微柱结构表面核态沸腾单气泡的数值模拟

利用计算流体力学方法（computational fluid dynamics, CFD）对三维均匀微柱结构表面单气泡核态沸腾过程进行数值模拟研究，使用VOF模型（volume of fluid model, VOF）在界面网格追踪加密的条件下精确捕捉气液界面，同时考虑气液界面和微层处的蒸发，准确获得三维微柱表面单气泡核态沸腾过程中的气泡动力学、温度演化和蒸发换热性能。结果表明，气泡脱离时间为1.79ms，体现了微柱结构促进气泡脱离的强化作用。通过气泡横向和纵向直径的变化准确表征了气泡在脱离过程中的变形过程，并模拟得到该过程流场热边界层及壁面温度的演变规律。同时，通过微层蒸发和气液交界面蒸发功率随时间变化的监测，指出气泡生长过程微层蒸发量占总蒸发量的52%；t=0.95ms后微层蒸发消失，气液界面蒸发维持相对稳定值（0.1~0.2W）直至气泡脱离。蒸发换热特性耦合气泡与壁面接触情况随时间的变化，揭示了单气泡核态沸腾过程蒸发换热机理的阶段性特征及时间分区，为在核态沸腾单个气泡生长脱离过程中更准确划分时间阶段、建立沸腾换热模型奠定基础，提供了参考。

Numerical simulation of single bubble boiling on micro-pillar structure surface

A three-dimensional numerical simulation for the nucleate boiling of a single bubble on a micropillar array is carried out. The Volume of Fluid model (VOF) is used to accurately capture the vapor-liquid interface coupling with an adaptive refinement for interface grids. With consideration of two parts evaporation at the vapor-liquid interface and at the microlayer, the bubble dynamics, temperature evolution and heat transfer performance for the single-bubble boiling on a micropillar array are obtained. As results, the departure time is 1.79ms which indicates that the micro-pillar structure promotes the bubble departure, which bubble deformation is accurately characterized by the diameter evolutions in the horizontal and vertical directions, and accordingly changes of the thermal boundary layer and wall surface temperature are shown. As to two parts evaporation, the micro-layer evaporation accounted for 52% of the total evaporation in bubble growth period. After t=0.95ms, accompanied by the disappearance of the microlayer evaporation, the vapor-liquid interface evaporation maintains a relatively stable value (0.1-0.2W) until the bubble departure. These various characters showing in different stages could offer a guidance on more accurate time division and establishing nucleate boiling heat transfer model for the single bubble nucleate boiling process at low heat fluxes.