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Unsteady characteristics of vortex structures in front of surface-mounted obstacles
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J
DOI：10.1017/jfm.2026.11772.png)
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Abstract
En 中文
The flow characteristics over isolated surface-mounted obstacles are investigated with time-resolved particle image velocimetry. Three different geometries (square cylinder; circular cylinder; and hemisphere) are considered maintaining the same aspect ratio of 0.5; and are completely submerged in the laminar boundary layer. The height-based Reynolds number is 1530. The time-averaged flow topologies around the three obstacles are quite similar. However; the unsteady characteristics over the square cylinder are significantly stronger than those over the circular cylinder and hemisphere. The vortices upstream of the square cylinder experience periodic amplification and decay while their cores oscillate along the flow direction. These two dynamic mechanisms corresponding to different characteristic frequencies collectively contribute to the oscillation of the entire horseshoe vortex system. Furthermore; a direct correlation between vortex number and flow pattern is established. Three categories of patterns exist in the flow field upstream of the square cylinder; corresponding to different numbers of clockwise vortices. The upstream flow field intermittently switches between these three patterns. In addition; the separation region above the square cylinder exhibits the same high-frequency characteristics as the upstream region due to the spatial oscillations of the horseshoe vortex system. Its low-frequency characteristics; however; originate from the instability of the shear layer at the free end. These findings help fill gaps in the relevant field and contribute to the study on the dynamics of the flow over surface-mounted obstacles.
Keywords:
vortex dynamics
separated flows
vortex interactions
Journal
IF:
3.9
Papers:
2.0W
Citations:
9.4W
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