Lattice Boltzmann Simulation Of The Droplet Impact Onto Liquid Film

The process of the droplet impact onto the liquid film, as one of the basic multiphase problems, is very important in many fields of science and engineering, and the problem is also very complicated since the movement of interface is complex and there are manydimensionless parameters that may influence the process of the droplet impact on the liquid film. In this thesis, we will investigate the interface change during process of droplet impact onto the liquid film which is on the smooth and rough solid surfaces based on a recently developed lattice Boltzmann (LB) method. We mainly focus on the effects of the Reynolds number (Re), the Weber number (We), the relative thickness of film (h), the relative width of cavity (d*) and the relative depth of cavity (L*) on the process of droplet impact onto the liquid film. The main conclusions are summarized as follows.For the smooth solid wall, firstly, it is found that Re and We make a great interface on the process of droplet impact onto the liquid film, with the increase of Re and We, the phenomena of entrainment and splashing can be observed obviously;secondly, h also has an effect onthe movement of spray which produce in the process of droplet impact onto the liquid film, with the increase of h, the radius become small, the height of spray also becomes low and the splashing will vanish; finally, it is found that the spray radius is related to time through the relation , in this relation, the coefficient ? changes little for different Re and We, but decrease with the increase of h, and the relationship between radius and time is not satisfied any morewhen h> 3.In terms of the rough solid surface, firstly, with the increase of d*, the a will be first decrease, and then increase, the increase of the cavity width will have little influence on the change of spray when d*>8; secondly, the L* almost has no effect onthe formation of spray, but it brings a great influence on the splashing of spray; thirdly, Re still influence the splashing of spray, and with the increase of Re, the coefficient ? still has little change, but is smaller than that of the smooth solid surface; finally the splashing will vanish when h?2, and the spreading rate of spray will decrease with the increase of relative thickness of film.