Weak-strong uniqueness and extreme wall events at high Reynolds number

Weak Euler solutions have been hypothesized to explain the d'Alembert paradox of non-vanishing drag. A difficulty is the ``weak-strong uniqueness'' property, which requires that an admissible weak Euler solution must coincide with the smooth Euler solution for the same initial data. Using the Josephson-Anderson relation adapted from superfluids, we show that weak-strong uniqueness for d'Alembert's solution requires mild conditions. To explain drag we therefore predict that these conditions are violated by violent eruption of very thin boundary layers. We discuss observational signatures and explain how the small length-scales involved could threaten the validity of a hydrodynamic description.