CHAPTER 12
291HYDRAULICS
AND WATERWORKS
FORMULAS
To simplify using the formulas in this chapter, Table 12.1 presents symbols,
nomenclature, and United States Customary System(USCS) and System Inter-
national(SI) units found in each expression.
CAPILLARY ACTION
Capillarityis due to both the cohesive forces between liquid molecules and
adhesive forces of liquid molecules. It shows up as the difference in liquid sur-
face elevations between the inside and outside of a small tube that has one end
submerged in the liquid (Fig. 12.1).
Capillarity is commonly expressed as the height of this rise. In equation form,
(12.1)
where hcapillary rise, ft (m)
surface tension, lb/ft (N/m)
w 1 andw 2 specific weights of fluids below and above meniscus, respec-
tively, lb/ft (N/m)
angle of contact
rradius of capillary tube, ft (m)
Capillarity, like surface tension, decreases with increasing temperature. Its
temperature variation, however, is smalland insignificant in most problems.
VISCOSITY
Viscosityof a fluid, also called the coefficient of viscosity,absolute viscosity,
ordynamic viscosity, is a measure of itsresistance to flow. It is expressed as the
h2 cos
(w 1 w 2 )r