大液滴撞击不同润湿性小球的三维格子Boltzmann方法模拟

Three-dimensional Lattice Boltzmann Method Simulation of A Large Droplet Impacting A Small Sphere with Different Wettability

采用三维多松弛(MRT)Shan-Chen的格子玻尔兹曼方法(LBM)模拟液滴撞击不同润湿性固体小球(液滴直径与小球直径比大于1)的动态过程,在多种方法验证计算模型准确性的基础上,探究液滴韦伯数、小球表面润湿性对液滴撞击小球动态过程的影响,以及液滴撞击小球后形成片层的几何特征与球面润湿性的关系。结果表明:液滴撞击小球后将形成钟罩形的片层,撞击亲水小球后的片层则会出现凹痕。当小球表面润湿程度一定时,片层的最大底径随韦伯数增大而增加。撞击亲水小球时,片层形成后会完全闭合,韦伯数越大,且片层完全闭合的时刻越早,并在闭合过程中片层容易发生破裂。而撞击疏水小球时,韦伯数越大,则片层发生破裂的时刻越早;在片层打开过程中,破裂后的片层成环条状下落,即片层的几何特征受韦伯数和小球润湿程度的共同影响。

The three-dimensional multi-relaxation(MRT)Shan-Chen Lattice Boltzmann method(LBM)is used to simulate the dynamic process of a droplet impacting small solid spheres with different wettability(The ratio of droplet diameter to small sphere diameter is greater than 1.)On the basis of verifying the accuracy of the calculation model by various methods,the influence of the Weber number of the droplet and the surface wettability of the small sphere on the dynamic process and the relationship of the geometry of the lamella formed with wettability are explored.The results show that the lamella formed after impacting the hydrophilic sphere is bell-shaped,When the surface wetting degree is constant,the maximum bottom diameter of the lamella increases with the increase of Weber number.When impacting the hydrophilic small sphere,the lamella completely closes after the formation of the lamella;the larger the Weber number,the earlier the lamella is completely closed,and the lamella is prone to break during the closing process.When impacting the hydrophobic small sphere,a larger Weber number leads to an earlier breakage of the lamella,and the broken lamellas fall down in a ring strip during the opening of the lamella.The geometric characteristics of the lamella are affected by the Weber number and wettability of the small sphere.