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Highlighting strain-induced thermoelastic effect in mesoscopic liquids

Abstract : In depth understanding of liquids stand as a great challenge. Their fast molecular dynamics lead to inability of supporting transverse (shear) waves, which energy should dissipate in a liquid medium. However, recent experimental and theoretical reports argue against this notion and highlight finite shear elasticity in mesoscale (semi-confined) liquids. In the frame of finite shear elasticity in mesoscopic liquids, we probe the thermal response under mechanical oscillatory shear excitation within the conventional viscous regime for a frequency range of 0.5 – 5 rad/s (0.08 – 0.8 Hz). The studied liquids (glycerol, polypropylene glycol and water) are confined between high-energy surfaces with thickness gap varying between 100 – 1000μm. We show that the applied shear strain generates nearly instant and reversible (hot and cold) thermal waves, whose amplitude and shape are linearly modulated by the shear strain at moderate shear strain and frequency, while leading to the generation of a non-linear thermal signal (harmonics) at large amplitude or larger frequency. We also examine the stability of the thermal equilibrium while the liquid is submitted to a sudden step shear strain. We evidence fast thermal changes reaching +0.04°C and -0.04°C amplitude that relax following a stretched-exponential while keeping the global temperature unchanged. Finally, we highlight a scale dependence of the thermal wave similar to that of the shear elasticity. The observed thermal effects indicate that mesoscopic liquids are able to convert (partly) the mechanical shear energy in non-uniform and non-equilibrium thermodynamic states, thus are endowed with thermoelasticity, a property so far identified in solids. Finally, in the frame of the dynamic study of the solid-liquid interface, we reveal via inelastic x-ray scattering, the impact of wetting on the solid surface dynamics.
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Submitted on : Monday, December 6, 2021 - 11:43:14 AM
Last modification on : Monday, January 10, 2022 - 10:16:08 AM

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104952_KUME_2021_archivage.pdf
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  • HAL Id : tel-03466885, version 1

Citation

Eni Kume. Highlighting strain-induced thermoelastic effect in mesoscopic liquids. Thermics [physics.class-ph]. Université Paris-Saclay, 2021. English. ⟨NNT : 2021UPASP099⟩. ⟨tel-03466885⟩

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