Lattice Boltzmann Simulation Of Droplet Impact On Non-ideal Surfaces

The phenomenon of droplet impacting on a solid surface ubiquitously exists in nature and industry,including droplets penetrating a stone,ink-jet printing,etc.The study on above phenomenon has been taken into account by scholars about a century ago,However,the research of droplet impacting on non-ideal surfaces which are more realistic in nature has not been investigated sufficiently,which is attributed to the limitation of laboratory conditions and theoretical methods.Consequently,how the non-ideal surface influences each stage in the process of the droplet collision remain unclear.This thesis has established both two-and three-dimensional models of droplet collision by Lattice Boltzmann Method(LBM).Several specific non-ideal surfaces are provided by changing the structure and wettability of the solid wall.The main content of this thesis are structured as following:1.How the micro-structure affect the consequence of droplet collision and the contact time before droplet bouncing back is investigated by adding a ridge on a flat surface.The results show that the ridge can significantly reduce the contact time during the droplet collision.The mechanism of contact time reduced by the ridge is different between the droplets with different diameters and impact velocities.2.Droplet impact on the surface composed of stripes with alternate wettability is simulated.The results show that with a stripe of proper width,the alternate wettability heterogeneous surface shows a great influence on the relaxation stage of droplet collision which can reduce the amplitude and duration of relaxation stage.3.Droplet with high initial velocity impacting on the wettability-gradient surface and then divided into two parts is simulated to investigate the mechanism that how a gradient surface promote the droplets merging.According to the rule of droplets merging on wettability gradient surface,a new surface is designed to promote the droplets merge more efficiently.As a conclusion,using a proper non-ideal surface in the process of droplet collision can effectively reduce the contact time before droplet bouncing back,decrease the amplitude and duration of the relaxation phase,promote split droplets merge,which has a great significance on guiding the industrial practice such as protecting airplane wings from freezing,improving the quality of dyeing and printing,optimizing self-cleaning function,etc.