Effect of Upsweep Angle on Afterbody Vortices

Bulathsinghala, Dinitha; Wang, Zhijin; Gursul, Ismet

doi:10.2514/6.2016-4344

Cited by 9 publications

(8 citation statements)

References 23 publications

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“…The current analysis was performed using a MATLAB ® code that employs the method of snapshots 24,25 . 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 Decompositionmentioning

confidence: 97%

“…This vortex footprint is the reason for the vortex drag since it represents the lowest pressures acting on the upsweep surface due to the vortex. Further discussions about the same baseline flowfield has been published previously 9 . For the spoiler placed at x′s /c = 2.5% ( Fig.…”

Section: Particle Image Velocimetrymentioning

confidence: 99%

“…An axisymmetric vortex core region starts appearing beyond the third measurement plane x/L = 0.6, which gradually starts to move away from the upsweep surface towards the trailing-edge where the fully developed vortex is present. Further details pertinent to this baseline flow can be found in studies published previously 8,9 .…”

Section: Time-averaged Flowfieldmentioning

confidence: 99%

“…Hence placing the spoiler closer to the mid-chord of the upsweep has resulted in a slightly weaker afterbody vortex at the trailing-edge, with the h/D = 2.5% and 5% heights resulting in 4% and 8% lower circulations compared to the baseline respectively. A weaker vortex at the trailing-edge is desirable, since it has been shown previously that the vortex strength at the trailing-edge can have direct implications on the overall drag coefficient 9 . However, with the spoiler at this location, this decrease in vortex strength was inadequate to result in a drag reduction due to the parasitic drag of the spoilers discussed previously.…”

Section: Time-averaged Flowfieldmentioning

confidence: 99%

“…Tests were performed within two different experimental facilities. Effects of angle of attack and yaw on the baseline flowfield were examined 8 , along with changing the upsweep angle within a range more relevant to military transport aircraft 9 . It was found that the drag coefficient was directly proportional to the trailing-edge vortex strength.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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