{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5519f0a1b0e20fde5ec6b33ad36f7b792b210dc93aa9842613b235ccad531ac2","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"770f4982831cc5af03c6c7c770de8ca4c99b536db8cf0aaa45f7a62df7ea0819","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"bio.granular-rheology.silo-clogging","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Grains pouring through a small hole in a silo eventually jam by forming an arch. It is disputed whether there is a hole size above which jamming never happens, or whether jamming only becomes extremely rare.","posed_since":"","precise":"For grains of diameter $d$ discharging through an orifice of diameter $D$, the mean number of grains $\\langle s\\rangle$ discharged between clogs grows with $D/d$. Determine whether $\\langle s\\rangle$ diverges at a finite critical $D_c/d$ as (D_c - D)^(-gamma), or grows exponentially in a power of $D/d$ with no true transition, in 2D and 3D silos.","problem_ref":null,"references":"","settled_by":"Measurements or simulations of $\\langle s\\rangle(D/d)$ over enough decades to separate a power-law divergence from exponential growth, supported by a theory of arch formation.","status_note":"Thomas and Durian (2015, https://doi.org/10.1103/PhysRevLett.114.178001) found exponential growth with no critical outlet size, contradicting the earlier power-law divergence of Zuriguel et al. (2005); the issue is unresolved in 3D and for frictional grains (2026).","title":"Is there a critical outlet size for clogging of granular 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