基于SPH方法的液滴撞击可湿润固壁模拟  

Numerical studies on droplet impact to wettable solid boundary based on SPH method

作　　者：王志超[1] 李大鸣[2] 李杨杨[2] 牛娇[1] 

机构地区：[1]江西省水利科学研究院,南昌330029 [2]天津大学建筑工程学院,水利工程仿真与安全国家重点实验室,天津300073

出　　处：《科学通报》2017年第24期2788-2795,共8页Chinese Science Bulletin

基　　金：国家自然科学基金(51079095,51369011)资助

摘　　要：液滴撞击固体壁面是一种常见的自然现象和工业过程,在这些现象和过程中液滴运动往往受到壁面可湿润性的影响.本文提出了一种可湿润性固壁边界条件的计算方法,即假设壁面粒子的亲水性以及毛细吸附作用统一表现为对支持域内流体粒子的吸附力.吸附力的大小与流体压强、材料饱和度及亲水性有关.基于光滑粒子流体动力学(SPH)方法,模拟了静态液滴在不同可湿润性壁面上由变形至稳定的过程.考虑壁面可湿润性的影响,模拟了液滴撞击疏水壁面的过程.结合试验数据,分析了壁面可湿润性对液滴运动过程的影响.研究表明:根据模拟液滴静态接触角的变化特点,本文可湿润性固壁边界条件可以较好地反映出壁面可湿润性;液滴撞击输水表面的模拟数据与试验结果趋势上吻合良好,液滴回弹时在壁面可湿润性的影响下形成液柱;壁面可湿润性对撞击后液滴的铺展过程影响很小,在该阶段壁面摩擦力起主要作用,回缩和回弹阶段壁面可湿润性对液滴运动特征的影响较明显.Droplet impact on solid surface is a common natural phenomenon and industrial process which is also a complex polyphase conditions coupling process with gas, liquid and solid. And during the droplet＇s deformation and movement, it is often affected by the wettability of solid wall. In this paper, a lagrange SPH numerical method, with the attraction of the van der Waals state equation added to simulate the surface tension of the droplet, is applicated to simulate the process of single droplet impact on wettable surface and investigate the influence mechanism of surface wettability to the droplet＇s deformation and movement. Several improvements for traditional SPH methd are presented such as, a Lagrange wettable solid wall boundary condition of which solid wall pariticles＇ hydrophilia and capillary action are unified supposed to be a adsorption force to the liquid particles of support domains. The force is deemed relevant to fluid pressure, saturation and solid wall＇s hydrophilia. Then a stress correction method is proposed for the stress instability caused by the SPH kernel function. The method uses two different shapes of kernel functions to calculate the tensile and compressive stresses, respectively. After that, a SPH model compiled in Fortran language and based on the above two improved methods is established to simulate static and dynamic droplets＇ deformation processes on different wettable wall. The following studies were carded out based on the simulation results. Firstly, the effect of stress correction method is investigated by the comparison between simulating results with the stress correction before and after used. Secondly, the validity of the wettable solid wall boundary condition is studied based on the simulation results of static droplet deformation. Finally, the influence of the wall wettability on the droplet movement process after the collision is analyzed. Researches show that, the stress correction method improves the stress instability problem in the traditional SPH method, even in

关 键 词：光滑粒子流体动力学 固体壁面 可湿润性 液滴 

分 类 号：O35[理学—流体力学]