Hey! So if the vorticity of a fluid = 0, it is in steady state laminar flow and friction is negligible (and viscosity too?), you can use the bernoulli equation between any two arbitrary points in the fluid, regardless if they are connected by a streamline. If the vorticity is non-zero, can you still use bernoulli, but only if you follow a streamline? And how does the viscosity of a fluid come into this? I believe the viscosity must be negligible for the Bernoulli-equation to be used. However, without viscosity you wouldn't even have laminar flow, so what's up with that?