  Flow of viscous fluids are not usually discussed in detail in general and
basic courses of physics. This is due in part to the fact that the
Navier-Stokes equation has analytical solution only for a few restricted cases,
while more sophisticated problems can only be solved by numerical methods. In
this text, we present a computer simulation of wind tunnel, i.e., we present a
set of programs to solve the Navier-Stokes equation for an arbitrary object
inserted in a wind tunnel. The tunnel enables us to visualize the formation of
vortices behind object, the so-called von K\'arm\'an vortices, and calculate
the drag force on the object. We believe that this numerical wind tunnel can
support the teacher and allow a more elaborate discussion of viscous flow. The
potential of the tunnel is exemplified by the study of the drag on a simplified
model of wing whose angle of attack can be controlled. A link to download the
programs that make up the tunnel appears at the end.
