{
  "abstract": "The downwash wake of a hovering quadrotor governs both the vehicle's own performance and the safe spacing of multi-rotor formations. Prior measurements have largely characterized the mean flow, using single-point anemometry, volumetric tracking, or planar cuts through part of the rotor system. Higher-order turbulent statistics of the merged wake, and how they relate to canonical jet scaling, have remained unresolved, particularly for small quadrotors at the low-Reynolds-number end of the size range. Here, we present a detailed particle image velocimetry (PIV) study of the downwash of a hovering Crazyflie 2.1 quadrotor (arm length, $l = 46$ mm), sampled along a diagonal cut, passing through rotors along the symmetry axis of the quadrotor, and a front-rotor cut, passing through adjacent rotors. The four rotor jets merge into a single column by $z/l \\approx 5$, beyond which the mean velocity profiles progressively approach the canonical round-jet self-similar form, collapsing by $z/l \\approx 13$ when scaled by the local centerline velocity and half-width. Centerline decay and half-width growth follow canonical scaling laws with an effective source diameter $D_\\text{eff} = 2.29\\,l$, effective Reynolds number $Re_{D_\\text{eff}} = 3 \\times 10^4$, at the low end of the range over which canonical jet scaling has been established, and spreading and decay constants nonetheless within the canonical round-jet range. Resolving both cuts shows that the turbulent normal stresses retain a bimodal, cut-dependent signature of the four-rotor source throughout the measurement domain.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.30900",
  "author_total": 3,
  "authors": [
    {
      "name": "Anoop Kiran"
    },
    {
      "name": "Nora Ayanian"
    },
    {
      "name": "Kenneth Breuer"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8may1mt2fb30t.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.30900",
  "fulltext_url": null,
  "id": "8may1mt2fb30t",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.30900",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cs.RO"
    ],
    [
      "arxiv",
      "physics.flu-dyn"
    ],
    [
      "openalex",
      "2206|Fluid Dynamics and Turbulent Flows"
    ]
  ],
  "openalex": "W7204948651",
  "pdf_url": "https://arxiv.org/pdf/2608.30900",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-31",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8may1mt2fb30t.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:41Z",
      "native_id": "2608.30900",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.30900"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.flu-dyn",
      "subfield": "fluid-dynamics"
    }
  ],
  "title": "The Structure of Merging Turbulent Jets Beneath a Small Quadrotor",
  "title_text": "The Structure of Merging Turbulent Jets Beneath a Small Quadrotor",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:41Z",
  "url": "https://research.draconitic.com/paper/8may1mt2fb30t",
  "venue": "arXiv",
  "versions": []
}