text: Consider two stationary plane walls with a constant volume flow rate  is injected/sucked at the point of intersection of plane walls and let the angle subtended by two walls be . Take the cylindrical coordinate  system with  representing point of intersection and  the centerline and  are the corresponding velocity components. The resulting flow is two-dimensional if the plates are infinitely long in the axial  direction, or the plates are longer but finite, if one were neglect edge effects and for the same reason the flow can be assumed to be entirely radial i.e., .
  Then the continuity equation and the incompressible Navier–Stokes equations reduce to
  The boundary conditions are no-slip condition at both walls and the third condition is derived from the fact that the volume flux injected/sucked at the point of intersection is constant across a surface at any radius.