摘要：
The flow characteristic of the droplets impacting on solid surface is extremely significant for practical engineering applications.The problem is also very complicated since there are many parameters that may influence the process of droplets impacting on a solid surface.Therefore the numerical study of behaviors of droplets impacting on a solid surface is performed in this work.With a given impact velocity,two two-dimensional axisymmetric droplets subsequently interact on the solid surface.To conduct numerical simulations,a mass conserved level set method is adopted,and the gravity and surface tension are taken into consideration in the process of droplet development on the solid surface.The effects of Weber number,surface contact angle,the horizontal distance between the two droplets,and droplet arrangement on the dynamic behaviors of droplet impact are systematically investigated.It is found that two droplets vertically impacting on solid surface simultaneously can produce a columnar liquid jet column,and the horizontally spreading liquid on the solid surface will break up in several segments as time goes by.With the increase of Weber number,the secondary droplets are generated from liquid jet,and the columnar liquid jet rebounds away from the surface subsequently.If the Reynolds number,surface contact angle and the horizontal distance are set to be,respectively,2000,90°and 2,in particular,the non-dimensional length of liquid spread is unrelated to Weber number when the non-dimensional time T ＜ 2,and it increases as the Weber number increases when T ＞ 2.Meanwhile,the dynamic change characteristics of the non-dimensional liquid jet height are about the same during the jet rising,but the jet falling time becomes shorter as the Weber number decreases.Obviously,the bigger the Weber number,the bigger the biggest non-dimensional height of liquid jet and length of liquid spread are.On the other hand,with the increase of surface contact angle,the columnar liquid jet rebounds away from the surface and the spreading liquid breaks up much earlier on the surface.Also,the non-dimensional height of liquid jet and length of liquid spread grow with the increase of surface contact angle.In addition,in the case that the Weber number,Reynolds number and surface contact angle are set to be 32,2000 and 90° respectively,we also find that the correlation between the biggest non-dimensional jet height and horizontal distance is not monotonic.Under the circumstances,the biggest non-dimensional height of liquid jet is achieved when the distance is set to be 2,and the phenomenon of liquid jet rebound occurs subsequently,whether the rebound phenomenon of the jet liquid column is related to the horizontal distance of the droplet or not.And finally,as the horizontal distance between the two droplets increases from 1.5 to 3,the non-dimensional length of liquid spread gradually increases.%采用质量守恒的level set方法对双液滴同时垂直撞击干壁面后的流动过程进行了模拟研究,主要讨论了韦伯数(We)、壁面接触角(θ)以及双液滴水平间距(S)等物理参数对相界面流动过程的影响,分析了不同参数下射流高度和水平铺展半长随时间的变化规律.研究表明:We数较大时,中心射流液柱将产生二次液滴,随后液柱反弹至空中,且We数越大,中心射流产生的二次液滴次数越多,最大无量纲射流高度和最大无量纲铺展半长越大;随壁面接触角的增大,中心射流液柱出现反弹现象,水平铺展液流出现断裂的时间越早,最大无量纲射流高度和最大无量纲铺展半长越小;最大无量纲射流高度值与液滴水平间距的相关性不单调,铺展半长随水平间距的增大而增大.
