Non-monotonic ice-core thawing in a water pool driven by competition between anomaly-triggered chaotic flow and normal natural convection

This study demonstrates a non-monotonic relation between pool temperature and thawing time for the ice-core thawing problem in a water pool. Numerical simulations reveal that this non-monotonicity arises from competing flow mechanisms from the non-Oberbeck–Boussinesq effect driven by the density-temperature anomaly at 4\, ^ C of water. The sides come from the anomaly-triggered chaotic flow and the normal natural convection stabilised by the buoyancy force. During the thawing process, the flow in the pool experiences a transient stable, an oscillatory, a transitional and the finally chaotic state over time. The pool size modulates the competition between chaotic flow and natural convection through the Rayleigh numbers with a critical value ₂. Within the considerations of this study, a smaller pool size leads to a more non-monotonic appearance. The competition governs both the extreme points in thawing time and the extent of the non-monotonic effect, thereby enabling accurate control over thawing kinetics. These insights clarify how the non-Oberbeck–Boussinesq effects from density and viscosity govern the ice-core thawing dynamics and pave the way for advanced controlled-thawing technologies in applications such as cryopreservation and organ resuscitation.