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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Applications of adaptive-wall wind tunnels

A novel processing technique for the flowfield data generated by an adaptive wall wind tunnel is presented whose basic premise is the possible undesirability of forcing such a wind tunnel to simulate free-air conditions. The concept of a 'phantom' wind tunnel is introduced for both two- and three-dimensional wind tunnels, yielding a continuous spectrum of flow fields, ranging from the original passive and ventilated configuration to a fully adaptive one. In order to implement these procedures, active control is limited to floor and ceiling surfaces.

Davis, S. S.↗
NASA NTRS1975

An experimental study of several wind tunnel wall configurations using two V/STOL model configurations

Experiments were conducted in the low speed wind tunnel using two V/STOL models, a jet-flap and a jet-in-fuselage configuration, to search for a wind tunnel wall configuration to minimize wall interference on V/STOL models. Data were also obtained on the jet-flap model with a uniform slotted wall configuration to provide comparisons between theoretical and experimental wall interference. A test section configuration was found which provided some data in reasonable agreement with interference-free results over a wide range of momentum coefficients.

Binion, T. W., Jr.↗
NASA NTRS1987

Evaluation of influence coefficient matrices for an adaptive-wall wind tunnel and applications to one-step convergence scheme

Within the framework of ventilated adaptive-wall wind tunnel testing, experiments were conducted to evaluate the influence coefficients from the side-wall pressure distribution, the streamwise velocity distribution, and the vertical velocity distribution on two control surfaces. Consideration is given to the effects of Mach number, superposition, suction, blowing, and the presence of a nonlifting model. It is shown that a single-step convergence scheme reduces the testing time by eliminating the intermediate experimental iterations; however, its success depends on the accuracy of the influence coefficients.

Celik, Z. Z.↗
NASA NTRS1983

Experiments in a three-dimensional adaptive-wall wind tunnel

Three dimensional adaptive-wall experiments were performed in the Ames Research Center (ARC) 25- by 13-cm indraft wind tunnel. A semispan wing model was mounted to one sidewall of a test section with solid sidewalls, and slotted top and bottom walls. The test section had separate top and bottom plenums which were divided into streamwise and cross-stream compartments. An iterative procedure was demonstrated for measuring wall interference and for adjusting the plenum compartment pressures to eliminate such interference. The experiments were conducted at a freestream Mach number of 0.60 and model angles of attack between 0 and 6 deg. Although in all the experiments wall interference was reduced after the plenum pressures were adjusted, interference could not be completely eliminated.

Schairer, E. T.↗
NASA NTRS1984

The influence of wind-tunnel walls on discrete frequency noise

This paper describes an analytical model that can be used to examine the effects of wind-tunnel walls on discrete frequency noise. First, a complete physical model of an acoustic source in a wind tunnel is described, and a simplified version is then developed. This simplified model retains the important physical processes involved, yet it is more amenable to analysis. Second, the simplified physical model is formulated as a mathematical problem. An inhomogeneous partial differential equation with mixed boundary conditions is set up and then transformed into an integral equation. The integral equation has been solved with a panel program on a computer. Preliminary results from a simple model problem will be shown and compared with the approximate analytic solution.

Mosher, M.↗
NASA NTRS1976

Report on the status of a slotted wind tunnel wall representation using the vortex-lattice technique

A combined analytical/experimental program for development of an improved slotted wind-tunnel wall representation is described. The effort is scheduled for completion in 1977. The vortex-lattice technique which is being used as the primary analytical tool for representing both the wind-tunnel and the lifting model is discussed. Comparisons of results obtained to date with available data are presented.

Heltsley, F. L.↗
NASA NTRS1988

Velocity profile similarity for viscous flow development along a longitudinally slotted wind-tunnel wall

A discussion of the flow field measurements on the slot centerline of two different longitudinally slotted wind-tunnel walls is presented. The longitudinal and transverse components of these data are then transformed using the concept of flow similarity to demonstrate the applicability of the technique to the development of the viscous shear flow along and through a slotted wall. Results are presented showing the performance of the similarity transformations with variations in tunnel station, Mach number, and airfoil-induced curvature of the tunnel free stream.

Everhart, Joel L.↗
NASA NTRS1977

An experimental investigation of boundary layer and crossflow characteristics of the Ames 2 by 2 foot and 11 by 11 foot transonic wind-tunnel walls

The boundary layer and crossflow characteristics of 2- by 2-foot and 11- by 11-foot transonic wind-tunnel wall configurations have been studied for Mach numbers ranging from 0.5 to 1.2 and for various crossflow to free stream unit mass flow ratios. For the 2- by 2-ft and 11- by 11-ft wall configurations, these ratios ranged from 0 to 0.12 and from 0 to 0.07, respectively. Most notably, for both wall configurations, the pressure-drop coefficient across the wall was nonlinear with mass flow and invariant with Mach number.

Matyk, G.↗
NASA NTRS1981

A compatibility assessment method for adaptive-wall wind tunnels

A new method is described for assessing the compatibility between inner and outer flow regimes in adaptive-wall wind tunnels. The method is applicable to both two- and three-dimensional flows, and unlike other schemes, requires the measurement of only one velocity component. Moreover, a complete solution to the outer flowfield is not required with the new method. Computer simulations of two- and three-dimensional flows are presented along with data from a two-dimensional pilot wind tunnel test using the new method.

Davis, S. S.↗
NASA NTRS1953

Considerations on the effect of wind-tunnel walls on oscillating air forces for two-dimensional subsonic compressible flow

This report treats the effect of wind-tunnel walls on the oscillating two-dimensional air forces in a compressible medium. The walls are simulated by the usual method of placing images at appropriate distances above and below the wing. An important result shown is that, for certain conditions of wing frequency, tunnel height, and Mach number, the tunnel and wing may form a resonant system so that the forces on the wing are greatly changed from the condition of no tunnel walls. It is pointed out that similar conditions exist for three-dimensional flow in circular and rectangular tunnels and apparently, within certain Mach number ranges, in tunnels of nonuniform cross section or even in open tunnels or jets.

Runyan, Harry L↗
NASA NTRS1991

Mass flux similarity for slotted transonic-wind-tunnel walls

A discussion of the flow field measurements obtained in the vertical plane at several stations along the centerline of slots in two different longitudinally slotted wind tunnel walls is presented. The longitudinal and transverse components of the data are then transformed using the concept of flow similarity to demonstrate the applicability of the technique to the development of the viscous shear flow along and through a slotted wall of an airfoil tunnel. Results are presented showing the performance of the similarity transformations with variations in tunnel station, Mach number, and airfoil induced curvature of the tunnel free stream.

Everhart, Joel L.↗
NASA NTRS1986

Development of an impulsive noise source to study the acoustic reflection characteristics of hard-walled wind tunnels

Two impulsive sound sources, one using multiple acoustic drivers and the other using a spark discharge were developed to study the acoustic reflection characteristics of hard-walled wind tunnels, and the results of laboratory tests are presented. The analysis indicates that though the intensity of the pulse generated by the spark source was higher than that obtained from the acoustic source, the number of averages needed for a particular test may require an unacceptibly long tunnel-run time due to the low spark generation repeat rate because of capacitor charging time. The additional hardware problems associated with the longevity of electrodes and electrode holders in sustaining the impact of repetitive spark discharges, show the multidriver acoustic source to be more suitable for this application.

Salikuddin, M.↗
NASA NTRS1981

A theory for predicting boundary impedance and resonance frequencies of slotted-wall wind tunnels, including plenum effects

Wave-induced resonance associated with the geometry of wind-tunnel test sections can occur. A theory that uses acoustic impedance concepts to predict resonance modes in a two dimensional, slotted wall wind tunnel with a plenum chamber is described. The equation derived is consistent with known results for limiting conditions. The computed resonance modes compare well with appropriate experimental data. When the theory is applied to perforated wall test sections, it predicts the experimentally observed closely spaced modes that occur when the wavelength is not long compared with he plenum depth.

Barger, R. L.↗
NASA NTRS1989

Wind tunnel wall interference investigations in NAE/NRC High Reynolds Number 2D Facility and NASA Langley 0.3m Transonic Cryogenic Tunnel

Results are reported from a NAE/NRC and NASA cooperative program on two-dimensional wind-tunnel wall-interference research, aimed at developing the technology for correcting or eliminating wall interference effects in two-dimensional transonic wind-tunnel investigations. Both NASA Langley and NAE facilities are described, along with a NASA-designed and fabricated airfoil model. It is shown that data from the NAE facility, corrected for wall interference, agree with those obtained from the NASA tunnel, which has adaptive walls; the comparison of surface pressure data shows that the flowfield conditions in which the model is investigated appear to be nearly identical under most conditions. It is concluded that both approaches, posttest correction and an adaptive wall, adequately eliminate the tunnel-wall interference effects.

Chan, Y. Y.↗
NASA NTRS1978

Transonic assessment of two-dimensional wind tunnel wall interference using measured wall pressures

A method is described for assessing wall interference in two dimensional wind tunnels with better realism and accuracy than is achieved with methods based on classical wall interference theory. Measured pressure distributions were imposed as boundary conditions on a nonlinear transonic form of the potential equation to obtain an accurate computational reproduction of the actual tunnel flow. Wall-induced velocity perturbations were then extracted to yield both corrections to the tunnel test conditions and a measure of the adequacy of these corrections to account for tunnel interference. Application of the method to a transonic tunnel with variable porosity walls is illustrated.

Kemp, W. B., Jr.↗
NASA NTRS1982

Wind-tunnel wall interference corrections for three-dimensional flows

A procedure for the evaluation of wall interference corrections for three-dimensional aircraft configurations is presented. The Mach number and angle-of-attack corrections are obtained by numerically solving the Laplace equation in a parallelepiped with boundary conditions supplied mainly from experimental pressure measurements. A portion of these measurements and other wind-tunnel data required by the procedure may be replaced by theoretical estimates if not available from experiments. The accuracy of the correction results will then depend on the accuracy of these estimates. The correction procedure is applied to an isolated wing and to a wing-tail configuration in a solid-wall wind tunnel. It is found that neglecting twist and camber corrections for the wing effectively increases the tail angle-of-attack correction. Two different Mach number corrections can be calculated for the wing and tail. However, since only one Mach number correction is allowed for both the wing and the tail, and since the wing surface area is larger than the tail surface area, the final correction tends to be closer to the required wing correction. This is a source of error for the tail results.

Rizk, M. H.↗