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  • 1
    Electronic Resource
    Electronic Resource
    Control of low-speed turbulent separated flow using jet vortex generators (1992)
    Springer
    Experiments in fluids 12 (1992), S. 394-400 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A parametric study has been performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and jet location (distance from the separation region in the free-stream direction). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193886
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Control of low-speed turbulent separated flow using jet vortex generators (1992)
    Springer
    Details
    Publication Date: 1992-04-01
    Print ISSN: 0723-4864
    Electronic ISSN: 1432-1114
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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    PAPER CURRENT
  • 3
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    Control of turbulent separated flow over a rearward-facing ramp using longitudinal grooves (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Aircraft (ISSN 0021-8669); 27; 283-285
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Applicability of the independence principle to subsonic turbulent flow over a swept rearward-facing step (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Prandtl (1946) has concluded that for yawed laminar incompressible flows the streamwise flow is independent of the spanwise flow. However, Ashkenas and Riddell (1955) have reported that for turbulent flow the 'independence principle' does not apply to yawed flat plates. On the other hand, it was also found that this principle may be applicable to many turbulent flows. As the sweep angle is increased, a sweep angle is reached which defines the interval over which the 'independence principle' is valid. The results obtained in the present investigation indicate the magnitude of the critical angle for subsonic turbulent flow over a swept rearward-facing step.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1603
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Exploratory study of vortex-generating devices for turbulent flow separation control (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Flow phenomena and the relative performance associated with several devices for controlling turbulent separated flow were investigated at low speeds. Vortex-generating devices examined included: submerged vortex generators (Wheeler doublet and wishbone types), spanwise cylinders, large-eddy breakup devices (LEBU) at small angle of attack (alpha), and vortex-generator jets (VGJ). Dye flow visualization tests in a water tunnel indicated that wishbone vortex generators in the forward orientation shed horseshoe vortices; wishbone vortex generators oriented in the reverse direction and doublet vortex generators shed streamwise counterrotating vortices; a spanwise cylinder located near the wall and LEBUs at alpha = -10 deg produced eddies which rotated with the same sign as the mean vorticity in a turbulent boundary layer; and the most effective VGJs produced streamwise corotating vortices. Comparative wind tunnel tests conducted on a curved backward-facing ramp indicated that transferring momentum from the outer region of a turbulent boundary layer by embedded streamwise vortices is more effective than by transverse vortices for separation control applications.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0042
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Vapor-screen flow-visualization experiments in the NASA Langley 0.3-m transonic cryogenic tunnel (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The vortical flow on the leeward side of a delta-wing model has been visualized at several different tunnel conditions in the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel using a vapor-screen flow-visualization technique. Vapor-screen photographs of the subject flow field are presented and interpreted relative to phenomenological implications. Results indicate that the use of nitrogen fog in conjunction with the vapor-screen technique is feasibile.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3984 , NAS 1.26:3984
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Investigation of several passive and active methods for turbulent flow separation control (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Relative performance of several passive and active methods for controlling two-dimensional turbulent separated flow associated with a curved backward-facing ramp were investigated at low speeds. Surface static pressure measurement and oil flow visualization results indicate that submerged vortex generators, vortex generator jets, elongated arches at +-alpha, and large-eddy breakup devices at +-alpha placed near the baseline separation location reduce flow separation and increase pressure recovery. Spanwise cylinders reduce flow separation but decrease pressure recovery downstream. Arches with alpha = 0 deg, Helmholtz resonators, and Viets' fluidic flappers examined so far have no significant effect in reducing separation. Wall cooling computation indicates that separation delay on a partially cooled ramp is nearly the same as on a fully-cooled ramp while minimizing the frictional drag increase associated with the wall cooling process.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-1598
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Turbulent flow separation control through passive techniques (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Several passive separation control techniques for controlling moderate two-dimensional turbulent flow separation over a backward-facing ramp are studied. Small transverse and swept grooves, passive porous surfaces, large longitudinal grooves, and vortex generators were among the techniques used. It was found that, unlike the transverse and longitudinal grooves of an equivalent size, the 45-deg swept-groove configurations tested tended to enhance separation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 89-0976
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Phenomenological study of subsonic turbulent flow over a swept rearward-facing step (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The phenomenology of turbulent, subsonic flow over a swept, rearward-facing step was studied. Effects of variations in step height, sweep angle, base geometry, and end conditions on the 3-D separated flow were examined. The separated flow was visualized using smoke wire, oil drop, and surface tuft techniques. Measurements include surface pressure, reattachment distance and swirl angle. Results indicate: (1) model/test section coupling affects the structure of the separated flow, but spanwise end conditions do not; (2) the independence principle is evidently valid for sweep angles up to 38 deg; (3) a sweep angle/swirl angle correlation exists; and (4) base modifications can significantly reduce the reattachment distance.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-84757 , NAS 1.15:84757
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Control of low-speed turbulent separated flow using jet vortex generators (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A parametric study has been performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction, and jet location (distance from the separation region in the free-stream direction). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Experiments in Fluids (ISSN 0723-4864); 12; 6 Ap
    Format: text
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    NASA TECHNICAL REPORTS
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