{
  "abstract": "The most energetic coherent structure of a hovering full-scale quadcopter is associated with a self-organizing process in which the individual rotor vortices synchronize their frequencies while undergoing merging events, yielding a globally correlated structure. We identify and characterize this phenomenon by applying spectral modal and conditional analyses to assimilated three-dimensional velocity data acquired via Shake-The-Box Lagrangian particle tracking. The dataset captures a high-Re, turbulent flow further complicated by time-varying rotor speeds stemming from active flight control, low-frequency vehicle drift, finite spatio-temporal resolution, and measurement uncertainty. Most coherent structures recover established single-rotor features such as tip vortices and their subharmonic pairing. The globally synchronized vortex merging manifests as a spectral peak at an incommensurate frequency below the rotor band, which cannot be explained by single-rotor aerodynamics, subharmonic instabilities, or band-to-band triadic interactions. Instead, conditional averaging provides evidence of the aforementioned intermittent, distinctly non-subharmonic vortex-merging process involving all four rotor wakes. Establishing whether or not this phenomenon is observed across different flight conditions and configurations remains speculative; however, the consistent characterization of the globally synchronized vortex merging using complementary frequency- and time-domain analyses despite experimental complexities, in particular rotor speed variations, demonstrates its robustness.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.19507",
  "author_total": 5,
  "authors": [
    {
      "name": "Elias S. Pratschke"
    },
    {
      "name": "Claus C. Wolf"
    },
    {
      "name": "Daniel Schanz"
    },
    {
      "name": "Andreas Schröder"
    },
    {
      "name": "Oliver T. Schmidt"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/acpz1p51fj8ew.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.19507",
  "fulltext_url": null,
  "id": "acpz1p51fj8ew",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.19507",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "nlin.AO"
    ],
    [
      "arxiv",
      "physics.data-an"
    ],
    [
      "arxiv",
      "physics.flu-dyn"
    ],
    [
      "arxiv",
      "physics.pop-ph"
    ],
    [
      "openalex",
      "2206|Fluid Dynamics and Turbulent Flows"
    ]
  ],
  "openalex": "W7213612409",
  "pdf_url": "https://arxiv.org/pdf/2609.19507",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/acpz1p51fj8ew.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2609.19507",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.19507"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.data-an",
      "subfield": "computational"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.flu-dyn",
      "subfield": "fluid-dynamics"
    },
    {
      "field": "physics",
      "origin": "arxiv:nlin.AO",
      "subfield": "statistical-nonlinear"
    }
  ],
  "title": "Wake interactions drive synchronized vortex merging in a hovering quadcopter",
  "title_text": "Wake interactions drive synchronized vortex merging in a hovering quadcopter",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:19Z",
  "url": "https://research.draconitic.com/paper/acpz1p51fj8ew",
  "venue": "arXiv",
  "versions": []
}