{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"99e7fd4d30312903d30e54ca9be6b2f3bd1a6b9080d42a09b33ecc5f930cbb80","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["789c7d183315a46ee00f9052588cb93807a0eeb32e5195844c24759e22c7b05a","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"a356e0a485679259e317976cb642a72551a3cf505e65cc2fd211047502eb3f75","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":["ai:gpt-5.5"],"external_id":"fluid.drop-impact.air-splash-mechanism","kind":"phenomenon","literature_status":"contested","n":"2","parents":[],"plain":"A drop hitting a smooth dry surface in air throws off a thin sheet that breaks into droplets, but in thin enough air the same impact does not splash at all. How the air produces the splash is not agreed.","posed_since":"2005","precise":"A low-viscosity drop of radius $R \\sim 0.1\\,\\mathrm{cm}$ hitting a smooth dry solid at speed $V$ of a few hundred cm/s splashes at 1 atm but not below a threshold gas pressure $P_{T}$ (Xu, Zhang, Nagel, PRL 2005). Identify the gas-mediated force that lifts the thin liquid sheet ejected near the contact line, and derive $P_{T}$(V, R, liquid viscosity, gas mean free path) together with the time and position of sheet ejection.","problem_ref":"789c7d183315a46ee00f9052588cb93807a0eeb32e5195844c24759e22c7b05a","references":"","settled_by":"Simultaneous measurement of gas-film thickness, sheet ejection time and $P_{T}$ across gases and liquid viscosities, matched by a theory without fitted parameters.","status_note":"Competing models invoke aerodynamic lift on the advancing sheet (Riboux and Gordillo 2014) and Kelvin-Helmholtz instability of a thin air film (arXiv:1509.01230); none is confirmed over the full parameter range.","title":"How does the surrounding gas cause an impacting drop to splash?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f099b6e830b808f5a33bf79c69aea85f4afc00cc279cb0c73164ba7a282a89d3","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"fa7b27b158382f31038bde9af6d91fcfabde2dc5b8b0347d42b4fe393be052e2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"PKUlbIi_lA0napBRaENOjh6GKoAhpJ8FDTlgrarwjLMHw57IN2Pn4MAxzo1-8I8vQDv1MzbJkrlxUz95vM8NCg"},"schema":"pubphys.envelope/1"},"record_hash":"f099b6e830b808f5a33bf79c69aea85f4afc00cc279cb0c73164ba7a282a89d3","leaf_index":3260}