Enhanced bubble growth near an advancing solidification front

TL;DR

This study investigates how gas bubbles nucleate and grow near an advancing ice front during freezing, revealing diffusion-driven growth influenced by concentration gradients and fluid flow, with experimental and numerical insights.

Contribution

It combines experimental and numerical methods to analyze initial bubble growth near a solidification front, linking it to mass transfer and fluid flow effects.

Findings

Bubble growth is diffusion-controlled and enhanced by concentration gradients.

Good agreement with existing mass transfer scaling laws.

Fluid flow around bubbles can significantly influence growth dynamics.

Abstract

Frozen water might appear opaque since gas bubbles can get trapped in the ice during the freezing process. They nucleate and then grow near the advancing solidification front, due to the formation of a gas supersaturation region in its vicinity. A delicate interplay between the rate of mass transfer and the rate of freezing dictates the final shapes and sizes of the entrapped gas bubbles. In this work, we experimentally and numerically investigate the initial growth of such gas bubbles that nucleate and grow near the advancing ice front. We show that the initial growth of these bubbles is governed by diffusion and is enhanced due to a combination of the presence of the background gas concentration gradient and the motion of the approaching front. Additionally, we recast the problem into that of mass transfer to a moving spherical object in a homogeneous concentration field, finding good agreement between our experimental data and the existing scaling relations for that latter problem. Lastly, we address how fluid flow around the bubble might further affect this growth and qualitatively explore this through numerical simulations.