Oscillations Foliations and Burger Laws

In this work we construct large amplitude oscillating waves which are local solutions on some open domain of time space of both the three dimensional Burger equations and the incompressible Euler equation. The solutions are mainly characterised by the fact that the corresponding jacobin matrix are nilpotent. our approach consists in performing some nonusual WKB analysis. The main difficulty is to understand what is the geometry of the phases brought into play.