Lift hysteresis at stall as an unsteady boundary-layer phenomenon

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Description

Analysis of rotating stall of compressor blade rows requires specification of a dynamic lift curve for the airfoil section at or near stall, presumably including the effect of lift hysteresis. Consideration of the magnus lift of a rotating cylinder suggests performing an unsteady boundary-layer calculation to find the movement of the separation points of an airfoil fixed in a stream of variable incidence. The consideration of the shedding of vorticity into the wake should yield an estimate of lift increment proportional to time rate of change of angle of attack. This increment is the amplitude of the hysteresis loop. An ... continued below

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Moore, Franklin K January 1, 1956.

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  • Main Title: Lift hysteresis at stall as an unsteady boundary-layer phenomenon
  • Series Title: NACA Technical Reports

Description

Analysis of rotating stall of compressor blade rows requires specification of a dynamic lift curve for the airfoil section at or near stall, presumably including the effect of lift hysteresis. Consideration of the magnus lift of a rotating cylinder suggests performing an unsteady boundary-layer calculation to find the movement of the separation points of an airfoil fixed in a stream of variable incidence. The consideration of the shedding of vorticity into the wake should yield an estimate of lift increment proportional to time rate of change of angle of attack. This increment is the amplitude of the hysteresis loop. An approximate analysis is carried out according to the foregoing ideas for a 6:1 elliptic airfoil at the angle of attack for maximum lift. The assumptions of small perturbations from maximum lift are made, permitting neglect of distributed vorticity in the wake. The calculated hysteresis loop is counterclockwise. Finally, a discussion of the forms of hysteresis loops is presented; and, for small reduced frequency of oscillation, it is concluded that the concept of a viscous "time lag" is appropriate only for harmonic variations of angle of attack with time at mean conditions other than maximum lift.

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  • : 93R21577
  • URL: http://hdl.handle.net/2060/19930092287 External Link
  • Report No.: NACA-TR-1291
  • Center for AeroSpace Information Number: 19930092287
  • Archival Resource Key: ark:/67531/metadc60687

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National Advisory Committee for Aeronautics Collection

The National Advisory Committee for Aeronautics (NACA) was a U.S. federal agency founded on March 3, 1915 to undertake, promote, and institutionalize aeronautical research. On October 1, 1958 the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and Space Administration (NASA).

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  • January 1, 1956

Added to The UNT Digital Library

  • Nov. 17, 2011, 5:13 p.m.

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  • Feb. 3, 2017, 12:21 p.m.

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Moore, Franklin K. Lift hysteresis at stall as an unsteady boundary-layer phenomenon, report, January 1, 1956; (digital.library.unt.edu/ark:/67531/metadc60687/: accessed December 11, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.