| Abstrakt: |
In this study, we numerically investigate two axisymmetric compound droplets successively impacting a nonwettable surface with the presence of a vertical temperature gradient. There are two outcomes: (1) the leading compound droplet rebounds and both compound droplets balance above the wall; and (2) the leading droplet stays on the surface and the trailing one suppresses it. In both cases, the leading and trailing droplets remain in contact. We investigate the influence of some critical dimensionless parameters including the Marangoni number Ma (varied from 50 to 175), the volume ratio of the trailing and leading compound dropletsVlt(varied from 0.064 to 1.0), the initial distance between two compound dropletsHd(changed from 1.25Doto 2Do), and the viscosity ratio of the outer fluid to the middle fluids (varied from 0.1 to 1.0). We find that the leading droplet detaches from the wall for Ma ≥ 125.However, if the trailing droplet is small (Vlt< 0.512) or it is placed far away from the leading one (Hd> 1.25Do), the leading droplet detaches from the wall at a smaller Ma (i.e., Ma = 100).Increasing the viscosity of the outer fluid causes the contact time of the leading droplet and the wall to decrease significantly with an increase in the rebound height.The contact time of the leading droplet decreases while its rebound height increases as increasing Ma, Hd,μom, or decreasing Vlt.The deformation of both droplets is also investigated. |
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