水滴动力学行为对其撞击特性影响

Effect of dynamic behaviour on its impingement characteristics for droplets

设计了一种压电式等径离散水滴发生器,利用高速摄影的手段对水滴变形现象进行了实验研究。建立了水滴变形后的非球形阻力模型,同时引入了水滴破碎和飞溅模型,采用欧拉法对不同条件下水滴撞击NACA23012翼型的过程进行了数值模拟,并与传统模型下水滴撞击特性计算进行了对比。研究表明:水滴变形会导致其阻力系数增大,水滴阻力系数曲线在雷诺数大于500时逐渐脱离球形阻力曲线,不断增大接近圆盘阻力系数;水滴阻力特性的改变会影响水滴运动轨迹,增强水滴的气流跟随性;水滴飞溅会造成水滴质量损失,减小翼型表面局部水收集系数,这与实验数据更加吻合。

A piezoelectric mono-dispersed droplet generator was designed to study the deformation of droplets under the aerodynamic force by the high speed imaging system.The non-spherical drag model was established for the deformed water droplets.The process of water droplets impinging on the NACA23012 airfoil was simulated while the breakup modeland splash model were introduced into Eulerian model.The simulated results were compared with the results from traditional model.It was found that the drag coefficient of water droplets increased because of the deformation.When the Reynolds number was larger than 500,water drag coefficient curve broke away with the spherical drag curve gradually and grew close to the disc drag coefficient curve.The droplet trajectory was affected because of the change of the drop＇s drag properties,making the droplet follow with the air.The mass loss from splashing decreased the local collection coefficient on the airfoil,which was in good agreement with the experiment data.