Solution
= Solution
{c}
For steady <inviscid flow> of constant density without a body-force potential, <Bernoulli's theorem> gives
$$
\boxed{\frac p\rho+\frac12|\mathbf u|^2
=\text{constant along each streamline}.}
$$
The constant can differ between streamlines, because this flow has nonzero <vorticity>. Dotting the steady Euler equation with $\mathbf u$ gives $\mathbf u\cdot\nabla(p/\rho+|\mathbf u|^2/2)=0$, which proves precisely the along-streamline form.