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Dynamic wetting plays an important role in the physics of multiphase flow, and has significant influence on many industrial and geotechnical applications. In this work, a modified smoothed particle hydrodynamics (SPH) model is employed to simulate surface tension, contact angle, and dynamic wetting effects. The wetting and dewetting phenomena are simulated in a capillary tube, where the liquid particles are raised or withdrawn by a shifting substrate. The SPH model is modified by introducing a newly-developed viscous force formulation at liquid-solid interface to reproduce the rate-dependent behaviour of moving contact line. Dynamic contact angle simulations with interfacial viscous force are conducted to verify the effectiveness and accuracy of this new formulation. In addition, the influence of interfacial viscous force with different magnitude on contact angle dynamics is examined by empirical power law correlations, and the derived constants suggest the dynamic contact angle changes monotonically with interfacial viscous force. The simulation results are consistent with the experimental observations and theoretical predictions, implying that the interfacial viscous force can be associated with slip length of flow and microscopic surface roughness. This work has demonstrated that the modified SPH model can successfully account for the rate-dependent effects of moving contact line, and can be used for realistic multiphase flow simulation under dynamic conditions.

The performance of polymer electrolyte membrane fuel cells (PEMFCs) is greatly influenced by the residual water content generated during the cell operation. A comprehensive understanding of water management at the interfacial regions of PEMFC components is critical for elevating the efficiency of PEMFCs. Herein, the liquid transport and accumulation at the interfacial region of 2D microporous layer (MPL) and catalyst layer (CL) are investigated numerically, considering the effects of compression stress, porosity, and wettability. The numerical scheme is assembled by finite element method (for interfacial contact mechanics) and lattice Boltzmann method (for multiphase flow and permeability calculation). Different levels of compression stress derived from fuel cell assembly pressure are applied on the MPL/CL components, which consequently lead to variations in the pore size distribution and porosity change of the MPL/CL. The results highlight the importance of considering porosity change in the compression process, where increasing compression stress significantly decreases the liquid saturation in the MPL and interfacial gap region. Additionally, strong hydrophobicity can alleviate the heterogeneity of liquid accumulation at the MPL/CL interfacial region. The liquid and gas relative permeability are also investigated to assess the liquid drainage and fuel supply efficiency with different compression stress.

coating, [1] inkjet printing, [2] deposition of pesticides, [3] and anti-icing applications. [4] Since the pioneering work of Worthington on rapid droplet impact, [5] the underlying dynamics of the interplay among liquid droplet, ambient gas, and substrate have been investigated by many researchers. [6][7][8] Experimental investigations of droplet impact on solid substrate revealed six identical modes, including deposition, partial bouncing, complete bouncing, receding breakup, prompt splash, and corona splash. [9] The outcome of droplet collision depends on various factors, such as droplet properties, [10] surface conditions, [11,12] ambient pressure, [13] and impacting angle and velocity. [14] Dimensionless numbers are used to characterize the droplet impact dynamics,

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