Engineering topics

Meyn, Larry A.

Publications and source records attributed to Meyn, Larry A..

25 records · Page 2

NASA NTRS1992

Forebody flow control on a full-scale F/A-18 aircraft

A full-scale F/A-18 was tested in the 80- by 120-Foot Wind Tunnel at NASA Ames Research Center to measure the effectiveness of pneumatic forebody vortex control devices. By altering the forebody vortex flow, yaw control can be maintained to angles of attack greater than 50 deg. Two forebody vortex control devices were tested: a discrete circular jet and a tangential slot. The tests were conducted for angles of attack between 25 and 50 deg, and angles of sideslip from 0 to +/- 15 deg. The Reynolds number based on wing mean aerodynamic chord ranged from 4.5 x 10 exp 6 to 12.0 x 10 exp 6. The time-averaged side forces and yawing moments, along with both time-averaged and time-dependent pressures on the forebody of the aircraft are presented here for various configurations. Of particular interest was the results that the tangential slot blowing had a greater effect on the yawing moment than the discrete circular jet. Additionally, it was found that blowing very close to the radome apex was not as effective as blowing slightly farther aft on the radome, and that a 16-inch slot was more effective than either an 8- or 48-inch long slot.

Lanser, Wendy R.↗

NASA NTRS1992

Full-scale high angle-of-attack tests of an F/A-18

This paper presents an overview of high angle-of-attack tests of a full-scale F/A-18 in the 80- by 120-Foot Wind Tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center at Moffett Field, California. A production aircraft was tested over an angle-of-attack range of 18 to 50 deg and at wind speeds of up to 100 knots. These tests had three primary test objectives. Pneumatic and mechanical forebody flow control devices were tested at full-scale and shown to produce significant yawing moments for lateral control of the aircraft at high angles of attack. Mass flow requirements for the pneumatic system were found to scale with freestream density and speed rather than freestream dynamic pressure. Detailed measurements of the pressures buffeting the vertical tail were made and spatial variations in the buffeting frequency were found. The LEX fence was found to have a significant effect on the frequency distribution on the outboard surface of the vertical fin. In addition to the above measurements, an extensive set of data was acquired for the validation of computational fluid dynamics codes and for comparison with flight test and small-scale wind tunnel test results.

Meyn, Larry A.↗

NASA NTRS1992

Analysis of a pneumatic forebody flow control concept about a full aircraft geometry

A full aircraft geometry is used to computationally analyze the effectiveness of a pneumatic forebody flow control concept. An overset grid technique is employed to model the aircraft and slot geometry. Steady-state solutions for both isolated forebody and full aircraft configurations are carried out using a thin-layer Navier-Stokes flow solver. A solution obtained using the full aircraft geometry and a flight sideslip condition investigates the effect of sideslip on the leading edge extention vortex burst point. A no-sideslip blowing solution using the isolated forebody at full-scale wind tunnel test conditions is compared with experimental data to determine the accuracy of the numerical method. A solution employing the full geometry and slot blowing at flight conditions is obtained.

Gee, Ken↗

NASA NTRS1991

A two camera video imaging system with application to parafoil angle of attack measurements

This paper describes the development of a two-camera, video imaging system for the determination of three-dimensional spatial coordinates from stereo images. This system successfully measured angle of attack at several span-wise locations for large-scale parafoils tested in the NASA Ames 80- by 120-Foot Wind Tunnel. Measurement uncertainty for angle of attack was less than 0.6 deg. The stereo ranging system was the primary source for angle of attack measurements since inclinometers sewn into the fabric ribs of the parafoils had unknown angle offsets acquired during installation. This paper includes discussions of the basic theory and operation of the stereo ranging system, system measurement uncertainty, experimental set-up, calibration results, and test results. Planned improvements and enhancements to the system are also discussed.

Meyn, Larry A.↗

NASA NTRS1990

Experimental studies of 90 deg corner cascades in the National Full-Scale Aerodynamic Complex

Two 90 deg, fixed geometry, turning vane cascades were replaced in the 40- by 80-foot wind tunnel circuit of the National Full-Scale Aerodynamic Complex as a part of a major facility upgrade. Prior to the replacement of these vanes, small-scale, two-dimensional tests were conducted to assess the aerodynamic performance of the original, 1930's technology vane geometry and a new vane geometry which was developed using a modern cascade design code. The small scale tests were conducted in the 1/10th-Scale Cascade Test Facility and included measurements of total pressure, static pressure, and flow angularity distributions in the wake of the cascade and static pressure distributions along the vane profiles. Test results and a detailed comparison of the two vanes designs are presented. Based on these results, the new design was chosen and subsequently installed in the wind tunnel. During the integrated systems test of the upgraded facility, two of the 52 vanes in the first cascade were instrumented near midspan. The full-scale test results are presented, these show the cascade pressure loss coefficient to be slightly larger than obtained in the small-scale tests. Elements of the three-dimensional flow field upstream of the cascade, which effect can impact cascade performance, are discussed and recommendations for future research are given.

Meyn, Larry A.↗

NASA NTRS1986

Optimum full-scale subsonic wind tunnel

The needs and reasons for performing full-scale subsonic research have been studied. Full-scale wind-tunnel requirements are described; recommended size, airspeed, acoustic capabilities, and flow quality are developed; and data-acquisition systems, productivity, automation, and some cost elements are discussed. It is proposed that the optimum full-scale, subsonic wind tunnel be large enough to accommodate aerodynamic and acoustic investigations on most advanced aircraft, which exhibit complex engine/lifting-surface flow-field interactions, including advanced rotorcraft.

Mort, K. W.↗

NASA NTRS1986

A new design concept for indraft wind-tunnel inlets with application to the national full-scale aerodynamic complex

The present inlet design concept for an indraft wind tunnel, which is especially suited to applications for which a specific test section flow quality is required with minimum inlet size, employs a cascade or vaneset to control flow at the inlet plane, so that test section total pressure variation is minimized. Potential flow panel methods, together with empirical pressure loss predictions, are used to predict inlet cascade performance. This concept has been used to develop an alternative inlet design for the 80 x 120-ft wind tunnel at NASA Ames Research Center. Experimental results show that a short length/diameter ratio wind tunnel inlet furnishing atmospheric wind isolation and uniform test section flow can be designed.

Ross, James C.↗