{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"625beda1f0748f0c0fe4611e00c1a4471cad500ba5c8a784e4b5de39272ffc14","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"86fe560ed192f6f13c61861c25daa32922fc47be010e6f945c2aaf5e4915c1aa","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"fluid.turbulent-combustion.flame-acceleration-runup","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"In a pipe filled with a fuel-air mixture and lit at the closed end, the flame speeds up until it becomes a detonation. How far it travels before that happens decides the safety of pipelines, mines and reactors, and it cannot yet be computed reliably.","posed_since":"","precise":"For a premixed mixture in a tube of diameter $D$, smooth or with obstacles of blockage ratio BR, predict the run-up distance $X_{\\mathrm{DDT}}/D$ and the location and mechanism of the final transition (hot-spot ignition through a gradient of ignition delay, shock-flame interaction, boundary-layer and wall effects) as functions of mixture reactivity, expansion ratio and $D$. An answer is a validated prediction without constants fitted to the same experiments.","problem_ref":null,"references":"","settled_by":"Blind predictions of $X_{\\mathrm{DDT}}$ for a set of mixtures and tube geometries, compared with new experiments.","status_note":"Resolved simulations of hydrogen-air DDT in channels reproduce experiments qualitatively; no quantitative run-up prediction across mixtures as of 2026 (not re-verified for 2024-2026).","title":"Predicting run-up distance to detonation in smooth and obstructed tubes","topic_ref":"ff8822779d7d3829d62f794eaee78060074a7c7c5588960c0eae974a587339ac"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"294e179ab5b7c3df6837dd8fe170966939be4498207aed19e818a90ecf49ad27","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"09d6b4cd593894b42ee66d9138c139f3a4c9a565deadc0f7ed32e19253fd5f3e","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ox7ueQ0mDBejmJCKpxyiQpvpUU2cQT59tpi4Sv3ViTze2QPBMOyaGOprPRktmmn8lIj-nbQ51q1Yymc46w-9DQ"},"schema":"pubphys.envelope/1"},"record_hash":"294e179ab5b7c3df6837dd8fe170966939be4498207aed19e818a90ecf49ad27","leaf_index":1448}