The effect of surface roughness on dynamic behaviour of the successive multiple droplets impacting onto aluminium hot surfaces

Abstract

The effects of hot surface roughness on dynamic behaviour of multiple droplets impacting hot solid surfaces were investigated in this research. The test material is Aluminium 6061 with surface roughness variation of 0.08 μm, 0.18 μm and 0.52 μm. The surface temperatures were 100 ?C, 120 ?C and 140 ?C. The droplet dynamics during the impact have been observed using high-speed video camera then the results were characterized by using image processing technique. It could be concluded that each temperature shows different thermodynamic impact regime. The results also reveal that at surface temperature lower than 140 ?C, the increase of surface roughness leads the increase of spreading diameter. In contrast, the spreading factor decreases with the increasing of surface roughness at 140 ?C due to incomplete wetting of droplet on the surface. Meanwhile, the maximum spreading factor is relatively independent to the change of surface roughness.