Wake dynamics of a square cylinder while moving upward in quiescent water
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866912682671603712 |
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| author | Ashraf, Intesaaf Dorbolo, Stephane Tiwari, Neetu |
| author_facet | Ashraf, Intesaaf Dorbolo, Stephane Tiwari, Neetu |
| contents | We experimentally investigate the wake dynamics of a square cylinder rising through quiescent water over a range of Froude numbers ($\mathrm{Fr}$). Time-resolved Particle Image Velocimetry provides velocity and vorticity fields that enable pressure reconstruction and vortex characterization. Diagnostics based on swirl strength ($λ_{ci}$), the Okubo-Weiss parameter ($W$), and a shear-vortex interaction measure ($Λ$) reveal that the wake is governed by a persistent pair of counter-rotating vortices rather than by periodic shedding. Circulation exhibits a two-regime dependence on $\mathrm{Fr}$, with a sharp increase below $\mathrm{Fr}\approx 1$ and saturation above this threshold, mirroring entrainment force scaling reported previously. While vortex area remains nearly constant, swirl strength and negative-$W$ regions expand with $\mathrm{Fr}$, indicating that entrainment enhancement arises from intensified rotation rather than an enlarged vortex footprint. These findings provide new physical insight into vortex-free-surface interactions and enrich the understanding of entrainment mechanisms in unsteady wakes, with implications for multiphase flows and the hydrodynamic design of naval and offshore structures. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_18305 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Wake dynamics of a square cylinder while moving upward in quiescent water Ashraf, Intesaaf Dorbolo, Stephane Tiwari, Neetu Fluid Dynamics We experimentally investigate the wake dynamics of a square cylinder rising through quiescent water over a range of Froude numbers ($\mathrm{Fr}$). Time-resolved Particle Image Velocimetry provides velocity and vorticity fields that enable pressure reconstruction and vortex characterization. Diagnostics based on swirl strength ($λ_{ci}$), the Okubo-Weiss parameter ($W$), and a shear-vortex interaction measure ($Λ$) reveal that the wake is governed by a persistent pair of counter-rotating vortices rather than by periodic shedding. Circulation exhibits a two-regime dependence on $\mathrm{Fr}$, with a sharp increase below $\mathrm{Fr}\approx 1$ and saturation above this threshold, mirroring entrainment force scaling reported previously. While vortex area remains nearly constant, swirl strength and negative-$W$ regions expand with $\mathrm{Fr}$, indicating that entrainment enhancement arises from intensified rotation rather than an enlarged vortex footprint. These findings provide new physical insight into vortex-free-surface interactions and enrich the understanding of entrainment mechanisms in unsteady wakes, with implications for multiphase flows and the hydrodynamic design of naval and offshore structures. |
| title | Wake dynamics of a square cylinder while moving upward in quiescent water |
| topic | Fluid Dynamics |
| url | https://arxiv.org/abs/2509.18305 |