**Jian Zhang, Xinhai Yu \* and Shan-Tung Tu**

Key Laboratory of Pressure Systems and Safety (MOE), School of Mechanical Engineering, East China University of Science and Technology, Shanghai 200237, China; zhangj9@ecust.edu.cn (J.Z.); sttu@ecust.edu.cn (S.-T.T.)

**\*** Correspondence: yxhh@ecust.edu.cn; Tel.: +86-021-64253108

Received: 29 October 2019; Accepted: 18 November 2019; Published: 22 November 2019

**Abstract:** The hydrodynamics of droplets passing through metal foam is investigated using the lattice Boltzmann method (LBM). The accurate 3D porous structure for the simulation is generated by X-ray micro-computed tomography. The simulated results are in good agreement with the experimental ones using high-speed video. The simulated results show that for droplets passing metal foam, there is a critical capillary number, *Cac* (around 0.061), above which the droplet continues to deform until it breaks up. The simulated results show that the capillary number, droplet size, pores diameter, and thickness of metal foam have the significant effect of droplets deforming and breaking up when the droplets pass through the metal foam. To avoid the calescence of two droplets at the inlet zone of the metal foam, the distance between droplets should be larger than three times the diameter of the droplet.

**Keywords:** lattice Boltzmann method; metal foam; droplet break; multiphase flow
