Numerical study of Leidenfrost effect suppression on structured thermal pillars using a lattice Boltzmann method

A three-dimensional pseudopotential central moments lattice Boltzmann method, coupled with a fourth-order Runge–Kutta scheme for the temperature field, is employed to study the impact of Leidenfrost droplets on overheated structured thermal pillar surfaces. The numerical method is validated through simulations of liquid–vapour phase-change processes and dynamic impingement of Leidenfrost droplet on overheated walls. A parametric study varying surface temperature, droplet inertia, and pillar dimensions provides insights into droplet dynamics and Leidenfrost point (LFP). Results demonstrate that structured thermal pillars significantly elevate the LFP compared to flat surfaces by enhancing vapour flow beneath the droplet. Detailed analyses reveal that increasing surface temperature promotes the Leidenfrost phenomenon, while droplet inertia affects the rebound height but not LFP, resulting in a lower average vaporisation rate when Leidenfrost effect happens. Furthermore, the influence of pillar dimensions on the LFP is explored by establishing phase diagrams of the Jacob number (<i>Ja</i>) against pillar width, height, and spatial distribution. The results indicate that narrower and taller pillars are more advantageous in suppressing the Leidenfrost effect. When the pillar height exceeds 40% of the droplet radius, the suppression effect diminishes. Moreover, increasing the number of pillars, resulting in smaller tunnel and pillar widths, tends to enhance the Leidenfrost effect.

采用耦合了温度场四阶龙格-库塔（Runge–Kutta）格式的三维伪势中心矩格子玻尔兹曼（lattice Boltzmann）方法，研究莱顿弗罗斯特（Leidenfrost）液滴撞击结构化热柱型过热表面的过程。通过液-气相变过程模拟以及莱顿弗罗斯特液滴在过热壁面上的动态撞击过程，验证了该数值方法的可靠性。通过开展表面温度、液滴惯性与热柱尺寸多参数变量的参数化研究，深入剖析了液滴动力学特性与莱顿弗罗斯特点（Leidenfrost point, LFP）的变化规律。研究结果表明，相较于平整壁面，结构化热柱可通过强化液滴下方的蒸汽流动，显著升高莱顿弗罗斯特点。详细分析显示，提升表面温度会加剧莱顿弗罗斯特现象的发生；而液滴惯性仅影响液滴的反弹高度，对莱顿弗罗斯特点无显著影响，当出现莱顿弗罗斯特效应时，会导致平均汽化速率降低。此外，通过构建雅各布数（Jacob number, Ja）与热柱宽度、高度及空间分布的相图，探究了热柱尺寸参数对莱顿弗罗斯特点的影响规律。结果表明，更窄且更高的热柱更利于抑制莱顿弗罗斯特效应。当热柱高度超过液滴半径的40%时，其抑制作用会逐渐减弱。此外，增加热柱数量会缩小热柱间通道与热柱自身的宽度，进而加剧莱顿弗罗斯特效应的发生。