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.