{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"35d0ba2c671c6f8957e6334ef8c5a4c643388ad9196b11d92453b7f07f420c93","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"c5e4333c9270df7412f5cfdb76c17efb775e03fd465a700199de56191b5f6936","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"fluid.shear-transition.discontinuous-transition","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Adding forces such as buoyancy, pipe curvature or magnetic fields to a pipe or channel flow can turn the gradual onset of turbulence into an abrupt jump with hysteresis, like boiling. No rule predicts which flows behave which way.","posed_since":"2024","precise":"In wall-bounded shear flows with body forces (curved, heated or magnetohydrodynamic pipes and channels) or with suppressed large-scale flow, the turbulent fraction can jump discontinuously to zero, with metastable turbulence (Yang et al., Nature Physics 2026; Gome et al., PRL 2024, plane Couette flow). Find a criterion, in measurable quantities such as the kinetic-energy advection across laminar-turbulent interfaces or the fluctuation intensity in a one-field stochastic front model, that predicts whether the transition is continuous (directed percolation) or first order, and locate the tricritical point if one exists.","problem_ref":null,"references":"","settled_by":"A parametric study in one flow family, such as a pipe with tunable body force, mapping the order of the transition against the proposed control parameter, including the tricritical point.","status_note":"The 2024 and 2026 works propose different controlling quantities (fluctuation intensity versus interfacial energy flux).","title":"When is the onset of shear-flow turbulence discontinuous?","topic_ref":"2aa8cdcaa55f798dfb19771ba7be3d165d6aebb316dba50bbe9ddce450fd9038"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"ac74b37416a56f2b087643fc809fb9b7f399e1731c1a197c90f6a225a8ccb7ec","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"9125642ef6637803eb095d8562e0c9944620415e736630c1dd9e82a7df6cde3a","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"eXx-OFssmOXDYtnEef7lkgmGksRt3pasPOm-pRc2rBUaCpZ5yLLBnKjA3dh4leBXz-OQFZAZ5HL6uyo1tqzFBw"},"schema":"pubphys.envelope/1"},"record_hash":"ac74b37416a56f2b087643fc809fb9b7f399e1731c1a197c90f6a225a8ccb7ec","leaf_index":1430}