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中文核心期刊

水滴撞击热同心微槽表面的定向运动行为研究

EXPERIMENTAL STUDY ON DIRECTIONAL MOTION OF WATER DROPLETS IMPACTING ON A HOT CONCENTRIC MICROGROOVE SUBSTRATE

  • 摘要: 调控液滴有序运动对提升工业换热设备的热管理效率和保障系统运行安全具有重要的工程意义. 针对高温环境下液滴定向输运的难题, 本文通过实验研究了水滴撞击梯度槽宽高温同心微槽基板后的动力学行为, 系统分析了过渡沸腾(250 °C)与膜态沸腾(350 °C)下液滴动力学特性及驱动机理. 结果表明, 两种沸腾状态下液滴均表现出稳定的单向输运特性, 即始终朝向基板曲率中心运动. 通过定量表征归一化固液接触线长度、最大铺展因子及横向位移等关键参数, 揭示了其随偏心距离(撞击位置)与韦伯数的演化规律. 最大铺展因子在两种热态下均主要受韦伯数主导, 偏心距离的影响并不显著; 液滴横向位移在膜态沸腾下随偏心距离先增大后趋于稳定, 在过渡沸腾下呈现先增大后减小的变化趋势, 二者均在偏心距离为半槽长时达到最大值. 最后, 进一步阐明了水滴定向运动的内在机理:过渡沸腾下, 梯度槽宽诱导的不对称润湿性与Janus热状态共同驱动液滴定向起飞; 膜态沸腾下, 微槽结构引发的非对称收缩与毛细渗透作用形成指向曲率中心的合力, 推动液滴持续定向运动. 上述发现为高温热管理系统中液滴有序运动的精准调控提供了实验依据与理论支撑.

     

    Abstract: Controlling the ordered motion of droplets is of great engineering significance for improving the thermal management efficiency of industrial heat exchange equipment and ensuring the safe operation of systems. To address the challenge of directional droplet transport in high-temperature environments, this study experimentally investigates the dynamic behavior of water droplets impacting a high-temperature concentric microgroove substrate with gradient groove widths. The droplet dynamic characteristics and driving mechanisms under both transition boiling (250 °C) and film boiling (350 °C) regimes are systematically analyzed. The results indicate that, in both boiling states, water droplets exhibit stable unidirectional transport behaviors and always move leftward toward the curvature center of the substrate. Key normalized motion parameters, including the solid-liquid contact line length, maximum spreading factor, and lateral displacement ratio, are quantitatively characterized to reveal their evolutionary laws with off-center distance (i.e., the impact position relative to the curvature center of the substrate) and Weber number. The maximum spreading factor in both boiling states is found to be primarily dominated by the Weber number, while the effect of off-center distance is insignificant. The lateral displacement ratio shows a trend of first increasing and then stabilizing with off-center distance under film boiling, whereas it first increases and then decreases under transition boiling, with both reaching their maximum values at half length of the radius of the microgroove substrate. Furthermore, the intrinsic directional motion mechanisms are elucidated. For transition boiling, the directional take-off is co-driven by the asymmetric wettability and Janus thermal state induced by gradient microgroove widths. For film boiling, asymmetric contraction and capillary penetration induced by the microgroove structure generate a resultant force directed toward the curvature center, thereby driving the continuous directional motion of the droplets. These findings provide experimental evidence and theoretical support for the precise regulation of ordered droplet motion in high-temperature thermal management systems.

     

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