Your grid is a filter
July 4, 2026
Research project
The exact unresolved stress
A finite-volume discretization is exactly a filter, so the stress a coarse simulation leaves unresolved can be written down exactly. The result looks different from the classical subgrid stress that sixty years of models aim at: it knows the numerical scheme, it is not symmetric, and it is not local. Fit a model to this target and the a-posteriori error vanishes where classical targets drift.
Paper
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