{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"e489eec4fc02bb9f2a0fbfbe875f8172f8fb3e54d427c003c5bf064d27448416","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"1eae216b4c2a6cbd1e77d54167a822abc4b9bd0e30b5eebc6fd3da59992166ec","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"fluid.wall-turbulence.separation-closure","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Engineering simulations cannot afford to resolve every eddy, so they use approximate models of turbulence. These models still fail to predict reliably where a turbulent flow detaches from a smooth curved surface, which governs stall and drag, and it is not known what information they are missing.","posed_since":"","precise":"For turbulent boundary layers separating under an adverse pressure gradient from a smooth surface (benchmarks such as $2\\mathrm{D}\\ \\text{and}\\ 3\\mathrm{D}$ smooth bumps at $\\mathrm{Re}_L \\sim 10^6\\ \\text{to}\\ 10^7$), identify which non-local or history information absent from single-point Reynolds-averaged equations (for example upstream pressure-gradient history, transport of Reynolds-stress anisotropy, or large-scale unsteadiness) is needed to predict separation and reattachment locations within experimental uncertainty. Answer: the minimal added information, demonstrated by a model that uses it and predicts an unseen geometry blind.","problem_ref":null,"references":"","settled_by":"Blind predictions of separation and reattachment on a new benchmark geometry agreeing with experiment within stated uncertainty, by a model whose added inputs are stated.","status_note":"Data-driven closures improve agreement on training cases but have not shown reliable transfer to unseen geometries as of 2026.","title":"What information do Reynolds-averaged models lack to predict smooth-surface separation?","topic_ref":"4f4b48fcb04737e7db5b7791039558ed9bddcd8c13b10abe847d72acfa6e0d0c"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d2d18d6bbf5d608bf9c7a6fb8896569906aefd1a98c382c904b3d2a48e94d4b9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"876bb803c2add121d121bc4817e531fc4ed6b9da0837ee54dcb55bf5abbdf635","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"gjwiDKQnS3ues2En1-cpGQHXcOmx58sBDIgtaeqIIVzanAGDFJKtsujDV8sSyl79qSqUpvm0bdYfrOEhOat3Ag"},"schema":"pubphys.envelope/1"},"record_hash":"d2d18d6bbf5d608bf9c7a6fb8896569906aefd1a98c382c904b3d2a48e94d4b9","leaf_index":1455}