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  • AERODYNAMICS  (8)
  • crystal structure
  • 1980-1984  (8)
  • 1
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    Data from tests of a R4 airfoil in the Langley 0.3-meter transonic cryogenic tunnel (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Aerodynamic data for the DFVLR R4 airfoil are presented in both graphic and tabular form. The R4 was tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel (TCT) at Mach number from 0.60 to 0.78 at angles of attack from -2.0 to 8.0 degrees. The airfoil was tested at Reynolds numbers of 4, 6, 10, 15, 30, and 40 million based on the 152.32 mm chord.
    Keywords: AERODYNAMICS
    Type: NASA-TM-85739 , NAS 1.15:85739
    Format: application/pdf
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  • 2
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    Experimental studies of the boundary layer on an airfoil at low Reynolds numbers (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An experimental wind tunnel investigation was carried out to study the effect of laminar separation bubbles on a NACA 66(3)-018 airfoil for Reynolds numbers less than 4.0 x 10 to the 5th. Leading edge laminar separation bubbles formed for angles of attack of approximately 7 to 12 deg. To study the leading edge separation bubble more closely, hotwire anemometer measurements were made in the airfoil a Reynolds number of 8.0 x 10 to the 4th. Velocity and turbulence intensity profiles were obtained and boundary layer parameters were calculated. Frequency spectra were also calculated at key points in the airfoil boundary layer for this case. Correlation of the anemometry data with static pressure distributions, and flow visualization data provided insight into laminar separation bubble behavior at low Reynolds numbers.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 83-1671
    Format: text
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  • 3
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    The influence of free-stream disturbances on low Reynolds number airfoil experiments (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The results of an investigation of the influence of free stream disturbances on the lift and drag performance of the Lissaman 7769 airfoil are presented. The wind tunnel disturbance environment is described using hot-wire anemometer and sound pressure level measurements. The disturbance level is increased by the addition of a 'turbulence screen' upstream of the test section and/or the addition of a flow restrictor downstream of the test section. For the Lissaman airfoil it was found that the problems associated with obtaining accurate wind tunnel data at low chord Reynolds numbers (i.e., below 200,000) are compounded by the extreme sensitivity of the boundary layers to the free stream disturbance environment. The effect of free stream disturbances varies with magnitude, frequency content, and source of the disturbance.
    Keywords: AERODYNAMICS
    Type: Experiments in Fluids (ISSN 0723-4864); 1; 1 19; 1983
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  • 4
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    The influence of laminar separation and transition on low Reynolds number airfoil hysteresis (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An experimental study of the Lissaman 7769 and Miley MO6-13-128 airfoils at low chord Reynolds numbers is presented. Although both airfoils perform well near their design Reynolds number of about 600,000, they each produce a different type of hysteresis loop in the lift and drag forces when operated below chord Reynolds numbers of 300,000. The type of hysteresis loop was found to depend upon the relative location of laminar separation and transition. The influence of disturbance environment and experimental procedure on the low Reynolds number airfoil boundary layer behavior is also presented. The use of potential flow solutions to help predict how a given airfoil will behave at low Reynolds numbers is also discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-1617
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  • 5
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    Experimental and numerical studies of the incompressible viscous flow over a two-dimensional airfoil (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Physical and numerical experiments for the low Reynolds number flow over a two-dimensional NACA 66(3)-018 airfoil have been performed. Pressure distributions and smoke flow photographs have been obtained for a Reynolds number based on airfoil chord and free-stream conditions of approximately 40,000 at angles of attack of 0 and 6 deg, and for a Reynolds number based on airfoil chord and free-stream conditions of approximately 400,000 at angles of attack of 0 and 12 deg in a low turbulence wind tunnel. Finite difference numerical experiments, using an approximate factorization method, have been obtained for a Reynolds number of 40,000 at angles of attack of 0 and 6 deg. Although the comparison of the wind tunnel and computer results is encouraging, further studies of this type are clearly necessary.
    Keywords: AERODYNAMICS
    Type: Computers in flow predictions and fluid dynamics experiments; Nov 15, 1981 - Nov 20, 1981; Washington, DC
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  • 6
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    Experimental studies of the Eppler 61 airfoil at low Reynolds numbers (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The results of an experimental study to document the effects of separation and transition on the performance of an airfoil designed for low Reynolds number operation are presented. Lift, drag and flow visualization data were obtained for the Eppler 61 airfoil section for chord Reynolds numbers from about 30,000 to over 200,000. Smoke flow visualization was employed to document the boundary layer behavior and was correlated with the Eppler airfoil design and analysis computer program. Laminar separation, transition and turbulent reattachment had significant effects on the performance of this airfoil.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 82-0345 , Aerospace Sciences Meeting; Jan 11, 1982 - Jan 14, 1982; Orlando, FL
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  • 7
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    Experimental studies of the laminar separation bubble on a two-dimensional airfoil at low Reynolds numbers (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The laminar separation, transition and turbulent reattachment near the leading edge of a two-dimensional NACA 663-018 airfoil were investigated using a low speed, smoke visualization wind tunnel. Lift and drag force measurements were made using an external strain gauge balance for a chord Reynolds number range of 40,000 to 400,000. An extensive flow visualization study was performed and correlated with the force measurements. Experiments were also conducted with distributed surface roughness at the leading edge and external acoustic excitation to influence the development of the airfoil boundary layer. This study delineates the effects of angle of attack and chord Reynolds number on the separation bubble characteristics and airfoil performance
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-1440 , Fluid and Plasma Dynamics Conference; Jul 14, 1980 - Jul 16, 1980; Snowmass, CO
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  • 8
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    The structure of separated flow regions occurring near the leading edge of airfoils, including transition (1983)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Data was obtained for the NACA 663-018 airfoil in order to assess the advantages of tripping the boundary layer very near the leading edge for chord Reynolds numbers between 40,000 and 200,000. Single element trips were made from tape 2.5 mm wide and 0.15 mm thick. The unmodified tape trip in five thicknesses was placed across the span at 1.1% chord and the results of lift and drag measurements compared with the smooth airfoil case. Saw tooth geometry trips were also cut from tape and studied using five thicknesses. The saw tooth trips were placed across the span with the sharp points facing upstream at 1.1% chord and with the valley of the teeth at the 2.5% chord position. A large number of bumps and wiggles were produced in the lift coefficient versus angle of attack curves with various combinations of Reynolds number, thickness, and type of trips. The main result in the drag coefficient was an increase in C sub d min with increase in trip thickness.
    Keywords: AERODYNAMICS
    Type: NASA-CR-170266 , NAS 1.26:170266
    Format: application/pdf
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