i'm a little bit confused.
if the velocity potential Φ = Φ(x,y,t).
and it says Φ satifies laplace's equation.
does that mean ∂²Φ/∂x² + ∂²Φ/∂y² = 0
or
∂²Φ/∂x² + ∂²Φ/∂y² + ∂²Φ/∂t² = 0.

does the time variable get included??

i'm thinking it isn't but i'm not exactly sure.