Injection of Fluid from a Slot into a Stream: Uniqueness

This is a sequel work on the existence of the solution to the free boundary problem on injection of fluid from a slot into a uniform stream with two free boundaries by Stojanovic (IMA J Appl Math 41:237–253, 1988). However, the uniqueness of the solution to the two-phase fluids problem with two free boundaries remains unresolved. In this paper, we will establish the asymptotic behavior of the flow in the upstream and prove the uniqueness of the solution to this problem.