Buffeting Flows over a Low-Sweep Delta Wing

Taylor, Gordon; Gursul, Ismet

doi:10.2514/1.5391

Cited by 65 publications

(46 citation statements)

References 19 publications

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“…The formation of dual LEV The LEV on a flapping wing contains sub-structures that are very similar to the flow structures on non-slender delta wings (Gordnier and Visbal, 2003;Taylor and Gursul, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…In fact, a similar LEV pair has been reported in butterfly free flight using smokewire visualization (Srygley and Thomas, 2002). This vortical system reminds us of the dual LEV structure on non-slender delta wings, which is defined as the large and small same-sense vortices (the primary vortex and minor vortex, respectively) located close to the leading edge on both sides of the secondary separation in-and outboard, respectively (Gordnier and Visbal, 2003;Taylor and Gursul, 2004). This interesting flow behavior implies that the LEV generated in flapping motions may involve sub-structures, and merit in-depth exploration.…”

mentioning

confidence: 90%

“…In addition, the secondary separation with opposite vorticity (yellow contour) can be detected between the two vortices just above the wing surface. These three vorticity regions constitute the basic structure of the dual LEV, reminding us of the dual-vortex structure on non-slender delta wings (Gordnier and Visbal, 2003;Taylor and Gursul, 2004). Note in Fig.·7A that a small separation layer with negative vorticity locates outboard from the minor vortex at the leading edge, where the sectional streamlines bend dramatically but form no focus.…”

Section: The Journal Of Experimental Biology Dual Leading-edge Vorticmentioning

confidence: 99%

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Dual leading-edge vortices on flapping wings

Yuan

Shen

Lai

2006

Journal of Experimental Biology

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). This type of vortical structure, at certain high Reynolds numbers, is analogous to the spiral conical vortex generated on each leading edge of a delta wing (Birch et al., 2004). However, whereas considerable importance is attached to the force performance and power efficiency of flapping flight (Birch and Dickinson, 2003;Sun and Tang, 2002a;Sun and Tang, 2002b), few studies have addressed the detailed structure of the LEV.In a recent flow visualization of a robotic wing moving in the motion of dragonfly hovering (Y.L., G.X.S. and W. H. Su, manuscript submitted), we observed that the LEV with intensive spanwise flow did not develop along the leading edge but moved inboard, leaving a space for the formation of a minor vortex outside the primary vortex (see Fig.·1). In fact, a similar LEV pair has been reported in butterfly free flight using smokewire visualization (Srygley and Thomas, 2002). This vortical system reminds us of the dual LEV structure on non-slender delta wings, which is defined as the large and small same-sense vortices (the primary vortex and minor vortex, respectively) located close to the leading edge on both sides of the secondary separation in-and outboard, respectively (Gordnier and Visbal, 2003;Taylor and Gursul, 2004). This interesting flow behavior implies that the LEV generated in flapping motions may involve sub-structures, and merit in-depth exploration.With both visualizations the two vortices were reported to rotate in the same direction, but it is difficult to distinguish them directly from the flow images. In this paper, dye flow visualization and high-resolution DPIV measurements were conducted to reveal the detailed features of the LEV region. Based on the validation of the dual LEV, systematic investigations were performed by altering the kinematic (Re, from 160 to 3200, and ␣ m , from 10 to 80°) and geometric (AR, from 1.3 to 10) parameters. The well-known case of the fruit fly was re-examined to see whether the dual LEV had been missed in the previous studies. All measurements were obtained with the robotic wings flapping in the hovering condition. Materials and methodsModel wing planform The planform of the simplified model dragonfly wing (AR=5.8, AR=R/c; where R is model wing length, measured from the translational axis to the wingtip; c is mean wing chord length) An experimental investigation was performed with two aims: (1) to clarify the existence of the dual leading-edge vortices (i.e. two vortices with the same sense of rotation located close to the leading edge above the leeward wing surface) observed on flapping wings in previous studies; (2) to study systematically the influences of kinematic and geometric parameters on such a vortical structure. Based on a scaled-up electromechanical model flapping in a water tank, the leading-edge vortex (LEV) cores were visualized via dye flow visualization, and the detailed substructures of LEV were revealed through digital particle image velocimetry (DPIV) with high spatial resolution. Five wing aspect ratios (AR) (1.3, 3.5, 5....

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 90%

Section: The Journal Of Experimental Biology Dual Leading-edge Vorticmentioning

confidence: 99%

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Dual leading-edge vortices on flapping wings

Yuan

Shen

Lai

2006

Journal of Experimental Biology

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“…In our previous work (Lu et al, 2006), based on the structural similarities, we tried to gain insight from the realms of delta wings (Gordnier and Visbal, 2003;Taylor and Gursul, 2004;Henning et al, 2005) to explain the formation of the dual-LEV (Lu et al, 2006). Admittedly, such an idea has an intrinsic problem.…”

Section: Discussion the Nature Of The Lev System On A Flapping Wingmentioning

confidence: 99%

Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

Yuan

Shen

2008

Journal of Experimental Biology

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SUMMARYFollowing the identification and confirmation of the substructures of the leading-edge vortex (LEV) system on flapping wings, it is apparent that the actual LEV structures could be more complex than had been estimated in previous investigations. In this experimental study, we reveal for the first time the detailed three-dimensional (3-D) flow structures and evolution of the LEVs on a flapping wing in the hovering condition at high Reynolds number (Re=1624). This was accomplished by utilizing an electromechanical model dragonfly wing flapping in a water tank (mid-stroke angle of attack=60°) and applying phase-lock based multi-slice digital stereoscopic particle image velocimetry (DSPIV) to measure the target flow fields at three typical stroke phases: at 0.125T (T=stroke period), when the wing was accelerating; at 0.25T, when the wing had maximum speed; and at 0.375T, when the wing was decelerating. The result shows that the LEV system is a collection of four vortical elements: one primary vortex and three minor vortices, instead of a single conical or tube-like vortex as reported or hypothesized in previous studies. These vortical elements are highly time-dependent in structure and show distinct ʻstay propertiesʼ at different spanwise sections. The spanwise flows are also time-dependent, not only in the velocity magnitude but also in direction.

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“…It is seen that the energy deposition efficiency increases with increasing of Mach number from V. A. Levin's work [10]. Nearly linear (but very shallow) decreasing trend in the percentage of drag reduced with increasing Mach number (lower than 6) was shown in T. Taylor's study [11].…”

Section: Introductionmentioning

confidence: 65%

Study of Key Non-dimensional Parameters for Wave Drag Reduction with High-Frequency Repetitive Laser Pulse Energy Depositions

Qing

Hong²,

Wang³

et al. 2016

MATEC Web Conf.

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Abstract. The problem of wave drag reduction with high-frequency repetitive laser pulse energy depositions is multivariable. Three key non-dimensional parameters, non-dimensional energy, non-dimensional depositing position and Mach number, were constructed from a number of original variables by using Buckingham pi theorem. Influences of these non-dimensional parameters on energy deposition performance, namely drag reduction and energy deposition efficiency, were investigated numerically by solving three-dimensional Navier-Stokes equations with an upwind scheme. Optimizing method of non-dimensional energy and non-dimensional depositing position is proposed. Drag reduction and energy deposition efficiency have exponential relationships with non-dimensional energy; Drag reduction and energy deposition efficiency have quadratic relationships with non-dimensional depositing position. Drag reduction has exponential relationship with freestream Mach number and energy deposition efficiency has quadratic relationship with Mach number. Non-dimensional laser energy and non-dimensional depositing position should be optimized synthetically for a given freestream.

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Buffeting Flows over a Low-Sweep Delta Wing

Cited by 65 publications

References 19 publications

Dual leading-edge vortices on flapping wings

Dual leading-edge vortices on flapping wings

Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

Study of Key Non-dimensional Parameters for Wave Drag Reduction with High-Frequency Repetitive Laser Pulse Energy Depositions

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