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Braden, J. A.

Publications and source records attributed to Braden, J. A..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Application of laser-velocimetry to the study of the flow around a two-dimensional airfoil

The experimental techniques employed by NASA researchers to obtain a high volume throughput of data in a study of high-lift multielement airfoils using a laser velocimeter (LV) are detailed. The two-dimensional LV system recorded mean velocity, turbulence intensities, Re shear stresses, skewness and kurtosis of the flow. A computer-controlled positioning mount for the LV allowed automated surveys of the flows with a 0.001 in. positioning accuracy. The flow was seeded with oil droplets and additional refinement of the wind tunnel controls permitted rapid speedup at selected areas of the flowfield over specific regions of the airfoil. Surface pressure taps furnished data for selecting regions for more detailed investigation. The data processing capabilities processed 30-40 samples every 10 min in an automated mode. Profiles of the data were computed automatically to furnish graphical displays on demand. Numerous samples of the data displays generated are provided.

Braden, J. A.↗
NASA NTRS1983

Experimental study of the separating confluent boundary-layer. Volume 2: Experimental data

An experimental low speed study of the separating confluent boundary layer on a NASA GAW-1 high lift airfoil is described. The airfoil was tested in a variety of high lift configurations comprised of leading edge slat and trailing edge flap combinations. The primary test instrumentation was a two dimensional laser velocimeter (LV) system operating in a backscatter mode. Surface pressures and corresponding LV derived boundary layer profiles are given in terms of velocity components, turbulence intensities and Reynolds shear stresses as characterizing confluent boundary layer behavior up to and beyond stall. LV derived profiles and associated boundary layer parameters and those obtained from more conventional instrumentation such as pitot static transverse, Preston tube measurements and hot-wire surveys are compared.

Braden, J. A.↗
NASA NTRS1982

Laser velocimeter applications to high-lift research

The application of the Lockheed-Georgia 2-D laser velocimeter (LV) burst-counter system to the flow field around a 2- and 3-element high-lift airfoil is discussed. The characteristic behavior of the confluent boundary layer (that is, the boundary layer existing downstream of a slot as it approaches and undergoes separation is evaluated. In this application, the LV represents all ideal instruments for nonintrusively probing into the narrow slots and cove areas characterizing mechanical high-lift systems. The work is being performed in the Lockheed-Georgia 10 x 30-inch low-speed test facility using a 9-inch (basic) chord section of the general aviation GAW-1 airfoil. The LV system employs a 4-W argon laser and operates in an off-axis, backscatter mode with a focus length of about 30 inches. Smoke is used as the seeding medium and is injected downstream of the model such that particle uniformity and size are constant upon completion of the tunnel circuit into the test area. The LV system is fully automated by utilizing a MAC-16 minicomputer for positioning, data acquisition, and preliminary data reduction.

Whipkey, R. R.↗
NASA NTRS1980

Exploratory studies of the cruise performance of upper surface blown configurations

The data and major conclusions obtained from an experimental/analytical study of upper-surface blown (USB) configurations at cruise are summarized. The high-speed (subsonic) experimental work, studying the aerodynamic effects of wing-nacelle geometric variations, was conducted around semi-span model configurations composed of diversified, interchangeable components. Power simulation was provided by high pressure air ducted through closed forebody nacelles. Nozzle geometry was varied across size, exit aspect ratio, exit position and boattail angle. Both 3-D force and 2-D pressure measurements were obtained at cruise Mach numbers from 0.5 to 0.8 and at nozzle pressure ratios up to about 3.0. The experimental investigation was supported by an analytical synthesis of the system using a vortex lattice representation with first-order power effects. Results are also presented from a compatibility study in which a short-haul transport is designed on the basis of the aerodynamic findings in the experimental study as well as acoustical data obtained in a concurrent program. High-lift test data are used to substantiate the projected performance of the selected transport design.

Braden, J. A.↗
NASA NTRS1980

Exploratory studies of the cruise performance of upper surface blown configurations. Experimental program: Test facilities, model design instrumentation, and lowspeed, high-lift tests

The model hardware, test facilities and instrumentation utilized in an experimental study of upper surface blown configurations at cruise is described. The high speed (subsonic) experimental work, studying the aerodynamic effects of wing nacelle geometric variations, was conducted around semispan model configurations composed of diversified, interchangeable components. Power simulation was provided by high pressure air ducted through closed forebody nacelles. Nozzle geometry was varied across size, exit aspect ratio, exit position and boattail angle. Three dimensional force and two dimensional pressure measurements were obtained at cruise Mach numbers from 0.5 to 0.8 and at nozzle pressure ratios up to about 3.0. The experimental investigation was supported by an analytical synthesis of the system using a vortex lattice representation with first order power effects. Results are also presented from a compatibility study in which a short haul transport is designed on the basis of the aerodynamic findings in the experimental study as well as acoustical data obtained in a concurrent program. High lift test data are used to substantiate the projected performance of the selected transport design.

Braden, J. A.↗
NASA NTRS1979

Exploratory studies of the cruise performance of upper surface blown configuration: Experimental program, high-speed force tests

The work to develop a wing-nacelle arrangement to accommodate a wide range of upper surface blown configuration is reported. Pertinent model and installation details are described. Data of the effects of a wide range of nozzle geometric variations are presented. Nozzle aspect ratio, boattail angle, and chordwise position are among the parameters investigated. Straight and swept wing configurations were tested across a range of nozzle pressure ratios, lift coefficients, and Mach numbers.

Braden, J. A.↗
NASA NTRS1979

Exploratory studies of the cruise performance of upper surface blown configurations: Experimental program, high-speed pressure tests

Basic pressure data are presented which was obtained from an experimental study of upper-surface blown configurations at cruise. The high-speed (subsonic) experimental work, studying the aerodynamic effects of wing-nacelle geometric variations, was conducted around semi-span model configurations composed of diversified, interchangeable components. Power simulation was provided by high-pressure air ducted through closed forebody nacelles. Nozzle geometry was varied across size, exit aspect ratio, exit position and boattail angle. Both 3-D force and 2-D pressure measurements were obtained at cruise Mach numbers from 0.5 to 0.8 and at nozzle pressure ratios up to about 3.0. The experimental investigation was supported by an analytical synthesis of the system using a vortex lattice representation with first-order power effects. Results are also presented from a compatibility study in which a short-haul transport is designed on the basis of the aerodynamic findings in the experimental study as well as acoustical data obtained in a concurrent program. High-lift test data are used to substantiate the projected performance of the selected transport design.

Braden, J. A.↗
NASA NTRS1977

Upper surface blowing aerodynamic and acoustic characteristics

Aerodynamic performance at cruise, and noise effects due to variations in nacelle and wing geometry and mode of operation are studied using small aircraft models that simulate upper surface blowing (USB). At cruise speeds ranging from Mach .50 to Mach .82, the key determinants of drag/thrust penalties are found to be nozzle aspect ratio, boattailing angle, and chordwise position; number of nacelles; and streamlined versus symmetric configuration. Recommendations are made for obtaining favorable cruise configurations. The acoustic studies, which concentrate on the noise created by the jet exhaust flow and its interaction with wing and flap surfaces, isolate several important sources of USB noise, including nozzle shape, exit velocity, and impingement angle; flow pathlength; and flap angle and radius of curvature. Suggestions for lessening noise due to trailing edge flow velocity, flow pathlength, and flow spreading are given, though compromises between some design options may be necessary.

Ryle, D. M., Jr.↗
NASA NTRS1976

Cruise aerodynamics of USB nacelle/wing geometric variations

Experimental results are presented on aerodynamic effects of geometric variations in upper surface blown nacelle configurations at high speed cruise conditions. Test data include both force and pressure measurements on two and three dimensional models powered by upper surface blowing nacelles of varying geometries. Experimental results are provided on variations in nozzle aspect ratio, nozzle boattail angle, and multiple nacelle installations. The nacelles are ranked according to aerodynamic drag penalties as well as overall installed drag penalties. Sample effects and correlations are shown for data obtained with the pressure model.

Braden, J. A.↗
NASA NTRS1971

Mathematical model for two-dimensional multi-component airfoils in viscous flow.

A computerized analytical model of a multi-component airfoil in viscous, subsonic flow has been developed. The model, representing attached flow, defines viscous pressure distributions, lift, moments, and local boundary-layer properties on each element of an arbitrarily arranged slotted airfoil. The final viscous solution is obtained by an iterative technique for successively combining an inviscid solution with boundary-layer displacement thicknesses. Ordinary boundary-layers include laminar, transition, and turbulent types. A significant feature of the program is an analytical model representing the merging of the upper surface boundary layer with the slot efflux. Typical correlations with experiment are provided and program applications are discussed.

Stevens, W. A.↗