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  • 1
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    Forebody vortex control (1991)
    Elsevier
    Details
    Publication Date: 1991-01-01
    Print ISSN: 0376-0421
    Electronic ISSN: 1873-1724
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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    PAPER CURRENT
  • 2
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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
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Aerodynamic control using forebody strakes (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Aerodynamic control using a rotatable, miniature nose-tip strake system was investigated in a water tunnel with a forebody model. Flow visualization and yawing moment measurements were performed. The results show that the system was highly effective in controlling the forebody vortices and producing controlled yawing moments at moderate-to-high angles of attack. In comparison with the forebody strakes used in several previous studies, the system can potentially be substantially smaller in size, simpler in operation, and effective over wide ranges of angles of attack and sideslip.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0618
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Aerodynamic control using forebody blowing and suction (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Aerodynamic control using pneumatic forebody flow control was studied. Three methods of control were investigated: (1) blowing from a localized jet, (2) blowing from a slot, and (3) surface suction. Flow visualization and yawing moment measurements were performed on F/A-18 models in a water tunnel. The results show that all the methods were effective in controlling the forebody flow over a wide range of angles of attack and sideslip. The advantages and limitations of each of the control methods were discussed. The experiments suggested that all the control methods work basically on the principle of separation control. Based on the results of the water tunnel tests, the blowing or suction mass flow requirements appear to be within the limits of typical engine-bleed available from a modern fighter engine.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0619
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Aerodynamic control of fighter aircraft by manipulation of forebody vortices (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods of enhancing aircraft controllability and maneuverability at high angles of attack by manipulating the forebody vortices are discussed. Pneumatic control methods including jet blowing, slot blowing, and suction, and mechanical control methods using forebody and nose tip strakes are reviewed. The potential of various control devices in controlling the forebody flow, and thus, providing controlled yawing moments at high angles of attack are illustrated using wind tunnel results from a generic fighter and water tunnel results from an F/A-18.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AGARD, Manoeuvring Aerodynamics; 22 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Development of non-conventional control methods for high angle of attack flight using vortex manipulation (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods of manipulating the forebody vortices on a generic fighter model to produce controlled yawing moments at high angles of attack were investigated. Forces and moments were measured on the complete configuration and on the isolated forebody. Two schemes for vortex control on the forebody were evaluated: individually-controlled tip strakes and individually-controlled blowing ports. The effectiveness of the forebody strakes in controlling forebody side forces was strongly dependent on the size and location of the strakes. A yawing moment can be produced by deploying the forebody strakes asymmetrically, or can be eliminated by deploying the strakes symmetrically. The most effective strake position was found to be near the primary separation point, between 105 and 120 deg from windward. Blowing on the surface of the model was also shown to have a strong effect on the yawing moment. Blowing either forward or aft tangential to the surface appears to be more effective than blowing normal to the surface. The most effective method to control the yawing moment on the forebody was to minimize the natural asymmetry with a pair of small symmetrically mounted tip strakes and to perturb the vortex system away from the symmetric condition with asymmetric blowing.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AGARD, Aerodynamics of Combat Aircraft Controls and of Ground Effects; 17 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Water facilities in retrospect and prospect: An illuminating tool for vehicle design (1987)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady 3-D flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AGARD, Aerodynamic and Related Hydrodynamic Studies Using Water Facilities; 28 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Forebody vortex control with miniature, rotatable nose-boom strakes (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Experiments have been conducted in water and wind tunnel facilities to investigate the effectiveness of using rotatable miniaturized forebody nose-boom strakes to manipulate and control fighter aircraft forebody vortices at moderate to high angles of attack to provide potential aerodynamic control power in yaw. Water tunnel tests including flow visualization and yaw moment measurements were conducted on several different models of the F-16 fighter. Wind tunnel force and moment tests investigated the effects of several nose-boom strake configurations on an isolated 1/8th-scale X-29A forebody model. The primary variables of interest were strake size, configuration and roll angle orientation on the nose-boom. Both experiments showed clearly that small nose-boom strakes can be very effective in controlling the forebody vortex flowfield. Different degrees of flow asymmetry can be obtained by rotating a single or a pair of small strakes located on the nose-boom. With large fixed forebody strakes, such as those on the X-29A configuration, the effectiveness of the nose-boom strakes is significantly reduced.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 92-0022
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Static and dynamic force/moment measurements in the Eidetics water tunnel (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Water tunnels have been utilized in one form or another to explore fluid mechanics and aerodynamics phenomena since the days of Leonardo da Vinci. Water tunnel testing is attractive because of the relatively low cost and quick turn-around time to perform flow visualization experiments and evaluate the results. The principal limitation of a water tunnel is that the low flow speed, which provides for detailed visualization, also results in very small hydrodynamic (aerodynamic) forces on the model, which, in the past, have proven to be difficult to measure accurately. However, the advent of semi-conductor strain gage technology and devices associated with data acquisition such as low-noise amplifiers, electronic filters, and digital recording have made accurate measurements of very low strain levels feasible. The principal objective of this research effort was to develop a multi-component strain gage balance to measure forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models.
    Keywords: AERODYNAMICS
    Type: NASA. Dryden Flight Research Center, Fourth High Alpha Conference, Volume 1; 24 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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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.
    Format: text
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