{
  "abstract": "We explore the collision hydrodynamics of a ferrofluid droplet falling freely onto a sessile droplet of the same liquid, in the presence of a horizontal magnetic field; a configuration that couples droplet-on-droplet coalescence with concomitant field-governed wetting and spreading. Using high-speed imaging, we track the events through crown formation, radial spreading, and rim detachment (under specific conditions), across three ferrofluid concentrations, two substrates of different wettability (glass and PET), and a range of impact velocities and magnetic field strengths. The maximum crown height is noted to scale as $H_{c,\\max}/D_t\\sim Fr^{0.5}$ ($Fr:$ Froude number); well below the ballistic upper bound of $H_{c,\\max}/D_t\\sim Fr$. At zero-field, the maximum spreading collapses onto the boundary-layer scaling $β_{0,\\max}\\sim (We_0/Oh)^{1/6}$ ($We_0$: Weber number, $Oh:$ Ohnesorge number) when expressed in terms of the merged impact velocity, and coalesced-drop size . With the field applied, a bulk-dissipation energy balance predicts $β_{\\max}\\sim Z^{1/5}$, where $Z$ combines the magnetic-driving, and inertial-capillary-viscous terms, but the observations instead follow a markedly weaker $\\sim Z^{1/11}$, a deficit traced to enhanced dissipation from the magnetoviscous effects, and manifested via an effective Ohnesorge number. Finally, rim detachment occurs beyond a field- and height-dependent threshold, described by a size-independent criterion $Fr^2Bo\\approx 3550$ ($Bo:$ Bond number), above which the rim may fragment into daughter droplets. These scalings provide predictive tools for magnetically assisted printing, droplet-on-demand systems, and coating processes, where repeated droplet collisions occur on the residual liquid droplet or layer.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.30116",
  "author_total": 4,
  "authors": [
    {
      "name": "Neeladri Sekhar Bera"
    },
    {
      "name": "Abhishek Kumar Jaiswal"
    },
    {
      "name": "Devranjan Samanta"
    },
    {
      "name": "Purbarun Dhar"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ez4vx07rj5qap.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.30116",
  "fulltext_url": null,
  "id": "ez4vx07rj5qap",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.30116",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.flu-dyn"
    ],
    [
      "openalex",
      "2206|Fluid Dynamics and Heat Transfer"
    ]
  ],
  "openalex": "W7214317837",
  "pdf_url": "https://arxiv.org/pdf/2609.30116",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-24",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ez4vx07rj5qap.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:11Z",
      "native_id": "2609.30116",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.30116"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.flu-dyn",
      "subfield": "fluid-dynamics"
    }
  ],
  "title": "Magneto-coalescence phenomena in colliding ferrofluid droplets",
  "title_text": "Magneto-coalescence phenomena in colliding ferrofluid droplets",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:11Z",
  "url": "https://research.draconitic.com/paper/ez4vx07rj5qap",
  "venue": "arXiv",
  "versions": []
}