Interference-free measurements of the subsonic aerodynamics of slanted-base ogive cylinders

Britcher, Colin P.; Alcorn, Charles

doi:10.2514/3.10614

Cited by 43 publications

(15 citation statements)

References 3 publications

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“…There is a sudden drop in the drag coefficient at the critical upsweep angle. Similar experiments have been performed by Maull (1980), Xia and Bearman (1983) and Britcher and Alcorn (1991), which have used similar slanted base cylindrical models and reported the same trends in the drag coefficient. Epstein et al (1994) and Peake et al (1972) claimed the absence of a vortex shedding frequency in the vortex pair regime, and similarities in the structure of the flow field were drawn to delta wings.…”

Section: List Of Symbols a Msupporting

confidence: 61%

“…The model used in the water tunnel experiments has an upsweep angle in the mid-range and provides an opportunity to assess the influence of Reynolds number. The cylindrical slanted base models used in this experiment allow for comparisons with studies discussed previously (Morel 1980;Maull 1980;Xia and Bearman 1983;Britcher and Alcorn 1991). In-depth analysis of the instantaneous PIV snapshots, vortex meandering and proper orthogonal decomposition (POD) was carried out to understand the unsteady aspects of the vortex flow.…”

Section: List Of Symbols a Mmentioning

confidence: 99%

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Afterbody vortices of axisymmetric cylinders with a slanted base

et al. 2017

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Section: List Of Symbols a Msupporting

confidence: 61%

Section: List Of Symbols a Mmentioning

confidence: 99%

Afterbody vortices of axisymmetric cylinders with a slanted base

et al. 2017

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“…1,2 Force measurements on geometries with an axisymmetric forebody and a slanted base have shown that the drag coefficient increases with upsweep angle for a given Reynolds number. 3,4 This evidence demonstrates why the issue is more pertinent to military transport aircraft compared to their civil counterparts. Alongside an increase in drag coefficient, the vortex pair can disrupt the trajectory of objects during airdrop missions.…”

Section: Introductionmentioning

confidence: 91%

Control of Afterbody Vortices by Blowing

Jackson

Wang

Gursul

2015

45th AIAA Fluid Dynamics Conference

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An experimental study has been performed to examine the effect of blowing via a pair of jets from the upswept face of a slanted base cylinder, upon the development of the afterbody vortex flow field. Jet vortices initially interact with the shear layer separated from the upswept section. The nature of the early interactions between the jet and shear layer is highly dependent upon the blowing direction. For most blowing configurations tested, the shear layer becomes wrapped around the jet vortex. The most significant evidence of modification of the afterbody vortex pair was found when initiating a jet vortex further outboard and closer to the shear layer. The jet/vortex interactions initially cause the afterbody vortices to form further outboard, at a greater distance from the surface, and with a smaller vortex core. There is a reduction in the circulation over the first half of the afterbody length, before it recovers to baseline levels at the trailing edge. The vortex pair appears more diffuse near the trailing edge, but this is a result of increased meandering. Nomenclature am = meandering amplitude xj = streamwise jet location Aj = cross-sectional area of jet y = normal distance c = chord length of upswept face z = spanwise distance Cµ = jet momentum coefficient, ρAjUj 2 /0.5ρU∞ 2 S zj = spanwise jet location D = diameter of fuselage α = fuselage incidence angle L = length of afterbody αj = jet incidence angle r = distance from vortex center β = fuselage yaw angle Re = Reynolds number, ρU∞D/µ βj = jet yaw angle S = cross-sectional area of fuselage Γ = circulation Uj = jet velocity µ = viscosity U∞ = freestream velocity ρ = density V = crossflow velocity ω = vorticity x = streamwise distance

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“…Flow field analysis has previously shown that an upsweep angle in the range 0° < φ < 45° promotes threedimensional flow separation, leading to a reduction in the pressure on the upswept surface and the formation of a counter-rotating vortex pair [4][5][6] . The low pressure on the upswept face causes a reduction in lift, in addition to an increase in drag 2,7 . Furthermore, the vortices are capable of disrupting the initial path of payloads and paratroopers during airdrop missions.…”

Section: Introductionmentioning

confidence: 99%

Afterbody Drag Reduction Using Active Flow Control

Jackson¹,

Wang²,

Gursul³

2017

55th AIAA Aerospace Sciences Meeting

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Experiments were performed in a water tunnel to assess the efficacy of blowing via pairs of circular and high aspect ratio slot jets to modify the counter-rotating vortices in the near-wake of a slanted base cylinder. Drag force and crossflow Particle Image Velocimetry measurements were collected. Drag reductions achieved by circular jets on the upswept face were highly dependent on blowing direction and location. These reductions reached close to 7% when blowing outboard at further upstream and inboard locations, caused by jet vortices restricting the shear layer development, which lead to smaller vortex cores further from the surface. Upstream blowing into the vortex cores produced highly diffuse vortices at the trailing-edge, as a result of a reduction in peak instantaneous vorticity and increased meandering. Surface-normal slot blowing from the upswept face had little effect on the afterbody flow field, while spanwise blowing from the upsweep edge deflected the vortices away from the surface, but at the expense of increasing the drag coefficient. A jet flap nearly parallel to the freestream achieved drag reductions close to 9%, equating to energy savings of almost 3%. Jet vortices shortened the shear layer, resulting in weaker afterbody vortices with smaller cores and lower circulation. Instantaneous analysis revealed reduced separation on the upswept surface, and less turbulent kinetic energy in the vortices.

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Interference-free measurements of the subsonic aerodynamics of slanted-base ogive cylinders

Cited by 43 publications

References 3 publications

Afterbody vortices of axisymmetric cylinders with a slanted base

Afterbody vortices of axisymmetric cylinders with a slanted base

Control of Afterbody Vortices by Blowing

Afterbody Drag Reduction Using Active Flow Control

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