Subsonic flows with a contact discontinuity in a two-dimensional finitely long curved nozzle

In this paper, we establish the existence and uniqueness of subsonic flows with a contact discontinuity in a two-dimensional finitely long slightly curved nozzle by prescribing the entropy, the Bernoulli’s quantity, and the horizontal mass flux distribution at the entrance and the flow angle at the exit. The problem is formulated as a nonlinear boundary value problem for a hyperbolic–elliptic mixed system with a free boundary. The Lagrangian transformation is employed to straighten the contact discontinuity and the Euler system is reduced to a second-order nonlinear elliptic equation for the stream function. One of the key points in the analysis is to solve the associated linearized elliptic boundary value problem with mixed boundary conditions in a weighted Hölder space. Another one is to employ the implicit function theorem to locate the contact discontinuity.