The present Note discusses an attempt to delay breakdown of the leading-edge vortex over a highly swept wing at high angles of attack by means of along-core blowing, incorporating an air jet directed down the core of the vortex. The high-velocity jet provides additional momentum to the flow in the core preserving its jetlike profile over the entire length of the wing. This provides the core with the energy needed to maintain stability against the adverse pressure gradients that are naturally present on the suction surface of the wing, pushing breakdown farther downstream. A half-span model of a 60-deg delta wing mounted on half a cylindrical fuselage was tested on the wall of a low-speed wind tunnel. Flow visualizations and LDV-measurements of axial velocity contours were carried out at an angle of attack alpha = 15 deg, whereas for the force measurements alpha varied from 0 to 27 deg. Jets are emitted from three nozzles located beneath the vortex core at x/c = 30, 60, and 80% (x = distance between nozzle and wing apex, c = chord length) and with pitch angles of 25, 35 and 45 deg. Pressure is measured on the upper surface of the wing via 30 pressure taps. The majority of previous studies used jets that originated directly from the apex of the wing. However, the location of the jet at 30% chord length rather than at the apex is important for effective control because the leading-edge vortex should be allowed to develop to a certain level before the control jet is injected. Visualization of the flow using vertex-blowing configuration showed that the jet entered the core smoothly and rapidly. As a result, vortex breakdown was delayed from its natural position of approximately x/c = 35% to near the trailing edge. Axial velocity measurements showed a jetlike profile at x/c = 95% with a core velocity of 1.6 times the freestream. At 30% of the chord, the pressure coefficient was 35% lower than that of the baseline (i.e., without control) resulting in 15% more lift. The trailing-edge blowing arrangement at x/c = 80% has also a significant effect on the flow over the entire surface by creating a low-pressure region at the rear of the wing, which yields a more favorable pressure gradient along the wing with stronger axial flow in the vortex and delayed breakdown. A well-defined core was observed in this case which was present until at least 80% of the chord. Velocity measurements showed an increased axial velocity over the entire surface of the wing, not only in the core but near the surface as well. All three blowing arrangements show steady improvements in the lift coefficient over the baseline for attack angles larger than 8 deg. The nozzle at 30% chord length shows maximum lift at alpha = 15 deg, 15% more than the baseline. Stall is reached at 25 deg, where the wing with the flow control experiences still 7% greater lift than the baseline. The downstream nozzle experiences continued gains in performance over the baseline with increasing alpha. Stall occurs at 23 deg, where the lift coefficient is 1.9, i.e., 22% hover the baseline.


    Access

    Access via TIB

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Control of vortex breakdown over highly swept wings


    Additional title:

    Maßnahmen zur Verzögerung des Zusammenbruchs des Spitzenwirbels von Deltaflügeln


    Contributors:

    Published in:

    AIAA Journal ; 43 , 9 ; 2065-2069


    Publication date :

    2005


    Size :

    5 Seiten, 9 Bilder, 6 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




    Control of Vortex Breakdown over Highly Swept Wings

    Ephraim Gutmark / Stephen Guillot | AIAA | 2005


    Computational study of vortex breakdown over swept delta wings

    Rizzi, Arthur / GOERTZ, STEFAN / Munukka, Kari | AIAA | 1999




    Occurrence of Vortex Breakdown on the Swept and Delta Wings

    Srigrarom, S. / American Institute of Aeronautics and Astronautics | British Library Conference Proceedings | 2006