Experimental and numerical investigation of a strongly-forced precessing cylinder flow

Planar particle image velocimetry (PIV) and direct numerical simulations (DNS) of the flow in a precessing cylinder of height-to-radius ratio of 1.835 are presented for a nutation angle of 15° and a Reynolds number 6430 based on the cylinder's angular frequency. We find excellent agreement in terms of time-averaged velocity profiles and Kelvin mode amplitudes during the initial development and in the asymptotic state. In the experiment, a rapid transition to a disordered state follows a brief appearance of azimuthal structures with a predominant wavenumber m=9. In the DNS, the transition occurs later than in the experiment, and shows dominance of a triad of azimuthal wavenumbers m=1,4,5 during the transient evolution. Adding a small random perturbation to the simulation after the forced mode is established accelerates transition to flow dominated by m=9 which eventually transitions to a disordered state, consistent with observations from PIV. The breaking of rotoreflection (inversion) symmetry of the system is found to be critical in establishing evolution paths to the disordered and asymmetric asymptotic state.