  Planar flows with a free boundary in a partially filled and nonuniformly
rotating container, with a strongly noncircular shape of the cross-section, are
investigated numerically within the ideal fluid approximation. Vorticity is
assumed constant across the fluid, thus allowing us to apply the recently
developed, highly efficient numerical method based upon exact equations of
motion of the free boundary in terms of conformal variables and on the fast
Fourier transform algorithms. It is shown that decelerated rotation of such
centrifuge leads to formation of strongly nonlinear breaking waves with sharp
crests, and the wave overturning occurs either in the rotation direction or
against it, depending on value of the (negative) angular acceleration.
