Wang Geng, Fei Linlin, Luo Kai H
Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom.
Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland.
Phys Rev E. 2022 Apr;105(4-2):045314. doi: 10.1103/PhysRevE.105.045314.
As a powerful mesoscale approach, the lattice Boltzmann method (LBM) has been widely used for the numerical study of complex multiphase flows. Recently, Luo et al. [Philos. Trans. R. Soc. A: Math. Phys. Eng. Sci. 379, 20200397 (2021)10.1098/rsta.2020.0397] proposed a unified lattice Boltzmann method (ULBM) to integrate the widely used lattice Boltzmann collision operators into a unified framework. In this study, we incorporate additional features into this ULBM in order to simulate multiphase flow under realistic conditions. A nonorthogonal moment set [Fei et al., Phys. Rev. E 97, 053309 (2018)10.1103/PhysRevE.97.053309] and the entropic-multi-relaxation-time (KBC) lattice Boltzmann model are used to construct the collision operator. An extended combined pseudopotential model is proposed to realize multiphase flow simulation at high-density ratio with tunable surface tension over a wide range. The numerical results indicate that the improved ULBM can significantly decrease the spurious velocities and adjust the surface tension without appreciably changing the density ratio. The ULBM is validated through reproducing various droplet dynamics experiments, such as binary droplet collision and droplet impingement on superhydrophobic surfaces. Finally, the extended ULBM is applied to complex droplet dynamics, including droplet pancake bouncing and droplet splashing. The maximum Weber number and Reynolds number in the simulation reach 800 and 7200, respectively, at a density ratio of 1000. The study demonstrates the generality and versatility of ULBM for incorporating schemes to tackle challenging multiphase problems.
作为一种强大的中尺度方法，格子玻尔兹曼方法（LBM）已被广泛用于复杂多相流的数值研究。最近，罗等人[《皇家学会哲学学报A：数学、物理和工程科学》379, 20200397 (2021)10.1098/rsta.2020.0397]提出了一种统一格子玻尔兹曼方法（ULBM），将广泛使用的格子玻尔兹曼碰撞算子整合到一个统一框架中。在本研究中，我们将额外的特性纳入此ULBM，以便在实际条件下模拟多相流。使用非正交矩集[费等人，《物理评论E》97, 053309 (2018)10.1103/PhysRevE.97.053309]和熵多弛豫时间（KBC）格子玻尔兹曼模型来构建碰撞算子。提出了一种扩展的组合伪势模型，以实现高密度比下具有宽范围可调表面张力的多相流模拟。数值结果表明，改进后的ULBM可以显著降低虚假速度，并在不明显改变密度比的情况下调节表面张力。通过再现各种液滴动力学实验，如二元液滴碰撞和液滴撞击超疏水表面，对ULBM进行了验证。最后，将扩展的ULBM应用于复杂的液滴动力学，包括液滴薄饼弹跳和液滴飞溅。在密度比为1000时，模拟中的最大韦伯数和雷诺数分别达到800和7200。该研究证明了ULBM在纳入解决具有挑战性的多相问题的方案方面的通用性和多功能性。
