动态湿润与动态接触角的实验

利用精密步进电机、高速CCD图像采集系统、立体显微镜,采用液槽法测试硅酮油在玻璃、铝、不锈钢表面上的动态湿润行为。实验结果与前驱膜模型对比表明,无量纲参数λ在玻璃、铝和不锈钢表面上分别取值0.07,0.16和0.35时,二者吻合较好,表明动态接触角不仅是静接触角和毛细数的函数,也和固体表面性质有关。实验同时发现,对于低毛细数下成立的Hoffman-Voinov-Tanner定律(Cazabat推荐适用于CaD<1或θD<10°),直到动态接触角达到70°依然成立,用前驱膜模型可给出合理解释。 

An Experimental Investigation on Dynamic Wetting and Dynamic Contact Angle

An experimental system,composed of a liquid tank,a solid thin plate,a step-motor,a CCD camera connected with stereoscopic microscope,a high-speed image acquisition card,and a computer,was utilized to investigate dynamic wetting behavior of silicone oil on glass,aluminum and stainless steel surfaces and understand the effect of the solid surface properties on the dynamic wetting behavior.It concludes that when the value of the dimensionless parameter,λ,was selected as 0.07,0.16 and 0.35 for glass,aluminum and stainless steel,respectively,the experimental results are in good accordance with the prediction of the precursor film model presented by Wang and Peng et al.Clearly, the dynamic contact angle is dependent not only on the capillary number and static contact angle but also on λ describing the solid surface properties.Furthermore,it is shown that the Hoffman-Voinov-Tanner law valid at low capillary number (Ca1 or θ_D<10°) recommended by Cazabat still keeps true for a wide range of contact angles,up to 70°,which is reasonably explained by the precursor film model.