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  • 1
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    Wind tunnel measurements on a full-scale F/A-18 with a tangentially blowing slot (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: 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 a tangentially blowing slot in generating significant yawing moments while minimizing coupling in the pitch and roll axes. Various slot configurations were tested to determine the optimum configuration. The test was conducted for angles of attack from 25 to 50 deg, angles of sideslip from -15 to +15 deg, and freestream velocities from 67 ft/sec to 168 ft/sec. By altering the forebody vortex flow, yaw control was maintained for angles of attack up to 50 deg. Of particular interest was the result that blowing very close to the radome apex was not as effective as blowing slightly farther aft on the radome, that a 16-inch slot was more efficient, and that yawing moments were generated without inducing significant rolling or pitching moments.
    Keywords: AERODYNAMICS
    Type: 1993 Technical Paper Contest for Women. Gear Up 2000: Women in Motion; p 27-36
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  • 2
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    Comparison of full-scale, small-scale, and CFD results for F/A-18 forebody slot blowing (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It has been shown experimentally that forebody flow control devices provide a significant increase in yaw control for fighter aircraft at high angle-of-attack. This study presents comparisons of the various experimental and computational results for tangential slot blowing on the F/A-18 configuration. Experimental results are from the full-scale and 6 percent-scale model test and computational solutions are from both isolated forebody and and full aircraft configurations. The emphasis is on identifying trends in the variation of yawing moment with blowing-slot exit conditions. None of the traditional parameters (mass flow ratio, blowing momentum coefficient, velocity ratio) succeeded in collapsing all of the results into a common curve. Several factors may effect the agreement between the 6 percent- and full-scale results including Reynolds number effects, sensitivity of boundary layer transition from laminar to turbulent flow, and poor geometric fidelity, particularly of the blowing slot. The disagreement between the full-scale and computed yawing moments may be due to a mismatch in the slot exit conditions for the same mass flow ratio or aircraft configuration modeling. The general behavior of slot blowing on the 6 percent-scale and computational models is correct, but neither matches the full-scale results.
    Keywords: AERODYNAMICS
    Type: NASA. Dryden Flight Research Center, Fourth High Alpha Conference, Volume 3; 19 p
    Format: application/pdf
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  • 3
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    Flight and full-scale wind-tunnel comparison of pressure distributions from an F-18 aircraft at high angles of attack (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Pressure distributions were obtained at nearly identical fuselage stations and wing chord butt lines in flight on the F-18 HARV at NASA Dryden Flight Research Center and in the NASA Ames Research Center's 80 by 120 ft wind tunnel on a full-scale F/A-18 aircraft. The static pressures were measured at the identical five stations on the forebody, three stations on the left and right leading-edge extensions, and three spanwise stations on the wing. Comparisons of the flight and wind-tunnel pressure distributions were made at alpha = 30 deg, 45 deg, and 60 deg/59 deg. In general, very good agreement was found. Minor differences were noted at the forebody at alpha = 45 deg and 60 deg in the magnitude of the vortex footprints and a Mach number effect was noted at the leading-edge extension at alpha = 30 deg. The inboard leading edge flap data from the wind tunnel at alpha = 59 deg showed a suction peak that did not appear in the flight data. This was the result of a vortex from the corner of the leading edge flap whose path was altered by the lack of an engine simulation in the wind tunnel.
    Keywords: AERODYNAMICS
    Type: Fourth High Alpha Conference, Volume 1 20 p(SEE N95-14229 03-02); Fourth High Alpha Co
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  • 4
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    High Alpha Technology Program (HATP) ground test to flight comparisons (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This status paper reviews the experimental ground test program of the High Alpha Technology Program (HATP). The reasons for conducting this ground test program had their origins during the 1970's when several difficulties were experienced during the development programs of both the F-18 and F-16. A careful assessment of ground test to flight correlations appeared to be important for reestablishing a high degree of confidence in our ground test methodology. The current paper will then focus on one aspect of the HATP program that is intended to improve the correlation between ground test and flight, high-alpha gritting. The importance of this work arises from the sensitivity of configurations with smooth-sided forebodies to Reynolds number. After giving examples of the effects of Reynolds number, the paper will highlight efforts at forebody gritting. Finally, the paper will conclude by summarizing the charter of the HATP Experimental Aerodynamics Working Group and future experimental testing plans.
    Keywords: AERODYNAMICS
    Type: NASA. Dryden Flight Research Center, Fourth High Alpha Conference, Volume 1; 25 p
    Format: application/pdf
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  • 5
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    Effect of Actuated Forebody Strakes on the Forebody Aerodynamics of the NASA F-18 HARV (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Extensive pressure measurements and off-surface flow visualization were obtained on the forebody and strakes of the NASA F-18 High Alpha Research Vehicle (HARV) equipped with actuated forebody strakes. Forebody yawing moments were obtained by integrating the circumferential pressures on the forebody and strakes. Results show that large yawing moments can be generated with forebody strakes. At angles of attack greater than 40 deg., deflecting one strake at a time resulted in a forebody yawing moment control reversal for small strake deflection angles. At alpha = 40 deg. and 50 deg., deflecting the strakes differentially about a 20 deg. symmetric strake deployment eliminated the control reversal and produced a near linear variation of forebody yawing moment with differential strake deflection. At alpha = 50 deg. and for 0 deg. and 20 deg. symmetric strake deployments, a larger forebody yawing moment was generated by the forward fuselage (between the radome and the apex of the leading-edge extensions), than on the radome where the actuated forebody strakes were located. Cutouts on the flight vehicle strakes that were not on the wind tunnel models are believed to be responsible for deficits in the suction peaks on the flight radome pressure distributions and differences in the forebody yawing moments.
    Keywords: Aerodynamics
    Type: NASA-TM-4774 , H-2136 , NAS 1.15:4774
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  • 6
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    Aerodynamic performance of a drag reduction device on a full-scale tractor/trailer (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effectiveness of an aerodynamic boattail on a tractor/trailer road vehicle was measured in the NASA Ames Research Center 80- by 120-Foot Wind Tunnel. Results are examined for the tractor/trailer with and without the drag reduction device. Pressure measurements and flow visualization show that the aerodynamic boattail traps a vortex or eddy in the corner formed between the device and the rear corner of the trailer. This recirculating flow turns the flow inward as it separates from the edges of the base of the trailer. This modified flow behavior increases the pressure acting over the base area of the truck, thereby reducing the net aerodynamic drag of the vehicle. Drag measurements and pressure distributions in the region of the boattail device are presented for selected configurations. The optimum configuration reduces the overall drag of the tractor/trailer combination by about 10 percent at a zero yaw angle. Unsteady pressure measurements do not indicate strong vortex shedding, although the addition of the boattail plates increases high frequency content of the fluctuating pressure.
    Keywords: ENGINEERING (GENERAL)
    Type: SAE PAPER 912125
    Format: text
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  • 7
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    Full-scale high angle-of-attack tests of an F/A-18 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2676
    Format: text
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  • 8
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    Forebody flow control on a full-scale F/A-18 aircraft (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2674
    Format: text
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  • 9
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    Wind Tunnel Visualization of the Flow Over a Full-Scale F/A-18 Aircraft (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The proposed paper presents flow visualization performed during experiments conducted on a full-scale F/A-18 aircraft in the 80- by 120-Foot Wind-Tunnel at NASA Ames Research Center. This investigation used both surface and off-surface flow visualization techniques to examine the flow field on the forebody, canopy, leading edge extensions (LEXs), and wings. The various techniques used to visualize the flow field were fluorescent tufts, flow cones treated with reflective material, smoke in combination with a laser light sheet, and a video imaging system. The flow visualization experiments were conducted over an angle of attack range from 20deg to 45deg and over a sideslip range from -10deg to 10deg. The results show regions of attached and separated flow on the forebody, canopy, and wings. Additionally, the vortical flow is clearly visible over the leading-edge extensions, canopy, and wings.
    Keywords: Aerodynamics
    Type: SAE Aerospace Atlantic Conference; Apr 18, 1994 - Apr 22, 1994; Dayton, OH; United States
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  • 10
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    Wind tunnel measurements on a full-scale F/A-18 with forebody slot blowing or forebody strakes (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Results are presented of tests, conducted on a full-scale F/A-18 in the 120-Foot Wind Tunnel at NASA Ames Research Center, to measure the effectiveness of a 16-in.-long tangentially blown slot and of deployable strakes (measuring 4 ft in length) positioned on the aircraft's forebody. Fixed strakes with deflections of 30, 60, or 90 deg were tested to simulate the deployment of conformal actuated forebody strakes. It is shown that both the tangentially blown slot and the deployable strakes are effective in generating large yawing momemts at high angles of attack, without inducing significant coupling in the other axes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-1018 , AIAA, AHS, and ASEE, Aerospace Design Conference; Feb 16, 1993 - Feb 19, 1993; Irvine, CA; United States|; 13 p.
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