Oscillating grid generating turbulence near gas-liquid interfaces in shear-thinning dilute polymer solutions
Résumé
Understanding the behaviour of liquid phase turbulence near gas-liquid interfaces is of great interest in many fundamental, environmental, or industrial applications. For example, near-surface liquid side turbulence is known to enhance the mass transfers between the two phases. Descriptions of this behaviour for air-water systems exist in the literature, but the case of turbulence in a shearthinning liquid phase below a flat gas-liquid interface has never been considered so far. This paper consists in an experimental characterization of low Reynolds number, oscillating grid generated, near-surface turbulence in shear-thinning dilute polymer solutions, in the surface-influenced and in the viscous sub-layers. The energy transfer mechanism, known in the water case, is evidenced in dilute polymer solutions (DPS). An horizontal damping mechanism, similar to the one introduced by surfactants, is evidenced. The evolution of the viscous sub-layer depth can be explained by both viscous and shear-thinning effects, and it appears that a critical polymer concentration may exist within the dilute regime.
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