Viscous Instability of an Incompressible Fluid Half-Jet Flow

The instability of the free laminar boundary layer between parallel streams is investigated for an incompressible fluid. It is found that the minimum critical Reynolds number for instability is 3.6 based on the assumption of parallel unperturbed flow. However, when the parallel flow theory is corrected for the nonparallelism that actually exists at low Reynolds numbers, the minimum critical Reynolds number for instability becomes 12.