Vortex-wake formation and evolution on a prolate spheroid at subcritical Reynolds numbers

Guo, Pengming; Kaiser, Frieder; Rival, David E.

doi:10.1007/s00348-023-03702-y

Cited by 1 publication

(2 citation statements)

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“…Figure 6(a-c) presents results for the steady case as a reference. As discussed in a related study on steady wakes (Guo et al 2023), a helical vortex tube is formed at relatively small x/L; see figure 6(a). Travelling downstream, the core of the vortex tube aligns with the mean flow direction, resulting in a high-velocity region away from the model, as highlighted in figure 6(b).…”

Section: Streamwise Vorticity and Velocity Distributionsmentioning

confidence: 73%

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Dynamic separation on an accelerating prolate spheroid

Guo,

Kaiser,

Rival

2023

J. Fluid Mech.

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Time-varying flow separation on an accelerating prolate spheroid has been studied at various angles of incidence. Instantaneous pressure and scanning stereoscopic particle image velocimetry were used to shed light on the evolution of cross-flow structures for the Reynolds number ( $Re$ ) range of $1.0\times 10^6\leq Re \leq 1.5\times 10^6$ . The movement of separation lines is examined for various model accelerations to investigate on the interplay between acceleration and flow separation. The results demonstrate that for axial accelerations, the streamwise pressure distribution in the rear part of the prolate spheroid switches from an adverse to a favourable pressure gradient. At the same time, the circumferential adverse pressure gradient present during steady motion vanishes during said accelerations. In contrast, both streamwise and circumferential adverse pressure gradients strengthen when the model is axially decelerated. These dynamic pressure distributions influence the location of the separation line, which in turn moves closer to the model meridian during accelerations while moving outwards during decelerations. The streamwise vorticity distribution and the streamwise circulation both show how the separation-line position impacts the vortex formation. A high-vorticity region near the model surface is established during acceleration. In contrast, a decelerating model leads to transport of high-vorticity fluid into the outer area of the cross-flow separation. We further assess the memory effects following the near-impulsive velocity changes. The cross-flow retains the memory of moving separation lines shortly after the acceleration. However, the separation recovers quickly to a steady state.

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Section: Streamwise Vorticity and Velocity Distributionsmentioning

confidence: 73%

“…An Re range was selected where the observed flow structures remain similar (Guo, Kaiser & Rival 2023). Weak Re scaling was observed for steady flow in the range of 1.0 × 10 6 ≤ Re ≤ 1.5 × 10 6 .…”

Section: Kinematicsmentioning

confidence: 99%