{
  "abstract": "Wall traction in a rarefied gas is a half-range functional of molecules arriving at and leaving a surface, whereas hybrid solvers, moment methods, and learned wall models often transmit only finite full-range moments. We determine which directional information is lost and what restores the wall functional using direct simulation Monte Carlo (DSMC) of Mach-6 flow over three triangular-protrusion orientations. Output-specialized neural networks interpolate a 57-condition DSMC database. A distinct ExtraTrees regression holds learner capacity, auxiliary features, train/test split, and seeds fixed while comparing the primitive state $S_0$, the momentum-flux-augmented state $S_1$, and the heat-flux-augmented state $S_2$. Adding the momentum-flux tensor $P_{ij}$ reduces aggregate pressure error by 31\\% but does not make signed shear transferable. An analytic null-space construction supplies the mechanism: strictly positive distributions can share all full-range moments through degree three while producing different pressure and opposite signed shear because the wall kernel selects the incident half space. A finite-distance off-wall ExtraTrees state $S_{\\mathrm{off}}$ shows that partial directionality is useful but representation-dependent. Finally, a parameter-free kinetic reconstruction combines the incident half-range wall-arrival state $S_{\\mathrm{HR}}$ with the prescribed diffuse kernel and agrees with both a same-window DSMC tally sharing the incident events and a separate 40,000-step DSMC wall-tally window. The resulting design principle is direct: a rarefied wall closure must preserve the incident normal--tangential correlations required by the target load rather than merely adding higher full-range moments.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2606.25752",
  "author_total": 2,
  "authors": [
    {
      "name": "Elyas Lekzian"
    },
    {
      "name": "Ehsan Roohi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/a0t31qva368n6.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.25752",
  "fulltext_url": null,
  "id": "a0t31qva368n6",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.25752",
  "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",
      "2604|Gas Dynamics and Kinetic Theory"
    ]
  ],
  "openalex": "W7165913437",
  "pdf_url": "https://arxiv.org/pdf/2606.25752",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/a0t31qva368n6.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:31Z",
      "native_id": "2606.25752",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.25752"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.flu-dyn",
      "subfield": "fluid-dynamics"
    }
  ],
  "title": "Bulk-to-Wall Observability in Rarefied Hypersonic Flow: Moment Limits and Incident Half-Range Sufficiency",
  "title_text": "Bulk-to-Wall Observability in Rarefied Hypersonic Flow: Moment Limits and Incident Half-Range Sufficiency",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:31Z",
  "url": "https://research.draconitic.com/paper/a0t31qva368n6",
  "venue": "arXiv",
  "versions": []
}