Numerical investigation of multi-droplets deposited lines morphology with a multiple-relaxation-time lattice Boltzmann model

- Multi-droplets deposited line process is simulated by three dimensional MRT LB model.
- Contact angle hysteresis is modeled by geometric formulations.
- The lines morphologies with different overlap ratios are quantitatively identified.
- An optimal droplet overlap ratio for uniform line is proposed.
- The proposed optimal overlap ratio is valid in the out-of-phase coalescence mode.

The formation and morphology of multi-droplets deposited lines are investigated by employing a 3D MRT pseudopotential LB model with large density ratios and high Reynolds numbers. A geometric formulation is considered to replace the fluid-solid interaction scheme to model the contact angles hysteresis. Of particular interest in this study is to find out the optimal conditions of uniform line formation. The effects of droplet overlap ratios and advancing contact angles on the lines morphology are investigated numerically. With the droplet overlap ratio increasing, the lines morphologies including isolate, scalloped, uniform and bulging formation are quantitatively identified. An optimal droplet overlap ratio is proposed to obtain uniform morphology of lines and validated via varying Ohnesorge numbers. The effects of vertical droplet spacing on the lines morphology at the optimal droplet overlap ratio is investigated and two coalescence modes are identified. Results show that the proposed optimal overlap ratio for uniform line formation is not sufficient condition and is valid in the case of out-of-phase coalescence mode.