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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1953

The zero-lift drag of a slender body of revolution (NACA RM-10 research model) as determined from tests in several wind tunnels and in flight at supersonic speeds

Presents zero-lift drag data of an NACA RM-10 slender body of revolution with and without stabilizing fins attached. The results from several wind tunnels and in flight are compared. The results cover a Reynolds number range from about 1 time 10 to the 6th power to 40 times 10 to the 6th power for the flight models. The Mach numbers covered include 1.5 to 2.4 in the wind tunnels and 0.85 to 2.5 in flight.

FLOW, SUPERSONIC↗
NASA NTRSDate not supplied

Techniques in Assessing Random Uncertainty of Wind Tunnel Replicate Test Data

The preferred method to determine the random uncertainty of variables of interest during wind tunnel tests is by direct analysis of replicate data. However, current information is limited to analysis of a single replicate set condition that does not consider data covariance. This paper provides additional information on considerations for quantifying random uncertainty including the evaluation and correction of replicate data covariance, the selection of replicate set conditions for the test, and the interpolation of random uncertainty at other than replicate set conditions. The analysis and techniques are supported by data from a conventional aircraft configuration test at the Oran Nicks Low-Speed Wind Tunnel and an ASME nozzle flow characterization at the Propulsion Systems Laboratory.

Uncertainty↗
NASA NTRS2016

Review of Potential Wind Tunnel Balance Technologies

This manuscript reviews design, manufacture, materials, sensors, and data acquisition technologies that may benefit wind tunnel balances for the aerospace research community. Current state-of-the-art practices are used as the benchmark to consider advancements driven by researcher and facility needs. Additive manufacturing is highlighted as a promising alternative technology to conventional fabrication and has the potential to reduce both the cost and time required to manufacture force balances. Material alternatives to maraging steels are reviewed. Sensor technologies including piezoresistive, piezoelectric, surface acoustic wave, and fiber optic are compared to traditional foil based gages to highlight unique opportunities and shared challenges for implementation in wind tunnel environments. Finally, data acquisition systems that could be integrated into force balances are highlighted as a way to simplify the user experience and improve data quality. In summary, a rank ordering is provided to support strategic investment in exploring the technologies reviewed in this manuscript.

Burns, Devin E.↗
NASA NTRS1972

Flight and wind tunnel investigation of the effects of Reynolds number on installed boattail drag at subsonic speeds

A flight and wind tunnel investigation was conducted to determine the effects of Reynolds number on the installed boattail drag of an underwing nacelle. Tests were run on a modified F-106B aircraft and 0.05 and 0.22 scale wind tunnel models. Tests were conducted at Mach numbers of 0.6 and 0.9 and over a 16 to 1 range of Reynolds numbers. Highest drag was obtained at intermediate Reynolds numbers corresponding to about the lowest flight values and that of the 0.22 scale model. Significantly lower drag was obtained at both higher and lower Reynolds numbers.

Chamberlin, R.↗
NASA NTRS1973

Flight and wind tunnel investigation of the effects of Reynolds number on installed boattail drag at subsonic speeds.

A flight and wind tunnel investigation was conducted to determine the effects of Reynolds number on the installed boattail drag of an underwing nacelle. Tests were run on a modified F-106B aircraft and 0.05 and 0.22 scale wind tunnel models. Tests were conducted at Mach numbers of 0.6 and 0.9 and over a 16 to 1 range of Reynolds numbers. Highest drag was obtained at intermediate Reynolds numbers corresponding to about the lowest flight values and that of the 0.22 scale model. Significantly lower drag was obtained at both higher and lower Reynolds numbers.

Chamberlin, R.↗
NASA NTRS1936

Full-scale Wind-tunnel and Flight Tests of a Fairchild 22 Airplane Equipped with a Fowler Flap

Full-scale wind-tunnel and flight tests were made of a Fairchild 22 airplane equipped with a Fowler flap to determine the effect of the flap on the performance and control characteristics of the airplane. In the wind-tunnel tests of the airplane with the horizontal tail surfaces removed, the flap was found to increase the maximum lift coefficient from 1.27 to 2.41. In the flight test, the flap was found to decrease the minimum speed from 58.8 to 44.4 miles per hour. The required take-off run to attain an altitude of 50 feet was reduced from 935 feet to 700 feet by the use of the flap, the minimum distance being obtained with five-sixths full deflection. The landing run from a height of 50 feet was reduced one-third. The longitudinal and directional control was adversely affected by the flap, indicating that the design of the tail surfaces is more critical with a flapped than a plain wing.

Dearborn, C H↗
NASA NTRS1994

Development of Doppler Global Velocimetry for Wind Tunnel Testing

The development of Doppler global velocimetry is described. Emphasis is placed on the modifications necessary to advance this nonintrusive laser based measurement technique from a laboratory prototype to a viable wind tunnel flow diagnostics tool. Several example wind tunnel flow field investigations are described to illustrate the versatility of the technique. Flow conditions ranged from incompressible to Mach 2.8 with measurement distances extending from 1 to 15 m.

Meyers, James F.↗
NASA NTRS1991

Wind tunnel wall effects in a linear oscillating cascade

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flowfield, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

Buffum, D. H.↗
NASA NTRS2019

Additional Findings from the Common Research Model Natural Laminar Flow Wind Tunnel Test

An experimental investigation of the Common Research Model with Natural Laminar Flow (CRM-NLF) took place in the National Transonic Facility (NTF) at the NASA Langley Research Center in 2018. The 5.2% scale semispan model was designed using a new natural laminar flow design method, Crossflow Attenuated NLF (CATNLF). CATNLF enables laminar flow on typical transport wings with high sweep and Reynolds number by reshaping the wing airfoils to obtain specific pressure distribution characteristics that control the crossflow growth near the leading edge. The CATNLF method also addresses Tollmien- Schlichting transition, attachment line transition, and Görtler vortices. During the wind tunnel test, data were acquired to address three primary test objectives: validate the CATNLF design method, characterize the NTF laminar flow testing capabilities, and establish best practices for laminar flow wind tunnel testing. The present paper provides both experimental and computational data to understand the CRM-NLF laminar flow characteristics, as well as address the three primary test objectives. The effects of angle of attack and Reynolds number on the CRM-NLF laminar flow extent are studied, and the dominant transition mechanism is evaluated at a variety of test conditions. Critical N-factors are calculated for the NTF environment, and a discussion on best practices for laminar flow wind tunnel testing is provided. The CRM-NLF in the NTF provided initial confirmation of the ability of the CATNLF method to suppress crossflow growth and enable significant extents of laminar flow on transport wings with high sweep and Reynolds numbers.

Lynde, Michelle N.↗
NASA NTRS1991

Wind tunnel wall effects in a linear oscillating cascade

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

Buffum, Daniel H.↗
NASA NTRS1973

Wind sensitivity studies of a non-return wind tunnel with a 216- by 432-mm (8.5- by 17.0-inches) test section, phase 2

The refinement of inlet and exit treatments were studied which would minimize the effect of external wind on the test-section flow quality of a nonreturn wind tunnel. The investigation was conducted in the Ames Research Center 40- by 80-foot Wind Tunnel which served as the wind source. Several inlets and two exits were tested at wind directions ranging from 0 to 180 degrees and at wind-to-test-section velocity ratios from zero to somewhat greater than one. For the best inlet configuration the flow quality was good, with a velocity deviation in each of the three component directions generally less. The loss in total pressure due to the inlet treatment was low: about 0.035 of the test-section dynamic pressure for the no-wind case.

Eckert, W. T.↗
NASA NTRS1979

Wind tunnel performance of four energy efficient propellers designed for Mach 0.8 cruise

Several advanced aerodynamic and acoustic concepts were investigated in recent wind tunnel tests performed in the NASA-Lewis Research Center 8x6 foot wind tunnel. These concepts included aerodynamically integrated propeller/nacelles, area-ruling, blade sweep, reduced blade thickness, and power (disk) loadings several times higher than conventional designs. Four eight-bladed propeller models were tested to determine aerodynamic performance. Relative noise measurements were made on three of the models at cruise conditions. Three of the models were designed with swept blades and one with straight blades. At the design Mach number of 0.8, power coefficient of 1.7, and advance ratio of 3.06, the straight bladed model had the lowest net efficiency of 75.8 percent. Increasing the sweep to 30 deg improved the performance to near 77 percent. Installation of an area-ruled spinner on a 30 deg sweep model further improved the efficiency to about 78 percent. The model with the highest blade sweep (45 deg) and an area-ruled spinner had the highest net efficiency of 78.7 percent, and at lower power loadings the efficiency exceeded 80 percent. At lower Mach numbers the 30 deg swept model had the highest efficiency. Values near 81 percent were obtained for the design loading at speeds to Mach 0.7. Relative noise measurements indicated that the acoustically designed 45 deg sweep model reduced the near field cruise noise by between 5 and 6 dB.

Jeracki, R. J.↗
NASA NTRS1972

Wind sensitivity studies of a non-return wind tunnel, with a 216- by 432-mm (8.5- by 17.0-inch) test section, phase 1

The study to develop inlet and exit treatments which would minimize the effect of external wind on the test-section flow quality of a nonreturn wind tunnel is reported. The investigation was conducted in the Ames Research Center 40- by 80-Foot Wind Tunnel which served as the wind source. Several inlets and two exits were tested at wind directions ranging from 0 to 180 degrees and at wind-to-test-section velocity ratios between zero and one. For the best inlet configuration the flow quality was good, with a velocity deviation in each of the three directions generally less than 1/2 knot (0.26 m/sec) for wind velocities of 15 knots (7.7 m/sec) or less. The loss in total pressure due to the inlet treatment was low: about 0.03 of the test-section dynamic pressure.

Eckert, W. T.↗
NASA NTRS1922

The Efficiency of a Wind Tunnel

If, by some means, a steady state of motion of a perfect fluid were established in an ideal wind tunnel, there would be no losses, and the motion would persist indefinitely. In the actual tunnel, the function of the motor-fan group is overcome by the total loss of head in the tube due to friction and eddies.

WIND TUNNELS - EFFICIENCY↗
NASA NTRS1978

Mean velocity, turbulence intensity and turbulence convection velocity measurements for a convergent nozzle in a free jet wind tunnel

The effect of light on the mean flow and turbulence properties of a 0.056 m circular jet were determined in a free jet wind tunnel. The nozzle exit velocity was 122 m/sec, and the wind tunnel velocity was set at 0, 12, 37, and 61 m/sec. Measurements of flow properties including mean velocity, turbulence intensity and spectra, and eddy convection velocity were carried out using two linearized hot wire anemometers. Normalization factors were determined for the mean velocity and turbulence convection velocity.

Mccolgan, C. J.↗