Experimental characterization of elasto-inertial turbulence

The addition of polymers in flows in pipes has been shown to delay the subcritical transition of Newtonian type turbulence (NTT) to higher Reynolds numbers (Re). Increasing the polymer concentration within the dilute regime causes a continuous transition to a novel state of turbulence dubbed Elasto-inertial turbulence (EIT). Recent studies have shown that by controlling the parameters of the flow, one can observe the salient features of EIT at Re far lower than that of classical transition to NTT, showing that the transition can happen even at Re of the order of 1. In the present study we show that the structural composition of EIT persists from Reynolds numbers of order one to the  maximum drag reduction limit. In particular we show that energy spectra across the entire EIT regime collapse and are distinct from the Kolmogrov scaling associated with NTT. We explore further the existence of the EIT flow structures at much higher Re far away from the transition regime, deeper into the Maximum Drag Reduction (MDR) range.