Interactions of a counter-rotating vortex pair at multiple offsets

Abstract

The interactions between two streamwise vortices were investigated by wind tunnel testing of two NACA0012 vanes at various lateral offsets. One vane was spaced 10 chord lengths (C) downstream of the other, with both at an angle of incidence of 8 degrees and a Reynolds number of 7 10 4. The evolution of the vortex pair was observed until 6.5C behind the downstream vane using Particle Image Velocimetry (PIV). It was found that proximity of the upstream vortex to the downstream vane had a significant effect on the rotational rate of the subsequent vortex pair, with far offset cases having little rotation, and near field cases having angle changes of 19.6 degrees per chord length travelled downstream. At the point of vortex impingement on the downstream vane, the rotational rate dropped to near zero due to a significant strength reduction of both vortices. The point of strongest interaction was found to be laterally offset from the point of closest vortex proximity to the downstream vane by 0.15C, with the vortex on the suction side of the vane. In the offset range investigated, a significant instability was observed in only the upstream vortex. These instabilities increased as the proximity between the vortices decreased, peaking where the vortex interaction was strongest.

Аpplication of scientific visualization tools in the study of supersonic vortex pair

“…In the section x = 0.1, the values of λ2 are shown by filling in red and blue, in the section x = 0.2 -by a green circle, in the section x = 0.3 -by a black circle. It is noted the displacement of counter-rotating vortices upside (to leeward wing side) and their divergence at considered distances downstream from the wing axis, which correlates with the data of other authors [21,22]. The diameter of the vortex zone expands downstream from the wing axis, forming a cone-like shape of the vortices.…”

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“…axes displacement in the direction of the y axis decreasing, which is directed from the leeward wing side to the windward wing side. This fact is in agreement with other data from a literature [19,20]. Also it can be stated that the convergence of vortices is not observed at the considered distances.…”

“…On the contrary, there is a slight repulsion of the vortex axes from each other. Similar results were obtained in [20]. Small differences in the graphs of vortex axes coordinates require a further study.…”

Deployable vortex generators for low Reynolds numbers applications powered by cephalopods inspired artificial muscles

“…It has been demonstrated that each VG orientation offers several advantages over the other. 17 , 18 , 19 The counter-rotating VG orientation generates vortices that promote more efficient mixing of fluid streams compared to co-rotating vortices. Since counter-rotating vortices are characterized by two or more vortices rotating in opposite directions, when such vortices are formed, the opposing rotation directions of the vortices results in the formation of a higher-pressure regions between them which results in the generation of additional lift.…”