NORMAL FORMS FOR 3-DIMENSIONAL PARAMETRIC-INSTABILITIES IN IDEAL HYDRODYNAMICS

We derive and analyze several low dimensional Hamiltonian normal forms describing system symmetry breaking in ideal hydrodynamics. The equat ions depend on two parameters (epsilon, lambda), where epsilon is the strength of a system symmetry breaking perturbation and lambda is a de tuning parameter. In many cases the resulting equations are completely integrable and have an interesting Hamiltonian structure. Our work is motivated by three-dimensional instabilities of rotating columnar flu id flows with circular streamlines (such as the Burger vortex) subject ed to precession, elliptical distortion or off-center displacement.