Non-monotonic Ice-core Thawing in Water Pool Leading by Flow Competition

This study demonstrates a non-monotonic dependence between pool temperature and thawing time for the ice-core thawing problem. Numerical simulations reveal that this anomaly arises from competing convective mechanisms driven by the density-temperature anomaly at ~4°C of water. The sides come from the anomaly chaotic flow induced by boundary-core thermal gradients, and the normal natural convection stabilized by buoyancy from the density extremum near the core. As the pool temperature increases from 2.5 to 80 °C, the flow transitions from a chaotic to a steady state. Within the transitional regime, however, flow stability decreases with the Fourier number, eventually can leading to re‑chaotization. The pool size modulates the competition between chaotic flow and natural convection through the Rayleigh numbers, which govern both the extreme points in thawing time and the extent of the non‑monotonic effect, thereby enabling precise control over thawing kinetics. These insights clarify how the non‑Oberbeck–Boussinesq effects of density and viscosity govern ice‑core thawing dynamics and pave the way for advanced controlled‑thawing technologies in applications such as cryopreservation and organ resuscitation.本研究揭示了冰芯解冻问题中池温与解冻时间之间的非单调依赖关系（non-monotonic dependence）。数值模拟（numerical simulations）结果表明，该异常现象源于由4℃左右水体的密度-温度异常（density-temperature anomaly）驱动的两类竞争对流机制：一类源自边界-核心热梯度（boundary-core thermal gradients）诱导的异常混沌流，另一类则是由核心附近密度极值（density extremum）产生的浮力所稳定的常规自然对流。当池温从2.5℃升高至80℃时，流场从混沌态转变为稳态；但在过渡区间内，流场稳定性随傅里叶数（Fourier number）降低，最终会引发重混沌化（re-chaotization）。池尺寸通过瑞利数（Rayleigh numbers）调控混沌流与自然对流间的竞争关系，而瑞利数同时决定了解冻时间的极值点与非单调效应的作用范围，从而实现对解冻动力学（thawing kinetics）的精准调控。本研究阐明了密度与粘度的非奥伯贝克-布辛涅斯克效应（non-Oberbeck–Boussinesq effects）如何支配冰芯解冻的动力学过程，并为低温保存（cryopreservation）、器官复苏（organ resuscitation）等应用场景中的先进可控解冻技术开辟了发展路径。