the trail aircraft is shown to be maximum when the aircraft are laterally offset by a full wingspan and the trail aircraft is vertically positioned so as to be in the wake of the lead aircraft. Furthermore, the roll moment is maximal when operating near 50 knots full-scale flight speed. Because the interaction persists far downstream and the vertical position of the wake is dependent on descent angle and flight speed, lateral separation has been determined to be the best means of avoiding adverse interactions between aircraft.

PIV (PARTICLE IMAGE VELOCIMETRY)↗
NASA NTRS2019

Acoustic Testing of the Tiltrotor Test Rig in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel

The Tiltrotor Test Rig (TTR) was tested in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel from 2017 to 2018. The primary goal of the test was to understand the operational capabilities of the TTR, while also acquiring research data, including acoustic data. Four microphones were placed around the TTR: two on the wind tunnel floor and two on struts. Acoustic measurements of the TTR rotor were acquired to 1) understand the acoustic testing capabilities of the TTR in the NFAC 40- by 80-FootWind Tunnel, 2) compare to previous XV-15 rotor acoustic data acquired in the NFAC 80- by 120-Foot Wind Tunnel, and 3) provide data for future validation studies. A data quality study revealed that the NFAC 40- by 80-Foot Wind Tunnel is an adequate acoustic environment to test the TTR rotor. For a given thrust and advance ratio, a shaft angle sweep was performed and acoustic measurements were compared against 1996 and 1999 XV-15 data in the NFAC 80- by 120-Foot Wind Tunnel; differences between the three tests are discussed.

40- by 80-FootWind Tunnel↗
NASA NTRS1986

Study of ice accretion on icing wind tunnel components

In a closed loop icing wind tunnel the icing cloud is simulated by introducing tiny water droplets through an array of nozzles upstream of the test section. This cloud will form ice on all tunnel components (e.g., turning vanes, inlet guide vanes, fan blades, and the heat exchanger) as the cloud flows around the tunnel. These components must have the capacity to handle their icing loads without causing significant tunnel performance degradation during the course of an evening's run. To aid in the design of these components for the proposed Altitude Wind Tunnel (AWT) at NASA Lewis Research Center the existing Icing Research Tunnel (IRT) is used to measure icing characteristics of the IRT's components. The results from the IRT are scaled to the AWT to account for the AWT's larger components and higher velocities. The results show that from 90 to 45 percent of the total spray cloud froze out on the heat exchanger. Furthermore, the first set of turning vanes downstream of the test section, the FOD screen and the fan blades show significant ice formation. The scaling shows that the same results would occur in the AWT.

Newton, J. E.↗
NASA NTRS1986

Study of ice accretion on icing wind tunnel components

In a closed loop icing wind tunnel the icing cloud is simulated by introducing tiny water droplets through an array of nozzles upstream of the test section. This cloud will form ice on all tunnel components (e.g., turning vanes, inlet guide vanes, fan blades, and the heat exchanger) as the cloud flows around the tunnel. These components must have the capacity to handle their icing loads without causing significant tunnel performance degradation during the course of an evening's run. To aid in the design of these components for the proposed Altitude Wind Tunnel (AWT) at NASA Lewis Research Center the existing Icing Research Tunnel (IRT) is used to measure icing characteristics of the IRT's components. The results from the IRT are scaled to the AWT to account for the AWT's larger components and higher velocities. The results show that from 90 to 45 percent of the total spray cloud froze out on the heat exchanger. Furthermore, the first set of turning vanes downstream of the test section, the FOD screen and the fan blades show significant ice formation. The scaling shows that the same results would occur in the AWT.

Newton, J. E.↗
NASA NTRS1927

Method of Correcting Wind Tunnel Data for Omitted Parts of Airplane Models

Wind tunnel models do not have complete similarity to the full scale airplane. Part of the dissimilarity is due to the difference between the stationary model in the artificial wind stream of the tunnel and the moving airplane in still air. There are a number of other reasons for departing from exact geometrical similitude. For reasons of accuracy and economy, all minor parts of the full scale airplane, such as struts, wires, fittings, control horns and other parts whose scale corrections are large are removed from wind tunnel models. By omitting the minor parts of the airplane in the wind tunnel model and adding to the forces and moments of the model those omitted parts measured full scale and properly reduced, the scale effects of such parts disappear from the model data. Scale effects due to major parts of the airplane, particularly the fuselage and wings, can be corrected by omitting the propeller and making the surface of the model as smooth as possible, two further departures from geometrical similitude between model and full scale that add considerably to the accuracy and economy of model tests.

Smith, R H↗
NASA NTRS1977

Transonic wind-tunnel wall interference

A method for analyzing wall interference is described which avoids the assumption of linear superposition of perturbations in extracting the wall induced velocity field. Measurements of pressure distribution on or near the tunnel walls during the actual wind tunnel test, are imposed as boundary values to be matched. Instead of applying wall interference corrections to the wind tunnel data, some property of the wall is adjusted until a calculated interference free criterion is satisfied for each tunnel data point. The mode of operation for the National Transonic Facility, envisioned as a correctable interference transonic tunnel, combines the capability for accurate assessment of wall interference with a limited capability for wall control.

Kemp, W. B., Jr.↗
NASA NTRS1982

A remote millivolt multiplexer and amplifier module for wind tunnel data acquisition

A 30-channel remotely located multiplexer and amplifier module is developed for the measurement of wind tunnel models, which substantially reduces the amount of wiring necessary and thus provides higher accuracy. The module provides for a wide variety of transducer voltage outputs to be multiplexed and amplified within the model, and all signals are able to exit the module on two wires. The module is self-calibrating, and when coupled with the electronically scanned pressure instrumentation widely used in wind tunnels, it allows the modular wind tunnel models to be fabricated and checked before installation into the wind tunnel.

Juanarena, D. B.↗
NASA NTRS1992

Screens Would Protect Wind-Tunnel Fan Blades

Butterfly screen installed in wind tunnel between test section and fan blades to prevent debris from reaching fan blades if model structure fails. Protective screens deployed manually or automatically. Concept beneficial anywhere wind tunnels employed. Also useful in areas outside of aerospace industry, such as in airflow design of automobiles and other vehicles.

Farmer, Moses G.↗
NASA NTRS1982

Laser velocimeter for large wind tunnels

The measurement of velocity in large wind tunnels is normally performed using mechanical probes. This practice can entail considerable complexity in connection with the structure often required for probe support. The use of laser velocimetry for the flowfield measurements in large wind tunnels is, therefore, far more desirable since it can be implemented with minimal mechanical complexity and with minimal modifications to the test section structure. A description is provided of a velocimeter which is intended for use in investigations which include V/STOL vehicle flowfield mapping for location and sizing of wakes and plumes, wing-loading distribution determination without the need for pressure taps, the aerodynamics of high-lift airfoils as well as rotating rotor blades, and vehicle wake studies. Use is made of a single-color dual-beam backscatter system which is capable of sensing two orthogonal components of velocity.

Reinath, M. S.↗
NASA NTRS2001

Static and Wind Tunnel Aero-Performance Tests of NASA AST Separate Flow Nozzle Noise Reduction Configurations

This report presents the results of cold flow model tests to determine the static and wind tunnel performance of several NASA AST separate flow nozzle noise reduction configurations. The tests were conducted by Aero Systems Engineering, Inc., for NASA Glenn Research Center. The tests were performed in the Channels 14 and 6 static thrust stands and the Channel 10 transonic wind tunnel at the FluiDyne Aerodynamics Laboratory in Plymouth, Minnesota. Facility checkout tests were made using standard ASME long-radius metering nozzles. These tests demonstrated facility data accuracy at flow conditions similar to the model tests. Channel 14 static tests reported here consisted of 21 ASME nozzle facility checkout tests and 57 static model performance tests (including 22 at no charge). Fan nozzle pressure ratio varied from 1.4 to 2.0, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Channel 10 wind tunnel tests consisted of 15 tests at Mach number 0.28 and 31 tests at Mach 0.8. The sting was checked out statically in Channel 6 before the wind tunnel tests. In the Channel 6 facility, 12 ASME nozzle data points were taken and 7 model data points were taken. In the wind tunnel, fan nozzle pressure ratio varied from 1.73 to 2.8, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Test results include thrust coefficients, thrust vector angle, core and fan nozzle discharge coefficients, total pressure and temperature charging station profiles, and boat-tail static pressure distributions in the wind tunnel.

Mikkelsen, Kevin L.↗