  A tube conveying a large amount of fluid with a free outlet does not sit
still. We construct and analyze a nonlinear evolution equation describing such
phenomena. Two types of boundary conditions at the inlet are considered, one
for which it is clamped and one for which it is hinged. Analyzing the linear
stability of the trivial solution, we find that with the former boundary
conditions, it exhibits a ``flutter'' instability, while with the latter
boundary conditions, it exhibits a ``rotation'' instability. These
instabilities and the nonlinear behaviors of the system are also studied
numerically.
