For example, in the case of an unbounded Euclidean domain with three-dimensional — incompressible, stationary and with zero viscosity (ν = 0) — radial flow in Cartesian coordinates (x, y, z), the velocity vector v and pressure p are: v ( x , y , z ) = A x 2 + y 2 + z 2 ( x y z ) , p ( x , y , z ) = − − A 2 2 ( x 2 + y 2 + z 2 ) .