The goal of this note is to show that, also in a bounded domain $\Omega \subset \mathbb{ R}^n$, with $\partial \Omega\in C^2$, any weak solution, $(u(x,t),p(x,t))$, of the Euler equations of ideal incompressible fluid in $\Omega\times (0,T) \subset \mathbb{ R}^n\times\mathbb{ R}_t$, with the impermeability boundary condition: $u\cdot \vec n =0$ on $\partial\Omega\times(0,T)$, is of constant energy on the interval $(0,T)$ provided the velocity field $u \in L^3((0,T); C^{ 0,\alpha}(\overline{ \Omega}))$, with $\alpha>\frac13\,.$
Categories: math.AP physics.flu-dyn