(11.3.1)--6.3-1WettingandNonwettingCapilla.pdf

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1、Wetting and Nonwetting Capillary Phenomena 1.Wetting and Nonwetting Phenomena The phenomenon that liquid accumulates on a surface of a solid or not is considered as wetting and nonwetting phenomena.For example,water can wet(or infiltrate)clean glass but fails to wet the greased glassFor instance,wat

2、er failing to wet lotus leaves,the glittering spherical drops are generated on the lotus leaves,which can be derived from the small water drops.2.Qualitative interpretation of wetting and nonwetting phenomena The adhesive layer:a thin layer of liquid generated when a liquid is exposed to a solid.The

3、 attraction of liquid molecules to molecule A is defined as the cohesive force.The attraction of a solid molecule to a liquid molecule A is regarded as the adhesive force.If f附附 f内内,A wetting phenomenon occurs；If f附附 f内内,An nonwetting phenomenon appears；3.Contact Angle The two tangential lines the t

4、angential line of the surface of the liquid and the tangential line of the surface of the solid,which are drawn at the common junction of solid,gas,and are directed at the side of solid-liquid contact surface will produce an angle by passing through the interior of liquid,or the contact angle.Obviou

5、sly:wetting phenomenon follows the condition 090，while nonwetting phenomenon follows the condition 90180.Usually,the liquid surface is fully wetting when=0 and the liquid surface is completely nonwetting when=180.For example,when it comes to the homogeneous cube block featuring complete nonwetting a

6、nd floating on the liquid,its surface tension direction is vertically upward,which means that the gravitational force of the object,the force exerted by gravity,is balanced by the buoyancy and surface tension exerted by the object.Surface tensionbuoyancy4.capillary phenomena The tube with small inte

7、rnal diameter is called capillary which can be inserted into the wettable water,leading to the increased water level in the tube.Whats more,the smaller the internal diameter of the capillary tube is,the higher the water level will rise.The capillary tube being inserted into the non-wetting mercury,t

8、he mercury level in the capillary will reduce,which reveals that the smaller the inner diameter is,the lower the mercury level will become.Capillary phenomenon is triggered by the additional pressure at the curved surface in the capillary.2/AppRgh0/cosRr2cos/hgr hr DiscussionPut one end of the newspaper or towel into the water,after a period of time,what will happen?The water flows upwards along the newspaper or towelThanks！