Transition to turbulence in suspension Taylor-Couette flow

The pattern transition routes to turbulence are explored via experiments in a Taylor-Couette setup for neutrally-buoyant suspensions of non-colloidal particles in the counter-rotation regime. For small counterrotations, the super-critical bifurcation scenario holds, leading to turbulent Taylor vortices (TTV) that are characterized by large-scale stationary toroidal rolls in the background of small-scale structures. At strong counterrotations, however, the primary bifurcation is sub-critical, leading to spiral vortices, and the final bifurcating state represents a featureless turbulent (TUR) state, devoid of large-scale structures. The spectral routes towards TTV and TUR are analysed, and compared with particle-free cases to infer possible roles of inertial particles.