This chapter is dedicated to phenomena where surface tension and gravity govern the dynamics. The balance between these two forces generally leads to a static configuration and the object of interest is the geometric shape of the interface.
Gravity is characterized by the specific weight of the liquid , where is the liquid density and is the acceleration due to gravity. The dimensions of specific gravity are , where denotes the dimensions of force and those of length. Since the dimensions of surface tension are , a balance of surface tension and gravity invariably yields the ratio , which has the dimensions . Based on this arises the capillary length defined as . For a fluid like water, with N/m and N/m, the capillary length is mm.