润湿梯度表面液滴运动特征及流场特性研究

Study on the Motion Features and Flow Field Characteristics of Liquid Droplets on Wettability Gradient Surface

液滴的定向驱动在微流控、淡水收集及工业冷凝过程等领域具有重要作用,本文基于VOF方法建立了润湿梯度表面液滴运动模型,研究了不同梯度条件和重力方向下液滴的运动特征和流场特性。结果表明,润湿梯度越大液滴的运动速度变化越快,当接触角突变足够大时,液滴无法通过接触角突变线。液滴在“T”型梯度表面上,出现“撞击”、“反弹”等现象,在“J”型和直“U”型梯度表面上,出现“波浪”型运动轨迹,而在液滴圆“U”型梯度表面上,出现沿润湿梯度外边界滑动的现象。同时研究了梯度表面双液滴的碰撞过程,对液滴驱离的应用具有参考价值。

Directional drive of droplet is of great importance in the fields of microfluidics,fresh water collection and industrial condensation processes.Based on VOF method,the droplet motion model on the wettability gradient surface was established,and the motion features and fow field characteristics of liquid droplets under different wettability gradient conditions and gravity directions were investigated.The results show that the change of droplet velocity increases with the augment of wetting gradient,and the droplet cannot pass through the contact angle change line when the change of the contact angle at the boundary is large enough.On T-type gradient surface,liquid droplets exhibit the motion of impact,rebound and etc.On J-type and straight U-type gradient surfaces,wave-type motion trajectories occur,while on a circular U-type gradient surface,liquid droplets experience sliding along the outer boundary of the wetting gradient.At the same time,the collision process of two liquid droplets on the gradient surface was investigated,which provides reference for the application of liquid droplets departing.