For example, in the case of an unbounded planar domain with two-dimensional — incompressible and stationary — flow in polar coordinates (r, φ), the velocity components (u r, u φ) and pressure p are: u r = A r , u φ φ = B ( 1 r − − r A ν ν + 1 ) , p = − − A 2 + B 2 2 r 2 − − 2 B 2 ν ν r A ν ν A + B 2 r ( 2 A ν ν + 2 ) 2 A ν ν + 2