Experimental study of the linear and nonlinear regimes of inertial wave attractors in a rotating cylinder with non-axisymmetric ends

The flow in a nonuniformly rotating (librating) cylinder with ends symmetrically inclined relative to the cross section is experimentally investigated. Due to librations, inertial waves are supported; at certain frequencies, they are focused on a closed path, called a wave attractor. The velocity of the pulsation flow changes nonmonotonically with frequency and reaches its maximum value when the attractor takes a square shape. With an increase in the oscillation amplitude, new vorticity centers appear in a threshold way, corresponding to inertial waves with a frequency different from the libration frequency. The Fourier analysis of perturbations in the supercritical regime shows that, in addition to the fundamental frequency, the spectrum contains two additional harmonics that satisfy the triadic resonance condition.