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Wednesday, July 22, 2020 | History

3 edition of Effect of acoustic excitation on stalled flows over an airfoil found in the catalog.

Effect of acoustic excitation on stalled flows over an airfoil

Effect of acoustic excitation on stalled flows over an airfoil

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Published by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC], [Springfield, Va .
Written in English

    Subjects:
  • Acoustic excitation.,
  • Aerodynamic stalling.,
  • Airfoil profiles.,
  • Boundary layer separation.,
  • Flow distribution.

  • Edition Notes

    StatementK.B.M.Q. Zama.
    SeriesNASA technical memorandum -- 103183.
    ContributionsUnited States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL15405867M

      Genç MS, Akpolat MT, Açıkel HH, Karasu I (c) An experimental study of perpendicular acoustic disturbances effect on flow over an aerofoil at low Reynolds numbers. In: ASME ınternational mechanical engineering congress & exposition IMECE Houston, Texas, USA, 9–15 Nov Google Scholar. Abstract. The suppression of post-stall separation over an unconventional 2-D airfoil at moderate Reynolds numbers (up to 10 6) using synthetic (zero net mass flux) jet actuators is shown by the authors in earlier investigations, the apparent modification of the surface shape by the interaction domain between the actuator jets and the cross flow results in a local displacement of Cited by:

      Airfoil Performance at Low Reynolds Numbers in the Presence of Periodic Disturbances low-frequency structural vibrations are found to have a significant effect on airfoil performance, as they enhance the sound pressure levels within the test section. Issue Section: Effect of Acoustic Excitation on Stalled Flows Over an Airfoil,”Cited by: The effects of internal acoustic excitation on the leading edge separated boundary layers and the aerodynamic performance over an airfoil of NACA 63(3) cross section are examined as a function of excitation amplitude and frequency. Tests are conducted in an open-type suction wind tunnel at the Reynolds number of ,

    Zaman, K.B.M.Q. () Effect of Acoustic Excitation on Stalled Flows over an Airfoil. AIAA Journal, 6, Hasegawa, H. and Kumagai, S. () Active Boundary Layer Control System Using Vortex Generating Jets and Operating by the Detection of Precursor of Flow Separation. International Journal of Flow Control, 2,   V.V. Kozlov, V.N. Lushin, and Zanin, Separated flow reattachment at an airfoil under sonic effect, in: Separated Flows and Jets, Eds. V.V. Kozlov and A.V. Dovgal, Berlin, Effect of acoustic excitation on stalled flows over an airfoil, AIAA J., V.V. Global response of laminar flow separation to local flow perturbations (review Cited by: 4.


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Effect of acoustic excitation on stalled flows over an airfoil Download PDF EPUB FB2

Around the onset of static stall (a = ), for the airfoil under considera- tion, a transitory stall occurred at an unusually low frequency The effect of acoustic excitation on this phenomenon was rather complex and depending on the range of fp the low Cited by:   Effect of acoustic excitation on flow over a partially grooved circular cylinder Experiments in Fluids, Vol.

19, No. 3 Controlling unsteady separation with acoustic active surfacesCited by:   adshelp[at] The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86ACited by: The effect of acoustic excitation on post-stalled flows over an airfoil, i.e., flows that are fully separated from near the leading edge, is investigated.

The excitation results in a tendency towards reattachment, which is accompanied by an increased lift and reduced drag, although the flow may still remain fully : K. Zaman. Wind-tunnel measurements of lift, drag and wake velocity spectra were carried out under (tonal) acoustic excitation for a smooth airfoil in the chord-Reynolds-number (Re c) range of 4 × 10 4 − × 10 5.

The data are supported by smoke-wire flowvisualization pictures. The effect of acoustic excitation on poststalled flows over an airfoil, i.e., flows that are fully separated from near the leading edge, is investigated.

The excitation results in a tendency toward reattachment, which is accompanied by an increased lift and reduced drag, although the flow may still remain fully : K.

Zaman. 4 attack increases, higher excitation amplitudes are required to produce appreciable effect on airfoil characteristics. In such situations when high excitation amplitude is required, wind tunnel resonance has been reported to influence the results.7 It should be noted that internal excitation usually requires smaller excitation amplitude compared to external by: Control of post-stall flow separation over an airfoil under acoustic excitation is studied.

The excitation is imparted via an internal cavity within the airfoil and slots near the leading edge. The effects of internal acoustic excitation on the leading edge separated boundary layers and the aerodynamic performance over an airfoil of NACA 63(3) cross section are examined as a function.

An experimental investigation was carried out on the flow over a partially grooved circular cylinder over a Reynolds number range of 3 × 10 4 to × 10 5 with and without acoustic excitation.

Without excitation the flow over the smooth half of the cylinder was observed to shift to higher subcritical by: 4. He examined the effect of acoustic excitation on poststalled flow over an airfoil at high angles of attack, and found that when the excitation amplitude was increased, a large increase in the lift coefficient occurred but the effect shifted progressively to a lower Strouhal number that is much lower than that expected from linear, inviscid instability of the separated shear by: 1.

Results indicate that the acoustic excitation technique is able to alter the flow properties and thus to improve the aerodynamic performance, especially when the airfoil is fully stalled at high AOA.

Get this from a library. Effect of acoustic excitation on stalled flows over an airfoil. [K B M Q Zaman; United States. National Aeronautics and Space Administration.].

the separation bubble or the airfoil wake. Relatively new methods of flow control involve the use of some kind of external periodic forcing. One such method is the excitation of the boundary layer with an acoustic source.

Various studies have been performed showing that introduction of either external or internal acoustic excitation at an.

Instead of physically displacing the airfoil, the flow is modulated by loudspeakers. The loudspeakers are tuned to the first transversal eigenfrequency of the wind tunnel, which results in a 2D acoustic field.

The paper first describes the experimental investigation of the acoustic field without a main by: 9. It is in this type of flows where acoustic excitation can have a very pronounced effect in reducing the unsteady fluctuations.

Examples of the steadying effect for the flow over airfoils were reported in refs. 5,6. Two sets of data are reproduced from ref. 6 in figs. Zaman, K.B.M.Q. () Effect of Acoustic Excitation on Stalled Flows over an Airfoil. AIAA Journal, 6, Hasegawa, H.

and Kumagai, S. () Active Boundary Layer Control System Using Vortex Generating Jets and Operating by the Detection of Precursor of Flow : Hiroaki Hasegawa, Shigeru Obayashi.

The results of experiments investigating excitation of flow instability over a VR-7 airfoil at a post-stall angle of attack of 19° are presented.

The Reynolds number based on the chord was fixed at Author: Ata Esfahani, Nathan Webb, Mo Samimy. The origin of the flow fluctuations traces to the upper surface of the airfoil and is associated with a periodic switching between stalled and unstalled states.

The mechanism of the frequency selection remains unresolved, but any connection to blower instabilities, acoustic standing waves or structural resonances has been ruled by:   The response of the boundary layer over an airfoil with cavity to external acoustic forcing, across a sweep of frequencies, was measured.

The boundary layer downstream of the cavity trailing edge was found to respond strongly and selectively at the natural airfoil tonal by: 5. the external acoustic excitation in which the sound is radiated onto the wall from a source outside the flow system.

This technique has been applied by Zaman et al. [] which studied the effect of external acoustic excitation about a stall airfoil (LRN-(1)). He founded that a .Chapter 4.

Active Control of Stalled Airfoil Flow 49 generated by the loudspeaker. They have also found that the most effective position of excitation is near the separation location with the frequencies in the range of shear-layer instability frequency.

If the frequencies of the acoustic .In this study, the effect of perpendicular acoustic excitation on laminar separation bubble over a NACA aerofoil and stall characteristics of the aerofoil was investigated experimentally at low Reynolds numbers ( and ) and various angles of attack on the aerofoil using force measurement, pressure measurement and smoke-wire flow visualization techniques.