Intermittency and hibernation in elasto-inertial Taylor–Couette flow at moderate Reynolds number

We investigate the presence of intermittency, a well-known phenomenon in Newtonian turbulence, in viscoelastic Taylor–Couette flow at fixed inertia, (Reynolds number, italic Re Re Re = 120). Using particle image velocimetry measurements in the r–z plane for a broad range of elasticities, italic El El El = 0–0.64, we reveal a dual role of viscoelasticity, even at moderate italic Re Re Re : it can destabilise the flow and trigger turbulence at moderate elasticity but suppress turbulence intensity at higher values. Gradual turbulence suppression is evident through reduced velocity fluctuations, longer integral time scales proportional to the polymer relaxation time and weakened coherent structures as the flow approaches elasto-inertial turbulence. Higher-order statistics indicate that elasticity increases spatial and temporal intermittency while altering the dynamics: spatially, through a reduced viscous range and enhanced large-scale decorrelation; temporally, via a characteristic time scale consistent with polymer-driven state switching rather than a classical cascade. This spatio-temporal intermittency manifests as alternating active/hibernating turbulence cycles. During hibernation, the flow reorganises into a state distinct from active turbulence, characterised by low velocity fluctuations and Reynolds stresses, suppressing not only turbulence but also linearly unstable Newtonian states such as Taylor vortices. Rather than being featureless, this state exhibits weakened coherent structures in the bulk of the flow and sustained near-wall dynamics, where elastic stresses are likely generated. The present results demonstrate that hibernation is not exclusive to Newtonian turbulence, but also emerges in viscoelastic flows under conditions where inertia alone is insufficient to trigger or sustain turbulent motion.