We study the asymptotic behaviour
of the following nonlinear problem:
$$\{
\begin{array}{ll}
-{\rm div}(a( Du_h))+
\vert u_h\vert^{p-2}u_h =f \quad\hbox{in }\Omega_h,
a( Du_h)\cdot\nu
= 0 \quad\hbox{on }\partial\Omega_h, \end{array}
.$$
in a domain Ωh of $\mathbb{R}^n$
whose boundary ∂Ωh
contains an oscillating part with respect to h
when h tends to ∞.
The oscillating boundary is defined
by a set of cylinders with axis 0xn that are
h-1-periodically distributed. We prove that the limit
problem in the domain corresponding to
the oscillating boundary identifies
with a diffusion operator with respect to
xn coupled with an algebraic problem
for the limit fluxes.