Oscillatory flow of surfactant concentration on the fluid surface of a non-Newtonian fluid

What is it about?

We study the spreading dynamics of an insoluble and non-diffusive surfactant on the free surface of a deep layer of a Carreau fluid. When a non-uniform distribution of surfactant is imposed on the free surface of an initially motionless fluid, variations in surface tension are induced, causing the fluid motion from regions of lower surface tension to those of higher tension. Such movement redistributes the surfactant concentration until a uniform condition is reached.

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Photo by Tim Johnson on Unsplash

Photo by Tim Johnson on Unsplash

Why is it important?

The present work focuses on determining how the convective effects and the inertia of the flow affect the surfactant distribution on the free surface of a deep fluid layer initially motionless, where the Carreau model describes the fluid rheology. The results show that the temporal decay of the surfactant concentration on the fluid surface increases significantly for high values of the Reynolds number, it is more attenuated in pseudoplastic fluids than in Newtonian fluids, and the surfactant concentration decay exhibits asymmetric oscillations when inertial effects increase.

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