液滴撞击不同粗糙度固体表面动力学行为实验研究

Experimental Study on the Droplet Impact on Solid Surface with Different Roughness

针对液滴撞击固体表面时动力学行为的不同影响因素,利用高速摄像技术捕捉了4种物性不同的液滴,即癸烷、十四烷、蒸馏水和无水乙醇液滴撞击不同粗糙度固体表面后的铺展与飞溅形态。探究了黏度、表面张力与实验壁面粗糙度对液滴撞击壁面后的最大铺展因数和铺展-飞溅临界韦伯数的影响。结果表明:实验流体的动力黏度越大,液滴在铺展过程中受到的阻力越大,也就越不容易铺展,相同韦伯数下的最大铺展因数越小;表面张力越大,液滴碰壁后更有可能发生回缩。在实验过程中也观察到,只有表面张力明显大于其他工质的蒸馏水液滴在碰壁后发生了回缩。壁面越粗糙,液滴在铺展过程中需要润湿越大面积的壁面,增加了黏性耗散,且受到的阻力也更大,相同韦伯数的液滴碰壁后的最大铺展因数也越小。对Laan的公式进行了粗糙度的补充,得到了最大铺展因数与韦伯数、雷诺数及粗糙度的关系。壁面粗糙度对液滴铺展后的边缘造成扰动,使液滴更容易发生飞溅,铺展-飞溅的临界韦伯数随着壁面粗糙度的增加而减小,且壁面粗糙度对小奥内佐格数流体的临界韦伯数影响更大。

The impact dynamics of droplets of different roughness was investigated by using the high-speed viscosity, surface tension and surface roughness diameter and the critical Weber number for transiti The results showed that the non-dimensional ma Increasing Impacting on the experime needs to wet roughness, 1 uid viscosity, and er the solid surface. It was nt since it has larger surface eading to th number. The relationship number and surface rough liquids onto solid surfaces with different microphotography. The influences of on from spreading to splas ximum spreading diamete maximum hing were spreading discussed. r decreases with the surface tension makes droplet more possible to retract after also observed that water is the only liquid that retracts in obviously higher surface tension than other three and will have higher viscous dissipation e decrease of the maximum spreading diameter of the maximum spreading diameter with Weber ness was obtained by introducing surface roughness liquids. The droplet e increase of surface at the same Weber number, Ohnesorge to Laan＇s equation.The ＂finger-like＂ disturbance around the rim becomes more obvious with the increase of surface roughness, which makes the droplet more likely to splash after impact onto the solid surface and leads to lower critical Weber number for transition from spreading to splashing. In addition, the surface roughness influences the critical Weber number more significantly for the liquids with smaller Ohnesorge number.