Mixed-mode self-oscillations, stochastic excitability, and coherence resonance in flows of highly concentrated suspensions

Complex mixed-mode oscillatory regimes in flows of concentrated suspensions are studied on the base of the nonlinear dynamical model. A mechanism of the generation of such regimes is associated with the N-shaped flow curve which reflects the dependence of the shear rate on the shear stress. In the zone of the unstable equilibria, amplitude and frequency characteristics of mixed-mode self-sustained oscillations are investigated. A transformation of quasi-harmonic oscillations to non-harmonic ones under increase of the stiffness of the flow curve is discussed. In the zone of the stable equilibria, a phenomenon of stochastic excitement of spike oscillations is studied by the analytical stochastic sensitivity method along with direct numerical simulations. For these mixed-mode stochastic oscillations, a parametric analysis of statistics of interspike intervals is carried out and a phenomenon of coherence resonance is discussed.