A three-dimensional nonorthogonal lattice Boltzmann model is employed to simulate a single droplet impacting a nonuniform wettable surface at the bottom of a proton exchange membrane fuel cell. The effects of nonuniform surface wettability differences in the flow channel, the impact Weber number, and the central stripe width on the energy evolution during the spreading stage are investigated. Qualitative and quantitative comparisons between the numerical simulations and experimental results indicate that the main energy loss during the initial spreading stage is attributable to momentum redistribution, while viscous dissipation is caused by shear stress and vorticity in the rim. A larger wettability difference leads to a higher net unbalanced Young’s force, resulting in stronger shear and viscous dissipation near the wettability contrast line. For smaller Weber numbers, in the early impact stage, the main loss of kinetic energy is caused by the redistribution of momentum; in the later spreading stage, the increase in surface energy is the main sink of kinetic energy. The unbalanced Young’s force hinders the spreading of the droplet at larger stripe widths, leading to a larger vortex intensity within the rim.

中文翻译：

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影响不均匀化学图案燃料电池表面的液滴的能量演变


采用三维非正交晶格玻尔兹曼模型来模拟单个液滴撞击质子交换膜燃料电池底部不均匀的可湿性表面。研究了流道中不均匀表面润湿性差异、影响韦伯数和中心条纹宽度对扩散阶段能量演变的影响。数值模拟与实验结果的定性和定量比较表明，初始展宽阶段的主要能量损失归因于动量再分布，而粘性耗散是由边缘的剪切应力和涡度引起的。润湿性差异越大，净不平衡杨氏力就越高，导致润湿性对比线附近的剪切和粘性耗散更强。对于较小的韦伯数，在早期撞击阶段，动能的主要损失是由动量的重新分配引起的;在扩散后期，表面能的增加是动能的主要汇。不平衡的杨氏力阻碍了液滴在较大条纹宽度下的扩散，从而导致轮辋内的涡流强度更大。