An Asymptotic Approach to Compare Coupling 2 Mechanisms for Different Partial Differential 3 Equations 4

In many applications the viscous terms become only important in parts of the computational domain. A typical example is the flow of air around the wing of an airplane. It can then be desirable to use an expensive viscous model only where the viscosity is essential for the solution and an inviscid one elsewhere. This leads to the interesting problem of coupling partial differential equations of different types.