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  • 1
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    F/A-18 forebody vortex control. Volume 1: Static tests (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A wind tunnel test was conducted on a six percent model of the F/A-18 at the NASA Ames 7 X 10-Foot Low Speed Wind Tunnel. The primary objective of the test was to evaluate several forebody vortex control configurations at high angles of attack in order to determine the most effective method of obtaining well behaved yawing moments, in preparation for the rotary balance test. Both mechanical and pneumatic systems were tested. Single and dual rotating nose tip strakes and a vertical nose strake were tested at different sizes and deflections. A series of jet blowing configurations were located at various fuselage stations, azimuth angles, and pointing angles ranging from straight aft to 60 deg canted inboard. Slot blowing was investigated for several slot lengths and fuselage stations. The effect of blowing rate was tested for both of these pneumatic systems. The most effective configurations were then further tested with a variation of both sideslip angle and Reynolds number over a range of angles of attack from 0 to 60 deg. It was found that a very robust system can be developed that provides yawing moments at angles of attack up to 60 deg that significantly exceeds that available from 30 deg of rudder deflection (F/A-18 maximum) at 0 deg angle of attack.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4582-VOL-1 , A-94056-VOL-1 , NAS 1.26:4582-VOL-1
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  • 2
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    Forebody vortex control on an F/A-18 using small, rotatable 'tip-strakes' (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A mechanical scheme for manipulating the forebody vortices of an F/A-18, therefore creating controlled yawing moments at moderate and high angles of attack, was investigated in a wind tunnel. The technique consists of rotating miniature strakes (single or dual) about the radome centerline very close to the tip of the model. Forces, moments, and pressures were measured for angles of attack up to 60 deg and sideslip angles up to -10 deg. Results indicate that single and dual strakes can produce changes in side force and yawing moment, with magnitudes comparable to, or in some cases higher than, the directional changes produced by a 30-deg rudder deflection at 0-deg angle of attack. According to its circumferential position, the strake alters the separation location, inducing different degrees of asymmetry in the forebody vortex flow field that are translated into changes in side force and yawing moment. In comparison, the dual strakes appear to provide more gradual and better behaved changes than the single strake. Excellent correlation was found between this test and water tunnel tests performed on a similar configuration.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 93-3450 , In: AIAA Applied Aerodynamics Conference, 11th, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 1 (A93-47201 19-02); p. 398-408.
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  • 3
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    Forebody vortex control with jet and slot blowing on an F/A-18 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A wind tunnel test program was conducted in October, 1992, on a 6-percent F/A-18 model, to determine the most effective methods of forebody vortex control for providing increased yaw control at high angles of attack. A series of circular jet blowing configurations were investigated with variations in blowing rate, fuselage station, circumferential position, and blowing angle. Slot configurations were also tested and included variations in blowing rate, forward fuselage station, and length. The optimum jet and slot configurations were then also tested at -10 deg of sideslip. Yawing moments from both the jet and slot blowing configurations were found to have very good trends with increasing blowing rates and the maximum yaw control available at 50-deg angle of attack (where rudder power had dropped to near zero) was found to be 40 percent greater than the level provided by the rudder at 0-deg angle of attack.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 93-3449 , In: AIAA Applied Aerodynamics Conference, 11th, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 1 (A93-47201 19-02); p. 387-397.
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  • 4
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    Development of a multicomponent force and moment balance for water tunnel applications, volume 1 (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. An internal balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The five-components to applied loads, low interactions between the sections and no hysteresis. Static experiments (which are discussed in this Volume) were conducted in the Eidetics water tunnel with delta wings and a model of the F/A-18. Experiments with the F/A-18 model included a thorough baseline study and investigations of the effect of control surface deflections and of several Forebody Vortex Control (FVC) techniques. Results were compared to wind tunnel data and, in general, the agreement is very satisfactory. The results of the static tests provide confidence that loads can be measured accurately in the water tunnel with a relatively simple multicomponent internal balance. Dynamic experiments were also performed using the balance, and the results are discussed in detail in Volume 2 of this report.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-4642-VOL-1 , H-2030-VOL-1 , NAS 1.26:4642-VOL-1
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  • 5
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    Development of a multicomponent force and moment balance for water tunnel applications, volume 2 (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. Static experiments (which are discussed in Volume 1 of this report) were conducted, and the results showed good agreement with wind tunnel data on similar configurations. Dynamic experiments, which are the main topic of this Volume, were also performed using the balance. Delta wing models and two F/A-18 models were utilized in a variety of dynamic tests. This investigation showed that, as expected, the values of the inertial tares are very small due to the low rotating rates required in a low-speed water tunnel and can, therefore, be ignored. Oscillations in pitch, yaw and roll showed hysteresis loops that compared favorably to data from dynamic wind tunnel experiments. Pitch-up and hold maneuvers revealed the long persistence, or time-lags, of some of the force components in response to the motion. Rotary-balance experiments were also successfully performed. The good results obtained in these dynamic experiments bring a whole new dimension to water tunnel testing and emphasize the importance of having the capability to perform simultaneous flow visualization and force/moment measurements during dynamic situations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-4642-VOL-2 , H-2030-VOL-2 , NAS 1.26:4642-VOL-2
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  • 6
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    F/A-18 forebody vortex control. Volume 2: Rotary-balance tests (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A rotary-balance wind tunnel test was conducted on a six percent model of the F/A-18 at the NASA Ames 7 X 10-Foot Low Speed Wind Tunnel. The data reduction was specially written for the test in National Instruments' LabVIEW. The data acquisition, reduction and analysis was performed with a Macintosh computer. The primary objective of the test was to evaluate the effectiveness of several forebody vortex control configurations in a rotary flow field. The devices that were found to be the most effective during the static tests (Volume 1) were investigated and included both mechanical and pneumatic configurations. The mechanical systems evaluated were small, single and dual, rotating nose tip strakes and a vertical nose strake. The jet blowing configuration used nozzles canted inboard 60 degrees. A two segment tangential slot was also evaluated. The different techniques were evaluated at angles of attack of 30 degrees, 45 degrees, 51 degrees, and 60 degrees. Sideslip and Reynolds number were varied for some of the configurations. All of the techniques proved to be effective in the rotating flow field. The vertical nose strake had the largest 'envelope' of effectiveness. Forebody vortex control provides large, robust yawing moments at medium to high angles of attack, even during combat maneuvers such as loaded roll.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4582-VOL-2 , A-94055-VOL-2 , NAS 1.26:4582-VOL-2
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  • 7
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    Aerodynamic control of NASP-type vehicles through vortex manipulation. Volume 3: Wing rock experiments (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Free-to-roll tests were conducted in water and wind tunnels in an effort to investigate the mechanisms of wing rock on a NASP-type vehicle. The configuration tested consisted of a highly-slender forebody and a 78 deg swept delta wing. In the water tunnel test, extensive flow visualization was performed and roll angle histories were obtained. In the wind tunnel test, the roll angle, forces and moments, and limited forebody and wing surface pressures were measured during the wing rock motion. A limit cycle oscillation was observed for angles of attack between 22 deg and 30 deg. In general, the experiments confirmed that the main flow phenomena responsible for the wing-body-tail wing rock are the interactions between the forebody and the wing vortices. The variation of roll acceleration (determined from the second derivative of the roll angle time history) with roll angle clearly slowed the energy balance necessary to sustain the limit cycle oscillation. Different means of suppressing wing rock by controlling the forebody vortices using small blowing jets were also explored. Steady blowing was found to be capable of suppressing wing rock, but significant vortex asymmetrices are created, causing the model to stop at a non-zero roll angle. On the other hand, alternating pulsed blowing on the left and right sides of the fore body was demonstrated to be a potentially effective means of suppressing wing rock and eliminating large asymmetric moments at high angles of attack.
    Keywords: AERODYNAMICS
    Type: NASA-CR-177626 , A-93138 , NAS 1.26:177626
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  • 8
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    Aerodynamic control of NASP-type vehicles through Vortex manipulation. Volume 2: Static wind tunnel tests (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Forebody Vortex Control (FVC) was explored in this research program for potential application to a NASP-type configuration. Wind tunnel tests were conducted to evaluate a number of jet blowing schemes. The configuration tested has a slender forebody and a 78 deg swept delta wing. Blowing jets were implemented on the leeward side of the forebody with small circular tubes tangential to the surface that could be directed aft, forward, or at angles in between. The effects of blowing are observed primarily in the yawing and rolling moments and are highly dependent on the jet configuration and the angle of attack. Results show that the baseline flow field, without blowing activated, is quite sensitive to the geometry differences of the various protruding jets, as well as being sensitive to the blowing, particularly in the angle of attack range where the forebody vortices are naturally asymmetric. The time lag of the flow field response to the initiation of blowing was also measured. The time response was very short, on the order of the time required for the flow disturbance to travel the distance from the nozzle to the specific airframe location of interest at the free stream velocity. Overall, results indicate that sizable yawing and rolling moments can be induced with modest blowing levels. However, direct application of this technique on a very slender forebody would require thorough wind tunnel testing to optimize the jet location and configuration.
    Keywords: AERODYNAMICS
    Type: NASA-CR-177626-VOL-2 , A-93138-VOL-2 , NAS 1.26:177626-VOL-2
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  • 9
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    Reduction of Aircraft Cruise Drag By Using Boundary Layer Heating To Minimize Fuselage Skin Friction (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The data reduction and results of the F-15B Flight Test Fixture experiment conducted at NASA Dryden are discussed. In addition, the feasibility of using the Orbital Sciences L-1011 was studied and a cost estimate prepared. Initial discussions have begun with Edwards Flight Research to explore the possibility of using their T-39 aircraft for the second flight experiment.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/CR-97-206450 , NAS 1.26:206450
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  • 10
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    Forebody vortex control for suppressing wing rock on a highly-swept wing configuration (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Free-to-roll tests were conducted in a wind tunnel with a configuration that consisted of a highly-slender forebody and a 78 deg swept delta wing. A limit cycle oscillation was observed for angles of attack between 22 and 30 deg. In general, the main flow phenomena responsible for the wing-body-tail wing rock are the interactions between the forebody and the wing vortices. Various blowing techniques were evaluated as means of wing rock suppression. Blowing tangentially aft from leeward side nozzles near the forebody tip can damp the roll motion at low blowing rates and stop it completely at higher blowing rates. At the high rates, significant vortex asymmetries are created, causing the model to stop at a non-zero roll angle. Forward blowing and alternating right/left pulsed blowing appear to be more efficient techniques for suppressing wing rock. The oscillations can be damped almost completely at lower blowing coefficients, and, apparently, no major vortex asymmetries are induced. Good agreement is observed between this study and previous water tunnel tests on the same configuration.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2716 , AIAA Applied Aerodynamics Conference; Jun 22, 1992 - Jun 24, 1992; Palo Alto, CA; United States
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