ABSTRACT
The methods of the boundary layer theory can be effectively applied to various problems in fluid and gas dynamics, especially to those describing the motion of multicomponent media with sharp borders between different components. This chapter considers two types of problems for the Prandtl system with the transmission conditions on a certain surface. It describes the boundary layer about a wall through which another fluid is injected, and the properties of that fluid are distinct from those of the main stream. The chapter deals with two fluids with different properties being mixed together. A thin layer of plasma with a distinct boundary is formed on the melting surface of a space vehicle entering the atmosphere at high speed. A thin layer where two fluids become mixed together can be observed at the interface between two fluids that move with different speeds and have different rheologic properties.
