  We present an original study on the numerical stabiliy of explicit schemes
solving the incompressible Euler equations on an open domain with slipping
boundary conditions. Relying on the skewness property of the non-linear term,
we demonstrate that some explicit schemes are numerically stable for small
perturbations under the condition $\delta t\leq C \delta x^{2r/(2r-1)}$ where
$r$ is an integer, $\delta t$ the time step and $\delta x$ the space step.
