The thermoviscous fingering instability in cooling spreading fluid flows

What is it about?

This paper develops a mathematical model investigating the coupling between the fluid mechanics and heat transfer in a molten flow which cools as it spreads. A novel spatial fingering instability is identified near the leading edge of the spreading flow. This instability is mapped in parameter space and a necessary condition for its existence is identified using linear stability analysis and numerical simulations.

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Why is it important?

The thermoviscous fingering instability identified and characterized in this paper will enhance the understanding of the interplay between the flow and cooling. This interplay results in a variety of real-world dynamical flow patterns, such as the flow front branching in a fingering-type instability, e.g., observed in advancing pahoehoe lava flow fronts which develop toe-shaped protrusions. A common theme in these flow scenarios is that these spatial instabilities are unwanted. A fingering instability can prevent uniform coating of a molten metal on a substrate in spray metallizing applications or in making a pancake of uniform thickness; branching of lava flows enhances its spreading, which can be hazardous and can cause damage to infrastructure and buildings; similarly with the spreading of core melt in a nuclear reactor accident. Our results will help in better understanding the mechanisms driving these fluid instabilities and develop strategies on how to control or eliminate them

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