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Drag Reduction by Manipulation of Afterbody Vortices
OAI: oai:purehost.bath.ac.uk:openaire_cris_publications/710f65d8-49dd-4d51-9de5-54b8e7cc6dc2
Abstract
Drag force, surface pressure and particle image velocimetry measurements have
been carried out in wind tunnel experiments in order to study the effect of minispoilers on the drag of an axisymmetric cylinder with a slanted base that has an upsweep angle of Φ = 28°. Two different spoiler heights (h/D = 2.5% and 5%) were examined at various chordwise locations along the slanted surface. Placing the spoiler closer to the beginning of the slanted section caused an increased drag due to the separation induced by the spoiler itself, although a more diffused afterbody vortex was produced due to the turbulence ingestion. Drag reduction was observed when placing the spoiler closer to the trailing-edge, with the optimum location x′s /c = 87.5%, resulting in approximately 5% drag reduction for both spoiler heights. This reduction is due to the displacement of the afterbody vortex away from the surface as the mini-spoiler acts similarly to a Gurney flap. The same effect can also be produced by introducing a smaller co-rotating vortex to manipulate the afterbody vortex
trajectory.
been carried out in wind tunnel experiments in order to study the effect of minispoilers on the drag of an axisymmetric cylinder with a slanted base that has an upsweep angle of Φ = 28°. Two different spoiler heights (h/D = 2.5% and 5%) were examined at various chordwise locations along the slanted surface. Placing the spoiler closer to the beginning of the slanted section caused an increased drag due to the separation induced by the spoiler itself, although a more diffused afterbody vortex was produced due to the turbulence ingestion. Drag reduction was observed when placing the spoiler closer to the trailing-edge, with the optimum location x′s /c = 87.5%, resulting in approximately 5% drag reduction for both spoiler heights. This reduction is due to the displacement of the afterbody vortex away from the surface as the mini-spoiler acts similarly to a Gurney flap. The same effect can also be produced by introducing a smaller co-rotating vortex to manipulate the afterbody vortex
trajectory.