{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a681570d187a193f8e2813291e0d339ae4053a8846fbf6f0e80e2e91a501e149","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"159df10ff38ac0d70d061b95809025191854fff897bf319304b572704e5258de","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"fluid.shear-transition.sustained-turbulence","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Single turbulent puffs in a pipe always decay eventually, with lifetimes that grow faster than exponentially with flow speed. Whether fully turbulent flow at high speed is truly permanent, or also only a very long-lived transient, is unknown.","posed_since":"2006","precise":"Puff lifetimes in pipe flow grow superexponentially with Re without diverging (Hof et al. 2006, 2008). For featureless turbulence at $\\mathrm{Re} >> \\mathrm{Re}_c$ in a periodic pipe of fixed length $L/D$, does the mean relaminarization time diverge at a finite Re (a chaotic attractor appears), or stay finite for all Re (a chaotic saddle)? Answer: yes or no for fixed $L/D$, with the Re and $L$ dependence of the escape rate.","problem_ref":null,"references":"","settled_by":"Large ensembles of DNS in short and moderate periodic pipes measuring escape-rate statistics versus Re and L, or a proof in a reduced model with controlled error.","status_note":"","title":"Is uniform pipe turbulence permanent or an extremely long transient?","topic_ref":"2aa8cdcaa55f798dfb19771ba7be3d165d6aebb316dba50bbe9ddce450fd9038"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"e0a2190f53a5617b97512611bc44d7e0a22551eb6279c946d2aea2e706ed9293","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"d24f7c066d5e8622332f699f1c222632c4d93105f13d964867717643a9440f04","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"K9pDXOe8Av7pVBZKyfDkkZgkIebhNZYxiBSYC7xFde3ffOowyC2MmLQKb110yXF3Ucv4qvsHv684IqRXEuKZAA"},"schema":"pubphys.envelope/1"},"record_hash":"e0a2190f53a5617b97512611bc44d7e0a22551eb6279c946d2aea2e706ed9293","leaf_index":1431}