Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing

Michael Hites, Hassan Nagib, Tomer Bachar, Israel J Wygnanski

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Citations (Scopus)

Abstract

Oscillatory wall-jets were introduced through spanwise slots along a flapped NACA 0015 airfoil to establish lift augmentation and drag reduction by the unsteady forcing of the separated flow. Pressure coefficient distributions, lift coefficients, and wake velocity profiles, to determine the drag coefficient, were measured over the test-section speed range of 25m/s < U < 140m/s in the NDF. The present results demonstrated for the first time (Kites; 1997) the effectiveness of the oscillatory blowing technique as a separation control scheme at moderate Mach numbers, which exhibit compressibility effects. It is encouraging that lift-enhancement was observed over the entire range 0.1 < M < 0.4, even with the small amount of unsteady blowing applied in these experiments. As a result of the pulsed blowing, the lift coefficient increased by as much as 80%. Maximum pressure coefficients of nearly -5.0 for A/ = 0.4 experiments indicated the flow was supercritical near the leading edge of the airfoil, whereas it was not before the application of oscillatory blowing. The improvement in lift coefficient was found to be sensitive to the forcing frequency, even at the higher Mach numbers. Measurements at low angles of attack with a 20° flap showed that low amplitude pulsed blowing (0.02%) from the flap provided a 27% increasing in lift while steady blowing from the flap was detrimental to lift even at blowing coefficients as high as 3.5%. Oscillatory blowing with coefficients <Cμ> between 0.01% and 0.02%, based on RMS velocity, was shown to yield substantially better performance than steady blowing with Cμ in the range 0.5% to 3.5%. In is estimated that steady blowing of at least 10% would be required to reach the same levels of lift coefficient seen with the oscillatory blowing.

Original languageEnglish (US)
Title of host publication39th Aerospace Sciences Meeting and Exhibit
StatePublished - 2001
Externally publishedYes
Event39th Aerospace Sciences Meeting and Exhibit 2001 - Reno, NV, United States
Duration: Jan 8 2001Jan 11 2001

Other

Other39th Aerospace Sciences Meeting and Exhibit 2001
CountryUnited States
CityReno, NV
Period1/8/011/11/01

Fingerprint

blowing
drag coefficient
airfoils
Blow molding
velocity profile
Airfoils
Mach number
drag
lift coefficients
Mass transfer
lift augmentation
wall jets
separated flow
drag reduction
Drag reduction
drag coefficients
Drag coefficient
slots
wakes
velocity distribution

ASJC Scopus subject areas

  • Space and Planetary Science
  • Aerospace Engineering

Cite this

Hites, M., Nagib, H., Bachar, T., & Wygnanski, I. J. (2001). Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing. In 39th Aerospace Sciences Meeting and Exhibit

Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing. / Hites, Michael; Nagib, Hassan; Bachar, Tomer; Wygnanski, Israel J.

39th Aerospace Sciences Meeting and Exhibit. 2001.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Hites, M, Nagib, H, Bachar, T & Wygnanski, IJ 2001, Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing. in 39th Aerospace Sciences Meeting and Exhibit. 39th Aerospace Sciences Meeting and Exhibit 2001, Reno, NV, United States, 1/8/01.
Hites M, Nagib H, Bachar T, Wygnanski IJ. Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing. In 39th Aerospace Sciences Meeting and Exhibit. 2001
Hites, Michael ; Nagib, Hassan ; Bachar, Tomer ; Wygnanski, Israel J. / Enhanced performance of airfoils at moderate mach numbers using zero-mass flux pulsed blowing. 39th Aerospace Sciences Meeting and Exhibit. 2001.
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abstract = "Oscillatory wall-jets were introduced through spanwise slots along a flapped NACA 0015 airfoil to establish lift augmentation and drag reduction by the unsteady forcing of the separated flow. Pressure coefficient distributions, lift coefficients, and wake velocity profiles, to determine the drag coefficient, were measured over the test-section speed range of 25m/s < U∞ < 140m/s in the NDF. The present results demonstrated for the first time (Kites; 1997) the effectiveness of the oscillatory blowing technique as a separation control scheme at moderate Mach numbers, which exhibit compressibility effects. It is encouraging that lift-enhancement was observed over the entire range 0.1 < M < 0.4, even with the small amount of unsteady blowing applied in these experiments. As a result of the pulsed blowing, the lift coefficient increased by as much as 80{\%}. Maximum pressure coefficients of nearly -5.0 for A/ = 0.4 experiments indicated the flow was supercritical near the leading edge of the airfoil, whereas it was not before the application of oscillatory blowing. The improvement in lift coefficient was found to be sensitive to the forcing frequency, even at the higher Mach numbers. Measurements at low angles of attack with a 20° flap showed that low amplitude pulsed blowing (0.02{\%}) from the flap provided a 27{\%} increasing in lift while steady blowing from the flap was detrimental to lift even at blowing coefficients as high as 3.5{\%}. Oscillatory blowing with coefficients <Cμ> between 0.01{\%} and 0.02{\%}, based on RMS velocity, was shown to yield substantially better performance than steady blowing with Cμ in the range 0.5{\%} to 3.5{\%}. In is estimated that steady blowing of at least 10{\%} would be required to reach the same levels of lift coefficient seen with the oscillatory blowing.",
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N2 - Oscillatory wall-jets were introduced through spanwise slots along a flapped NACA 0015 airfoil to establish lift augmentation and drag reduction by the unsteady forcing of the separated flow. Pressure coefficient distributions, lift coefficients, and wake velocity profiles, to determine the drag coefficient, were measured over the test-section speed range of 25m/s < U∞ < 140m/s in the NDF. The present results demonstrated for the first time (Kites; 1997) the effectiveness of the oscillatory blowing technique as a separation control scheme at moderate Mach numbers, which exhibit compressibility effects. It is encouraging that lift-enhancement was observed over the entire range 0.1 < M < 0.4, even with the small amount of unsteady blowing applied in these experiments. As a result of the pulsed blowing, the lift coefficient increased by as much as 80%. Maximum pressure coefficients of nearly -5.0 for A/ = 0.4 experiments indicated the flow was supercritical near the leading edge of the airfoil, whereas it was not before the application of oscillatory blowing. The improvement in lift coefficient was found to be sensitive to the forcing frequency, even at the higher Mach numbers. Measurements at low angles of attack with a 20° flap showed that low amplitude pulsed blowing (0.02%) from the flap provided a 27% increasing in lift while steady blowing from the flap was detrimental to lift even at blowing coefficients as high as 3.5%. Oscillatory blowing with coefficients <Cμ> between 0.01% and 0.02%, based on RMS velocity, was shown to yield substantially better performance than steady blowing with Cμ in the range 0.5% to 3.5%. In is estimated that steady blowing of at least 10% would be required to reach the same levels of lift coefficient seen with the oscillatory blowing.

AB - Oscillatory wall-jets were introduced through spanwise slots along a flapped NACA 0015 airfoil to establish lift augmentation and drag reduction by the unsteady forcing of the separated flow. Pressure coefficient distributions, lift coefficients, and wake velocity profiles, to determine the drag coefficient, were measured over the test-section speed range of 25m/s < U∞ < 140m/s in the NDF. The present results demonstrated for the first time (Kites; 1997) the effectiveness of the oscillatory blowing technique as a separation control scheme at moderate Mach numbers, which exhibit compressibility effects. It is encouraging that lift-enhancement was observed over the entire range 0.1 < M < 0.4, even with the small amount of unsteady blowing applied in these experiments. As a result of the pulsed blowing, the lift coefficient increased by as much as 80%. Maximum pressure coefficients of nearly -5.0 for A/ = 0.4 experiments indicated the flow was supercritical near the leading edge of the airfoil, whereas it was not before the application of oscillatory blowing. The improvement in lift coefficient was found to be sensitive to the forcing frequency, even at the higher Mach numbers. Measurements at low angles of attack with a 20° flap showed that low amplitude pulsed blowing (0.02%) from the flap provided a 27% increasing in lift while steady blowing from the flap was detrimental to lift even at blowing coefficients as high as 3.5%. Oscillatory blowing with coefficients <Cμ> between 0.01% and 0.02%, based on RMS velocity, was shown to yield substantially better performance than steady blowing with Cμ in the range 0.5% to 3.5%. In is estimated that steady blowing of at least 10% would be required to reach the same levels of lift coefficient seen with the oscillatory blowing.

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