  Feedback from supernovae is an essential aspect of galaxy formation. In order
to improve subgrid models of feedback we perform a series of numerical
experiments to investigate how supernova explosions power galactic winds. We
use the Flash hydrodynamic code to model a simplified ISM, including gravity,
hydrodynamics, radiative cooling above 10,000 K, and star formation that
reproduces the Kennicutt-Schmidt relation. By simulating a small patch of the
ISM in a tall box perpendicular to the disk, we obtain sub-parsec resolution
allowing us to resolve individual supernova events and we investigate how the
wind properties depend on those of the ISM and the galaxy. We find that
outflows are more efficient in disks with lower surface densities or gas
fractions. A simple model in which the warm cloudy medium is the barrier that
limits the expansion of blast waves reproduces the scaling of outflow
properties with disk parameters at high star formation rates. The scaling we
find sets the investigation of galaxy winds on a new footing, providing a
physically motivated sub-grid description of winds that can be implemented in
cosmological hydrodynamic simulations and phenomenological models. [Abridged]
