粗糙圆柱水平入水的界面流动分离特性试验研究

Separation of surface low during water entry of cylinders with various surface roughness

针对具有微米级颗粒的粗糙圆柱水平入水开展试验研究,通过以高速摄影为工具的流动显示技术研究了粗糙圆柱以不同初速度入水后,水与圆柱表面的界面流动发生的几何形态、运动的变化,对流动分离位置进行了较准确的测量.研究表明,粗糙表面会导致圆柱入水时气-固-液三相接触线出现锯齿形失稳,接触线速度明显降低,液面更容易与圆柱表面分离.其次,对液面分离的影响因素开展研究,发现随着表面颗粒尺寸减小和单位面积的颗粒数目增加,分离角呈现先增大后减小再增加的变化规律;随着入水速度的增加,分离角度减小,界面流动更容易发生分离.最后,通过对不同粗糙表面静态及动态接触角的测量,对粗糙表面动态接触角滞后特性与入水界面流动分离的相关性问题开展了研究.

An experimental research on the rough surface cylinders with different micron particle sizes falling into water is carried out.By means of high-speed photography,the geometry and motion of the interface flow on the cylindrical surface after the entry at different initial speeds are studied.The location of the flow separation was measured accurately.The result shows that the serrated instability can be observed at the three-phase contact line,the velocity of the three-phase contact line decreases and the liquid surface is easier to be separated from the rough surface cylinder.Secondly,several factors on the separation are studied.It is found that with the surface roughness decrease,the distance from the separation position to the bottom base of the cylinder increases first and then decreases;with the falling velocity increase,the separation of the solid-fluid interaction becomes easier and the separation position approaches more to the bottom base.Finally,the contact angle of different rough surfaces are measured,the correlation between the hysteresis characteristics of dynamic contact angles and the separation position is studied.