{
  "id": "2401.02089",
  "version": "v1",
  "published": "2024-01-04T06:24:14.000Z",
  "updated": "2024-01-04T06:24:14.000Z",
  "title": "Effect of rotation on wake vortices in stratified flow",
  "authors": [
    "Jinyuan Liu",
    "Pranav Puthan",
    "Sutanu Sarkar"
  ],
  "categories": [
    "physics.flu-dyn",
    "physics.ao-ph"
  ],
  "abstract": "Stratified wakes past an isolated conical seamount are simulated at a Froude number of $Fr = 0.15$ and Rossby numbers of $Ro = 0.15$, 0.75, and $\\infty$. The wakes exhibit a K{\\' a}rm{\\' a}n vortex street, unlike their unstratified, non-rotating counterpart. Vortex structures are studied in terms of large-scale global modes, as well as spatially localised vortex evolution, with a focus on rotation effects. The global modes are extracted by spectral proper orthogonal decomposition (SPOD). For all three studied $Ro$ ranging from mesoscale, submesoscale, and non-rotating cases, the frequency of the SPOD modes at different heights remains coupled as a global constant. However, the shape of the SPOD modes changes from slanted `tongues' at zero rotation ($Ro=\\infty$) to tall hill-height columns at strong rotation ($Ro=0.15$). A novel method for vortex centre tracking shows that, in all three cases, the vortices at different heights advect uniformly at about $ 0.9U_{\\infty}$ beyond the near wake, consistent with the lack of variability of the global modes. Under system rotation, cyclonic vortices (CVs) and anticyclonic vortices (AVs) present considerable asymmetry, especially at $Ro = 0.75$. The vorticity distribution as well as the stability of AVs are tracked downstream using statistics conditioned to the identified vortex centres. At $Ro=0.75$, intense AVs with relative vorticity up to $\\omega_z/f_{\\rm c}=-2.4$ are seen with small regions of instability but all AVs evolve towards a more stable state. Recent stability analysis that accounts for stratification and viscosity is found to improve on earlier criteria.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-01-04T06:24:14.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "wake vortices",
      "stratified flow",
      "vortex centre",
      "spectral proper orthogonal decomposition",
      "tall hill-height columns"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}