Spatiotemporal signatures of elastoinertial turbulence in viscoelastic planar jets

Yamani, Sami; Raj, Y. E. A.; Zaki, Tamer A.; McKinley, Gareth H.; Bischofberger, Irmgard

doi:10.1103/physrevfluids.8.064610

Cited by 9 publications

(2 citation statements)

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“…To probe the universality of turbulent states, we plot the PSD of the flow maps at the same Re (Re = 200) for different values of El (figure 15c). The decay exponent of EIT is equal to −2.5 and seemingly independent of the fluid El, pointing to a universality of the decay exponent as reported by Yamani et al (2021) and Moazzen et al (2023).…”

Section: On the Formation Of Elastic Vortex Pairssupporting

confidence: 74%

“…Recently, experimental (Zhang et al 2021) and numerical (Rosti, Perlekar & Mitra 2023) studies also point towards a decay exponent of −2.3 in EIT, as the inertial small scales are not completely suppressed by elasticity. It is worth noting that in many studies, experimental and numerical limitations mean that such scalings are observed over less than a frequency/wavelength decade (Dubief et al 2013;Song et al 2021b;Yamani et al 2021), which poses a challenge in the accurate estimation of the decay exponent and results in discrepancies between the reported values.…”

Section: On the Formation Of Elastic Vortex Pairsmentioning

confidence: 99%

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Coherent structures of elastoinertial instabilities in Taylor–Couette flows

Boulafentis,

Lacassagne,

Cagney

et al. 2024

J. Fluid Mech.

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We combine flow visualisation techniques and particle image velocimetry to experimentally investigate the higher-order transition to elastoinertial turbulence of Boger fluids ( $El = 0.11\unicode{x2013}0.34$ ) in Taylor–Couette flows. The observed route to turbulence is associated with the appearance of chaotic inflow jets, termed flame patterns, for increasing inertia, and stable structures of solitons, known as diwhirls, for decreasing inertia. We also report for the first time spatially and temporally resolved flow fields in the meridional plane for the three characteristic viscoelastic flow regimes (diwhirls, flame patterns and elastoinertial turbulence). We observe in all cases coherent structures of dynamically independent solitary vortex pairs. The stability of these coherent structures is jet-dominated and can be mainly ascribed to the high extension of the polymer chains in the inflow boundaries in the $r$ – $z$ plane. Solitary pairs are self-sustained when created through random events and do not split; instead, they merge when moving sufficiently close and annihilate when hoop stresses are not sufficient to sustain them. The highly localised and random events result in highly fluctuating, chaotic flow states. We estimate the decay exponent of spatial power spectral density, illustrating a universal scaling of $-2.5$ for elastoinertial turbulence. Based on our observations and in an effort to unify and combine precedent theories with our results, we suggest a mechanism for the origins of elastoinertial instabilities, accounting for both the effect of elasticity on the vortex formation and the effect of increasing/decreasing inertia on the flow dynamics.

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Section: On the Formation Of Elastic Vortex Pairssupporting

confidence: 74%