{
  "abstract": "We study hydrodynamic spin coupling in a two-rotor corral using DNS of 2D incompressible viscous fluid flow. An active rotor is driven at angular velocity W, and a nearby torque-free passive rotor selects an angular velocity w through hydrodynamic torque balance. The signed gear ratio Gamma=w/W distinguishes corotation from counterrotation, with Reynolds number Re=|Ω|r^2/ν. Motivated by a recent quasi-two-dimensional experiment, we use a DLM/FD method to compute planar phase diagrams of $Γ(G,Re)$ at corral sizes C=3, 4.5, and 6. The planar model recovers the benchmark gap route at Re=20: an intermediate counterrotation band, a wide-gap transition to corotation, gear-ratio magnitudes of order 10^{-2}, and the observed sequence of vortex attachment, detachment, and merger. It also produces a reentrant-like gap structure with a small-gap corotation region whose relation to the experimental close-range geometric state remains unresolved. The main discrepancy is the high-Re boundary. At the experimental mid-gap transect G about 0.3, the planar gear ratio approaches zero from the counterrotating side but does not cross through Re=400; at the narrower gap G=0.22, by contrast, the planar terminal spin reverses near Re=44. Wall-traction diagnostics show that this crossing is not the experimental shear-competition mechanism: the gap-facing counterrotating arc narrows but does not collapse or deflect as in the experiment, and the reversal at G=0.22 occurs by redistribution of the integrated planar torque. The strictly planar model therefore captures the broad gap-route architecture and the existence of a Reynolds-driven spin boundary, but displaces that boundary in gap and alters its surface-stress mechanism. The remaining mismatch points to finite-depth secondary motion, end-wall stresses, and apparatus geometry as plausible contributors to the experimental shear balance.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Physical Review Fluids 11, 104305, 2026",
  "arxiv": "2607.01533",
  "author_total": 2,
  "authors": [
    {
      "name": "Tsorng-Whay Pan"
    },
    {
      "name": "Jiwen He"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/c2rk33ev1rmyj.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.01533",
  "fulltext_url": null,
  "id": "c2rk33ev1rmyj",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.01533",
  "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",
      "physics.flu-dyn"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2607.01533",
  "pmcid": null,
  "pmid": null,
  "published": "2026-07-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/c2rk33ev1rmyj.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:34Z",
      "native_id": "2607.01533",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.01533"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.flu-dyn",
      "subfield": "fluid-dynamics"
    }
  ],
  "title": "Two-dimensional simulations of hydrodynamic spin coupling in a two-rotor corral",
  "title_text": "Two-dimensional simulations of hydrodynamic spin coupling in a two-rotor corral",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:34Z",
  "url": "https://research.draconitic.com/paper/c2rk33ev1rmyj",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/qkw5-btdw",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}