Interaction of Multiple Vortices over a Double Delta Wing

Xi, Zhang; Wang, Zhijin; Gursul, Ismet

doi:10.2514/6.2015-2308

Cited by 8 publications

(9 citation statements)

References 16 publications

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“…The POD modes of the baseline case have been extensively discussed in previous studies 9 which revealed the dominant m = 1 helical displacement mode at the trailing-edge for the fully developed afterbody vortex. This same m = 1 mode had previously been identified with wing tip vortices 26,27 , delta wing vortices 28 and inlet vortices 29 .…”

Section: E Proper Orthogonal Decompositionsupporting

confidence: 74%

Mini-Spoilers for Afterbody Base Drag Reduction

Bulathsinghala¹,

Wang²,

Gursul³

2017

47th AIAA Fluid Dynamics Conference

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Wind tunnel experiments have been carried out in order to study the effect of full-span minispoilers on the afterbody vortex drag of a slanted base cylinder. Two different protrusion heights (h/D = 2.5% and 5%) were examined at various chordwise locations along the upsweep. The tests were performed on a slanted base cylindrical model with an afterbody upsweep angle Φ = 28° at a test Reynolds number of 200,000 based on model diameter. Drag measurements, surface pressure measurements and 2D Particle Image Velocimetry measurements were the main experimental tools utilized within this investigation. Placing the spoilers closer to the leading edge of the upsweep caused an increased drag due to the separation induced by the spoiler itself, leading to a more diffused vortex, but with a larger circulation at the trailing-edge. Drag reductions were observed when placing the spoiler closer to the trailing-edge, with the optimum location being x′s /c = 87.5% resulting in drag reductions of 4.5% and 4.8% for h/D = 2.5% and 5% heights respectively. This reduction is due to an increase in surface pressure upstream of the spoiler. For the drag reducing spoiler location, the vortex was found to be displaced away from the surface, with the streamlines of the model trailing-edge deflected downwards into the wake of the spoiler, altering the trailing-edge flow. Unsteady aspects are discussed and underlying flow mechanisms are presented using the Proper Orthogonal Decomposition. Further results are also presented for a vortex generator configuration that was examined which may present a useful starting point for future studies. A co-rotating half delta wing type vortex generator placed at an incidence of β = 20° at x/c = 20% with a leading edge sweep of Λ = 70° was found to show the most promising results.

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Section: E Proper Orthogonal Decompositionsupporting

confidence: 74%

Mini-Spoilers for Afterbody Base Drag Reduction

Bulathsinghala¹,

Wang²,

Gursul³

2017

47th AIAA Fluid Dynamics Conference

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“…Antkowiak and Brancher (2004) proposed the possibility of a relationship between meandering of vortex cores and transient amplification of |m| = 1 disturbances (first helical mode). This mode has been documented in wing-tip vortices (Roy and Leweke 2005;del Pino et al 2011;Chen et al 2016) and leading-edge vortices (Zhang et al 2016;Ma et al 2017). Recently, this mode was measured and also predicted by a spatial stability analysis (Edstrand et al 2016) in tip vortices.…”

Section: Meandering Of Tip Vorticesmentioning

confidence: 72%

“…The two-dimensional POD modes cannot reveal the dominant wavelength. Note that the same first helical mode was also identified in the meandering of the trailing vortices (Roy and Leweke 2005;del Pino et al 2011;Chen et al 2016;Edstrand et al 2016), delta wing vortices (Zhang et al 2016;Ma et al 2017), afterbody vortices (Bulathsinghala et al 2017), and inlet vortices (Wang and Gursul 2012). Higher modes are also shown in Fig.…”

Section: Proper Orthogonal Decomposition (Pod) Analysismentioning

confidence: 75%

Experiments on tip vortices interacting with downstream wings

2018

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The interaction of meandering tip vortices shed from a leading wing with a downstream wing was investigated experimentally in a water tunnel using flow visualization, particle image velocimetry measurements, and volumetric velocity measurements. Counter-rotating upstream vortices may exhibit sudden variations of the vortex core location when the wing-tip separation is within approximately twice the vortex core radius. This is caused by the formation of vortex dipoles near the wing tip. In contrast, co-rotating upstream vortices do not exhibit such sensitivity. Large spanwise displacement of the trajectory due to the image vortex is possible when the incident vortex is further inboard. For both co-rotating and counter-rotating vortices, as long as there is no direct impingement upon the wing, there is a little change in the structure of the time-averaged vortex past the wing, even though the tip vortex shed from the downstream wing may be substantially weakened or strengthened. In the absence of the downstream wing, as well as for weak interactions, the most energetic unsteady modes represent the first helical mode |m| = 1, which is estimated from the three-dimensional Proper Orthogonal Decomposition modes and has a very large wavelength, on the order of 10 2 times the vortex core radius, λ/a = O(10 2). Instantaneous vorticity measurements as well as flow visualization suggest the existence of a smaller wavelength, λ/a = 5-6, which is not among the most energetic modes. These two-orders of magnitude different wavelengths are in agreement with the previous measurements of tip vortices and also exhibit qualitative agreement with the transient energy growth analysis. The very long wavelength mode in the upstream vortex may persist during the interaction, and reveal coupling with the trailing vortex as well as increased meandering.

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“…In the recent times, experiments made by Zhang et al. 13 using PIV on a 70°/50° double-delta wing indicated the upstream effect of wing vortex on the formation of the strake vortex. The formation of the strake and wing vortex, their intermingling and breakdown could be well captured.…”

Section: Introductionmentioning

confidence: 99%

“…Experiments have been performed on a round leading-edged double-delta (cropped 80 /45 sweep) wing body model at subsonic and transonic speed by Rao et al, 12 which indicated the complex phenomena emerging due to the strake and wing vortices. In the recent times, experiments made by Zhang et al 13 using PIV on a 70 /50 double-delta wing indicated the upstream effect of wing vortex on the formation of the strake vortex. The formation of the strake and wing vortex, their intermingling and breakdown could be well captured.…”

Section: Introductionmentioning

confidence: 99%

Effect of leading edge shapes on 81°/45° double-delta wing at low speeds

Kumar

Das

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part G:

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Investigations were performed on an 81 /45 sweep double-delta wing at a freestream velocity of 20 m/s. Experiments consisted of the measurement of forces, static pressures, and surface flow visualizations. Effect of the leading edge shapes of the double-delta wing was studied. Results indicated a strong influence of the leading edge shape on the aerodynamic performance of the body. The increase in the bluntness of the leading edge augments the suction pressure and delays the vortex lift phenomena at higher angles of attack, which in turn enhances the lift over the wing. A reasonable agreement between the experiments and computations were observed.

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Interaction of Multiple Vortices over a Double Delta Wing

Cited by 8 publications

References 16 publications

Mini-Spoilers for Afterbody Base Drag Reduction

Mini-Spoilers for Afterbody Base Drag Reduction

Experiments on tip vortices interacting with downstream wings

Effect of leading edge shapes on 81°/45° double-delta wing at low speeds

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