重庆大学 航空航天学院
国家自然科学基金项目（面上项目，重点项目，重大项目）项目编号：12102071，12172070
ChongQing University College of Aerospace Engineerinring
The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)， Foundation number：12102071，12172070
表面张力梯度驱动的液桥热毛细对流，随着液桥上下端温差的增大，流体系统经过一系列分岔，最终演化为混沌状态。通过三维数值模拟研究了微重力条件下，熔体普朗特数为0.01和0.02，高径比(液桥高度与半径的比值)为1的等径液桥热毛细对流向湍流转捩的途径。利用时间序列频谱分析(FFT)和动力学模态分解(DMD)方法揭示了流场的时空结构特征。结果表明，普朗特数为0.01和0.02的液桥热毛细对流向湍流转捩的途径均始于准周期分岔途径，前者经历了三频准周期运动, 后者经历了锁频特征的二频准周期运动。在周期振荡阶段，普朗特数为0.02的液桥热毛细对流经历了从脉冲型振荡到旋转型振荡的转变，周向波数由1和2的混合模态变为波数为2的模态。相比之下，普朗特数为0.01的液桥热毛细对流在周期和准周期流动阶段均表现为脉冲型振荡，周向波数为1和2的混合模态。
Thermocapillary convection driven by surface tension gradient undergoes a series of bifurcation and ultimately evolves into a chaotic state, while temperature difference between the upper and lower ends of the liquid bridge increases. This study employed three-dimensional numerical simulations to investigate the convection transition for Prandtl numbers(Pr) of 0.01 and 0.02 with aspect ratio (a ratio between height to radius) of 1 under microgravity. This study utilized time series spectrum analysis and dynamic mode decomposition to elucidate the spatiotemporal structure of the flow field. The results show that thermocapillary convection in liquid bridges with Pr=0.01 and Pr=0.02 transitions to turbulence through quasi-periodic bifurcation pathways. Specifically, the Pr=0.01 case exhibits a two-frequency quasi-periodic oscillation with frequency-locking characteristics, while the Pr=0.02 case demonstrates a three-frequency quasi-periodic oscillation. During the periodic oscillation stage, thermocapillary convection in liquid bridges with Pr=0.02 shifts from pulse oscillation to rotational oscillation, with wave number changing from a mixture of 1 and 2 to a dominant 2. In contrast, the Pr=0.01 case remains pulsed in both periodic and quasi-periodic phases, with a wave number that remains a mixture of 1 and 2.
