Mixing Dynamics during Radial Viscous Fingering
Abstract
Viscous fingering is a hydrodynamic instability that occurs when a less viscous fluid displaces a more viscous one. Instead of progressing as a uniform front, the less viscous fluid forms fingers that vary in size and shape to create complex patterns. Understanding how these patterns and their associated gradients evolve over time is of critical importance in characterizing the mixing of two fluids, which in turn is important to applications such as enhanced oil recovery and microfluidics.
Mixing relies on the presence of concentration gradients, and we explore experimentally how the mixing zone (the collection of all these gradients) changes in time during radial viscous fingering. For different fluid injection rates and various viscosity ratios, we measure the local concentration field temporally and spatially with the use of a fluorescein tracer in the injected fluid, and with this high-resolution information calculate the local gradients and the changing role of dispersion with time. We observe two regimes in the mixing zone thickness: an initial regime with constant thickness and a latter regime where the thickness scales as the square root of time. We present here the competing factors of dispersion and interface stretching in the formation of these two regimes, and the overall effect this has on mixing, as characterized by the scalar dissipation rate. Coupling our understanding of the dynamics of the interface length (previous work) with this understanding of the dynamics of the mixing zone thickness, we propose a theoretical model for the overall impact of viscous fingering on mixing.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H53D..02C
- Keywords:
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- 1829 Groundwater hydrology;
- HYDROLOGY;
- 1835 Hydrogeophysics;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY;
- 1869 Stochastic hydrology;
- HYDROLOGY