Vorticity dynamics of a dipole colliding with a no-slip wall

W. Kramer, H.J.H. Clercx, G.J.F. van Heijst

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    Abstract

    The active role of vorticity in the collision of a Lamb-like dipole with a no-slip wall is studied for Re values ranging between 625 and 20000. The initial approach of the dipole does not differ from the stress-free case or from a point-vortex model that incorporates the diffusive growth of the dipole core. When closer to the wall, the detachment and subsequent roll-up of the boundary layer leads to a viscous rebound, as was observed by Orlandi Phys. Fluids A 2, 1429 1990 in numerical simulations with Re up to 3200. The net translation of the vortex core along the wall is strongly reduced due to the cycloid-like trajectory. For Re2500 wall-generated vorticity is wrapped around the separate dipole halves, which hence become partially shielded monopoles. For ReO104, however, a shear instability causes the roll-up of the boundary layer before it is detached from the wall. This leads to the formation of a number of small-scale vortices, between which intensive, narrow eruptions of boundary-generated vorticity occur. Quantitative measures are given for the influx of vorticity at the wall and the consequent increase of boundary layer vorticity and enstrophy.
    Original languageEnglish
    Article number126603
    Number of pages13
    JournalPhysics of fluids
    Volume19
    Issue number12
    DOIs
    Publication statusPublished - 2007

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    Kramer, W., Clercx, H. J. H., & van Heijst, G. J. F. (2007). Vorticity dynamics of a dipole colliding with a no-slip wall. Physics of fluids, 19(12), [126603]. https://doi.org/10.1063/1.2814345