Tension Superficial
Videos
Flow into a porous media from a drip source :
When water is applied on the surface of a uniform homogeneous soil, the capillary and gravitational forces will draw the water into the soil. Because capillary forces act in all directions and gravitational forces act only downwards, the wetted bulb that is formed will tend to be elongated in the vertical direction. This can be observed in this video, where horizontal movement from the source occurs at a smaller rate that vertical movement.
Effect of tensioactive materials:
Surface tension is affected by impurities in water. This video shows a string loop on a water surface. When a tensioactive material (soap) is put in contact with the water inside the loop, the surface tension inside the loop is reduced. As a result, surface tension outside the loop is larger than that inside the loop causing the loop to extend and tend to form a circle.
Capillary rise:
Capillary rise refers to the phenomenon in which water tends to be absorbed into tubes of small diameter or porous media. This can be observed in soils with a water table. When water comes into contact with a dry soil, capillary forces will draw water into the soil. Water will rise from the water table into the soil. The band of soil above the water table that is saturated is referred to as the capillary fringe. The width of this band is the capillary rise of water in the soil.
NOTE
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